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Revision 1.369 by root, Mon May 30 18:34:28 2011 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
…		…
98	=head2 FEATURES	106	=head2 FEATURES
99		107
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
108	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
109	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
110		119
111	It also is quite fast (see this	120	It also is quite fast (see this
112	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
113	for example).	122	for example).
114		123
…		…
117	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)
118	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
120	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
121	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
122	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
123	this argument.	132	this argument.
124		133
125	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
126		135
127	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
128	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
129	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
130	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
131	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
132	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
133	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
134	throughout libev.	144	time differences (e.g. delays) throughout libev.
135		145
136	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
137		147
138	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
139	and internal errors (bugs).	149	and internal errors (bugs).
…		…
163		173
164	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
165		175
166	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
167	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
168	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
169		180
170	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
171		182
172	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
173	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
190	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
191	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
192	not a problem.	203	not a problem.
193		204
194	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
195	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
196		208
197	assert (("libev version mismatch",	209	assert (("libev version mismatch",
198	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
199	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
200		212
…		…
211	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
212	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
213		225
214	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
215		227
216	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
217	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
218	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
219	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
220	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
221	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
222		235
223	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
224		237
225	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
226	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
227	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
229	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
230		243
231	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
232		245
233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
234		247
235	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
237	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
238	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
264	}	277	}
265		278
266	...	279	...
267	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
268		281
269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
270		283
271	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
272	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
273	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
274	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
286	}	299	}
287		300
288	...	301	...
289	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
290		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
291	=back	317	=back
292		318
293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
294		320
295	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
296	is I<not> optional in this case, as there is also an C<ev_loop>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
297	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
298		324
299	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
300	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
301	not.	327	do not.
302		328
303	=over 4	329	=over 4
304		330
305	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
306		332
307	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
308	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
309	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
310	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
311		343
312	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
313	function.	345	function (or via the C<EV_DEFAULT> macro).
314		346
315	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
316	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
317	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
318		351
319	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
320	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
321	for C<SIGCHLD>. If this is a problem for your application you can either	354	a problem for your application you can either create a dynamic loop with
322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
324	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
325		376
326	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
327	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
328		379
329	The following flags are supported:	380	The following flags are supported:
…		…
344	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
345	around bugs.	396	around bugs.
346		397
347	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
348		399
349	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
350	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
351	enabling this flag.
352		402
353	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
354	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
355	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
356	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
362	flag.	412	flag.
363		413
364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365	environment variable.	415	environment variable.
366		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
		451
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		453
369	This is your standard select(2) backend. Not I<completely> standard, as	454	This is your standard select(2) backend. Not I<completely> standard, as
370	libev tries to roll its own fd_set with no limits on the number of fds,	455	libev tries to roll its own fd_set with no limits on the number of fds,
371	but if that fails, expect a fairly low limit on the number of fds when	456	but if that fails, expect a fairly low limit on the number of fds when
…		…
395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	480	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	481	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
397		482
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	483	=item C<EVBACKEND_EPOLL> (value 4, Linux)
399		484
		485	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		486	kernels).
		487
400	For few fds, this backend is a bit little slower than poll and select,	488	For few fds, this backend is a bit little slower than poll and select, but
401	but it scales phenomenally better. While poll and select usually scale	489	it scales phenomenally better. While poll and select usually scale like
402	like O(total_fds) where n is the total number of fds (or the highest fd),	490	O(total_fds) where total_fds is the total number of fds (or the highest
403	epoll scales either O(1) or O(active_fds).	491	fd), epoll scales either O(1) or O(active_fds).
404		492
405	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
406	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
407	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
408	descriptor (and unnecessary guessing of parameters), problems with dup and	496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(and only giving 5ms accuracy while select on the same platform gives
409	so on. The biggest issue is fork races, however - if a program forks then	499	0.1ms) and so on. The biggest issue is fork races, however - if a program
410	I<both> parent and child process have to recreate the epoll set, which can	500	forks then I<both> parent and child process have to recreate the epoll
411	take considerable time (one syscall per file descriptor) and is of course	501	set, which can take considerable time (one syscall per file descriptor)
412	hard to detect.	502	and is of course hard to detect.
413		503
414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
415	of course I<doesn't>, and epoll just loves to report events for totally	505	of course I<doesn't>, and epoll just loves to report events for totally
416	I<different> file descriptors (even already closed ones, so one cannot	506	I<different> file descriptors (even already closed ones, so one cannot
417	even remove them from the set) than registered in the set (especially	507	even remove them from the set) than registered in the set (especially
418	on SMP systems). Libev tries to counter these spurious notifications by	508	on SMP systems). Libev tries to counter these spurious notifications by
419	employing an additional generation counter and comparing that against the	509	employing an additional generation counter and comparing that against the
420	events to filter out spurious ones, recreating the set when required.	510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
421		517
422	While stopping, setting and starting an I/O watcher in the same iteration	518	While stopping, setting and starting an I/O watcher in the same iteration
423	will result in some caching, there is still a system call per such	519	will result in some caching, there is still a system call per such
424	incident (because the same I<file descriptor> could point to a different	520	incident (because the same I<file descriptor> could point to a different
425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		588
493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
494	it's really slow, but it still scales very well (O(active_fds)).	590	it's really slow, but it still scales very well (O(active_fds)).
495		591
496	Please note that Solaris event ports can deliver a lot of spurious
497	notifications, so you need to use non-blocking I/O or other means to avoid
498	blocking when no data (or space) is available.
499
500	While this backend scales well, it requires one system call per active	592	While this backend scales well, it requires one system call per active
501	file descriptor per loop iteration. For small and medium numbers of file	593	file descriptor per loop iteration. For small and medium numbers of file
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	595	might perform better.
504		596
505	On the positive side, with the exception of the spurious readiness	597	On the positive side, this backend actually performed fully to
506	notifications, this backend actually performed fully to specification
507	in all tests and is fully embeddable, which is a rare feat among the	598	specification in all tests and is fully embeddable, which is a rare feat
508	OS-specific backends (I vastly prefer correctness over speed hacks).	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
509		611
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
512		614
513	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
514		616
515	Try all backends (even potentially broken ones that wouldn't be tried	617	Try all backends (even potentially broken ones that wouldn't be tried
516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		620
519	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
520		630
521	=back	631	=back
522		632
523	If one or more of these are or'ed into the flags value, then only these	633	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	634	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	635	here). If none are specified, all backends in C<ev_recommended_backends
526		636	()> will be tried.
527	Example: This is the most typical usage.
528
529	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
531
532	Example: Restrict libev to the select and poll backends, and do not allow
533	environment settings to be taken into account:
534
535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
536
537	Example: Use whatever libev has to offer, but make sure that kqueue is
538	used if available (warning, breaks stuff, best use only with your own
539	private event loop and only if you know the OS supports your types of
540	fds):
541
542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
543
544	=item struct ev_loop *ev_loop_new (unsigned int flags)
545
546	Similar to C<ev_default_loop>, but always creates a new event loop that is
547	always distinct from the default loop. Unlike the default loop, it cannot
548	handle signal and child watchers, and attempts to do so will be greeted by
549	undefined behaviour (or a failed assertion if assertions are enabled).
550
551	Note that this function I<is> thread-safe, and the recommended way to use
552	libev with threads is indeed to create one loop per thread, and using the
553	default loop in the "main" or "initial" thread.
554		637
555	Example: Try to create a event loop that uses epoll and nothing else.	638	Example: Try to create a event loop that uses epoll and nothing else.
556		639
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	641	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
560		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
561	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
562		650
563	Destroys the default loop again (frees all memory and kernel state	651	Destroys an event loop object (frees all memory and kernel state
564	etc.). None of the active event watchers will be stopped in the normal	652	etc.). None of the active event watchers will be stopped in the normal
565	sense, so e.g. C<ev_is_active> might still return true. It is your	653	sense, so e.g. C<ev_is_active> might still return true. It is your
566	responsibility to either stop all watchers cleanly yourself I<before>	654	responsibility to either stop all watchers cleanly yourself I<before>
567	calling this function, or cope with the fact afterwards (which is usually	655	calling this function, or cope with the fact afterwards (which is usually
568	the easiest thing, you can just ignore the watchers and/or C<free ()> them	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
570		658
571	Note that certain global state, such as signal state (and installed signal	659	Note that certain global state, such as signal state (and installed signal
572	handlers), will not be freed by this function, and related watchers (such	660	handlers), will not be freed by this function, and related watchers (such
573	as signal and child watchers) would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
574		662
575	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
576	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	except in the rare occasion where you really need to free its resources.
577	pipe fds. If you need dynamically allocated loops it is better to use	669	If you need dynamically allocated loops it is better to use C<ev_loop_new>
578	C<ev_loop_new> and C<ev_loop_destroy>).	670	and C<ev_loop_destroy>.
579		671
580	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
581		673
582	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.
584
585	=item ev_default_fork ()
586
587	This function sets a flag that causes subsequent C<ev_loop> iterations	674	This function sets a flag that causes subsequent C<ev_run> iterations to
588	to reinitialise the kernel state for backends that have one. Despite the	675	reinitialise the kernel state for backends that have one. Despite the
589	name, you can call it anytime, but it makes most sense after forking, in	676	name, you can call it anytime, but it makes most sense after forking, in
590	the child process (or both child and parent, but that again makes little	677	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
591	sense). You I<must> call it in the child before using any of the libev	678	child before resuming or calling C<ev_run>.
592	functions, and it will only take effect at the next C<ev_loop> iteration.	679
		680	Again, you I<have> to call it on I<any> loop that you want to re-use after
		681	a fork, I<even if you do not plan to use the loop in the parent>. This is
		682	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		683	during fork.
593		684
594	On the other hand, you only need to call this function in the child	685	On the other hand, you only need to call this function in the child
595	process if and only if you want to use the event library in the child. If	686	process if and only if you want to use the event loop in the child. If
596	you just fork+exec, you don't have to call it at all.	687	you just fork+exec or create a new loop in the child, you don't have to
		688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
597		691
598	The function itself is quite fast and it's usually not a problem to call	692	The function itself is quite fast and it's usually not a problem to call
599	it just in case after a fork. To make this easy, the function will fit in	693	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
602	pthread_atfork (0, 0, ev_default_fork);	705	pthread_atfork (0, 0, post_fork_child);
603
604	=item ev_loop_fork (loop)
605
606	Like C<ev_default_fork>, but acts on an event loop created by
607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
608	after fork that you want to re-use in the child, and how you do this is
609	entirely your own problem.
610		706
611	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
612		708
613	Returns true when the given loop is, in fact, the default loop, and false	709	Returns true when the given loop is, in fact, the default loop, and false
614	otherwise.	710	otherwise.
615		711
616	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
617		713
618	Returns the count of loop iterations for the loop, which is identical to	714	Returns the current iteration count for the event loop, which is identical
619	the number of times libev did poll for new events. It starts at C<0> and	715	to the number of times libev did poll for new events. It starts at C<0>
620	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
621		717
622	This value can sometimes be useful as a generation counter of sorts (it	718	This value can sometimes be useful as a generation counter of sorts (it
623	"ticks" the number of loop iterations), as it roughly corresponds with	719	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		721	prepare and check phases.
625		722
626	=item unsigned int ev_loop_depth (loop)	723	=item unsigned int ev_depth (loop)
627		724
628	Returns the number of times C<ev_loop> was entered minus the number of	725	Returns the number of times C<ev_run> was entered minus the number of
629	times C<ev_loop> was exited, in other words, the recursion depth.	726	times C<ev_run> was exited normally, in other words, the recursion depth.
630		727
631	Outside C<ev_loop>, this number is zero. In a callback, this number is	728	Outside C<ev_run>, this number is zero. In a callback, this number is
632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
633	in which case it is higher.	730	in which case it is higher.
634		731
635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
636	etc.), doesn't count as exit.	733	throwing an exception etc.), doesn't count as "exit" - consider this
		734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
637		736
638	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
639		738
640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
641	use.	740	use.
…		…
650		749
651	=item ev_now_update (loop)	750	=item ev_now_update (loop)
652		751
653	Establishes the current time by querying the kernel, updating the time	752	Establishes the current time by querying the kernel, updating the time
654	returned by C<ev_now ()> in the progress. This is a costly operation and	753	returned by C<ev_now ()> in the progress. This is a costly operation and
655	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
656		755
657	This function is rarely useful, but when some event callback runs for a	756	This function is rarely useful, but when some event callback runs for a
658	very long time without entering the event loop, updating libev's idea of	757	very long time without entering the event loop, updating libev's idea of
659	the current time is a good idea.	758	the current time is a good idea.
660		759
…		…
662		761
663	=item ev_suspend (loop)	762	=item ev_suspend (loop)
664		763
665	=item ev_resume (loop)	764	=item ev_resume (loop)
666		765
667	These two functions suspend and resume a loop, for use when the loop is	766	These two functions suspend and resume an event loop, for use when the
668	not used for a while and timeouts should not be processed.	767	loop is not used for a while and timeouts should not be processed.
669		768
670	A typical use case would be an interactive program such as a game: When	769	A typical use case would be an interactive program such as a game: When
671	the user presses C<^Z> to suspend the game and resumes it an hour later it	770	the user presses C<^Z> to suspend the game and resumes it an hour later it
672	would be best to handle timeouts as if no time had actually passed while	771	would be best to handle timeouts as if no time had actually passed while
673	the program was suspended. This can be achieved by calling C<ev_suspend>	772	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
675	C<ev_resume> directly afterwards to resume timer processing.	774	C<ev_resume> directly afterwards to resume timer processing.
676		775
677	Effectively, all C<ev_timer> watchers will be delayed by the time spend	776	Effectively, all C<ev_timer> watchers will be delayed by the time spend
678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	777	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
679	will be rescheduled (that is, they will lose any events that would have	778	will be rescheduled (that is, they will lose any events that would have
680	occured while suspended).	779	occurred while suspended).
681		780
682	After calling C<ev_suspend> you B<must not> call I<any> function on the	781	After calling C<ev_suspend> you B<must not> call I<any> function on the
683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	782	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
684	without a previous call to C<ev_suspend>.	783	without a previous call to C<ev_suspend>.
685		784
686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
687	event loop time (see C<ev_now_update>).	786	event loop time (see C<ev_now_update>).
688		787
689	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
690		789
691	Finally, this is it, the event handler. This function usually is called	790	Finally, this is it, the event handler. This function usually is called
692	after you initialised all your watchers and you want to start handling	791	after you have initialised all your watchers and you want to start
693	events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
694		795
695	If the flags argument is specified as C<0>, it will not return until	796	If the flags argument is specified as C<0>, it will keep handling events
696	either no event watchers are active anymore or C<ev_unloop> was called.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
697		799
698	Please note that an explicit C<ev_unloop> is usually better than	800	Please note that an explicit C<ev_break> is usually better than
699	relying on all watchers to be stopped when deciding when a program has	801	relying on all watchers to be stopped when deciding when a program has
700	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
701	that automatically loops as long as it has to and no longer by virtue	803	that automatically loops as long as it has to and no longer by virtue
702	of relying on its watchers stopping correctly, that is truly a thing of	804	of relying on its watchers stopping correctly, that is truly a thing of
703	beauty.	805	beauty.
704		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
705	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
706	those events and any already outstanding ones, but will not block your	813	those events and any already outstanding ones, but will not wait and
707	process in case there are no events and will return after one iteration of	814	block your process in case there are no events and will return after one
708	the loop.	815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
709		817
710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
711	necessary) and will handle those and any already outstanding ones. It	819	necessary) and will handle those and any already outstanding ones. It
712	will block your process until at least one new event arrives (which could	820	will block your process until at least one new event arrives (which could
713	be an event internal to libev itself, so there is no guarantee that a	821	be an event internal to libev itself, so there is no guarantee that a
714	user-registered callback will be called), and will return after one	822	user-registered callback will be called), and will return after one
715	iteration of the loop.	823	iteration of the loop.
716		824
717	This is useful if you are waiting for some external event in conjunction	825	This is useful if you are waiting for some external event in conjunction
718	with something not expressible using other libev watchers (i.e. "roll your	826	with something not expressible using other libev watchers (i.e. "roll your
719	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	827	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
720	usually a better approach for this kind of thing.	828	usually a better approach for this kind of thing.
721		829
722	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does (this is for your
		831	understanding, not a guarantee that things will work exactly like this in
		832	future versions):
723		833
		834	- Increment loop depth.
		835	- Reset the ev_break status.
724	- Before the first iteration, call any pending watchers.	836	- Before the first iteration, call any pending watchers.
		837	LOOP:
725	* If EVFLAG_FORKCHECK was used, check for a fork.	838	- If EVFLAG_FORKCHECK was used, check for a fork.
726	- If a fork was detected (by any means), queue and call all fork watchers.	839	- If a fork was detected (by any means), queue and call all fork watchers.
727	- Queue and call all prepare watchers.	840	- Queue and call all prepare watchers.
		841	- If ev_break was called, goto FINISH.
728	- If we have been forked, detach and recreate the kernel state	842	- If we have been forked, detach and recreate the kernel state
729	as to not disturb the other process.	843	as to not disturb the other process.
730	- Update the kernel state with all outstanding changes.	844	- Update the kernel state with all outstanding changes.
731	- Update the "event loop time" (ev_now ()).	845	- Update the "event loop time" (ev_now ()).
732	- Calculate for how long to sleep or block, if at all	846	- Calculate for how long to sleep or block, if at all
733	(active idle watchers, EVLOOP_NONBLOCK or not having	847	(active idle watchers, EVRUN_NOWAIT or not having
734	any active watchers at all will result in not sleeping).	848	any active watchers at all will result in not sleeping).
735	- Sleep if the I/O and timer collect interval say so.	849	- Sleep if the I/O and timer collect interval say so.
		850	- Increment loop iteration counter.
736	- Block the process, waiting for any events.	851	- Block the process, waiting for any events.
737	- Queue all outstanding I/O (fd) events.	852	- Queue all outstanding I/O (fd) events.
738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	853	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
739	- Queue all expired timers.	854	- Queue all expired timers.
740	- Queue all expired periodics.	855	- Queue all expired periodics.
741	- Unless any events are pending now, queue all idle watchers.	856	- Queue all idle watchers with priority higher than that of pending events.
742	- Queue all check watchers.	857	- Queue all check watchers.
743	- Call all queued watchers in reverse order (i.e. check watchers first).	858	- Call all queued watchers in reverse order (i.e. check watchers first).
744	Signals and child watchers are implemented as I/O watchers, and will	859	Signals and child watchers are implemented as I/O watchers, and will
745	be handled here by queueing them when their watcher gets executed.	860	be handled here by queueing them when their watcher gets executed.
746	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	861	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
747	were used, or there are no active watchers, return, otherwise	862	were used, or there are no active watchers, goto FINISH, otherwise
748	continue with step *.	863	continue with step LOOP.
		864	FINISH:
		865	- Reset the ev_break status iff it was EVBREAK_ONE.
		866	- Decrement the loop depth.
		867	- Return.
749		868
750	Example: Queue some jobs and then loop until no events are outstanding	869	Example: Queue some jobs and then loop until no events are outstanding
751	anymore.	870	anymore.
752		871
753	... queue jobs here, make sure they register event watchers as long	872	... queue jobs here, make sure they register event watchers as long
754	... as they still have work to do (even an idle watcher will do..)	873	... as they still have work to do (even an idle watcher will do..)
755	ev_loop (my_loop, 0);	874	ev_run (my_loop, 0);
756	... jobs done or somebody called unloop. yeah!	875	... jobs done or somebody called break. yeah!
757		876
758	=item ev_unloop (loop, how)	877	=item ev_break (loop, how)
759		878
760	Can be used to make a call to C<ev_loop> return early (but only after it	879	Can be used to make a call to C<ev_run> return early (but only after it
761	has processed all outstanding events). The C<how> argument must be either	880	has processed all outstanding events). The C<how> argument must be either
762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	881	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	882	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
764		883
765	This "unloop state" will be cleared when entering C<ev_loop> again.	884	This "break state" will be cleared on the next call to C<ev_run>.
766		885
767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	886	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		887	which case it will have no effect.
768		888
769	=item ev_ref (loop)	889	=item ev_ref (loop)
770		890
771	=item ev_unref (loop)	891	=item ev_unref (loop)
772		892
773	Ref/unref can be used to add or remove a reference count on the event	893	Ref/unref can be used to add or remove a reference count on the event
774	loop: Every watcher keeps one reference, and as long as the reference	894	loop: Every watcher keeps one reference, and as long as the reference
775	count is nonzero, C<ev_loop> will not return on its own.	895	count is nonzero, C<ev_run> will not return on its own.
776		896
777	If you have a watcher you never unregister that should not keep C<ev_loop>	897	This is useful when you have a watcher that you never intend to
778	from returning, call ev_unref() after starting, and ev_ref() before	898	unregister, but that nevertheless should not keep C<ev_run> from
		899	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
779	stopping it.	900	before stopping it.
780		901
781	As an example, libev itself uses this for its internal signal pipe: It	902	As an example, libev itself uses this for its internal signal pipe: It
782	is not visible to the libev user and should not keep C<ev_loop> from	903	is not visible to the libev user and should not keep C<ev_run> from
783	exiting if no event watchers registered by it are active. It is also an	904	exiting if no event watchers registered by it are active. It is also an
784	excellent way to do this for generic recurring timers or from within	905	excellent way to do this for generic recurring timers or from within
785	third-party libraries. Just remember to I<unref after start> and I<ref	906	third-party libraries. Just remember to I<unref after start> and I<ref
786	before stop> (but only if the watcher wasn't active before, or was active	907	before stop> (but only if the watcher wasn't active before, or was active
787	before, respectively. Note also that libev might stop watchers itself	908	before, respectively. Note also that libev might stop watchers itself
788	(e.g. non-repeating timers) in which case you have to C<ev_ref>	909	(e.g. non-repeating timers) in which case you have to C<ev_ref>
789	in the callback).	910	in the callback).
790		911
791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	912	Example: Create a signal watcher, but keep it from keeping C<ev_run>
792	running when nothing else is active.	913	running when nothing else is active.
793		914
794	ev_signal exitsig;	915	ev_signal exitsig;
795	ev_signal_init (&exitsig, sig_cb, SIGINT);	916	ev_signal_init (&exitsig, sig_cb, SIGINT);
796	ev_signal_start (loop, &exitsig);	917	ev_signal_start (loop, &exitsig);
797	evf_unref (loop);	918	ev_unref (loop);
798		919
799	Example: For some weird reason, unregister the above signal handler again.	920	Example: For some weird reason, unregister the above signal handler again.
800		921
801	ev_ref (loop);	922	ev_ref (loop);
802	ev_signal_stop (loop, &exitsig);	923	ev_signal_stop (loop, &exitsig);
…		…
841	usually doesn't make much sense to set it to a lower value than C<0.01>,	962	usually doesn't make much sense to set it to a lower value than C<0.01>,
842	as this approaches the timing granularity of most systems. Note that if	963	as this approaches the timing granularity of most systems. Note that if
843	you do transactions with the outside world and you can't increase the	964	you do transactions with the outside world and you can't increase the
844	parallelity, then this setting will limit your transaction rate (if you	965	parallelity, then this setting will limit your transaction rate (if you
845	need to poll once per transaction and the I/O collect interval is 0.01,	966	need to poll once per transaction and the I/O collect interval is 0.01,
846	then you can't do more than 100 transations per second).	967	then you can't do more than 100 transactions per second).
847		968
848	Setting the I<timeout collect interval> can improve the opportunity for	969	Setting the I<timeout collect interval> can improve the opportunity for
849	saving power, as the program will "bundle" timer callback invocations that	970	saving power, as the program will "bundle" timer callback invocations that
850	are "near" in time together, by delaying some, thus reducing the number of	971	are "near" in time together, by delaying some, thus reducing the number of
851	times the process sleeps and wakes up again. Another useful technique to	972	times the process sleeps and wakes up again. Another useful technique to
…		…
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	980	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		981
861	=item ev_invoke_pending (loop)	982	=item ev_invoke_pending (loop)
862		983
863	This call will simply invoke all pending watchers while resetting their	984	This call will simply invoke all pending watchers while resetting their
864	pending state. Normally, C<ev_loop> does this automatically when required,	985	pending state. Normally, C<ev_run> does this automatically when required,
865	but when overriding the invoke callback this call comes handy.	986	but when overriding the invoke callback this call comes handy. This
		987	function can be invoked from a watcher - this can be useful for example
		988	when you want to do some lengthy calculation and want to pass further
		989	event handling to another thread (you still have to make sure only one
		990	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
866		991
867	=item int ev_pending_count (loop)	992	=item int ev_pending_count (loop)
868		993
869	Returns the number of pending watchers - zero indicates that no watchers	994	Returns the number of pending watchers - zero indicates that no watchers
870	are pending.	995	are pending.
871		996
872	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	997	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
873		998
874	This overrides the invoke pending functionality of the loop: Instead of	999	This overrides the invoke pending functionality of the loop: Instead of
875	invoking all pending watchers when there are any, C<ev_loop> will call	1000	invoking all pending watchers when there are any, C<ev_run> will call
876	this callback instead. This is useful, for example, when you want to	1001	this callback instead. This is useful, for example, when you want to
877	invoke the actual watchers inside another context (another thread etc.).	1002	invoke the actual watchers inside another context (another thread etc.).
878		1003
879	If you want to reset the callback, use C<ev_invoke_pending> as new	1004	If you want to reset the callback, use C<ev_invoke_pending> as new
880	callback.	1005	callback.
…		…
883		1008
884	Sometimes you want to share the same loop between multiple threads. This	1009	Sometimes you want to share the same loop between multiple threads. This
885	can be done relatively simply by putting mutex_lock/unlock calls around	1010	can be done relatively simply by putting mutex_lock/unlock calls around
886	each call to a libev function.	1011	each call to a libev function.
887		1012
888	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1013	However, C<ev_run> can run an indefinite time, so it is not feasible
889	wait for it to return. One way around this is to wake up the loop via	1014	to wait for it to return. One way around this is to wake up the event
890	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1015	loop via C<ev_break> and C<av_async_send>, another way is to set these
891	and I<acquire> callbacks on the loop.	1016	I<release> and I<acquire> callbacks on the loop.
892		1017
893	When set, then C<release> will be called just before the thread is	1018	When set, then C<release> will be called just before the thread is
894	suspended waiting for new events, and C<acquire> is called just	1019	suspended waiting for new events, and C<acquire> is called just
895	afterwards.	1020	afterwards.
896		1021
…		…
899		1024
900	While event loop modifications are allowed between invocations of	1025	While event loop modifications are allowed between invocations of
901	C<release> and C<acquire> (that's their only purpose after all), no	1026	C<release> and C<acquire> (that's their only purpose after all), no
902	modifications done will affect the event loop, i.e. adding watchers will	1027	modifications done will affect the event loop, i.e. adding watchers will
903	have no effect on the set of file descriptors being watched, or the time	1028	have no effect on the set of file descriptors being watched, or the time
904	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it	1029	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
905	to take note of any changes you made.	1030	to take note of any changes you made.
906		1031
907	In theory, threads executing C<ev_loop> will be async-cancel safe between	1032	In theory, threads executing C<ev_run> will be async-cancel safe between
908	invocations of C<release> and C<acquire>.	1033	invocations of C<release> and C<acquire>.
909		1034
910	See also the locking example in the C<THREADS> section later in this	1035	See also the locking example in the C<THREADS> section later in this
911	document.	1036	document.
912		1037
913	=item ev_set_userdata (loop, void *data)	1038	=item ev_set_userdata (loop, void *data)
914		1039
915	=item ev_userdata (loop)	1040	=item void *ev_userdata (loop)
916		1041
917	Set and retrieve a single C<void *> associated with a loop. When	1042	Set and retrieve a single C<void *> associated with a loop. When
918	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1043	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
919	C<0.>	1044	C<0>.
920		1045
921	These two functions can be used to associate arbitrary data with a loop,	1046	These two functions can be used to associate arbitrary data with a loop,
922	and are intended solely for the C<invoke_pending_cb>, C<release> and	1047	and are intended solely for the C<invoke_pending_cb>, C<release> and
923	C<acquire> callbacks described above, but of course can be (ab-)used for	1048	C<acquire> callbacks described above, but of course can be (ab-)used for
924	any other purpose as well.	1049	any other purpose as well.
925		1050
926	=item ev_loop_verify (loop)	1051	=item ev_verify (loop)
927		1052
928	This function only does something when C<EV_VERIFY> support has been	1053	This function only does something when C<EV_VERIFY> support has been
929	compiled in, which is the default for non-minimal builds. It tries to go	1054	compiled in, which is the default for non-minimal builds. It tries to go
930	through all internal structures and checks them for validity. If anything	1055	through all internal structures and checks them for validity. If anything
931	is found to be inconsistent, it will print an error message to standard	1056	is found to be inconsistent, it will print an error message to standard
…		…
942		1067
943	In the following description, uppercase C<TYPE> in names stands for the	1068	In the following description, uppercase C<TYPE> in names stands for the
944	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1069	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
945	watchers and C<ev_io_start> for I/O watchers.	1070	watchers and C<ev_io_start> for I/O watchers.
946		1071
947	A watcher is a structure that you create and register to record your	1072	A watcher is an opaque structure that you allocate and register to record
948	interest in some event. For instance, if you want to wait for STDIN to	1073	your interest in some event. To make a concrete example, imagine you want
949	become readable, you would create an C<ev_io> watcher for that:	1074	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1075	for that:
950		1076
951	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1077	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
952	{	1078	{
953	ev_io_stop (w);	1079	ev_io_stop (w);
954	ev_unloop (loop, EVUNLOOP_ALL);	1080	ev_break (loop, EVBREAK_ALL);
955	}	1081	}
956		1082
957	struct ev_loop *loop = ev_default_loop (0);	1083	struct ev_loop *loop = ev_default_loop (0);
958		1084
959	ev_io stdin_watcher;	1085	ev_io stdin_watcher;
960		1086
961	ev_init (&stdin_watcher, my_cb);	1087	ev_init (&stdin_watcher, my_cb);
962	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1088	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
963	ev_io_start (loop, &stdin_watcher);	1089	ev_io_start (loop, &stdin_watcher);
964		1090
965	ev_loop (loop, 0);	1091	ev_run (loop, 0);
966		1092
967	As you can see, you are responsible for allocating the memory for your	1093	As you can see, you are responsible for allocating the memory for your
968	watcher structures (and it is I<usually> a bad idea to do this on the	1094	watcher structures (and it is I<usually> a bad idea to do this on the
969	stack).	1095	stack).
970		1096
971	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1097	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
972	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1098	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
973		1099
974	Each watcher structure must be initialised by a call to C<ev_init	1100	Each watcher structure must be initialised by a call to C<ev_init (watcher
975	(watcher *, callback)>, which expects a callback to be provided. This	1101	*, callback)>, which expects a callback to be provided. This callback is
976	callback gets invoked each time the event occurs (or, in the case of I/O	1102	invoked each time the event occurs (or, in the case of I/O watchers, each
977	watchers, each time the event loop detects that the file descriptor given	1103	time the event loop detects that the file descriptor given is readable
978	is readable and/or writable).	1104	and/or writable).
979		1105
980	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1106	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
981	macro to configure it, with arguments specific to the watcher type. There	1107	macro to configure it, with arguments specific to the watcher type. There
982	is also a macro to combine initialisation and setting in one call: C<<	1108	is also a macro to combine initialisation and setting in one call: C<<
983	ev_TYPE_init (watcher *, callback, ...) >>.	1109	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1006	=item C<EV_WRITE>	1132	=item C<EV_WRITE>
1007		1133
1008	The file descriptor in the C<ev_io> watcher has become readable and/or	1134	The file descriptor in the C<ev_io> watcher has become readable and/or
1009	writable.	1135	writable.
1010		1136
1011	=item C<EV_TIMEOUT>	1137	=item C<EV_TIMER>
1012		1138
1013	The C<ev_timer> watcher has timed out.	1139	The C<ev_timer> watcher has timed out.
1014		1140
1015	=item C<EV_PERIODIC>	1141	=item C<EV_PERIODIC>
1016		1142
…		…
1034		1160
1035	=item C<EV_PREPARE>	1161	=item C<EV_PREPARE>
1036		1162
1037	=item C<EV_CHECK>	1163	=item C<EV_CHECK>
1038		1164
1039	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1165	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1040	to gather new events, and all C<ev_check> watchers are invoked just after	1166	to gather new events, and all C<ev_check> watchers are invoked just after
1041	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1167	C<ev_run> has gathered them, but before it invokes any callbacks for any
1042	received events. Callbacks of both watcher types can start and stop as	1168	received events. Callbacks of both watcher types can start and stop as
1043	many watchers as they want, and all of them will be taken into account	1169	many watchers as they want, and all of them will be taken into account
1044	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1170	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1045	C<ev_loop> from blocking).	1171	C<ev_run> from blocking).
1046		1172
1047	=item C<EV_EMBED>	1173	=item C<EV_EMBED>
1048		1174
1049	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1175	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1050		1176
1051	=item C<EV_FORK>	1177	=item C<EV_FORK>
1052		1178
1053	The event loop has been resumed in the child process after fork (see	1179	The event loop has been resumed in the child process after fork (see
1054	C<ev_fork>).	1180	C<ev_fork>).
		1181
		1182	=item C<EV_CLEANUP>
		1183
		1184	The event loop is about to be destroyed (see C<ev_cleanup>).
1055		1185
1056	=item C<EV_ASYNC>	1186	=item C<EV_ASYNC>
1057		1187
1058	The given async watcher has been asynchronously notified (see C<ev_async>).	1188	The given async watcher has been asynchronously notified (see C<ev_async>).
1059		1189
…		…
1106		1236
1107	ev_io w;	1237	ev_io w;
1108	ev_init (&w, my_cb);	1238	ev_init (&w, my_cb);
1109	ev_io_set (&w, STDIN_FILENO, EV_READ);	1239	ev_io_set (&w, STDIN_FILENO, EV_READ);
1110		1240
1111	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1241	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1112		1242
1113	This macro initialises the type-specific parts of a watcher. You need to	1243	This macro initialises the type-specific parts of a watcher. You need to
1114	call C<ev_init> at least once before you call this macro, but you can	1244	call C<ev_init> at least once before you call this macro, but you can
1115	call C<ev_TYPE_set> any number of times. You must not, however, call this	1245	call C<ev_TYPE_set> any number of times. You must not, however, call this
1116	macro on a watcher that is active (it can be pending, however, which is a	1246	macro on a watcher that is active (it can be pending, however, which is a
…		…
1129		1259
1130	Example: Initialise and set an C<ev_io> watcher in one step.	1260	Example: Initialise and set an C<ev_io> watcher in one step.
1131		1261
1132	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1262	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1133		1263
1134	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1264	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1135		1265
1136	Starts (activates) the given watcher. Only active watchers will receive	1266	Starts (activates) the given watcher. Only active watchers will receive
1137	events. If the watcher is already active nothing will happen.	1267	events. If the watcher is already active nothing will happen.
1138		1268
1139	Example: Start the C<ev_io> watcher that is being abused as example in this	1269	Example: Start the C<ev_io> watcher that is being abused as example in this
1140	whole section.	1270	whole section.
1141		1271
1142	ev_io_start (EV_DEFAULT_UC, &w);	1272	ev_io_start (EV_DEFAULT_UC, &w);
1143		1273
1144	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1145		1275
1146	Stops the given watcher if active, and clears the pending status (whether	1276	Stops the given watcher if active, and clears the pending status (whether
1147	the watcher was active or not).	1277	the watcher was active or not).
1148		1278
1149	It is possible that stopped watchers are pending - for example,	1279	It is possible that stopped watchers are pending - for example,
…		…
1174	=item ev_cb_set (ev_TYPE *watcher, callback)	1304	=item ev_cb_set (ev_TYPE *watcher, callback)
1175		1305
1176	Change the callback. You can change the callback at virtually any time	1306	Change the callback. You can change the callback at virtually any time
1177	(modulo threads).	1307	(modulo threads).
1178		1308
1179	=item ev_set_priority (ev_TYPE *watcher, priority)	1309	=item ev_set_priority (ev_TYPE *watcher, int priority)
1180		1310
1181	=item int ev_priority (ev_TYPE *watcher)	1311	=item int ev_priority (ev_TYPE *watcher)
1182		1312
1183	Set and query the priority of the watcher. The priority is a small	1313	Set and query the priority of the watcher. The priority is a small
1184	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1314	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1216	watcher isn't pending it does nothing and returns C<0>.	1346	watcher isn't pending it does nothing and returns C<0>.
1217		1347
1218	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1348	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1219	callback to be invoked, which can be accomplished with this function.	1349	callback to be invoked, which can be accomplished with this function.
1220		1350
		1351	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1352
		1353	Feeds the given event set into the event loop, as if the specified event
		1354	had happened for the specified watcher (which must be a pointer to an
		1355	initialised but not necessarily started event watcher). Obviously you must
		1356	not free the watcher as long as it has pending events.
		1357
		1358	Stopping the watcher, letting libev invoke it, or calling
		1359	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1360	not started in the first place.
		1361
		1362	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1363	functions that do not need a watcher.
		1364
1221	=back	1365	=back
1222		1366
		1367	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1368	OWN COMPOSITE WATCHERS> idioms.
1223		1369
1224	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1370	=head2 WATCHER STATES
1225		1371
1226	Each watcher has, by default, a member C<void *data> that you can change	1372	There are various watcher states mentioned throughout this manual -
1227	and read at any time: libev will completely ignore it. This can be used	1373	active, pending and so on. In this section these states and the rules to
1228	to associate arbitrary data with your watcher. If you need more data and	1374	transition between them will be described in more detail - and while these
1229	don't want to allocate memory and store a pointer to it in that data	1375	rules might look complicated, they usually do "the right thing".
1230	member, you can also "subclass" the watcher type and provide your own
1231	data:
1232		1376
1233	struct my_io	1377	=over 4
1234	{
1235	ev_io io;
1236	int otherfd;
1237	void *somedata;
1238	struct whatever *mostinteresting;
1239	};
1240		1378
1241	...	1379	=item initialiased
1242	struct my_io w;
1243	ev_io_init (&w.io, my_cb, fd, EV_READ);
1244		1380
1245	And since your callback will be called with a pointer to the watcher, you	1381	Before a watcher can be registered with the event looop it has to be
1246	can cast it back to your own type:	1382	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1383	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1247		1384
1248	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1385	In this state it is simply some block of memory that is suitable for
1249	{	1386	use in an event loop. It can be moved around, freed, reused etc. at
1250	struct my_io *w = (struct my_io *)w_;	1387	will - as long as you either keep the memory contents intact, or call
1251	...	1388	C<ev_TYPE_init> again.
1252	}
1253		1389
1254	More interesting and less C-conformant ways of casting your callback type	1390	=item started/running/active
1255	instead have been omitted.
1256		1391
1257	Another common scenario is to use some data structure with multiple	1392	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1258	embedded watchers:	1393	property of the event loop, and is actively waiting for events. While in
		1394	this state it cannot be accessed (except in a few documented ways), moved,
		1395	freed or anything else - the only legal thing is to keep a pointer to it,
		1396	and call libev functions on it that are documented to work on active watchers.
1259		1397
1260	struct my_biggy	1398	=item pending
1261	{
1262	int some_data;
1263	ev_timer t1;
1264	ev_timer t2;
1265	}
1266		1399
1267	In this case getting the pointer to C<my_biggy> is a bit more	1400	If a watcher is active and libev determines that an event it is interested
1268	complicated: Either you store the address of your C<my_biggy> struct	1401	in has occurred (such as a timer expiring), it will become pending. It will
1269	in the C<data> member of the watcher (for woozies), or you need to use	1402	stay in this pending state until either it is stopped or its callback is
1270	some pointer arithmetic using C<offsetof> inside your watchers (for real	1403	about to be invoked, so it is not normally pending inside the watcher
1271	programmers):	1404	callback.
1272		1405
1273	#include <stddef.h>	1406	The watcher might or might not be active while it is pending (for example,
		1407	an expired non-repeating timer can be pending but no longer active). If it
		1408	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1409	but it is still property of the event loop at this time, so cannot be
		1410	moved, freed or reused. And if it is active the rules described in the
		1411	previous item still apply.
1274		1412
1275	static void	1413	It is also possible to feed an event on a watcher that is not active (e.g.
1276	t1_cb (EV_P_ ev_timer *w, int revents)	1414	via C<ev_feed_event>), in which case it becomes pending without being
1277	{	1415	active.
1278	struct my_biggy big = (struct my_biggy *)
1279	(((char *)w) - offsetof (struct my_biggy, t1));
1280	}
1281		1416
1282	static void	1417	=item stopped
1283	t2_cb (EV_P_ ev_timer *w, int revents)	1418
1284	{	1419	A watcher can be stopped implicitly by libev (in which case it might still
1285	struct my_biggy big = (struct my_biggy *)	1420	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1286	(((char *)w) - offsetof (struct my_biggy, t2));	1421	latter will clear any pending state the watcher might be in, regardless
1287	}	1422	of whether it was active or not, so stopping a watcher explicitly before
		1423	freeing it is often a good idea.
		1424
		1425	While stopped (and not pending) the watcher is essentially in the
		1426	initialised state, that is, it can be reused, moved, modified in any way
		1427	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1428	it again).
		1429
		1430	=back
1288		1431
1289	=head2 WATCHER PRIORITY MODELS	1432	=head2 WATCHER PRIORITY MODELS
1290		1433
1291	Many event loops support I<watcher priorities>, which are usually small	1434	Many event loops support I<watcher priorities>, which are usually small
1292	integers that influence the ordering of event callback invocation	1435	integers that influence the ordering of event callback invocation
…		…
1335		1478
1336	For example, to emulate how many other event libraries handle priorities,	1479	For example, to emulate how many other event libraries handle priorities,
1337	you can associate an C<ev_idle> watcher to each such watcher, and in	1480	you can associate an C<ev_idle> watcher to each such watcher, and in
1338	the normal watcher callback, you just start the idle watcher. The real	1481	the normal watcher callback, you just start the idle watcher. The real
1339	processing is done in the idle watcher callback. This causes libev to	1482	processing is done in the idle watcher callback. This causes libev to
1340	continously poll and process kernel event data for the watcher, but when	1483	continuously poll and process kernel event data for the watcher, but when
1341	the lock-out case is known to be rare (which in turn is rare :), this is	1484	the lock-out case is known to be rare (which in turn is rare :), this is
1342	workable.	1485	workable.
1343		1486
1344	Usually, however, the lock-out model implemented that way will perform	1487	Usually, however, the lock-out model implemented that way will perform
1345	miserably under the type of load it was designed to handle. In that case,	1488	miserably under the type of load it was designed to handle. In that case,
…		…
1359	{	1502	{
1360	// stop the I/O watcher, we received the event, but	1503	// stop the I/O watcher, we received the event, but
1361	// are not yet ready to handle it.	1504	// are not yet ready to handle it.
1362	ev_io_stop (EV_A_ w);	1505	ev_io_stop (EV_A_ w);
1363		1506
1364	// start the idle watcher to ahndle the actual event.	1507	// start the idle watcher to handle the actual event.
1365	// it will not be executed as long as other watchers	1508	// it will not be executed as long as other watchers
1366	// with the default priority are receiving events.	1509	// with the default priority are receiving events.
1367	ev_idle_start (EV_A_ &idle);	1510	ev_idle_start (EV_A_ &idle);
1368	}	1511	}
1369		1512
…		…
1419	In general you can register as many read and/or write event watchers per	1562	In general you can register as many read and/or write event watchers per
1420	fd as you want (as long as you don't confuse yourself). Setting all file	1563	fd as you want (as long as you don't confuse yourself). Setting all file
1421	descriptors to non-blocking mode is also usually a good idea (but not	1564	descriptors to non-blocking mode is also usually a good idea (but not
1422	required if you know what you are doing).	1565	required if you know what you are doing).
1423		1566
1424	If you cannot use non-blocking mode, then force the use of a
1425	known-to-be-good backend (at the time of this writing, this includes only
1426	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1427	descriptors for which non-blocking operation makes no sense (such as
1428	files) - libev doesn't guarentee any specific behaviour in that case.
1429
1430	Another thing you have to watch out for is that it is quite easy to	1567	Another thing you have to watch out for is that it is quite easy to
1431	receive "spurious" readiness notifications, that is your callback might	1568	receive "spurious" readiness notifications, that is, your callback might
1432	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1569	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1433	because there is no data. Not only are some backends known to create a	1570	because there is no data. It is very easy to get into this situation even
1434	lot of those (for example Solaris ports), it is very easy to get into	1571	with a relatively standard program structure. Thus it is best to always
1435	this situation even with a relatively standard program structure. Thus	1572	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1436	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1437	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1573	preferable to a program hanging until some data arrives.
1438		1574
1439	If you cannot run the fd in non-blocking mode (for example you should	1575	If you cannot run the fd in non-blocking mode (for example you should
1440	not play around with an Xlib connection), then you have to separately	1576	not play around with an Xlib connection), then you have to separately
1441	re-test whether a file descriptor is really ready with a known-to-be good	1577	re-test whether a file descriptor is really ready with a known-to-be good
1442	interface such as poll (fortunately in our Xlib example, Xlib already	1578	interface such as poll (fortunately in the case of Xlib, it already does
1443	does this on its own, so its quite safe to use). Some people additionally	1579	this on its own, so its quite safe to use). Some people additionally
1444	use C<SIGALRM> and an interval timer, just to be sure you won't block	1580	use C<SIGALRM> and an interval timer, just to be sure you won't block
1445	indefinitely.	1581	indefinitely.
1446		1582
1447	But really, best use non-blocking mode.	1583	But really, best use non-blocking mode.
1448		1584
…		…
1476		1612
1477	There is no workaround possible except not registering events	1613	There is no workaround possible except not registering events
1478	for potentially C<dup ()>'ed file descriptors, or to resort to	1614	for potentially C<dup ()>'ed file descriptors, or to resort to
1479	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1615	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1480		1616
		1617	=head3 The special problem of files
		1618
		1619	Many people try to use C<select> (or libev) on file descriptors
		1620	representing files, and expect it to become ready when their program
		1621	doesn't block on disk accesses (which can take a long time on their own).
		1622
		1623	However, this cannot ever work in the "expected" way - you get a readiness
		1624	notification as soon as the kernel knows whether and how much data is
		1625	there, and in the case of open files, that's always the case, so you
		1626	always get a readiness notification instantly, and your read (or possibly
		1627	write) will still block on the disk I/O.
		1628
		1629	Another way to view it is that in the case of sockets, pipes, character
		1630	devices and so on, there is another party (the sender) that delivers data
		1631	on its own, but in the case of files, there is no such thing: the disk
		1632	will not send data on its own, simply because it doesn't know what you
		1633	wish to read - you would first have to request some data.
		1634
		1635	Since files are typically not-so-well supported by advanced notification
		1636	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1637	to files, even though you should not use it. The reason for this is
		1638	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1639	usually a tty, often a pipe, but also sometimes files or special devices
		1640	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1641	F</dev/urandom>), and even though the file might better be served with
		1642	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1643	it "just works" instead of freezing.
		1644
		1645	So avoid file descriptors pointing to files when you know it (e.g. use
		1646	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1647	when you rarely read from a file instead of from a socket, and want to
		1648	reuse the same code path.
		1649
1481	=head3 The special problem of fork	1650	=head3 The special problem of fork
1482		1651
1483	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1652	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1484	useless behaviour. Libev fully supports fork, but needs to be told about	1653	useless behaviour. Libev fully supports fork, but needs to be told about
1485	it in the child.	1654	it in the child if you want to continue to use it in the child.
1486		1655
1487	To support fork in your programs, you either have to call	1656	To support fork in your child processes, you have to call C<ev_loop_fork
1488	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1657	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1489	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1658	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1490	C<EVBACKEND_POLL>.
1491		1659
1492	=head3 The special problem of SIGPIPE	1660	=head3 The special problem of SIGPIPE
1493		1661
1494	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1662	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1495	when writing to a pipe whose other end has been closed, your program gets	1663	when writing to a pipe whose other end has been closed, your program gets
…		…
1498		1666
1499	So when you encounter spurious, unexplained daemon exits, make sure you	1667	So when you encounter spurious, unexplained daemon exits, make sure you
1500	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1668	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1501	somewhere, as that would have given you a big clue).	1669	somewhere, as that would have given you a big clue).
1502		1670
		1671	=head3 The special problem of accept()ing when you can't
		1672
		1673	Many implementations of the POSIX C<accept> function (for example,
		1674	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1675	connection from the pending queue in all error cases.
		1676
		1677	For example, larger servers often run out of file descriptors (because
		1678	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1679	rejecting the connection, leading to libev signalling readiness on
		1680	the next iteration again (the connection still exists after all), and
		1681	typically causing the program to loop at 100% CPU usage.
		1682
		1683	Unfortunately, the set of errors that cause this issue differs between
		1684	operating systems, there is usually little the app can do to remedy the
		1685	situation, and no known thread-safe method of removing the connection to
		1686	cope with overload is known (to me).
		1687
		1688	One of the easiest ways to handle this situation is to just ignore it
		1689	- when the program encounters an overload, it will just loop until the
		1690	situation is over. While this is a form of busy waiting, no OS offers an
		1691	event-based way to handle this situation, so it's the best one can do.
		1692
		1693	A better way to handle the situation is to log any errors other than
		1694	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1695	messages, and continue as usual, which at least gives the user an idea of
		1696	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1697	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1698	usage.
		1699
		1700	If your program is single-threaded, then you could also keep a dummy file
		1701	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1702	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1703	close that fd, and create a new dummy fd. This will gracefully refuse
		1704	clients under typical overload conditions.
		1705
		1706	The last way to handle it is to simply log the error and C<exit>, as
		1707	is often done with C<malloc> failures, but this results in an easy
		1708	opportunity for a DoS attack.
1503		1709
1504	=head3 Watcher-Specific Functions	1710	=head3 Watcher-Specific Functions
1505		1711
1506	=over 4	1712	=over 4
1507		1713
…		…
1539	...	1745	...
1540	struct ev_loop *loop = ev_default_init (0);	1746	struct ev_loop *loop = ev_default_init (0);
1541	ev_io stdin_readable;	1747	ev_io stdin_readable;
1542	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1748	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1543	ev_io_start (loop, &stdin_readable);	1749	ev_io_start (loop, &stdin_readable);
1544	ev_loop (loop, 0);	1750	ev_run (loop, 0);
1545		1751
1546		1752
1547	=head2 C<ev_timer> - relative and optionally repeating timeouts	1753	=head2 C<ev_timer> - relative and optionally repeating timeouts
1548		1754
1549	Timer watchers are simple relative timers that generate an event after a	1755	Timer watchers are simple relative timers that generate an event after a
…		…
1558	The callback is guaranteed to be invoked only I<after> its timeout has	1764	The callback is guaranteed to be invoked only I<after> its timeout has
1559	passed (not I<at>, so on systems with very low-resolution clocks this	1765	passed (not I<at>, so on systems with very low-resolution clocks this
1560	might introduce a small delay). If multiple timers become ready during the	1766	might introduce a small delay). If multiple timers become ready during the
1561	same loop iteration then the ones with earlier time-out values are invoked	1767	same loop iteration then the ones with earlier time-out values are invoked
1562	before ones of the same priority with later time-out values (but this is	1768	before ones of the same priority with later time-out values (but this is
1563	no longer true when a callback calls C<ev_loop> recursively).	1769	no longer true when a callback calls C<ev_run> recursively).
1564		1770
1565	=head3 Be smart about timeouts	1771	=head3 Be smart about timeouts
1566		1772
1567	Many real-world problems involve some kind of timeout, usually for error	1773	Many real-world problems involve some kind of timeout, usually for error
1568	recovery. A typical example is an HTTP request - if the other side hangs,	1774	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1654	ev_tstamp timeout = last_activity + 60.;	1860	ev_tstamp timeout = last_activity + 60.;
1655		1861
1656	// if last_activity + 60. is older than now, we did time out	1862	// if last_activity + 60. is older than now, we did time out
1657	if (timeout < now)	1863	if (timeout < now)
1658	{	1864	{
1659	// timeout occured, take action	1865	// timeout occurred, take action
1660	}	1866	}
1661	else	1867	else
1662	{	1868	{
1663	// callback was invoked, but there was some activity, re-arm	1869	// callback was invoked, but there was some activity, re-arm
1664	// the watcher to fire in last_activity + 60, which is	1870	// the watcher to fire in last_activity + 60, which is
…		…
1686	to the current time (meaning we just have some activity :), then call the	1892	to the current time (meaning we just have some activity :), then call the
1687	callback, which will "do the right thing" and start the timer:	1893	callback, which will "do the right thing" and start the timer:
1688		1894
1689	ev_init (timer, callback);	1895	ev_init (timer, callback);
1690	last_activity = ev_now (loop);	1896	last_activity = ev_now (loop);
1691	callback (loop, timer, EV_TIMEOUT);	1897	callback (loop, timer, EV_TIMER);
1692		1898
1693	And when there is some activity, simply store the current time in	1899	And when there is some activity, simply store the current time in
1694	C<last_activity>, no libev calls at all:	1900	C<last_activity>, no libev calls at all:
1695		1901
1696	last_actiivty = ev_now (loop);	1902	last_activity = ev_now (loop);
1697		1903
1698	This technique is slightly more complex, but in most cases where the	1904	This technique is slightly more complex, but in most cases where the
1699	time-out is unlikely to be triggered, much more efficient.	1905	time-out is unlikely to be triggered, much more efficient.
1700		1906
1701	Changing the timeout is trivial as well (if it isn't hard-coded in the	1907	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1739		1945
1740	=head3 The special problem of time updates	1946	=head3 The special problem of time updates
1741		1947
1742	Establishing the current time is a costly operation (it usually takes at	1948	Establishing the current time is a costly operation (it usually takes at
1743	least two system calls): EV therefore updates its idea of the current	1949	least two system calls): EV therefore updates its idea of the current
1744	time only before and after C<ev_loop> collects new events, which causes a	1950	time only before and after C<ev_run> collects new events, which causes a
1745	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1951	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1746	lots of events in one iteration.	1952	lots of events in one iteration.
1747		1953
1748	The relative timeouts are calculated relative to the C<ev_now ()>	1954	The relative timeouts are calculated relative to the C<ev_now ()>
1749	time. This is usually the right thing as this timestamp refers to the time	1955	time. This is usually the right thing as this timestamp refers to the time
…		…
1820	C<repeat> value), or reset the running timer to the C<repeat> value.	2026	C<repeat> value), or reset the running timer to the C<repeat> value.
1821		2027
1822	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2028	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1823	usage example.	2029	usage example.
1824		2030
1825	=item ev_timer_remaining (loop, ev_timer *)	2031	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1826		2032
1827	Returns the remaining time until a timer fires. If the timer is active,	2033	Returns the remaining time until a timer fires. If the timer is active,
1828	then this time is relative to the current event loop time, otherwise it's	2034	then this time is relative to the current event loop time, otherwise it's
1829	the timeout value currently configured.	2035	the timeout value currently configured.
1830		2036
1831	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2037	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1832	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2038	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1833	will return C<4>. When the timer expires and is restarted, it will return	2039	will return C<4>. When the timer expires and is restarted, it will return
1834	roughly C<7> (likely slightly less as callback invocation takes some time,	2040	roughly C<7> (likely slightly less as callback invocation takes some time,
1835	too), and so on.	2041	too), and so on.
1836		2042
1837	=item ev_tstamp repeat [read-write]	2043	=item ev_tstamp repeat [read-write]
…		…
1866	}	2072	}
1867		2073
1868	ev_timer mytimer;	2074	ev_timer mytimer;
1869	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2075	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1870	ev_timer_again (&mytimer); /* start timer */	2076	ev_timer_again (&mytimer); /* start timer */
1871	ev_loop (loop, 0);	2077	ev_run (loop, 0);
1872		2078
1873	// and in some piece of code that gets executed on any "activity":	2079	// and in some piece of code that gets executed on any "activity":
1874	// reset the timeout to start ticking again at 10 seconds	2080	// reset the timeout to start ticking again at 10 seconds
1875	ev_timer_again (&mytimer);	2081	ev_timer_again (&mytimer);
1876		2082
…		…
1902		2108
1903	As with timers, the callback is guaranteed to be invoked only when the	2109	As with timers, the callback is guaranteed to be invoked only when the
1904	point in time where it is supposed to trigger has passed. If multiple	2110	point in time where it is supposed to trigger has passed. If multiple
1905	timers become ready during the same loop iteration then the ones with	2111	timers become ready during the same loop iteration then the ones with
1906	earlier time-out values are invoked before ones with later time-out values	2112	earlier time-out values are invoked before ones with later time-out values
1907	(but this is no longer true when a callback calls C<ev_loop> recursively).	2113	(but this is no longer true when a callback calls C<ev_run> recursively).
1908		2114
1909	=head3 Watcher-Specific Functions and Data Members	2115	=head3 Watcher-Specific Functions and Data Members
1910		2116
1911	=over 4	2117	=over 4
1912		2118
…		…
1947		2153
1948	Another way to think about it (for the mathematically inclined) is that	2154	Another way to think about it (for the mathematically inclined) is that
1949	C<ev_periodic> will try to run the callback in this mode at the next possible	2155	C<ev_periodic> will try to run the callback in this mode at the next possible
1950	time where C<time = offset (mod interval)>, regardless of any time jumps.	2156	time where C<time = offset (mod interval)>, regardless of any time jumps.
1951		2157
1952	For numerical stability it is preferable that the C<offset> value is near	2158	The C<interval> I<MUST> be positive, and for numerical stability, the
1953	C<ev_now ()> (the current time), but there is no range requirement for	2159	interval value should be higher than C<1/8192> (which is around 100
1954	this value, and in fact is often specified as zero.	2160	microseconds) and C<offset> should be higher than C<0> and should have
		2161	at most a similar magnitude as the current time (say, within a factor of
		2162	ten). Typical values for offset are, in fact, C<0> or something between
		2163	C<0> and C<interval>, which is also the recommended range.
1955		2164
1956	Note also that there is an upper limit to how often a timer can fire (CPU	2165	Note also that there is an upper limit to how often a timer can fire (CPU
1957	speed for example), so if C<interval> is very small then timing stability	2166	speed for example), so if C<interval> is very small then timing stability
1958	will of course deteriorate. Libev itself tries to be exact to be about one	2167	will of course deteriorate. Libev itself tries to be exact to be about one
1959	millisecond (if the OS supports it and the machine is fast enough).	2168	millisecond (if the OS supports it and the machine is fast enough).
…		…
2040	Example: Call a callback every hour, or, more precisely, whenever the	2249	Example: Call a callback every hour, or, more precisely, whenever the
2041	system time is divisible by 3600. The callback invocation times have	2250	system time is divisible by 3600. The callback invocation times have
2042	potentially a lot of jitter, but good long-term stability.	2251	potentially a lot of jitter, but good long-term stability.
2043		2252
2044	static void	2253	static void
2045	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2254	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2046	{	2255	{
2047	... its now a full hour (UTC, or TAI or whatever your clock follows)	2256	... its now a full hour (UTC, or TAI or whatever your clock follows)
2048	}	2257	}
2049		2258
2050	ev_periodic hourly_tick;	2259	ev_periodic hourly_tick;
…		…
2073		2282
2074	=head2 C<ev_signal> - signal me when a signal gets signalled!	2283	=head2 C<ev_signal> - signal me when a signal gets signalled!
2075		2284
2076	Signal watchers will trigger an event when the process receives a specific	2285	Signal watchers will trigger an event when the process receives a specific
2077	signal one or more times. Even though signals are very asynchronous, libev	2286	signal one or more times. Even though signals are very asynchronous, libev
2078	will try it's best to deliver signals synchronously, i.e. as part of the	2287	will try its best to deliver signals synchronously, i.e. as part of the
2079	normal event processing, like any other event.	2288	normal event processing, like any other event.
2080		2289
2081	Note that only the default loop supports registering signal watchers	2290	If you want signals to be delivered truly asynchronously, just use
2082	currently.	2291	C<sigaction> as you would do without libev and forget about sharing
		2292	the signal. You can even use C<ev_async> from a signal handler to
		2293	synchronously wake up an event loop.
2083		2294
2084	If you want signals asynchronously, just use C<sigaction> as you would
2085	do without libev and forget about sharing the signal. You can even use
2086	C<ev_async> from a signal handler to synchronously wake up an event loop.
2087
2088	You can configure as many watchers as you like per signal. Only when the	2295	You can configure as many watchers as you like for the same signal, but
		2296	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2297	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2298	C<SIGINT> in both the default loop and another loop at the same time. At
		2299	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2300
2089	first watcher gets started will libev actually register something with	2301	When the first watcher gets started will libev actually register something
2090	the kernel (thus it coexists with your own signal handlers as long as you	2302	with the kernel (thus it coexists with your own signal handlers as long as
2091	don't register any with libev for the same signal).	2303	you don't register any with libev for the same signal).
2092
2093	Both the signal mask state (C<sigprocmask>) and the signal handler state
2094	(C<sigaction>) are unspecified after starting a signal watcher (and after
2095	sotpping it again), that is, libev might or might not block the signal,
2096	and might or might not set or restore the installed signal handler.
2097		2304
2098	If possible and supported, libev will install its handlers with	2305	If possible and supported, libev will install its handlers with
2099	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2306	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2100	not be unduly interrupted. If you have a problem with system calls getting	2307	not be unduly interrupted. If you have a problem with system calls getting
2101	interrupted by signals you can block all signals in an C<ev_check> watcher	2308	interrupted by signals you can block all signals in an C<ev_check> watcher
2102	and unblock them in an C<ev_prepare> watcher.	2309	and unblock them in an C<ev_prepare> watcher.
2103		2310
		2311	=head3 The special problem of inheritance over fork/execve/pthread_create
		2312
		2313	Both the signal mask (C<sigprocmask>) and the signal disposition
		2314	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2315	stopping it again), that is, libev might or might not block the signal,
		2316	and might or might not set or restore the installed signal handler (but
		2317	see C<EVFLAG_NOSIGMASK>).
		2318
		2319	While this does not matter for the signal disposition (libev never
		2320	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2321	C<execve>), this matters for the signal mask: many programs do not expect
		2322	certain signals to be blocked.
		2323
		2324	This means that before calling C<exec> (from the child) you should reset
		2325	the signal mask to whatever "default" you expect (all clear is a good
		2326	choice usually).
		2327
		2328	The simplest way to ensure that the signal mask is reset in the child is
		2329	to install a fork handler with C<pthread_atfork> that resets it. That will
		2330	catch fork calls done by libraries (such as the libc) as well.
		2331
		2332	In current versions of libev, the signal will not be blocked indefinitely
		2333	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2334	the window of opportunity for problems, it will not go away, as libev
		2335	I<has> to modify the signal mask, at least temporarily.
		2336
		2337	So I can't stress this enough: I<If you do not reset your signal mask when
		2338	you expect it to be empty, you have a race condition in your code>. This
		2339	is not a libev-specific thing, this is true for most event libraries.
		2340
		2341	=head3 The special problem of threads signal handling
		2342
		2343	POSIX threads has problematic signal handling semantics, specifically,
		2344	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2345	threads in a process block signals, which is hard to achieve.
		2346
		2347	When you want to use sigwait (or mix libev signal handling with your own
		2348	for the same signals), you can tackle this problem by globally blocking
		2349	all signals before creating any threads (or creating them with a fully set
		2350	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2351	loops. Then designate one thread as "signal receiver thread" which handles
		2352	these signals. You can pass on any signals that libev might be interested
		2353	in by calling C<ev_feed_signal>.
		2354
2104	=head3 Watcher-Specific Functions and Data Members	2355	=head3 Watcher-Specific Functions and Data Members
2105		2356
2106	=over 4	2357	=over 4
2107		2358
2108	=item ev_signal_init (ev_signal *, callback, int signum)	2359	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2123	Example: Try to exit cleanly on SIGINT.	2374	Example: Try to exit cleanly on SIGINT.
2124		2375
2125	static void	2376	static void
2126	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2377	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2127	{	2378	{
2128	ev_unloop (loop, EVUNLOOP_ALL);	2379	ev_break (loop, EVBREAK_ALL);
2129	}	2380	}
2130		2381
2131	ev_signal signal_watcher;	2382	ev_signal signal_watcher;
2132	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2383	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2133	ev_signal_start (loop, &signal_watcher);	2384	ev_signal_start (loop, &signal_watcher);
…		…
2519		2770
2520	Prepare and check watchers are usually (but not always) used in pairs:	2771	Prepare and check watchers are usually (but not always) used in pairs:
2521	prepare watchers get invoked before the process blocks and check watchers	2772	prepare watchers get invoked before the process blocks and check watchers
2522	afterwards.	2773	afterwards.
2523		2774
2524	You I<must not> call C<ev_loop> or similar functions that enter	2775	You I<must not> call C<ev_run> or similar functions that enter
2525	the current event loop from either C<ev_prepare> or C<ev_check>	2776	the current event loop from either C<ev_prepare> or C<ev_check>
2526	watchers. Other loops than the current one are fine, however. The	2777	watchers. Other loops than the current one are fine, however. The
2527	rationale behind this is that you do not need to check for recursion in	2778	rationale behind this is that you do not need to check for recursion in
2528	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2779	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2529	C<ev_check> so if you have one watcher of each kind they will always be	2780	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2697		2948
2698	if (timeout >= 0)	2949	if (timeout >= 0)
2699	// create/start timer	2950	// create/start timer
2700		2951
2701	// poll	2952	// poll
2702	ev_loop (EV_A_ 0);	2953	ev_run (EV_A_ 0);
2703		2954
2704	// stop timer again	2955	// stop timer again
2705	if (timeout >= 0)	2956	if (timeout >= 0)
2706	ev_timer_stop (EV_A_ &to);	2957	ev_timer_stop (EV_A_ &to);
2707		2958
…		…
2785	if you do not want that, you need to temporarily stop the embed watcher).	3036	if you do not want that, you need to temporarily stop the embed watcher).
2786		3037
2787	=item ev_embed_sweep (loop, ev_embed *)	3038	=item ev_embed_sweep (loop, ev_embed *)
2788		3039
2789	Make a single, non-blocking sweep over the embedded loop. This works	3040	Make a single, non-blocking sweep over the embedded loop. This works
2790	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3041	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2791	appropriate way for embedded loops.	3042	appropriate way for embedded loops.
2792		3043
2793	=item struct ev_loop *other [read-only]	3044	=item struct ev_loop *other [read-only]
2794		3045
2795	The embedded event loop.	3046	The embedded event loop.
…		…
2855	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3106	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2856	handlers will be invoked, too, of course.	3107	handlers will be invoked, too, of course.
2857		3108
2858	=head3 The special problem of life after fork - how is it possible?	3109	=head3 The special problem of life after fork - how is it possible?
2859		3110
2860	Most uses of C<fork()> consist of forking, then some simple calls to ste	3111	Most uses of C<fork()> consist of forking, then some simple calls to set
2861	up/change the process environment, followed by a call to C<exec()>. This	3112	up/change the process environment, followed by a call to C<exec()>. This
2862	sequence should be handled by libev without any problems.	3113	sequence should be handled by libev without any problems.
2863		3114
2864	This changes when the application actually wants to do event handling	3115	This changes when the application actually wants to do event handling
2865	in the child, or both parent in child, in effect "continuing" after the	3116	in the child, or both parent in child, in effect "continuing" after the
…		…
2881	disadvantage of having to use multiple event loops (which do not support	3132	disadvantage of having to use multiple event loops (which do not support
2882	signal watchers).	3133	signal watchers).
2883		3134
2884	When this is not possible, or you want to use the default loop for	3135	When this is not possible, or you want to use the default loop for
2885	other reasons, then in the process that wants to start "fresh", call	3136	other reasons, then in the process that wants to start "fresh", call
2886	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3137	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2887	the default loop will "orphan" (not stop) all registered watchers, so you	3138	Destroying the default loop will "orphan" (not stop) all registered
2888	have to be careful not to execute code that modifies those watchers. Note	3139	watchers, so you have to be careful not to execute code that modifies
2889	also that in that case, you have to re-register any signal watchers.	3140	those watchers. Note also that in that case, you have to re-register any
		3141	signal watchers.
2890		3142
2891	=head3 Watcher-Specific Functions and Data Members	3143	=head3 Watcher-Specific Functions and Data Members
2892		3144
2893	=over 4	3145	=over 4
2894		3146
2895	=item ev_fork_init (ev_signal *, callback)	3147	=item ev_fork_init (ev_fork *, callback)
2896		3148
2897	Initialises and configures the fork watcher - it has no parameters of any	3149	Initialises and configures the fork watcher - it has no parameters of any
2898	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3150	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2899	believe me.	3151	really.
2900		3152
2901	=back	3153	=back
2902		3154
2903		3155
		3156	=head2 C<ev_cleanup> - even the best things end
		3157
		3158	Cleanup watchers are called just before the event loop is being destroyed
		3159	by a call to C<ev_loop_destroy>.
		3160
		3161	While there is no guarantee that the event loop gets destroyed, cleanup
		3162	watchers provide a convenient method to install cleanup hooks for your
		3163	program, worker threads and so on - you just to make sure to destroy the
		3164	loop when you want them to be invoked.
		3165
		3166	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3167	all other watchers, they do not keep a reference to the event loop (which
		3168	makes a lot of sense if you think about it). Like all other watchers, you
		3169	can call libev functions in the callback, except C<ev_cleanup_start>.
		3170
		3171	=head3 Watcher-Specific Functions and Data Members
		3172
		3173	=over 4
		3174
		3175	=item ev_cleanup_init (ev_cleanup *, callback)
		3176
		3177	Initialises and configures the cleanup watcher - it has no parameters of
		3178	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3179	pointless, I assure you.
		3180
		3181	=back
		3182
		3183	Example: Register an atexit handler to destroy the default loop, so any
		3184	cleanup functions are called.
		3185
		3186	static void
		3187	program_exits (void)
		3188	{
		3189	ev_loop_destroy (EV_DEFAULT_UC);
		3190	}
		3191
		3192	...
		3193	atexit (program_exits);
		3194
		3195
2904	=head2 C<ev_async> - how to wake up another event loop	3196	=head2 C<ev_async> - how to wake up an event loop
2905		3197
2906	In general, you cannot use an C<ev_loop> from multiple threads or other	3198	In general, you cannot use an C<ev_loop> from multiple threads or other
2907	asynchronous sources such as signal handlers (as opposed to multiple event	3199	asynchronous sources such as signal handlers (as opposed to multiple event
2908	loops - those are of course safe to use in different threads).	3200	loops - those are of course safe to use in different threads).
2909		3201
2910	Sometimes, however, you need to wake up another event loop you do not	3202	Sometimes, however, you need to wake up an event loop you do not control,
2911	control, for example because it belongs to another thread. This is what	3203	for example because it belongs to another thread. This is what C<ev_async>
2912	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3204	watchers do: as long as the C<ev_async> watcher is active, you can signal
2913	can signal it by calling C<ev_async_send>, which is thread- and signal	3205	it by calling C<ev_async_send>, which is thread- and signal safe.
2914	safe.
2915		3206
2916	This functionality is very similar to C<ev_signal> watchers, as signals,	3207	This functionality is very similar to C<ev_signal> watchers, as signals,
2917	too, are asynchronous in nature, and signals, too, will be compressed	3208	too, are asynchronous in nature, and signals, too, will be compressed
2918	(i.e. the number of callback invocations may be less than the number of	3209	(i.e. the number of callback invocations may be less than the number of
2919	C<ev_async_sent> calls).	3210	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3211	of "global async watchers" by using a watcher on an otherwise unused
		3212	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3213	even without knowing which loop owns the signal.
2920		3214
2921	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3215	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2922	just the default loop.	3216	just the default loop.
2923		3217
2924	=head3 Queueing	3218	=head3 Queueing
2925		3219
2926	C<ev_async> does not support queueing of data in any way. The reason	3220	C<ev_async> does not support queueing of data in any way. The reason
2927	is that the author does not know of a simple (or any) algorithm for a	3221	is that the author does not know of a simple (or any) algorithm for a
2928	multiple-writer-single-reader queue that works in all cases and doesn't	3222	multiple-writer-single-reader queue that works in all cases and doesn't
2929	need elaborate support such as pthreads.	3223	need elaborate support such as pthreads or unportable memory access
		3224	semantics.
2930		3225
2931	That means that if you want to queue data, you have to provide your own	3226	That means that if you want to queue data, you have to provide your own
2932	queue. But at least I can tell you how to implement locking around your	3227	queue. But at least I can tell you how to implement locking around your
2933	queue:	3228	queue:
2934		3229
…		…
3018	trust me.	3313	trust me.
3019		3314
3020	=item ev_async_send (loop, ev_async *)	3315	=item ev_async_send (loop, ev_async *)
3021		3316
3022	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3317	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3023	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3318	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3319	returns.
		3320
3024	C<ev_feed_event>, this call is safe to do from other threads, signal or	3321	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3025	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3322	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3026	section below on what exactly this means).	3323	embedding section below on what exactly this means).
3027		3324
3028	Note that, as with other watchers in libev, multiple events might get	3325	Note that, as with other watchers in libev, multiple events might get
3029	compressed into a single callback invocation (another way to look at this	3326	compressed into a single callback invocation (another way to look at this
3030	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3327	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3031	reset when the event loop detects that).	3328	reset when the event loop detects that).
…		…
3073		3370
3074	If C<timeout> is less than 0, then no timeout watcher will be	3371	If C<timeout> is less than 0, then no timeout watcher will be
3075	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3372	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3076	repeat = 0) will be started. C<0> is a valid timeout.	3373	repeat = 0) will be started. C<0> is a valid timeout.
3077		3374
3078	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3375	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3079	passed an C<revents> set like normal event callbacks (a combination of	3376	passed an C<revents> set like normal event callbacks (a combination of
3080	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3377	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3081	value passed to C<ev_once>. Note that it is possible to receive I<both>	3378	value passed to C<ev_once>. Note that it is possible to receive I<both>
3082	a timeout and an io event at the same time - you probably should give io	3379	a timeout and an io event at the same time - you probably should give io
3083	events precedence.	3380	events precedence.
3084		3381
3085	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3382	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3086		3383
3087	static void stdin_ready (int revents, void *arg)	3384	static void stdin_ready (int revents, void *arg)
3088	{	3385	{
3089	if (revents & EV_READ)	3386	if (revents & EV_READ)
3090	/* stdin might have data for us, joy! */;	3387	/* stdin might have data for us, joy! */;
3091	else if (revents & EV_TIMEOUT)	3388	else if (revents & EV_TIMER)
3092	/* doh, nothing entered */;	3389	/* doh, nothing entered */;
3093	}	3390	}
3094		3391
3095	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3392	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3096		3393
3097	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3098
3099	Feeds the given event set into the event loop, as if the specified event
3100	had happened for the specified watcher (which must be a pointer to an
3101	initialised but not necessarily started event watcher).
3102
3103	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3394	=item ev_feed_fd_event (loop, int fd, int revents)
3104		3395
3105	Feed an event on the given fd, as if a file descriptor backend detected	3396	Feed an event on the given fd, as if a file descriptor backend detected
3106	the given events it.	3397	the given events it.
3107		3398
3108	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3399	=item ev_feed_signal_event (loop, int signum)
3109		3400
3110	Feed an event as if the given signal occurred (C<loop> must be the default	3401	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3111	loop!).	3402	which is async-safe.
3112		3403
3113	=back	3404	=back
		3405
		3406
		3407	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3408
		3409	This section explains some common idioms that are not immediately
		3410	obvious. Note that examples are sprinkled over the whole manual, and this
		3411	section only contains stuff that wouldn't fit anywhere else.
		3412
		3413	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3414
		3415	Each watcher has, by default, a C<void *data> member that you can read
		3416	or modify at any time: libev will completely ignore it. This can be used
		3417	to associate arbitrary data with your watcher. If you need more data and
		3418	don't want to allocate memory separately and store a pointer to it in that
		3419	data member, you can also "subclass" the watcher type and provide your own
		3420	data:
		3421
		3422	struct my_io
		3423	{
		3424	ev_io io;
		3425	int otherfd;
		3426	void *somedata;
		3427	struct whatever *mostinteresting;
		3428	};
		3429
		3430	...
		3431	struct my_io w;
		3432	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3433
		3434	And since your callback will be called with a pointer to the watcher, you
		3435	can cast it back to your own type:
		3436
		3437	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3438	{
		3439	struct my_io *w = (struct my_io *)w_;
		3440	...
		3441	}
		3442
		3443	More interesting and less C-conformant ways of casting your callback
		3444	function type instead have been omitted.
		3445
		3446	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3447
		3448	Another common scenario is to use some data structure with multiple
		3449	embedded watchers, in effect creating your own watcher that combines
		3450	multiple libev event sources into one "super-watcher":
		3451
		3452	struct my_biggy
		3453	{
		3454	int some_data;
		3455	ev_timer t1;
		3456	ev_timer t2;
		3457	}
		3458
		3459	In this case getting the pointer to C<my_biggy> is a bit more
		3460	complicated: Either you store the address of your C<my_biggy> struct in
		3461	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3462	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3463	real programmers):
		3464
		3465	#include <stddef.h>
		3466
		3467	static void
		3468	t1_cb (EV_P_ ev_timer *w, int revents)
		3469	{
		3470	struct my_biggy big = (struct my_biggy *)
		3471	(((char *)w) - offsetof (struct my_biggy, t1));
		3472	}
		3473
		3474	static void
		3475	t2_cb (EV_P_ ev_timer *w, int revents)
		3476	{
		3477	struct my_biggy big = (struct my_biggy *)
		3478	(((char *)w) - offsetof (struct my_biggy, t2));
		3479	}
		3480
		3481	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3482
		3483	Often (especially in GUI toolkits) there are places where you have
		3484	I<modal> interaction, which is most easily implemented by recursively
		3485	invoking C<ev_run>.
		3486
		3487	This brings the problem of exiting - a callback might want to finish the
		3488	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3489	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3490	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3491	other combination: In these cases, C<ev_break> will not work alone.
		3492
		3493	The solution is to maintain "break this loop" variable for each C<ev_run>
		3494	invocation, and use a loop around C<ev_run> until the condition is
		3495	triggered, using C<EVRUN_ONCE>:
		3496
		3497	// main loop
		3498	int exit_main_loop = 0;
		3499
		3500	while (!exit_main_loop)
		3501	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3502
		3503	// in a model watcher
		3504	int exit_nested_loop = 0;
		3505
		3506	while (!exit_nested_loop)
		3507	ev_run (EV_A_ EVRUN_ONCE);
		3508
		3509	To exit from any of these loops, just set the corresponding exit variable:
		3510
		3511	// exit modal loop
		3512	exit_nested_loop = 1;
		3513
		3514	// exit main program, after modal loop is finished
		3515	exit_main_loop = 1;
		3516
		3517	// exit both
		3518	exit_main_loop = exit_nested_loop = 1;
		3519
		3520	=head2 THREAD LOCKING EXAMPLE
		3521
		3522	Here is a fictitious example of how to run an event loop in a different
		3523	thread from where callbacks are being invoked and watchers are
		3524	created/added/removed.
		3525
		3526	For a real-world example, see the C<EV::Loop::Async> perl module,
		3527	which uses exactly this technique (which is suited for many high-level
		3528	languages).
		3529
		3530	The example uses a pthread mutex to protect the loop data, a condition
		3531	variable to wait for callback invocations, an async watcher to notify the
		3532	event loop thread and an unspecified mechanism to wake up the main thread.
		3533
		3534	First, you need to associate some data with the event loop:
		3535
		3536	typedef struct {
		3537	mutex_t lock; /* global loop lock */
		3538	ev_async async_w;
		3539	thread_t tid;
		3540	cond_t invoke_cv;
		3541	} userdata;
		3542
		3543	void prepare_loop (EV_P)
		3544	{
		3545	// for simplicity, we use a static userdata struct.
		3546	static userdata u;
		3547
		3548	ev_async_init (&u->async_w, async_cb);
		3549	ev_async_start (EV_A_ &u->async_w);
		3550
		3551	pthread_mutex_init (&u->lock, 0);
		3552	pthread_cond_init (&u->invoke_cv, 0);
		3553
		3554	// now associate this with the loop
		3555	ev_set_userdata (EV_A_ u);
		3556	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3557	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3558
		3559	// then create the thread running ev_run
		3560	pthread_create (&u->tid, 0, l_run, EV_A);
		3561	}
		3562
		3563	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3564	solely to wake up the event loop so it takes notice of any new watchers
		3565	that might have been added:
		3566
		3567	static void
		3568	async_cb (EV_P_ ev_async *w, int revents)
		3569	{
		3570	// just used for the side effects
		3571	}
		3572
		3573	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3574	protecting the loop data, respectively.
		3575
		3576	static void
		3577	l_release (EV_P)
		3578	{
		3579	userdata *u = ev_userdata (EV_A);
		3580	pthread_mutex_unlock (&u->lock);
		3581	}
		3582
		3583	static void
		3584	l_acquire (EV_P)
		3585	{
		3586	userdata *u = ev_userdata (EV_A);
		3587	pthread_mutex_lock (&u->lock);
		3588	}
		3589
		3590	The event loop thread first acquires the mutex, and then jumps straight
		3591	into C<ev_run>:
		3592
		3593	void *
		3594	l_run (void *thr_arg)
		3595	{
		3596	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3597
		3598	l_acquire (EV_A);
		3599	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3600	ev_run (EV_A_ 0);
		3601	l_release (EV_A);
		3602
		3603	return 0;
		3604	}
		3605
		3606	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3607	signal the main thread via some unspecified mechanism (signals? pipe
		3608	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3609	have been called (in a while loop because a) spurious wakeups are possible
		3610	and b) skipping inter-thread-communication when there are no pending
		3611	watchers is very beneficial):
		3612
		3613	static void
		3614	l_invoke (EV_P)
		3615	{
		3616	userdata *u = ev_userdata (EV_A);
		3617
		3618	while (ev_pending_count (EV_A))
		3619	{
		3620	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3621	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3622	}
		3623	}
		3624
		3625	Now, whenever the main thread gets told to invoke pending watchers, it
		3626	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3627	thread to continue:
		3628
		3629	static void
		3630	real_invoke_pending (EV_P)
		3631	{
		3632	userdata *u = ev_userdata (EV_A);
		3633
		3634	pthread_mutex_lock (&u->lock);
		3635	ev_invoke_pending (EV_A);
		3636	pthread_cond_signal (&u->invoke_cv);
		3637	pthread_mutex_unlock (&u->lock);
		3638	}
		3639
		3640	Whenever you want to start/stop a watcher or do other modifications to an
		3641	event loop, you will now have to lock:
		3642
		3643	ev_timer timeout_watcher;
		3644	userdata *u = ev_userdata (EV_A);
		3645
		3646	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3647
		3648	pthread_mutex_lock (&u->lock);
		3649	ev_timer_start (EV_A_ &timeout_watcher);
		3650	ev_async_send (EV_A_ &u->async_w);
		3651	pthread_mutex_unlock (&u->lock);
		3652
		3653	Note that sending the C<ev_async> watcher is required because otherwise
		3654	an event loop currently blocking in the kernel will have no knowledge
		3655	about the newly added timer. By waking up the loop it will pick up any new
		3656	watchers in the next event loop iteration.
		3657
		3658	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3659
		3660	While the overhead of a callback that e.g. schedules a thread is small, it
		3661	is still an overhead. If you embed libev, and your main usage is with some
		3662	kind of threads or coroutines, you might want to customise libev so that
		3663	doesn't need callbacks anymore.
		3664
		3665	Imagine you have coroutines that you can switch to using a function
		3666	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3667	and that due to some magic, the currently active coroutine is stored in a
		3668	global called C<current_coro>. Then you can build your own "wait for libev
		3669	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3670	the differing C<;> conventions):
		3671
		3672	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3673	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3674
		3675	That means instead of having a C callback function, you store the
		3676	coroutine to switch to in each watcher, and instead of having libev call
		3677	your callback, you instead have it switch to that coroutine.
		3678
		3679	A coroutine might now wait for an event with a function called
		3680	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3681	matter when, or whether the watcher is active or not when this function is
		3682	called):
		3683
		3684	void
		3685	wait_for_event (ev_watcher *w)
		3686	{
		3687	ev_cb_set (w) = current_coro;
		3688	switch_to (libev_coro);
		3689	}
		3690
		3691	That basically suspends the coroutine inside C<wait_for_event> and
		3692	continues the libev coroutine, which, when appropriate, switches back to
		3693	this or any other coroutine. I am sure if you sue this your own :)
		3694
		3695	You can do similar tricks if you have, say, threads with an event queue -
		3696	instead of storing a coroutine, you store the queue object and instead of
		3697	switching to a coroutine, you push the watcher onto the queue and notify
		3698	any waiters.
		3699
		3700	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3701	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3702
		3703	// my_ev.h
		3704	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3705	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3706	#include "../libev/ev.h"
		3707
		3708	// my_ev.c
		3709	#define EV_H "my_ev.h"
		3710	#include "../libev/ev.c"
		3711
		3712	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3713	F<my_ev.c> into your project. When properly specifying include paths, you
		3714	can even use F<ev.h> as header file name directly.
3114		3715
3115		3716
3116	=head1 LIBEVENT EMULATION	3717	=head1 LIBEVENT EMULATION
3117		3718
3118	Libev offers a compatibility emulation layer for libevent. It cannot	3719	Libev offers a compatibility emulation layer for libevent. It cannot
3119	emulate the internals of libevent, so here are some usage hints:	3720	emulate the internals of libevent, so here are some usage hints:
3120		3721
3121	=over 4	3722	=over 4
		3723
		3724	=item * Only the libevent-1.4.1-beta API is being emulated.
		3725
		3726	This was the newest libevent version available when libev was implemented,
		3727	and is still mostly unchanged in 2010.
3122		3728
3123	=item * Use it by including <event.h>, as usual.	3729	=item * Use it by including <event.h>, as usual.
3124		3730
3125	=item * The following members are fully supported: ev_base, ev_callback,	3731	=item * The following members are fully supported: ev_base, ev_callback,
3126	ev_arg, ev_fd, ev_res, ev_events.	3732	ev_arg, ev_fd, ev_res, ev_events.
…		…
3132	=item * Priorities are not currently supported. Initialising priorities	3738	=item * Priorities are not currently supported. Initialising priorities
3133	will fail and all watchers will have the same priority, even though there	3739	will fail and all watchers will have the same priority, even though there
3134	is an ev_pri field.	3740	is an ev_pri field.
3135		3741
3136	=item * In libevent, the last base created gets the signals, in libev, the	3742	=item * In libevent, the last base created gets the signals, in libev, the
3137	first base created (== the default loop) gets the signals.	3743	base that registered the signal gets the signals.
3138		3744
3139	=item * Other members are not supported.	3745	=item * Other members are not supported.
3140		3746
3141	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3747	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3142	to use the libev header file and library.	3748	to use the libev header file and library.
…		…
3161	Care has been taken to keep the overhead low. The only data member the C++	3767	Care has been taken to keep the overhead low. The only data member the C++
3162	classes add (compared to plain C-style watchers) is the event loop pointer	3768	classes add (compared to plain C-style watchers) is the event loop pointer
3163	that the watcher is associated with (or no additional members at all if	3769	that the watcher is associated with (or no additional members at all if
3164	you disable C<EV_MULTIPLICITY> when embedding libev).	3770	you disable C<EV_MULTIPLICITY> when embedding libev).
3165		3771
3166	Currently, functions, and static and non-static member functions can be	3772	Currently, functions, static and non-static member functions and classes
3167	used as callbacks. Other types should be easy to add as long as they only	3773	with C<operator ()> can be used as callbacks. Other types should be easy
3168	need one additional pointer for context. If you need support for other	3774	to add as long as they only need one additional pointer for context. If
3169	types of functors please contact the author (preferably after implementing	3775	you need support for other types of functors please contact the author
3170	it).	3776	(preferably after implementing it).
3171		3777
3172	Here is a list of things available in the C<ev> namespace:	3778	Here is a list of things available in the C<ev> namespace:
3173		3779
3174	=over 4	3780	=over 4
3175		3781
…		…
3193		3799
3194	=over 4	3800	=over 4
3195		3801
3196	=item ev::TYPE::TYPE ()	3802	=item ev::TYPE::TYPE ()
3197		3803
3198	=item ev::TYPE::TYPE (struct ev_loop *)	3804	=item ev::TYPE::TYPE (loop)
3199		3805
3200	=item ev::TYPE::~TYPE	3806	=item ev::TYPE::~TYPE
3201		3807
3202	The constructor (optionally) takes an event loop to associate the watcher	3808	The constructor (optionally) takes an event loop to associate the watcher
3203	with. If it is omitted, it will use C<EV_DEFAULT>.	3809	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3236	myclass obj;	3842	myclass obj;
3237	ev::io iow;	3843	ev::io iow;
3238	iow.set <myclass, &myclass::io_cb> (&obj);	3844	iow.set <myclass, &myclass::io_cb> (&obj);
3239		3845
3240	=item w->set (object *)	3846	=item w->set (object *)
3241
3242	This is an B<experimental> feature that might go away in a future version.
3243		3847
3244	This is a variation of a method callback - leaving out the method to call	3848	This is a variation of a method callback - leaving out the method to call
3245	will default the method to C<operator ()>, which makes it possible to use	3849	will default the method to C<operator ()>, which makes it possible to use
3246	functor objects without having to manually specify the C<operator ()> all	3850	functor objects without having to manually specify the C<operator ()> all
3247	the time. Incidentally, you can then also leave out the template argument	3851	the time. Incidentally, you can then also leave out the template argument
…		…
3280	Example: Use a plain function as callback.	3884	Example: Use a plain function as callback.
3281		3885
3282	static void io_cb (ev::io &w, int revents) { }	3886	static void io_cb (ev::io &w, int revents) { }
3283	iow.set <io_cb> ();	3887	iow.set <io_cb> ();
3284		3888
3285	=item w->set (struct ev_loop *)	3889	=item w->set (loop)
3286		3890
3287	Associates a different C<struct ev_loop> with this watcher. You can only	3891	Associates a different C<struct ev_loop> with this watcher. You can only
3288	do this when the watcher is inactive (and not pending either).	3892	do this when the watcher is inactive (and not pending either).
3289		3893
3290	=item w->set ([arguments])	3894	=item w->set ([arguments])
3291		3895
3292	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3896	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3293	called at least once. Unlike the C counterpart, an active watcher gets	3897	method or a suitable start method must be called at least once. Unlike the
3294	automatically stopped and restarted when reconfiguring it with this	3898	C counterpart, an active watcher gets automatically stopped and restarted
3295	method.	3899	when reconfiguring it with this method.
3296		3900
3297	=item w->start ()	3901	=item w->start ()
3298		3902
3299	Starts the watcher. Note that there is no C<loop> argument, as the	3903	Starts the watcher. Note that there is no C<loop> argument, as the
3300	constructor already stores the event loop.	3904	constructor already stores the event loop.
3301		3905
		3906	=item w->start ([arguments])
		3907
		3908	Instead of calling C<set> and C<start> methods separately, it is often
		3909	convenient to wrap them in one call. Uses the same type of arguments as
		3910	the configure C<set> method of the watcher.
		3911
3302	=item w->stop ()	3912	=item w->stop ()
3303		3913
3304	Stops the watcher if it is active. Again, no C<loop> argument.	3914	Stops the watcher if it is active. Again, no C<loop> argument.
3305		3915
3306	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3916	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3318		3928
3319	=back	3929	=back
3320		3930
3321	=back	3931	=back
3322		3932
3323	Example: Define a class with an IO and idle watcher, start one of them in	3933	Example: Define a class with two I/O and idle watchers, start the I/O
3324	the constructor.	3934	watchers in the constructor.
3325		3935
3326	class myclass	3936	class myclass
3327	{	3937	{
3328	ev::io io ; void io_cb (ev::io &w, int revents);	3938	ev::io io ; void io_cb (ev::io &w, int revents);
		3939	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3329	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3940	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3330		3941
3331	myclass (int fd)	3942	myclass (int fd)
3332	{	3943	{
3333	io .set <myclass, &myclass::io_cb > (this);	3944	io .set <myclass, &myclass::io_cb > (this);
		3945	io2 .set <myclass, &myclass::io2_cb > (this);
3334	idle.set <myclass, &myclass::idle_cb> (this);	3946	idle.set <myclass, &myclass::idle_cb> (this);
3335		3947
3336	io.start (fd, ev::READ);	3948	io.set (fd, ev::WRITE); // configure the watcher
		3949	io.start (); // start it whenever convenient
		3950
		3951	io2.start (fd, ev::READ); // set + start in one call
3337	}	3952	}
3338	};	3953	};
3339		3954
3340		3955
3341	=head1 OTHER LANGUAGE BINDINGS	3956	=head1 OTHER LANGUAGE BINDINGS
…		…
3387	=item Ocaml	4002	=item Ocaml
3388		4003
3389	Erkki Seppala has written Ocaml bindings for libev, to be found at	4004	Erkki Seppala has written Ocaml bindings for libev, to be found at
3390	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4005	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3391		4006
		4007	=item Lua
		4008
		4009	Brian Maher has written a partial interface to libev for lua (at the
		4010	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4011	L<http://github.com/brimworks/lua-ev>.
		4012
3392	=back	4013	=back
3393		4014
3394		4015
3395	=head1 MACRO MAGIC	4016	=head1 MACRO MAGIC
3396		4017
…		…
3409	loop argument"). The C<EV_A> form is used when this is the sole argument,	4030	loop argument"). The C<EV_A> form is used when this is the sole argument,
3410	C<EV_A_> is used when other arguments are following. Example:	4031	C<EV_A_> is used when other arguments are following. Example:
3411		4032
3412	ev_unref (EV_A);	4033	ev_unref (EV_A);
3413	ev_timer_add (EV_A_ watcher);	4034	ev_timer_add (EV_A_ watcher);
3414	ev_loop (EV_A_ 0);	4035	ev_run (EV_A_ 0);
3415		4036
3416	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4037	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3417	which is often provided by the following macro.	4038	which is often provided by the following macro.
3418		4039
3419	=item C<EV_P>, C<EV_P_>	4040	=item C<EV_P>, C<EV_P_>
…		…
3459	}	4080	}
3460		4081
3461	ev_check check;	4082	ev_check check;
3462	ev_check_init (&check, check_cb);	4083	ev_check_init (&check, check_cb);
3463	ev_check_start (EV_DEFAULT_ &check);	4084	ev_check_start (EV_DEFAULT_ &check);
3464	ev_loop (EV_DEFAULT_ 0);	4085	ev_run (EV_DEFAULT_ 0);
3465		4086
3466	=head1 EMBEDDING	4087	=head1 EMBEDDING
3467		4088
3468	Libev can (and often is) directly embedded into host	4089	Libev can (and often is) directly embedded into host
3469	applications. Examples of applications that embed it include the Deliantra	4090	applications. Examples of applications that embed it include the Deliantra
…		…
3549	libev.m4	4170	libev.m4
3550		4171
3551	=head2 PREPROCESSOR SYMBOLS/MACROS	4172	=head2 PREPROCESSOR SYMBOLS/MACROS
3552		4173
3553	Libev can be configured via a variety of preprocessor symbols you have to	4174	Libev can be configured via a variety of preprocessor symbols you have to
3554	define before including any of its files. The default in the absence of	4175	define before including (or compiling) any of its files. The default in
3555	autoconf is documented for every option.	4176	the absence of autoconf is documented for every option.
		4177
		4178	Symbols marked with "(h)" do not change the ABI, and can have different
		4179	values when compiling libev vs. including F<ev.h>, so it is permissible
		4180	to redefine them before including F<ev.h> without breaking compatibility
		4181	to a compiled library. All other symbols change the ABI, which means all
		4182	users of libev and the libev code itself must be compiled with compatible
		4183	settings.
3556		4184
3557	=over 4	4185	=over 4
3558		4186
		4187	=item EV_COMPAT3 (h)
		4188
		4189	Backwards compatibility is a major concern for libev. This is why this
		4190	release of libev comes with wrappers for the functions and symbols that
		4191	have been renamed between libev version 3 and 4.
		4192
		4193	You can disable these wrappers (to test compatibility with future
		4194	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4195	sources. This has the additional advantage that you can drop the C<struct>
		4196	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4197	typedef in that case.
		4198
		4199	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4200	and in some even more future version the compatibility code will be
		4201	removed completely.
		4202
3559	=item EV_STANDALONE	4203	=item EV_STANDALONE (h)
3560		4204
3561	Must always be C<1> if you do not use autoconf configuration, which	4205	Must always be C<1> if you do not use autoconf configuration, which
3562	keeps libev from including F<config.h>, and it also defines dummy	4206	keeps libev from including F<config.h>, and it also defines dummy
3563	implementations for some libevent functions (such as logging, which is not	4207	implementations for some libevent functions (such as logging, which is not
3564	supported). It will also not define any of the structs usually found in	4208	supported). It will also not define any of the structs usually found in
3565	F<event.h> that are not directly supported by the libev core alone.	4209	F<event.h> that are not directly supported by the libev core alone.
3566		4210
3567	In stanbdalone mode, libev will still try to automatically deduce the	4211	In standalone mode, libev will still try to automatically deduce the
3568	configuration, but has to be more conservative.	4212	configuration, but has to be more conservative.
		4213
		4214	=item EV_USE_FLOOR
		4215
		4216	If defined to be C<1>, libev will use the C<floor ()> function for its
		4217	periodic reschedule calculations, otherwise libev will fall back on a
		4218	portable (slower) implementation. If you enable this, you usually have to
		4219	link against libm or something equivalent. Enabling this when the C<floor>
		4220	function is not available will fail, so the safe default is to not enable
		4221	this.
3569		4222
3570	=item EV_USE_MONOTONIC	4223	=item EV_USE_MONOTONIC
3571		4224
3572	If defined to be C<1>, libev will try to detect the availability of the	4225	If defined to be C<1>, libev will try to detect the availability of the
3573	monotonic clock option at both compile time and runtime. Otherwise no	4226	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3637	be used is the winsock select). This means that it will call	4290	be used is the winsock select). This means that it will call
3638	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4291	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3639	it is assumed that all these functions actually work on fds, even	4292	it is assumed that all these functions actually work on fds, even
3640	on win32. Should not be defined on non-win32 platforms.	4293	on win32. Should not be defined on non-win32 platforms.
3641		4294
3642	=item EV_FD_TO_WIN32_HANDLE	4295	=item EV_FD_TO_WIN32_HANDLE(fd)
3643		4296
3644	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4297	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3645	file descriptors to socket handles. When not defining this symbol (the	4298	file descriptors to socket handles. When not defining this symbol (the
3646	default), then libev will call C<_get_osfhandle>, which is usually	4299	default), then libev will call C<_get_osfhandle>, which is usually
3647	correct. In some cases, programs use their own file descriptor management,	4300	correct. In some cases, programs use their own file descriptor management,
3648	in which case they can provide this function to map fds to socket handles.	4301	in which case they can provide this function to map fds to socket handles.
		4302
		4303	=item EV_WIN32_HANDLE_TO_FD(handle)
		4304
		4305	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4306	using the standard C<_open_osfhandle> function. For programs implementing
		4307	their own fd to handle mapping, overwriting this function makes it easier
		4308	to do so. This can be done by defining this macro to an appropriate value.
		4309
		4310	=item EV_WIN32_CLOSE_FD(fd)
		4311
		4312	If programs implement their own fd to handle mapping on win32, then this
		4313	macro can be used to override the C<close> function, useful to unregister
		4314	file descriptors again. Note that the replacement function has to close
		4315	the underlying OS handle.
3649		4316
3650	=item EV_USE_POLL	4317	=item EV_USE_POLL
3651		4318
3652	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4319	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3653	backend. Otherwise it will be enabled on non-win32 platforms. It	4320	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3700	as well as for signal and thread safety in C<ev_async> watchers.	4367	as well as for signal and thread safety in C<ev_async> watchers.
3701		4368
3702	In the absence of this define, libev will use C<sig_atomic_t volatile>	4369	In the absence of this define, libev will use C<sig_atomic_t volatile>
3703	(from F<signal.h>), which is usually good enough on most platforms.	4370	(from F<signal.h>), which is usually good enough on most platforms.
3704		4371
3705	=item EV_H	4372	=item EV_H (h)
3706		4373
3707	The name of the F<ev.h> header file used to include it. The default if	4374	The name of the F<ev.h> header file used to include it. The default if
3708	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4375	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3709	used to virtually rename the F<ev.h> header file in case of conflicts.	4376	used to virtually rename the F<ev.h> header file in case of conflicts.
3710		4377
3711	=item EV_CONFIG_H	4378	=item EV_CONFIG_H (h)
3712		4379
3713	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4380	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3714	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4381	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3715	C<EV_H>, above.	4382	C<EV_H>, above.
3716		4383
3717	=item EV_EVENT_H	4384	=item EV_EVENT_H (h)
3718		4385
3719	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4386	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3720	of how the F<event.h> header can be found, the default is C<"event.h">.	4387	of how the F<event.h> header can be found, the default is C<"event.h">.
3721		4388
3722	=item EV_PROTOTYPES	4389	=item EV_PROTOTYPES (h)
3723		4390
3724	If defined to be C<0>, then F<ev.h> will not define any function	4391	If defined to be C<0>, then F<ev.h> will not define any function
3725	prototypes, but still define all the structs and other symbols. This is	4392	prototypes, but still define all the structs and other symbols. This is
3726	occasionally useful if you want to provide your own wrapper functions	4393	occasionally useful if you want to provide your own wrapper functions
3727	around libev functions.	4394	around libev functions.
…		…
3749	fine.	4416	fine.
3750		4417
3751	If your embedding application does not need any priorities, defining these	4418	If your embedding application does not need any priorities, defining these
3752	both to C<0> will save some memory and CPU.	4419	both to C<0> will save some memory and CPU.
3753		4420
3754	=item EV_PERIODIC_ENABLE	4421	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4422	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4423	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3755		4424
3756	If undefined or defined to be C<1>, then periodic timers are supported. If	4425	If undefined or defined to be C<1> (and the platform supports it), then
3757	defined to be C<0>, then they are not. Disabling them saves a few kB of	4426	the respective watcher type is supported. If defined to be C<0>, then it
3758	code.	4427	is not. Disabling watcher types mainly saves code size.
3759		4428
3760	=item EV_IDLE_ENABLE	4429	=item EV_FEATURES
3761
3762	If undefined or defined to be C<1>, then idle watchers are supported. If
3763	defined to be C<0>, then they are not. Disabling them saves a few kB of
3764	code.
3765
3766	=item EV_EMBED_ENABLE
3767
3768	If undefined or defined to be C<1>, then embed watchers are supported. If
3769	defined to be C<0>, then they are not. Embed watchers rely on most other
3770	watcher types, which therefore must not be disabled.
3771
3772	=item EV_STAT_ENABLE
3773
3774	If undefined or defined to be C<1>, then stat watchers are supported. If
3775	defined to be C<0>, then they are not.
3776
3777	=item EV_FORK_ENABLE
3778
3779	If undefined or defined to be C<1>, then fork watchers are supported. If
3780	defined to be C<0>, then they are not.
3781
3782	=item EV_ASYNC_ENABLE
3783
3784	If undefined or defined to be C<1>, then async watchers are supported. If
3785	defined to be C<0>, then they are not.
3786
3787	=item EV_MINIMAL
3788		4430
3789	If you need to shave off some kilobytes of code at the expense of some	4431	If you need to shave off some kilobytes of code at the expense of some
3790	speed (but with the full API), define this symbol to C<1>. Currently this	4432	speed (but with the full API), you can define this symbol to request
3791	is used to override some inlining decisions, saves roughly 30% code size	4433	certain subsets of functionality. The default is to enable all features
3792	on amd64. It also selects a much smaller 2-heap for timer management over	4434	that can be enabled on the platform.
3793	the default 4-heap.
3794		4435
3795	You can save even more by disabling watcher types you do not need	4436	A typical way to use this symbol is to define it to C<0> (or to a bitset
3796	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4437	with some broad features you want) and then selectively re-enable
3797	(C<-DNDEBUG>) will usually reduce code size a lot.	4438	additional parts you want, for example if you want everything minimal,
		4439	but multiple event loop support, async and child watchers and the poll
		4440	backend, use this:
3798		4441
3799	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4442	#define EV_FEATURES 0
3800	provide a bare-bones event library. See C<ev.h> for details on what parts	4443	#define EV_MULTIPLICITY 1
3801	of the API are still available, and do not complain if this subset changes	4444	#define EV_USE_POLL 1
3802	over time.	4445	#define EV_CHILD_ENABLE 1
		4446	#define EV_ASYNC_ENABLE 1
		4447
		4448	The actual value is a bitset, it can be a combination of the following
		4449	values:
		4450
		4451	=over 4
		4452
		4453	=item C<1> - faster/larger code
		4454
		4455	Use larger code to speed up some operations.
		4456
		4457	Currently this is used to override some inlining decisions (enlarging the
		4458	code size by roughly 30% on amd64).
		4459
		4460	When optimising for size, use of compiler flags such as C<-Os> with
		4461	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4462	assertions.
		4463
		4464	=item C<2> - faster/larger data structures
		4465
		4466	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4467	hash table sizes and so on. This will usually further increase code size
		4468	and can additionally have an effect on the size of data structures at
		4469	runtime.
		4470
		4471	=item C<4> - full API configuration
		4472
		4473	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4474	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4475
		4476	=item C<8> - full API
		4477
		4478	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4479	details on which parts of the API are still available without this
		4480	feature, and do not complain if this subset changes over time.
		4481
		4482	=item C<16> - enable all optional watcher types
		4483
		4484	Enables all optional watcher types. If you want to selectively enable
		4485	only some watcher types other than I/O and timers (e.g. prepare,
		4486	embed, async, child...) you can enable them manually by defining
		4487	C<EV_watchertype_ENABLE> to C<1> instead.
		4488
		4489	=item C<32> - enable all backends
		4490
		4491	This enables all backends - without this feature, you need to enable at
		4492	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4493
		4494	=item C<64> - enable OS-specific "helper" APIs
		4495
		4496	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4497	default.
		4498
		4499	=back
		4500
		4501	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4502	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4503	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4504	watchers, timers and monotonic clock support.
		4505
		4506	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4507	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4508	your program might be left out as well - a binary starting a timer and an
		4509	I/O watcher then might come out at only 5Kb.
		4510
		4511	=item EV_AVOID_STDIO
		4512
		4513	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4514	functions (printf, scanf, perror etc.). This will increase the code size
		4515	somewhat, but if your program doesn't otherwise depend on stdio and your
		4516	libc allows it, this avoids linking in the stdio library which is quite
		4517	big.
		4518
		4519	Note that error messages might become less precise when this option is
		4520	enabled.
		4521
		4522	=item EV_NSIG
		4523
		4524	The highest supported signal number, +1 (or, the number of
		4525	signals): Normally, libev tries to deduce the maximum number of signals
		4526	automatically, but sometimes this fails, in which case it can be
		4527	specified. Also, using a lower number than detected (C<32> should be
		4528	good for about any system in existence) can save some memory, as libev
		4529	statically allocates some 12-24 bytes per signal number.
3803		4530
3804	=item EV_PID_HASHSIZE	4531	=item EV_PID_HASHSIZE
3805		4532
3806	C<ev_child> watchers use a small hash table to distribute workload by	4533	C<ev_child> watchers use a small hash table to distribute workload by
3807	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4534	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3808	than enough. If you need to manage thousands of children you might want to	4535	usually more than enough. If you need to manage thousands of children you
3809	increase this value (I<must> be a power of two).	4536	might want to increase this value (I<must> be a power of two).
3810		4537
3811	=item EV_INOTIFY_HASHSIZE	4538	=item EV_INOTIFY_HASHSIZE
3812		4539
3813	C<ev_stat> watchers use a small hash table to distribute workload by	4540	C<ev_stat> watchers use a small hash table to distribute workload by
3814	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4541	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3815	usually more than enough. If you need to manage thousands of C<ev_stat>	4542	disabled), usually more than enough. If you need to manage thousands of
3816	watchers you might want to increase this value (I<must> be a power of	4543	C<ev_stat> watchers you might want to increase this value (I<must> be a
3817	two).	4544	power of two).
3818		4545
3819	=item EV_USE_4HEAP	4546	=item EV_USE_4HEAP
3820		4547
3821	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4548	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3822	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4549	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3823	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4550	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3824	faster performance with many (thousands) of watchers.	4551	faster performance with many (thousands) of watchers.
3825		4552
3826	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4553	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3827	(disabled).	4554	will be C<0>.
3828		4555
3829	=item EV_HEAP_CACHE_AT	4556	=item EV_HEAP_CACHE_AT
3830		4557
3831	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4558	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3832	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4559	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3833	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4560	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3834	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4561	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3835	but avoids random read accesses on heap changes. This improves performance	4562	but avoids random read accesses on heap changes. This improves performance
3836	noticeably with many (hundreds) of watchers.	4563	noticeably with many (hundreds) of watchers.
3837		4564
3838	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4565	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3839	(disabled).	4566	will be C<0>.
3840		4567
3841	=item EV_VERIFY	4568	=item EV_VERIFY
3842		4569
3843	Controls how much internal verification (see C<ev_loop_verify ()>) will	4570	Controls how much internal verification (see C<ev_verify ()>) will
3844	be done: If set to C<0>, no internal verification code will be compiled	4571	be done: If set to C<0>, no internal verification code will be compiled
3845	in. If set to C<1>, then verification code will be compiled in, but not	4572	in. If set to C<1>, then verification code will be compiled in, but not
3846	called. If set to C<2>, then the internal verification code will be	4573	called. If set to C<2>, then the internal verification code will be
3847	called once per loop, which can slow down libev. If set to C<3>, then the	4574	called once per loop, which can slow down libev. If set to C<3>, then the
3848	verification code will be called very frequently, which will slow down	4575	verification code will be called very frequently, which will slow down
3849	libev considerably.	4576	libev considerably.
3850		4577
3851	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4578	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3852	C<0>.	4579	will be C<0>.
3853		4580
3854	=item EV_COMMON	4581	=item EV_COMMON
3855		4582
3856	By default, all watchers have a C<void *data> member. By redefining	4583	By default, all watchers have a C<void *data> member. By redefining
3857	this macro to a something else you can include more and other types of	4584	this macro to something else you can include more and other types of
3858	members. You have to define it each time you include one of the files,	4585	members. You have to define it each time you include one of the files,
3859	though, and it must be identical each time.	4586	though, and it must be identical each time.
3860		4587
3861	For example, the perl EV module uses something like this:	4588	For example, the perl EV module uses something like this:
3862		4589
…		…
3915	file.	4642	file.
3916		4643
3917	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4644	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3918	that everybody includes and which overrides some configure choices:	4645	that everybody includes and which overrides some configure choices:
3919		4646
3920	#define EV_MINIMAL 1	4647	#define EV_FEATURES 8
3921	#define EV_USE_POLL 0	4648	#define EV_USE_SELECT 1
3922	#define EV_MULTIPLICITY 0
3923	#define EV_PERIODIC_ENABLE 0	4649	#define EV_PREPARE_ENABLE 1
		4650	#define EV_IDLE_ENABLE 1
3924	#define EV_STAT_ENABLE 0	4651	#define EV_SIGNAL_ENABLE 1
3925	#define EV_FORK_ENABLE 0	4652	#define EV_CHILD_ENABLE 1
		4653	#define EV_USE_STDEXCEPT 0
3926	#define EV_CONFIG_H <config.h>	4654	#define EV_CONFIG_H <config.h>
3927	#define EV_MINPRI 0
3928	#define EV_MAXPRI 0
3929		4655
3930	#include "ev++.h"	4656	#include "ev++.h"
3931		4657
3932	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4658	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3933		4659
3934	#include "ev_cpp.h"	4660	#include "ev_cpp.h"
3935	#include "ev.c"	4661	#include "ev.c"
3936		4662
3937	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4663	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3938		4664
3939	=head2 THREADS AND COROUTINES	4665	=head2 THREADS AND COROUTINES
3940		4666
3941	=head3 THREADS	4667	=head3 THREADS
3942		4668
…		…
3993	default loop and triggering an C<ev_async> watcher from the default loop	4719	default loop and triggering an C<ev_async> watcher from the default loop
3994	watcher callback into the event loop interested in the signal.	4720	watcher callback into the event loop interested in the signal.
3995		4721
3996	=back	4722	=back
3997		4723
3998	=head4 THREAD LOCKING EXAMPLE	4724	See also L<THREAD LOCKING EXAMPLE>.
3999
4000	Here is a fictitious example of how to run an event loop in a different
4001	thread than where callbacks are being invoked and watchers are
4002	created/added/removed.
4003
4004	For a real-world example, see the C<EV::Loop::Async> perl module,
4005	which uses exactly this technique (which is suited for many high-level
4006	languages).
4007
4008	The example uses a pthread mutex to protect the loop data, a condition
4009	variable to wait for callback invocations, an async watcher to notify the
4010	event loop thread and an unspecified mechanism to wake up the main thread.
4011
4012	First, you need to associate some data with the event loop:
4013
4014	typedef struct {
4015	mutex_t lock; /* global loop lock */
4016	ev_async async_w;
4017	thread_t tid;
4018	cond_t invoke_cv;
4019	} userdata;
4020
4021	void prepare_loop (EV_P)
4022	{
4023	// for simplicity, we use a static userdata struct.
4024	static userdata u;
4025
4026	ev_async_init (&u->async_w, async_cb);
4027	ev_async_start (EV_A_ &u->async_w);
4028
4029	pthread_mutex_init (&u->lock, 0);
4030	pthread_cond_init (&u->invoke_cv, 0);
4031
4032	// now associate this with the loop
4033	ev_set_userdata (EV_A_ u);
4034	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4035	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4036
4037	// then create the thread running ev_loop
4038	pthread_create (&u->tid, 0, l_run, EV_A);
4039	}
4040
4041	The callback for the C<ev_async> watcher does nothing: the watcher is used
4042	solely to wake up the event loop so it takes notice of any new watchers
4043	that might have been added:
4044
4045	static void
4046	async_cb (EV_P_ ev_async *w, int revents)
4047	{
4048	// just used for the side effects
4049	}
4050
4051	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4052	protecting the loop data, respectively.
4053
4054	static void
4055	l_release (EV_P)
4056	{
4057	userdata *u = ev_userdata (EV_A);
4058	pthread_mutex_unlock (&u->lock);
4059	}
4060
4061	static void
4062	l_acquire (EV_P)
4063	{
4064	userdata *u = ev_userdata (EV_A);
4065	pthread_mutex_lock (&u->lock);
4066	}
4067
4068	The event loop thread first acquires the mutex, and then jumps straight
4069	into C<ev_loop>:
4070
4071	void *
4072	l_run (void *thr_arg)
4073	{
4074	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4075
4076	l_acquire (EV_A);
4077	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4078	ev_loop (EV_A_ 0);
4079	l_release (EV_A);
4080
4081	return 0;
4082	}
4083
4084	Instead of invoking all pending watchers, the C<l_invoke> callback will
4085	signal the main thread via some unspecified mechanism (signals? pipe
4086	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4087	have been called (in a while loop because a) spurious wakeups are possible
4088	and b) skipping inter-thread-communication when there are no pending
4089	watchers is very beneficial):
4090
4091	static void
4092	l_invoke (EV_P)
4093	{
4094	userdata *u = ev_userdata (EV_A);
4095
4096	while (ev_pending_count (EV_A))
4097	{
4098	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4099	pthread_cond_wait (&u->invoke_cv, &u->lock);
4100	}
4101	}
4102
4103	Now, whenever the main thread gets told to invoke pending watchers, it
4104	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4105	thread to continue:
4106
4107	static void
4108	real_invoke_pending (EV_P)
4109	{
4110	userdata *u = ev_userdata (EV_A);
4111
4112	pthread_mutex_lock (&u->lock);
4113	ev_invoke_pending (EV_A);
4114	pthread_cond_signal (&u->invoke_cv);
4115	pthread_mutex_unlock (&u->lock);
4116	}
4117
4118	Whenever you want to start/stop a watcher or do other modifications to an
4119	event loop, you will now have to lock:
4120
4121	ev_timer timeout_watcher;
4122	userdata *u = ev_userdata (EV_A);
4123
4124	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4125
4126	pthread_mutex_lock (&u->lock);
4127	ev_timer_start (EV_A_ &timeout_watcher);
4128	ev_async_send (EV_A_ &u->async_w);
4129	pthread_mutex_unlock (&u->lock);
4130
4131	Note that sending the C<ev_async> watcher is required because otherwise
4132	an event loop currently blocking in the kernel will have no knowledge
4133	about the newly added timer. By waking up the loop it will pick up any new
4134	watchers in the next event loop iteration.
4135		4725
4136	=head3 COROUTINES	4726	=head3 COROUTINES
4137		4727
4138	Libev is very accommodating to coroutines ("cooperative threads"):	4728	Libev is very accommodating to coroutines ("cooperative threads"):
4139	libev fully supports nesting calls to its functions from different	4729	libev fully supports nesting calls to its functions from different
4140	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4730	coroutines (e.g. you can call C<ev_run> on the same loop from two
4141	different coroutines, and switch freely between both coroutines running	4731	different coroutines, and switch freely between both coroutines running
4142	the loop, as long as you don't confuse yourself). The only exception is	4732	the loop, as long as you don't confuse yourself). The only exception is
4143	that you must not do this from C<ev_periodic> reschedule callbacks.	4733	that you must not do this from C<ev_periodic> reschedule callbacks.
4144		4734
4145	Care has been taken to ensure that libev does not keep local state inside	4735	Care has been taken to ensure that libev does not keep local state inside
4146	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4736	C<ev_run>, and other calls do not usually allow for coroutine switches as
4147	they do not call any callbacks.	4737	they do not call any callbacks.
4148		4738
4149	=head2 COMPILER WARNINGS	4739	=head2 COMPILER WARNINGS
4150		4740
4151	Depending on your compiler and compiler settings, you might get no or a	4741	Depending on your compiler and compiler settings, you might get no or a
…		…
4162	maintainable.	4752	maintainable.
4163		4753
4164	And of course, some compiler warnings are just plain stupid, or simply	4754	And of course, some compiler warnings are just plain stupid, or simply
4165	wrong (because they don't actually warn about the condition their message	4755	wrong (because they don't actually warn about the condition their message
4166	seems to warn about). For example, certain older gcc versions had some	4756	seems to warn about). For example, certain older gcc versions had some
4167	warnings that resulted an extreme number of false positives. These have	4757	warnings that resulted in an extreme number of false positives. These have
4168	been fixed, but some people still insist on making code warn-free with	4758	been fixed, but some people still insist on making code warn-free with
4169	such buggy versions.	4759	such buggy versions.
4170		4760
4171	While libev is written to generate as few warnings as possible,	4761	While libev is written to generate as few warnings as possible,
4172	"warn-free" code is not a goal, and it is recommended not to build libev	4762	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4208	I suggest using suppression lists.	4798	I suggest using suppression lists.
4209		4799
4210		4800
4211	=head1 PORTABILITY NOTES	4801	=head1 PORTABILITY NOTES
4212		4802
		4803	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4804
		4805	GNU/Linux is the only common platform that supports 64 bit file/large file
		4806	interfaces but I<disables> them by default.
		4807
		4808	That means that libev compiled in the default environment doesn't support
		4809	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4810
		4811	Unfortunately, many programs try to work around this GNU/Linux issue
		4812	by enabling the large file API, which makes them incompatible with the
		4813	standard libev compiled for their system.
		4814
		4815	Likewise, libev cannot enable the large file API itself as this would
		4816	suddenly make it incompatible to the default compile time environment,
		4817	i.e. all programs not using special compile switches.
		4818
		4819	=head2 OS/X AND DARWIN BUGS
		4820
		4821	The whole thing is a bug if you ask me - basically any system interface
		4822	you touch is broken, whether it is locales, poll, kqueue or even the
		4823	OpenGL drivers.
		4824
		4825	=head3 C<kqueue> is buggy
		4826
		4827	The kqueue syscall is broken in all known versions - most versions support
		4828	only sockets, many support pipes.
		4829
		4830	Libev tries to work around this by not using C<kqueue> by default on this
		4831	rotten platform, but of course you can still ask for it when creating a
		4832	loop - embedding a socket-only kqueue loop into a select-based one is
		4833	probably going to work well.
		4834
		4835	=head3 C<poll> is buggy
		4836
		4837	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4838	implementation by something calling C<kqueue> internally around the 10.5.6
		4839	release, so now C<kqueue> I<and> C<poll> are broken.
		4840
		4841	Libev tries to work around this by not using C<poll> by default on
		4842	this rotten platform, but of course you can still ask for it when creating
		4843	a loop.
		4844
		4845	=head3 C<select> is buggy
		4846
		4847	All that's left is C<select>, and of course Apple found a way to fuck this
		4848	one up as well: On OS/X, C<select> actively limits the number of file
		4849	descriptors you can pass in to 1024 - your program suddenly crashes when
		4850	you use more.
		4851
		4852	There is an undocumented "workaround" for this - defining
		4853	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4854	work on OS/X.
		4855
		4856	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4857
		4858	=head3 C<errno> reentrancy
		4859
		4860	The default compile environment on Solaris is unfortunately so
		4861	thread-unsafe that you can't even use components/libraries compiled
		4862	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4863	defined by default. A valid, if stupid, implementation choice.
		4864
		4865	If you want to use libev in threaded environments you have to make sure
		4866	it's compiled with C<_REENTRANT> defined.
		4867
		4868	=head3 Event port backend
		4869
		4870	The scalable event interface for Solaris is called "event
		4871	ports". Unfortunately, this mechanism is very buggy in all major
		4872	releases. If you run into high CPU usage, your program freezes or you get
		4873	a large number of spurious wakeups, make sure you have all the relevant
		4874	and latest kernel patches applied. No, I don't know which ones, but there
		4875	are multiple ones to apply, and afterwards, event ports actually work
		4876	great.
		4877
		4878	If you can't get it to work, you can try running the program by setting
		4879	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4880	C<select> backends.
		4881
		4882	=head2 AIX POLL BUG
		4883
		4884	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4885	this by trying to avoid the poll backend altogether (i.e. it's not even
		4886	compiled in), which normally isn't a big problem as C<select> works fine
		4887	with large bitsets on AIX, and AIX is dead anyway.
		4888
4213	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4889	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4890
		4891	=head3 General issues
4214		4892
4215	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4893	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4216	requires, and its I/O model is fundamentally incompatible with the POSIX	4894	requires, and its I/O model is fundamentally incompatible with the POSIX
4217	model. Libev still offers limited functionality on this platform in	4895	model. Libev still offers limited functionality on this platform in
4218	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4896	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4219	descriptors. This only applies when using Win32 natively, not when using	4897	descriptors. This only applies when using Win32 natively, not when using
4220	e.g. cygwin.	4898	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4899	as every compielr comes with a slightly differently broken/incompatible
		4900	environment.
4221		4901
4222	Lifting these limitations would basically require the full	4902	Lifting these limitations would basically require the full
4223	re-implementation of the I/O system. If you are into these kinds of	4903	re-implementation of the I/O system. If you are into this kind of thing,
4224	things, then note that glib does exactly that for you in a very portable	4904	then note that glib does exactly that for you in a very portable way (note
4225	way (note also that glib is the slowest event library known to man).	4905	also that glib is the slowest event library known to man).
4226		4906
4227	There is no supported compilation method available on windows except	4907	There is no supported compilation method available on windows except
4228	embedding it into other applications.	4908	embedding it into other applications.
4229		4909
4230	Sensible signal handling is officially unsupported by Microsoft - libev	4910	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4258	you do I<not> compile the F<ev.c> or any other embedded source files!):	4938	you do I<not> compile the F<ev.c> or any other embedded source files!):
4259		4939
4260	#include "evwrap.h"	4940	#include "evwrap.h"
4261	#include "ev.c"	4941	#include "ev.c"
4262		4942
4263	=over 4
4264
4265	=item The winsocket select function	4943	=head3 The winsocket C<select> function
4266		4944
4267	The winsocket C<select> function doesn't follow POSIX in that it	4945	The winsocket C<select> function doesn't follow POSIX in that it
4268	requires socket I<handles> and not socket I<file descriptors> (it is	4946	requires socket I<handles> and not socket I<file descriptors> (it is
4269	also extremely buggy). This makes select very inefficient, and also	4947	also extremely buggy). This makes select very inefficient, and also
4270	requires a mapping from file descriptors to socket handles (the Microsoft	4948	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4279	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4957	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4280		4958
4281	Note that winsockets handling of fd sets is O(n), so you can easily get a	4959	Note that winsockets handling of fd sets is O(n), so you can easily get a
4282	complexity in the O(n²) range when using win32.	4960	complexity in the O(n²) range when using win32.
4283		4961
4284	=item Limited number of file descriptors	4962	=head3 Limited number of file descriptors
4285		4963
4286	Windows has numerous arbitrary (and low) limits on things.	4964	Windows has numerous arbitrary (and low) limits on things.
4287		4965
4288	Early versions of winsocket's select only supported waiting for a maximum	4966	Early versions of winsocket's select only supported waiting for a maximum
4289	of C<64> handles (probably owning to the fact that all windows kernels	4967	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4304	runtime libraries. This might get you to about C<512> or C<2048> sockets	4982	runtime libraries. This might get you to about C<512> or C<2048> sockets
4305	(depending on windows version and/or the phase of the moon). To get more,	4983	(depending on windows version and/or the phase of the moon). To get more,
4306	you need to wrap all I/O functions and provide your own fd management, but	4984	you need to wrap all I/O functions and provide your own fd management, but
4307	the cost of calling select (O(n²)) will likely make this unworkable.	4985	the cost of calling select (O(n²)) will likely make this unworkable.
4308		4986
4309	=back
4310
4311	=head2 PORTABILITY REQUIREMENTS	4987	=head2 PORTABILITY REQUIREMENTS
4312		4988
4313	In addition to a working ISO-C implementation and of course the	4989	In addition to a working ISO-C implementation and of course the
4314	backend-specific APIs, libev relies on a few additional extensions:	4990	backend-specific APIs, libev relies on a few additional extensions:
4315		4991
…		…
4321	Libev assumes not only that all watcher pointers have the same internal	4997	Libev assumes not only that all watcher pointers have the same internal
4322	structure (guaranteed by POSIX but not by ISO C for example), but it also	4998	structure (guaranteed by POSIX but not by ISO C for example), but it also
4323	assumes that the same (machine) code can be used to call any watcher	4999	assumes that the same (machine) code can be used to call any watcher
4324	callback: The watcher callbacks have different type signatures, but libev	5000	callback: The watcher callbacks have different type signatures, but libev
4325	calls them using an C<ev_watcher *> internally.	5001	calls them using an C<ev_watcher *> internally.
		5002
		5003	=item pointer accesses must be thread-atomic
		5004
		5005	Accessing a pointer value must be atomic, it must both be readable and
		5006	writable in one piece - this is the case on all current architectures.
4326		5007
4327	=item C<sig_atomic_t volatile> must be thread-atomic as well	5008	=item C<sig_atomic_t volatile> must be thread-atomic as well
4328		5009
4329	The type C<sig_atomic_t volatile> (or whatever is defined as	5010	The type C<sig_atomic_t volatile> (or whatever is defined as
4330	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5011	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4353	watchers.	5034	watchers.
4354		5035
4355	=item C<double> must hold a time value in seconds with enough accuracy	5036	=item C<double> must hold a time value in seconds with enough accuracy
4356		5037
4357	The type C<double> is used to represent timestamps. It is required to	5038	The type C<double> is used to represent timestamps. It is required to
4358	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5039	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4359	enough for at least into the year 4000. This requirement is fulfilled by	5040	good enough for at least into the year 4000 with millisecond accuracy
		5041	(the design goal for libev). This requirement is overfulfilled by
4360	implementations implementing IEEE 754, which is basically all existing	5042	implementations using IEEE 754, which is basically all existing ones. With
4361	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5043	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4362	2200.
4363		5044
4364	=back	5045	=back
4365		5046
4366	If you know of other additional requirements drop me a note.	5047	If you know of other additional requirements drop me a note.
4367		5048
…		…
4435	involves iterating over all running async watchers or all signal numbers.	5116	involves iterating over all running async watchers or all signal numbers.
4436		5117
4437	=back	5118	=back
4438		5119
4439		5120
		5121	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5122
		5123	The major version 4 introduced some incompatible changes to the API.
		5124
		5125	At the moment, the C<ev.h> header file provides compatibility definitions
		5126	for all changes, so most programs should still compile. The compatibility
		5127	layer might be removed in later versions of libev, so better update to the
		5128	new API early than late.
		5129
		5130	=over 4
		5131
		5132	=item C<EV_COMPAT3> backwards compatibility mechanism
		5133
		5134	The backward compatibility mechanism can be controlled by
		5135	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5136	section.
		5137
		5138	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5139
		5140	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5141
		5142	ev_loop_destroy (EV_DEFAULT_UC);
		5143	ev_loop_fork (EV_DEFAULT);
		5144
		5145	=item function/symbol renames
		5146
		5147	A number of functions and symbols have been renamed:
		5148
		5149	ev_loop => ev_run
		5150	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5151	EVLOOP_ONESHOT => EVRUN_ONCE
		5152
		5153	ev_unloop => ev_break
		5154	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5155	EVUNLOOP_ONE => EVBREAK_ONE
		5156	EVUNLOOP_ALL => EVBREAK_ALL
		5157
		5158	EV_TIMEOUT => EV_TIMER
		5159
		5160	ev_loop_count => ev_iteration
		5161	ev_loop_depth => ev_depth
		5162	ev_loop_verify => ev_verify
		5163
		5164	Most functions working on C<struct ev_loop> objects don't have an
		5165	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5166	associated constants have been renamed to not collide with the C<struct
		5167	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5168	as all other watcher types. Note that C<ev_loop_fork> is still called
		5169	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5170	typedef.
		5171
		5172	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5173
		5174	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5175	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5176	and work, but the library code will of course be larger.
		5177
		5178	=back
		5179
		5180
4440	=head1 GLOSSARY	5181	=head1 GLOSSARY
4441		5182
4442	=over 4	5183	=over 4
4443		5184
4444	=item active	5185	=item active
4445		5186
4446	A watcher is active as long as it has been started (has been attached to	5187	A watcher is active as long as it has been started and not yet stopped.
4447	an event loop) but not yet stopped (disassociated from the event loop).	5188	See L<WATCHER STATES> for details.
4448		5189
4449	=item application	5190	=item application
4450		5191
4451	In this document, an application is whatever is using libev.	5192	In this document, an application is whatever is using libev.
		5193
		5194	=item backend
		5195
		5196	The part of the code dealing with the operating system interfaces.
4452		5197
4453	=item callback	5198	=item callback
4454		5199
4455	The address of a function that is called when some event has been	5200	The address of a function that is called when some event has been
4456	detected. Callbacks are being passed the event loop, the watcher that	5201	detected. Callbacks are being passed the event loop, the watcher that
4457	received the event, and the actual event bitset.	5202	received the event, and the actual event bitset.
4458		5203
4459	=item callback invocation	5204	=item callback/watcher invocation
4460		5205
4461	The act of calling the callback associated with a watcher.	5206	The act of calling the callback associated with a watcher.
4462		5207
4463	=item event	5208	=item event
4464		5209
4465	A change of state of some external event, such as data now being available	5210	A change of state of some external event, such as data now being available
4466	for reading on a file descriptor, time having passed or simply not having	5211	for reading on a file descriptor, time having passed or simply not having
4467	any other events happening anymore.	5212	any other events happening anymore.
4468		5213
4469	In libev, events are represented as single bits (such as C<EV_READ> or	5214	In libev, events are represented as single bits (such as C<EV_READ> or
4470	C<EV_TIMEOUT>).	5215	C<EV_TIMER>).
4471		5216
4472	=item event library	5217	=item event library
4473		5218
4474	A software package implementing an event model and loop.	5219	A software package implementing an event model and loop.
4475		5220
…		…
4483	The model used to describe how an event loop handles and processes	5228	The model used to describe how an event loop handles and processes
4484	watchers and events.	5229	watchers and events.
4485		5230
4486	=item pending	5231	=item pending
4487		5232
4488	A watcher is pending as soon as the corresponding event has been detected,	5233	A watcher is pending as soon as the corresponding event has been
4489	and stops being pending as soon as the watcher will be invoked or its	5234	detected. See L<WATCHER STATES> for details.
4490	pending status is explicitly cleared by the application.
4491
4492	A watcher can be pending, but not active. Stopping a watcher also clears
4493	its pending status.
4494		5235
4495	=item real time	5236	=item real time
4496		5237
4497	The physical time that is observed. It is apparently strictly monotonic :)	5238	The physical time that is observed. It is apparently strictly monotonic :)
4498		5239
4499	=item wall-clock time	5240	=item wall-clock time
4500		5241
4501	The time and date as shown on clocks. Unlike real time, it can actually	5242	The time and date as shown on clocks. Unlike real time, it can actually
4502	be wrong and jump forwards and backwards, e.g. when the you adjust your	5243	be wrong and jump forwards and backwards, e.g. when you adjust your
4503	clock.	5244	clock.
4504		5245
4505	=item watcher	5246	=item watcher
4506		5247
4507	A data structure that describes interest in certain events. Watchers need	5248	A data structure that describes interest in certain events. Watchers need
4508	to be started (attached to an event loop) before they can receive events.	5249	to be started (attached to an event loop) before they can receive events.
4509		5250
4510	=item watcher invocation
4511
4512	The act of calling the callback associated with a watcher.
4513
4514	=back	5251	=back
4515		5252
4516	=head1 AUTHOR	5253	=head1 AUTHOR
4517		5254
4518	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5256	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4519		5257

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