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Revision 1.356 by root, Tue Jan 11 01:42:47 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	// unloop was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
…		…
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	This flag's behaviour will become the default in future versions of libev.
		448
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		450
369	This is your standard select(2) backend. Not I<completely> standard, as	451	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,	452	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	453	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	477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
397		479
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
399		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
		484
400	For few fds, this backend is a bit little slower than poll and select,	485	For few fds, this backend is a bit little slower than poll and select,
401	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
402	like O(total_fds) where n is the total number of fds (or the highest fd),	487	like O(total_fds) where n is the total number of fds (or the highest fd),
403	epoll scales either O(1) or O(active_fds).	488	epoll scales either O(1) or O(active_fds).
404		489
405	The epoll mechanism deserves honorable mention as the most misdesigned	490	The epoll mechanism deserves honorable mention as the most misdesigned
406	of the more advanced event mechanisms: mere annoyances include silently	491	of the more advanced event mechanisms: mere annoyances include silently
407	dropping file descriptors, requiring a system call per change per file	492	dropping file descriptors, requiring a system call per change per file
408	descriptor (and unnecessary guessing of parameters), problems with dup and	493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(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	496	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	497	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	498	set, which can take considerable time (one syscall per file descriptor)
412	hard to detect.	499	and is of course hard to detect.
413		500
414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	501	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	502	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	503	I<different> file descriptors (even already closed ones, so one cannot
417	even remove them from the set) than registered in the set (especially	504	even remove them from the set) than registered in the set (especially
418	on SMP systems). Libev tries to counter these spurious notifications by	505	on SMP systems). Libev tries to counter these spurious notifications by
419	employing an additional generation counter and comparing that against the	506	employing an additional generation counter and comparing that against the
420	events to filter out spurious ones, recreating the set when required.	507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
421		514
422	While stopping, setting and starting an I/O watcher in the same iteration	515	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	516	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	517	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	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		585
493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	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)).	587	it's really slow, but it still scales very well (O(active_fds)).
495		588
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	589	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	590	file descriptor per loop iteration. For small and medium numbers of file
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	592	might perform better.
504		593
505	On the positive side, with the exception of the spurious readiness	594	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	595	specification in all tests and is fully embeddable, which is a rare feat
508	OS-specific backends (I vastly prefer correctness over speed hacks).	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
509		608
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	610	C<EVBACKEND_POLL>.
512		611
513	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
514		613
515	Try all backends (even potentially broken ones that wouldn't be tried	614	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	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		617
519	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
520		627
521	=back	628	=back
522		629
523	If one or more of these are or'ed into the flags value, then only these	630	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	631	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.	632	here). If none are specified, all backends in C<ev_recommended_backends
526		633	()> 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		634
555	Example: Try to create a event loop that uses epoll and nothing else.	635	Example: Try to create a event loop that uses epoll and nothing else.
556		636
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	638	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
560		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
561	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
562		647
563	Destroys the default loop again (frees all memory and kernel state	648	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	649	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	650	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>	651	responsibility to either stop all watchers cleanly yourself I<before>
567	calling this function, or cope with the fact afterwards (which is usually	652	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	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
570		655
571	Note that certain global state, such as signal state (and installed signal	656	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	657	handlers), will not be freed by this function, and related watchers (such
573	as signal and child watchers) would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
574		659
575	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
576	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	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	666	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>).	667	and C<ev_loop_destroy>.
579		668
580	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
581		670
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	671	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	672	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	673	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	674	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	675	child before resuming or calling C<ev_run>.
592	functions, and it will only take effect at the next C<ev_loop> iteration.	676
		677	Again, you I<have> to call it on I<any> loop that you want to re-use after
		678	a fork, I<even if you do not plan to use the loop in the parent>. This is
		679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		680	during fork.
593		681
594	On the other hand, you only need to call this function in the child	682	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	683	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.	684	you just fork+exec or create a new loop in the child, you don't have to
		685	call it at all (in fact, C<epoll> is so badly broken that it makes a
		686	difference, but libev will usually detect this case on its own and do a
		687	costly reset of the backend).
597		688
598	The function itself is quite fast and it's usually not a problem to call	689	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	690	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
602	pthread_atfork (0, 0, ev_default_fork);	702	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		703
611	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
612		705
613	Returns true when the given loop is, in fact, the default loop, and false	706	Returns true when the given loop is, in fact, the default loop, and false
614	otherwise.	707	otherwise.
615		708
616	=item unsigned int ev_loop_count (loop)	709	=item unsigned int ev_iteration (loop)
617		710
618	Returns the count of loop iterations for the loop, which is identical to	711	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	712	to the number of times libev did poll for new events. It starts at C<0>
620	happily wraps around with enough iterations.	713	and happily wraps around with enough iterations.
621		714
622	This value can sometimes be useful as a generation counter of sorts (it	715	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	716	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	717	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		718	prepare and check phases.
		719
		720	=item unsigned int ev_depth (loop)
		721
		722	Returns the number of times C<ev_run> was entered minus the number of
		723	times C<ev_run> was exited normally, in other words, the recursion depth.
		724
		725	Outside C<ev_run>, this number is zero. In a callback, this number is
		726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		727	in which case it is higher.
		728
		729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		730	throwing an exception etc.), doesn't count as "exit" - consider this
		731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
625		733
626	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
627		735
628	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
629	use.	737	use.
…		…
638		746
639	=item ev_now_update (loop)	747	=item ev_now_update (loop)
640		748
641	Establishes the current time by querying the kernel, updating the time	749	Establishes the current time by querying the kernel, updating the time
642	returned by C<ev_now ()> in the progress. This is a costly operation and	750	returned by C<ev_now ()> in the progress. This is a costly operation and
643	is usually done automatically within C<ev_loop ()>.	751	is usually done automatically within C<ev_run ()>.
644		752
645	This function is rarely useful, but when some event callback runs for a	753	This function is rarely useful, but when some event callback runs for a
646	very long time without entering the event loop, updating libev's idea of	754	very long time without entering the event loop, updating libev's idea of
647	the current time is a good idea.	755	the current time is a good idea.
648		756
…		…
650		758
651	=item ev_suspend (loop)	759	=item ev_suspend (loop)
652		760
653	=item ev_resume (loop)	761	=item ev_resume (loop)
654		762
655	These two functions suspend and resume a loop, for use when the loop is	763	These two functions suspend and resume an event loop, for use when the
656	not used for a while and timeouts should not be processed.	764	loop is not used for a while and timeouts should not be processed.
657		765
658	A typical use case would be an interactive program such as a game: When	766	A typical use case would be an interactive program such as a game: When
659	the user presses C<^Z> to suspend the game and resumes it an hour later it	767	the user presses C<^Z> to suspend the game and resumes it an hour later it
660	would be best to handle timeouts as if no time had actually passed while	768	would be best to handle timeouts as if no time had actually passed while
661	the program was suspended. This can be achieved by calling C<ev_suspend>	769	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
663	C<ev_resume> directly afterwards to resume timer processing.	771	C<ev_resume> directly afterwards to resume timer processing.
664		772
665	Effectively, all C<ev_timer> watchers will be delayed by the time spend	773	Effectively, all C<ev_timer> watchers will be delayed by the time spend
666	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	774	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
667	will be rescheduled (that is, they will lose any events that would have	775	will be rescheduled (that is, they will lose any events that would have
668	occured while suspended).	776	occurred while suspended).
669		777
670	After calling C<ev_suspend> you B<must not> call I<any> function on the	778	After calling C<ev_suspend> you B<must not> call I<any> function on the
671	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	779	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
672	without a previous call to C<ev_suspend>.	780	without a previous call to C<ev_suspend>.
673		781
674	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
675	event loop time (see C<ev_now_update>).	783	event loop time (see C<ev_now_update>).
676		784
677	=item ev_loop (loop, int flags)	785	=item ev_run (loop, int flags)
678		786
679	Finally, this is it, the event handler. This function usually is called	787	Finally, this is it, the event handler. This function usually is called
680	after you initialised all your watchers and you want to start handling	788	after you have initialised all your watchers and you want to start
681	events.	789	handling events. It will ask the operating system for any new events, call
		790	the watcher callbacks, an then repeat the whole process indefinitely: This
		791	is why event loops are called I<loops>.
682		792
683	If the flags argument is specified as C<0>, it will not return until	793	If the flags argument is specified as C<0>, it will keep handling events
684	either no event watchers are active anymore or C<ev_unloop> was called.	794	until either no event watchers are active anymore or C<ev_break> was
		795	called.
685		796
686	Please note that an explicit C<ev_unloop> is usually better than	797	Please note that an explicit C<ev_break> is usually better than
687	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
688	finished (especially in interactive programs), but having a program	799	finished (especially in interactive programs), but having a program
689	that automatically loops as long as it has to and no longer by virtue	800	that automatically loops as long as it has to and no longer by virtue
690	of relying on its watchers stopping correctly, that is truly a thing of	801	of relying on its watchers stopping correctly, that is truly a thing of
691	beauty.	802	beauty.
692		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
		808
693	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
694	those events and any already outstanding ones, but will not block your	810	those events and any already outstanding ones, but will not wait and
695	process in case there are no events and will return after one iteration of	811	block your process in case there are no events and will return after one
696	the loop.	812	iteration of the loop. This is sometimes useful to poll and handle new
		813	events while doing lengthy calculations, to keep the program responsive.
697		814
698	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	815	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
699	necessary) and will handle those and any already outstanding ones. It	816	necessary) and will handle those and any already outstanding ones. It
700	will block your process until at least one new event arrives (which could	817	will block your process until at least one new event arrives (which could
701	be an event internal to libev itself, so there is no guarantee that a	818	be an event internal to libev itself, so there is no guarantee that a
702	user-registered callback will be called), and will return after one	819	user-registered callback will be called), and will return after one
703	iteration of the loop.	820	iteration of the loop.
704		821
705	This is useful if you are waiting for some external event in conjunction	822	This is useful if you are waiting for some external event in conjunction
706	with something not expressible using other libev watchers (i.e. "roll your	823	with something not expressible using other libev watchers (i.e. "roll your
707	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
708	usually a better approach for this kind of thing.	825	usually a better approach for this kind of thing.
709		826
710	Here are the gory details of what C<ev_loop> does:	827	Here are the gory details of what C<ev_run> does:
711		828
		829	- Increment loop depth.
		830	- Reset the ev_break status.
712	- Before the first iteration, call any pending watchers.	831	- Before the first iteration, call any pending watchers.
		832	LOOP:
713	* If EVFLAG_FORKCHECK was used, check for a fork.	833	- If EVFLAG_FORKCHECK was used, check for a fork.
714	- If a fork was detected (by any means), queue and call all fork watchers.	834	- If a fork was detected (by any means), queue and call all fork watchers.
715	- Queue and call all prepare watchers.	835	- Queue and call all prepare watchers.
		836	- If ev_break was called, goto FINISH.
716	- If we have been forked, detach and recreate the kernel state	837	- If we have been forked, detach and recreate the kernel state
717	as to not disturb the other process.	838	as to not disturb the other process.
718	- Update the kernel state with all outstanding changes.	839	- Update the kernel state with all outstanding changes.
719	- Update the "event loop time" (ev_now ()).	840	- Update the "event loop time" (ev_now ()).
720	- Calculate for how long to sleep or block, if at all	841	- Calculate for how long to sleep or block, if at all
721	(active idle watchers, EVLOOP_NONBLOCK or not having	842	(active idle watchers, EVRUN_NOWAIT or not having
722	any active watchers at all will result in not sleeping).	843	any active watchers at all will result in not sleeping).
723	- Sleep if the I/O and timer collect interval say so.	844	- Sleep if the I/O and timer collect interval say so.
		845	- Increment loop iteration counter.
724	- Block the process, waiting for any events.	846	- Block the process, waiting for any events.
725	- Queue all outstanding I/O (fd) events.	847	- Queue all outstanding I/O (fd) events.
726	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	848	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
727	- Queue all expired timers.	849	- Queue all expired timers.
728	- Queue all expired periodics.	850	- Queue all expired periodics.
729	- Unless any events are pending now, queue all idle watchers.	851	- Queue all idle watchers with priority higher than that of pending events.
730	- Queue all check watchers.	852	- Queue all check watchers.
731	- Call all queued watchers in reverse order (i.e. check watchers first).	853	- Call all queued watchers in reverse order (i.e. check watchers first).
732	Signals and child watchers are implemented as I/O watchers, and will	854	Signals and child watchers are implemented as I/O watchers, and will
733	be handled here by queueing them when their watcher gets executed.	855	be handled here by queueing them when their watcher gets executed.
734	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	856	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
735	were used, or there are no active watchers, return, otherwise	857	were used, or there are no active watchers, goto FINISH, otherwise
736	continue with step *.	858	continue with step LOOP.
		859	FINISH:
		860	- Reset the ev_break status iff it was EVBREAK_ONE.
		861	- Decrement the loop depth.
		862	- Return.
737		863
738	Example: Queue some jobs and then loop until no events are outstanding	864	Example: Queue some jobs and then loop until no events are outstanding
739	anymore.	865	anymore.
740		866
741	... queue jobs here, make sure they register event watchers as long	867	... queue jobs here, make sure they register event watchers as long
742	... as they still have work to do (even an idle watcher will do..)	868	... as they still have work to do (even an idle watcher will do..)
743	ev_loop (my_loop, 0);	869	ev_run (my_loop, 0);
744	... jobs done or somebody called unloop. yeah!	870	... jobs done or somebody called unloop. yeah!
745		871
746	=item ev_unloop (loop, how)	872	=item ev_break (loop, how)
747		873
748	Can be used to make a call to C<ev_loop> return early (but only after it	874	Can be used to make a call to C<ev_run> return early (but only after it
749	has processed all outstanding events). The C<how> argument must be either	875	has processed all outstanding events). The C<how> argument must be either
750	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	876	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
751	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
752		878
753	This "unloop state" will be cleared when entering C<ev_loop> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
754		880
755	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
756		883
757	=item ev_ref (loop)	884	=item ev_ref (loop)
758		885
759	=item ev_unref (loop)	886	=item ev_unref (loop)
760		887
761	Ref/unref can be used to add or remove a reference count on the event	888	Ref/unref can be used to add or remove a reference count on the event
762	loop: Every watcher keeps one reference, and as long as the reference	889	loop: Every watcher keeps one reference, and as long as the reference
763	count is nonzero, C<ev_loop> will not return on its own.	890	count is nonzero, C<ev_run> will not return on its own.
764		891
765	If you have a watcher you never unregister that should not keep C<ev_loop>	892	This is useful when you have a watcher that you never intend to
766	from returning, call ev_unref() after starting, and ev_ref() before	893	unregister, but that nevertheless should not keep C<ev_run> from
		894	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
767	stopping it.	895	before stopping it.
768		896
769	As an example, libev itself uses this for its internal signal pipe: It	897	As an example, libev itself uses this for its internal signal pipe: It
770	is not visible to the libev user and should not keep C<ev_loop> from	898	is not visible to the libev user and should not keep C<ev_run> from
771	exiting if no event watchers registered by it are active. It is also an	899	exiting if no event watchers registered by it are active. It is also an
772	excellent way to do this for generic recurring timers or from within	900	excellent way to do this for generic recurring timers or from within
773	third-party libraries. Just remember to I<unref after start> and I<ref	901	third-party libraries. Just remember to I<unref after start> and I<ref
774	before stop> (but only if the watcher wasn't active before, or was active	902	before stop> (but only if the watcher wasn't active before, or was active
775	before, respectively. Note also that libev might stop watchers itself	903	before, respectively. Note also that libev might stop watchers itself
776	(e.g. non-repeating timers) in which case you have to C<ev_ref>	904	(e.g. non-repeating timers) in which case you have to C<ev_ref>
777	in the callback).	905	in the callback).
778		906
779	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	907	Example: Create a signal watcher, but keep it from keeping C<ev_run>
780	running when nothing else is active.	908	running when nothing else is active.
781		909
782	ev_signal exitsig;	910	ev_signal exitsig;
783	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
784	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
785	evf_unref (loop);	913	ev_unref (loop);
786		914
787	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
788		916
789	ev_ref (loop);	917	ev_ref (loop);
790	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
…		…
829	usually doesn't make much sense to set it to a lower value than C<0.01>,	957	usually doesn't make much sense to set it to a lower value than C<0.01>,
830	as this approaches the timing granularity of most systems. Note that if	958	as this approaches the timing granularity of most systems. Note that if
831	you do transactions with the outside world and you can't increase the	959	you do transactions with the outside world and you can't increase the
832	parallelity, then this setting will limit your transaction rate (if you	960	parallelity, then this setting will limit your transaction rate (if you
833	need to poll once per transaction and the I/O collect interval is 0.01,	961	need to poll once per transaction and the I/O collect interval is 0.01,
834	then you can't do more than 100 transations per second).	962	then you can't do more than 100 transactions per second).
835		963
836	Setting the I<timeout collect interval> can improve the opportunity for	964	Setting the I<timeout collect interval> can improve the opportunity for
837	saving power, as the program will "bundle" timer callback invocations that	965	saving power, as the program will "bundle" timer callback invocations that
838	are "near" in time together, by delaying some, thus reducing the number of	966	are "near" in time together, by delaying some, thus reducing the number of
839	times the process sleeps and wakes up again. Another useful technique to	967	times the process sleeps and wakes up again. Another useful technique to
…		…
844	more often than 100 times per second:	972	more often than 100 times per second:
845		973
846	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	974	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
847	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	975	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
848		976
		977	=item ev_invoke_pending (loop)
		978
		979	This call will simply invoke all pending watchers while resetting their
		980	pending state. Normally, C<ev_run> does this automatically when required,
		981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		986
		987	=item int ev_pending_count (loop)
		988
		989	Returns the number of pending watchers - zero indicates that no watchers
		990	are pending.
		991
		992	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		993
		994	This overrides the invoke pending functionality of the loop: Instead of
		995	invoking all pending watchers when there are any, C<ev_run> will call
		996	this callback instead. This is useful, for example, when you want to
		997	invoke the actual watchers inside another context (another thread etc.).
		998
		999	If you want to reset the callback, use C<ev_invoke_pending> as new
		1000	callback.
		1001
		1002	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1003
		1004	Sometimes you want to share the same loop between multiple threads. This
		1005	can be done relatively simply by putting mutex_lock/unlock calls around
		1006	each call to a libev function.
		1007
		1008	However, C<ev_run> can run an indefinite time, so it is not feasible
		1009	to wait for it to return. One way around this is to wake up the event
		1010	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1011	I<release> and I<acquire> callbacks on the loop.
		1012
		1013	When set, then C<release> will be called just before the thread is
		1014	suspended waiting for new events, and C<acquire> is called just
		1015	afterwards.
		1016
		1017	Ideally, C<release> will just call your mutex_unlock function, and
		1018	C<acquire> will just call the mutex_lock function again.
		1019
		1020	While event loop modifications are allowed between invocations of
		1021	C<release> and C<acquire> (that's their only purpose after all), no
		1022	modifications done will affect the event loop, i.e. adding watchers will
		1023	have no effect on the set of file descriptors being watched, or the time
		1024	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1025	to take note of any changes you made.
		1026
		1027	In theory, threads executing C<ev_run> will be async-cancel safe between
		1028	invocations of C<release> and C<acquire>.
		1029
		1030	See also the locking example in the C<THREADS> section later in this
		1031	document.
		1032
		1033	=item ev_set_userdata (loop, void *data)
		1034
		1035	=item void *ev_userdata (loop)
		1036
		1037	Set and retrieve a single C<void *> associated with a loop. When
		1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1039	C<0>.
		1040
		1041	These two functions can be used to associate arbitrary data with a loop,
		1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1043	C<acquire> callbacks described above, but of course can be (ab-)used for
		1044	any other purpose as well.
		1045
849	=item ev_loop_verify (loop)	1046	=item ev_verify (loop)
850		1047
851	This function only does something when C<EV_VERIFY> support has been	1048	This function only does something when C<EV_VERIFY> support has been
852	compiled in, which is the default for non-minimal builds. It tries to go	1049	compiled in, which is the default for non-minimal builds. It tries to go
853	through all internal structures and checks them for validity. If anything	1050	through all internal structures and checks them for validity. If anything
854	is found to be inconsistent, it will print an error message to standard	1051	is found to be inconsistent, it will print an error message to standard
…		…
865		1062
866	In the following description, uppercase C<TYPE> in names stands for the	1063	In the following description, uppercase C<TYPE> in names stands for the
867	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1064	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
868	watchers and C<ev_io_start> for I/O watchers.	1065	watchers and C<ev_io_start> for I/O watchers.
869		1066
870	A watcher is a structure that you create and register to record your	1067	A watcher is an opaque structure that you allocate and register to record
871	interest in some event. For instance, if you want to wait for STDIN to	1068	your interest in some event. To make a concrete example, imagine you want
872	become readable, you would create an C<ev_io> watcher for that:	1069	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1070	for that:
873		1071
874	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1072	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
875	{	1073	{
876	ev_io_stop (w);	1074	ev_io_stop (w);
877	ev_unloop (loop, EVUNLOOP_ALL);	1075	ev_break (loop, EVBREAK_ALL);
878	}	1076	}
879		1077
880	struct ev_loop *loop = ev_default_loop (0);	1078	struct ev_loop *loop = ev_default_loop (0);
881		1079
882	ev_io stdin_watcher;	1080	ev_io stdin_watcher;
883		1081
884	ev_init (&stdin_watcher, my_cb);	1082	ev_init (&stdin_watcher, my_cb);
885	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1083	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
886	ev_io_start (loop, &stdin_watcher);	1084	ev_io_start (loop, &stdin_watcher);
887		1085
888	ev_loop (loop, 0);	1086	ev_run (loop, 0);
889		1087
890	As you can see, you are responsible for allocating the memory for your	1088	As you can see, you are responsible for allocating the memory for your
891	watcher structures (and it is I<usually> a bad idea to do this on the	1089	watcher structures (and it is I<usually> a bad idea to do this on the
892	stack).	1090	stack).
893		1091
894	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1092	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
895	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1093	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
896		1094
897	Each watcher structure must be initialised by a call to C<ev_init	1095	Each watcher structure must be initialised by a call to C<ev_init (watcher
898	(watcher *, callback)>, which expects a callback to be provided. This	1096	*, callback)>, which expects a callback to be provided. This callback is
899	callback gets invoked each time the event occurs (or, in the case of I/O	1097	invoked each time the event occurs (or, in the case of I/O watchers, each
900	watchers, each time the event loop detects that the file descriptor given	1098	time the event loop detects that the file descriptor given is readable
901	is readable and/or writable).	1099	and/or writable).
902		1100
903	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1101	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
904	macro to configure it, with arguments specific to the watcher type. There	1102	macro to configure it, with arguments specific to the watcher type. There
905	is also a macro to combine initialisation and setting in one call: C<<	1103	is also a macro to combine initialisation and setting in one call: C<<
906	ev_TYPE_init (watcher *, callback, ...) >>.	1104	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
929	=item C<EV_WRITE>	1127	=item C<EV_WRITE>
930		1128
931	The file descriptor in the C<ev_io> watcher has become readable and/or	1129	The file descriptor in the C<ev_io> watcher has become readable and/or
932	writable.	1130	writable.
933		1131
934	=item C<EV_TIMEOUT>	1132	=item C<EV_TIMER>
935		1133
936	The C<ev_timer> watcher has timed out.	1134	The C<ev_timer> watcher has timed out.
937		1135
938	=item C<EV_PERIODIC>	1136	=item C<EV_PERIODIC>
939		1137
…		…
957		1155
958	=item C<EV_PREPARE>	1156	=item C<EV_PREPARE>
959		1157
960	=item C<EV_CHECK>	1158	=item C<EV_CHECK>
961		1159
962	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
963	to gather new events, and all C<ev_check> watchers are invoked just after	1161	to gather new events, and all C<ev_check> watchers are invoked just after
964	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1162	C<ev_run> has gathered them, but before it invokes any callbacks for any
965	received events. Callbacks of both watcher types can start and stop as	1163	received events. Callbacks of both watcher types can start and stop as
966	many watchers as they want, and all of them will be taken into account	1164	many watchers as they want, and all of them will be taken into account
967	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
968	C<ev_loop> from blocking).	1166	C<ev_run> from blocking).
969		1167
970	=item C<EV_EMBED>	1168	=item C<EV_EMBED>
971		1169
972	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.
973		1171
974	=item C<EV_FORK>	1172	=item C<EV_FORK>
975		1173
976	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
977	C<ev_fork>).	1175	C<ev_fork>).
		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
978		1180
979	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
980		1182
981	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
982		1184
…		…
1029		1231
1030	ev_io w;	1232	ev_io w;
1031	ev_init (&w, my_cb);	1233	ev_init (&w, my_cb);
1032	ev_io_set (&w, STDIN_FILENO, EV_READ);	1234	ev_io_set (&w, STDIN_FILENO, EV_READ);
1033		1235
1034	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1236	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1035		1237
1036	This macro initialises the type-specific parts of a watcher. You need to	1238	This macro initialises the type-specific parts of a watcher. You need to
1037	call C<ev_init> at least once before you call this macro, but you can	1239	call C<ev_init> at least once before you call this macro, but you can
1038	call C<ev_TYPE_set> any number of times. You must not, however, call this	1240	call C<ev_TYPE_set> any number of times. You must not, however, call this
1039	macro on a watcher that is active (it can be pending, however, which is a	1241	macro on a watcher that is active (it can be pending, however, which is a
…		…
1052		1254
1053	Example: Initialise and set an C<ev_io> watcher in one step.	1255	Example: Initialise and set an C<ev_io> watcher in one step.
1054		1256
1055	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1257	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1056		1258
1057	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1259	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1058		1260
1059	Starts (activates) the given watcher. Only active watchers will receive	1261	Starts (activates) the given watcher. Only active watchers will receive
1060	events. If the watcher is already active nothing will happen.	1262	events. If the watcher is already active nothing will happen.
1061		1263
1062	Example: Start the C<ev_io> watcher that is being abused as example in this	1264	Example: Start the C<ev_io> watcher that is being abused as example in this
1063	whole section.	1265	whole section.
1064		1266
1065	ev_io_start (EV_DEFAULT_UC, &w);	1267	ev_io_start (EV_DEFAULT_UC, &w);
1066		1268
1067	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1269	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1068		1270
1069	Stops the given watcher if active, and clears the pending status (whether	1271	Stops the given watcher if active, and clears the pending status (whether
1070	the watcher was active or not).	1272	the watcher was active or not).
1071		1273
1072	It is possible that stopped watchers are pending - for example,	1274	It is possible that stopped watchers are pending - for example,
…		…
1097	=item ev_cb_set (ev_TYPE *watcher, callback)	1299	=item ev_cb_set (ev_TYPE *watcher, callback)
1098		1300
1099	Change the callback. You can change the callback at virtually any time	1301	Change the callback. You can change the callback at virtually any time
1100	(modulo threads).	1302	(modulo threads).
1101		1303
1102	=item ev_set_priority (ev_TYPE *watcher, priority)	1304	=item ev_set_priority (ev_TYPE *watcher, int priority)
1103		1305
1104	=item int ev_priority (ev_TYPE *watcher)	1306	=item int ev_priority (ev_TYPE *watcher)
1105		1307
1106	Set and query the priority of the watcher. The priority is a small	1308	Set and query the priority of the watcher. The priority is a small
1107	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1309	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1139	watcher isn't pending it does nothing and returns C<0>.	1341	watcher isn't pending it does nothing and returns C<0>.
1140		1342
1141	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1343	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1142	callback to be invoked, which can be accomplished with this function.	1344	callback to be invoked, which can be accomplished with this function.
1143		1345
		1346	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1347
		1348	Feeds the given event set into the event loop, as if the specified event
		1349	had happened for the specified watcher (which must be a pointer to an
		1350	initialised but not necessarily started event watcher). Obviously you must
		1351	not free the watcher as long as it has pending events.
		1352
		1353	Stopping the watcher, letting libev invoke it, or calling
		1354	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1355	not started in the first place.
		1356
		1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1358	functions that do not need a watcher.
		1359
1144	=back	1360	=back
1145
1146		1361
1147	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1148		1363
1149	Each watcher has, by default, a member C<void *data> that you can change	1364	Each watcher has, by default, a member C<void *data> that you can change
1150	and read at any time: libev will completely ignore it. This can be used	1365	and read at any time: libev will completely ignore it. This can be used
…		…
1206	t2_cb (EV_P_ ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
1207	{	1422	{
1208	struct my_biggy big = (struct my_biggy *)	1423	struct my_biggy big = (struct my_biggy *)
1209	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
1210	}	1425	}
		1426
		1427	=head2 WATCHER STATES
		1428
		1429	There are various watcher states mentioned throughout this manual -
		1430	active, pending and so on. In this section these states and the rules to
		1431	transition between them will be described in more detail - and while these
		1432	rules might look complicated, they usually do "the right thing".
		1433
		1434	=over 4
		1435
		1436	=item initialiased
		1437
		1438	Before a watcher can be registered with the event looop it has to be
		1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1441
		1442	In this state it is simply some block of memory that is suitable for use
		1443	in an event loop. It can be moved around, freed, reused etc. at will.
		1444
		1445	=item started/running/active
		1446
		1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1448	property of the event loop, and is actively waiting for events. While in
		1449	this state it cannot be accessed (except in a few documented ways), moved,
		1450	freed or anything else - the only legal thing is to keep a pointer to it,
		1451	and call libev functions on it that are documented to work on active watchers.
		1452
		1453	=item pending
		1454
		1455	If a watcher is active and libev determines that an event it is interested
		1456	in has occurred (such as a timer expiring), it will become pending. It will
		1457	stay in this pending state until either it is stopped or its callback is
		1458	about to be invoked, so it is not normally pending inside the watcher
		1459	callback.
		1460
		1461	The watcher might or might not be active while it is pending (for example,
		1462	an expired non-repeating timer can be pending but no longer active). If it
		1463	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1464	but it is still property of the event loop at this time, so cannot be
		1465	moved, freed or reused. And if it is active the rules described in the
		1466	previous item still apply.
		1467
		1468	It is also possible to feed an event on a watcher that is not active (e.g.
		1469	via C<ev_feed_event>), in which case it becomes pending without being
		1470	active.
		1471
		1472	=item stopped
		1473
		1474	A watcher can be stopped implicitly by libev (in which case it might still
		1475	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1476	latter will clear any pending state the watcher might be in, regardless
		1477	of whether it was active or not, so stopping a watcher explicitly before
		1478	freeing it is often a good idea.
		1479
		1480	While stopped (and not pending) the watcher is essentially in the
		1481	initialised state, that is it can be reused, moved, modified in any way
		1482	you wish.
		1483
		1484	=back
1211		1485
1212	=head2 WATCHER PRIORITY MODELS	1486	=head2 WATCHER PRIORITY MODELS
1213		1487
1214	Many event loops support I<watcher priorities>, which are usually small	1488	Many event loops support I<watcher priorities>, which are usually small
1215	integers that influence the ordering of event callback invocation	1489	integers that influence the ordering of event callback invocation
…		…
1258		1532
1259	For example, to emulate how many other event libraries handle priorities,	1533	For example, to emulate how many other event libraries handle priorities,
1260	you can associate an C<ev_idle> watcher to each such watcher, and in	1534	you can associate an C<ev_idle> watcher to each such watcher, and in
1261	the normal watcher callback, you just start the idle watcher. The real	1535	the normal watcher callback, you just start the idle watcher. The real
1262	processing is done in the idle watcher callback. This causes libev to	1536	processing is done in the idle watcher callback. This causes libev to
1263	continously poll and process kernel event data for the watcher, but when	1537	continuously poll and process kernel event data for the watcher, but when
1264	the lock-out case is known to be rare (which in turn is rare :), this is	1538	the lock-out case is known to be rare (which in turn is rare :), this is
1265	workable.	1539	workable.
1266		1540
1267	Usually, however, the lock-out model implemented that way will perform	1541	Usually, however, the lock-out model implemented that way will perform
1268	miserably under the type of load it was designed to handle. In that case,	1542	miserably under the type of load it was designed to handle. In that case,
…		…
1282	{	1556	{
1283	// stop the I/O watcher, we received the event, but	1557	// stop the I/O watcher, we received the event, but
1284	// are not yet ready to handle it.	1558	// are not yet ready to handle it.
1285	ev_io_stop (EV_A_ w);	1559	ev_io_stop (EV_A_ w);
1286		1560
1287	// start the idle watcher to ahndle the actual event.	1561	// start the idle watcher to handle the actual event.
1288	// it will not be executed as long as other watchers	1562	// it will not be executed as long as other watchers
1289	// with the default priority are receiving events.	1563	// with the default priority are receiving events.
1290	ev_idle_start (EV_A_ &idle);	1564	ev_idle_start (EV_A_ &idle);
1291	}	1565	}
1292		1566
…		…
1342	In general you can register as many read and/or write event watchers per	1616	In general you can register as many read and/or write event watchers per
1343	fd as you want (as long as you don't confuse yourself). Setting all file	1617	fd as you want (as long as you don't confuse yourself). Setting all file
1344	descriptors to non-blocking mode is also usually a good idea (but not	1618	descriptors to non-blocking mode is also usually a good idea (but not
1345	required if you know what you are doing).	1619	required if you know what you are doing).
1346		1620
1347	If you cannot use non-blocking mode, then force the use of a
1348	known-to-be-good backend (at the time of this writing, this includes only
1349	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1350	descriptors for which non-blocking operation makes no sense (such as
1351	files) - libev doesn't guarentee any specific behaviour in that case.
1352
1353	Another thing you have to watch out for is that it is quite easy to	1621	Another thing you have to watch out for is that it is quite easy to
1354	receive "spurious" readiness notifications, that is your callback might	1622	receive "spurious" readiness notifications, that is, your callback might
1355	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1623	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1356	because there is no data. Not only are some backends known to create a	1624	because there is no data. It is very easy to get into this situation even
1357	lot of those (for example Solaris ports), it is very easy to get into	1625	with a relatively standard program structure. Thus it is best to always
1358	this situation even with a relatively standard program structure. Thus	1626	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1359	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1360	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1627	preferable to a program hanging until some data arrives.
1361		1628
1362	If you cannot run the fd in non-blocking mode (for example you should	1629	If you cannot run the fd in non-blocking mode (for example you should
1363	not play around with an Xlib connection), then you have to separately	1630	not play around with an Xlib connection), then you have to separately
1364	re-test whether a file descriptor is really ready with a known-to-be good	1631	re-test whether a file descriptor is really ready with a known-to-be good
1365	interface such as poll (fortunately in our Xlib example, Xlib already	1632	interface such as poll (fortunately in the case of Xlib, it already does
1366	does this on its own, so its quite safe to use). Some people additionally	1633	this on its own, so its quite safe to use). Some people additionally
1367	use C<SIGALRM> and an interval timer, just to be sure you won't block	1634	use C<SIGALRM> and an interval timer, just to be sure you won't block
1368	indefinitely.	1635	indefinitely.
1369		1636
1370	But really, best use non-blocking mode.	1637	But really, best use non-blocking mode.
1371		1638
…		…
1399		1666
1400	There is no workaround possible except not registering events	1667	There is no workaround possible except not registering events
1401	for potentially C<dup ()>'ed file descriptors, or to resort to	1668	for potentially C<dup ()>'ed file descriptors, or to resort to
1402	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1669	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1403		1670
		1671	=head3 The special problem of files
		1672
		1673	Many people try to use C<select> (or libev) on file descriptors
		1674	representing files, and expect it to become ready when their program
		1675	doesn't block on disk accesses (which can take a long time on their own).
		1676
		1677	However, this cannot ever work in the "expected" way - you get a readiness
		1678	notification as soon as the kernel knows whether and how much data is
		1679	there, and in the case of open files, that's always the case, so you
		1680	always get a readiness notification instantly, and your read (or possibly
		1681	write) will still block on the disk I/O.
		1682
		1683	Another way to view it is that in the case of sockets, pipes, character
		1684	devices and so on, there is another party (the sender) that delivers data
		1685	on it's own, but in the case of files, there is no such thing: the disk
		1686	will not send data on it's own, simply because it doesn't know what you
		1687	wish to read - you would first have to request some data.
		1688
		1689	Since files are typically not-so-well supported by advanced notification
		1690	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1691	to files, even though you should not use it. The reason for this is
		1692	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1693	usually a tty, often a pipe, but also sometimes files or special devices
		1694	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1695	F</dev/urandom>), and even though the file might better be served with
		1696	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1697	it "just works" instead of freezing.
		1698
		1699	So avoid file descriptors pointing to files when you know it (e.g. use
		1700	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1701	when you rarely read from a file instead of from a socket, and want to
		1702	reuse the same code path.
		1703
1404	=head3 The special problem of fork	1704	=head3 The special problem of fork
1405		1705
1406	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1706	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1407	useless behaviour. Libev fully supports fork, but needs to be told about	1707	useless behaviour. Libev fully supports fork, but needs to be told about
1408	it in the child.	1708	it in the child if you want to continue to use it in the child.
1409		1709
1410	To support fork in your programs, you either have to call	1710	To support fork in your child processes, you have to call C<ev_loop_fork
1411	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1711	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1412	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1712	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1413	C<EVBACKEND_POLL>.
1414		1713
1415	=head3 The special problem of SIGPIPE	1714	=head3 The special problem of SIGPIPE
1416		1715
1417	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1716	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1418	when writing to a pipe whose other end has been closed, your program gets	1717	when writing to a pipe whose other end has been closed, your program gets
…		…
1421		1720
1422	So when you encounter spurious, unexplained daemon exits, make sure you	1721	So when you encounter spurious, unexplained daemon exits, make sure you
1423	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1722	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1424	somewhere, as that would have given you a big clue).	1723	somewhere, as that would have given you a big clue).
1425		1724
		1725	=head3 The special problem of accept()ing when you can't
		1726
		1727	Many implementations of the POSIX C<accept> function (for example,
		1728	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1729	connection from the pending queue in all error cases.
		1730
		1731	For example, larger servers often run out of file descriptors (because
		1732	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1733	rejecting the connection, leading to libev signalling readiness on
		1734	the next iteration again (the connection still exists after all), and
		1735	typically causing the program to loop at 100% CPU usage.
		1736
		1737	Unfortunately, the set of errors that cause this issue differs between
		1738	operating systems, there is usually little the app can do to remedy the
		1739	situation, and no known thread-safe method of removing the connection to
		1740	cope with overload is known (to me).
		1741
		1742	One of the easiest ways to handle this situation is to just ignore it
		1743	- when the program encounters an overload, it will just loop until the
		1744	situation is over. While this is a form of busy waiting, no OS offers an
		1745	event-based way to handle this situation, so it's the best one can do.
		1746
		1747	A better way to handle the situation is to log any errors other than
		1748	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1749	messages, and continue as usual, which at least gives the user an idea of
		1750	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1751	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1752	usage.
		1753
		1754	If your program is single-threaded, then you could also keep a dummy file
		1755	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1756	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1757	close that fd, and create a new dummy fd. This will gracefully refuse
		1758	clients under typical overload conditions.
		1759
		1760	The last way to handle it is to simply log the error and C<exit>, as
		1761	is often done with C<malloc> failures, but this results in an easy
		1762	opportunity for a DoS attack.
1426		1763
1427	=head3 Watcher-Specific Functions	1764	=head3 Watcher-Specific Functions
1428		1765
1429	=over 4	1766	=over 4
1430		1767
…		…
1462	...	1799	...
1463	struct ev_loop *loop = ev_default_init (0);	1800	struct ev_loop *loop = ev_default_init (0);
1464	ev_io stdin_readable;	1801	ev_io stdin_readable;
1465	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1802	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1466	ev_io_start (loop, &stdin_readable);	1803	ev_io_start (loop, &stdin_readable);
1467	ev_loop (loop, 0);	1804	ev_run (loop, 0);
1468		1805
1469		1806
1470	=head2 C<ev_timer> - relative and optionally repeating timeouts	1807	=head2 C<ev_timer> - relative and optionally repeating timeouts
1471		1808
1472	Timer watchers are simple relative timers that generate an event after a	1809	Timer watchers are simple relative timers that generate an event after a
…		…
1480		1817
1481	The callback is guaranteed to be invoked only I<after> its timeout has	1818	The callback is guaranteed to be invoked only I<after> its timeout has
1482	passed (not I<at>, so on systems with very low-resolution clocks this	1819	passed (not I<at>, so on systems with very low-resolution clocks this
1483	might introduce a small delay). If multiple timers become ready during the	1820	might introduce a small delay). If multiple timers become ready during the
1484	same loop iteration then the ones with earlier time-out values are invoked	1821	same loop iteration then the ones with earlier time-out values are invoked
1485	before ones with later time-out values (but this is no longer true when a	1822	before ones of the same priority with later time-out values (but this is
1486	callback calls C<ev_loop> recursively).	1823	no longer true when a callback calls C<ev_run> recursively).
1487		1824
1488	=head3 Be smart about timeouts	1825	=head3 Be smart about timeouts
1489		1826
1490	Many real-world problems involve some kind of timeout, usually for error	1827	Many real-world problems involve some kind of timeout, usually for error
1491	recovery. A typical example is an HTTP request - if the other side hangs,	1828	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1577	ev_tstamp timeout = last_activity + 60.;	1914	ev_tstamp timeout = last_activity + 60.;
1578		1915
1579	// if last_activity + 60. is older than now, we did time out	1916	// if last_activity + 60. is older than now, we did time out
1580	if (timeout < now)	1917	if (timeout < now)
1581	{	1918	{
1582	// timeout occured, take action	1919	// timeout occurred, take action
1583	}	1920	}
1584	else	1921	else
1585	{	1922	{
1586	// callback was invoked, but there was some activity, re-arm	1923	// callback was invoked, but there was some activity, re-arm
1587	// the watcher to fire in last_activity + 60, which is	1924	// the watcher to fire in last_activity + 60, which is
…		…
1609	to the current time (meaning we just have some activity :), then call the	1946	to the current time (meaning we just have some activity :), then call the
1610	callback, which will "do the right thing" and start the timer:	1947	callback, which will "do the right thing" and start the timer:
1611		1948
1612	ev_init (timer, callback);	1949	ev_init (timer, callback);
1613	last_activity = ev_now (loop);	1950	last_activity = ev_now (loop);
1614	callback (loop, timer, EV_TIMEOUT);	1951	callback (loop, timer, EV_TIMER);
1615		1952
1616	And when there is some activity, simply store the current time in	1953	And when there is some activity, simply store the current time in
1617	C<last_activity>, no libev calls at all:	1954	C<last_activity>, no libev calls at all:
1618		1955
1619	last_actiivty = ev_now (loop);	1956	last_activity = ev_now (loop);
1620		1957
1621	This technique is slightly more complex, but in most cases where the	1958	This technique is slightly more complex, but in most cases where the
1622	time-out is unlikely to be triggered, much more efficient.	1959	time-out is unlikely to be triggered, much more efficient.
1623		1960
1624	Changing the timeout is trivial as well (if it isn't hard-coded in the	1961	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1662		1999
1663	=head3 The special problem of time updates	2000	=head3 The special problem of time updates
1664		2001
1665	Establishing the current time is a costly operation (it usually takes at	2002	Establishing the current time is a costly operation (it usually takes at
1666	least two system calls): EV therefore updates its idea of the current	2003	least two system calls): EV therefore updates its idea of the current
1667	time only before and after C<ev_loop> collects new events, which causes a	2004	time only before and after C<ev_run> collects new events, which causes a
1668	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2005	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1669	lots of events in one iteration.	2006	lots of events in one iteration.
1670		2007
1671	The relative timeouts are calculated relative to the C<ev_now ()>	2008	The relative timeouts are calculated relative to the C<ev_now ()>
1672	time. This is usually the right thing as this timestamp refers to the time	2009	time. This is usually the right thing as this timestamp refers to the time
…		…
1678		2015
1679	If the event loop is suspended for a long time, you can also force an	2016	If the event loop is suspended for a long time, you can also force an
1680	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2017	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1681	()>.	2018	()>.
1682		2019
		2020	=head3 The special problems of suspended animation
		2021
		2022	When you leave the server world it is quite customary to hit machines that
		2023	can suspend/hibernate - what happens to the clocks during such a suspend?
		2024
		2025	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2026	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2027	to run until the system is suspended, but they will not advance while the
		2028	system is suspended. That means, on resume, it will be as if the program
		2029	was frozen for a few seconds, but the suspend time will not be counted
		2030	towards C<ev_timer> when a monotonic clock source is used. The real time
		2031	clock advanced as expected, but if it is used as sole clocksource, then a
		2032	long suspend would be detected as a time jump by libev, and timers would
		2033	be adjusted accordingly.
		2034
		2035	I would not be surprised to see different behaviour in different between
		2036	operating systems, OS versions or even different hardware.
		2037
		2038	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2039	time jump in the monotonic clocks and the realtime clock. If the program
		2040	is suspended for a very long time, and monotonic clock sources are in use,
		2041	then you can expect C<ev_timer>s to expire as the full suspension time
		2042	will be counted towards the timers. When no monotonic clock source is in
		2043	use, then libev will again assume a timejump and adjust accordingly.
		2044
		2045	It might be beneficial for this latter case to call C<ev_suspend>
		2046	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2047	deterministic behaviour in this case (you can do nothing against
		2048	C<SIGSTOP>).
		2049
1683	=head3 Watcher-Specific Functions and Data Members	2050	=head3 Watcher-Specific Functions and Data Members
1684		2051
1685	=over 4	2052	=over 4
1686		2053
1687	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2054	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1713	C<repeat> value), or reset the running timer to the C<repeat> value.	2080	C<repeat> value), or reset the running timer to the C<repeat> value.
1714		2081
1715	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2082	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1716	usage example.	2083	usage example.
1717		2084
		2085	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2086
		2087	Returns the remaining time until a timer fires. If the timer is active,
		2088	then this time is relative to the current event loop time, otherwise it's
		2089	the timeout value currently configured.
		2090
		2091	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2092	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2093	will return C<4>. When the timer expires and is restarted, it will return
		2094	roughly C<7> (likely slightly less as callback invocation takes some time,
		2095	too), and so on.
		2096
1718	=item ev_tstamp repeat [read-write]	2097	=item ev_tstamp repeat [read-write]
1719		2098
1720	The current C<repeat> value. Will be used each time the watcher times out	2099	The current C<repeat> value. Will be used each time the watcher times out
1721	or C<ev_timer_again> is called, and determines the next timeout (if any),	2100	or C<ev_timer_again> is called, and determines the next timeout (if any),
1722	which is also when any modifications are taken into account.	2101	which is also when any modifications are taken into account.
…		…
1747	}	2126	}
1748		2127
1749	ev_timer mytimer;	2128	ev_timer mytimer;
1750	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2129	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1751	ev_timer_again (&mytimer); /* start timer */	2130	ev_timer_again (&mytimer); /* start timer */
1752	ev_loop (loop, 0);	2131	ev_run (loop, 0);
1753		2132
1754	// and in some piece of code that gets executed on any "activity":	2133	// and in some piece of code that gets executed on any "activity":
1755	// reset the timeout to start ticking again at 10 seconds	2134	// reset the timeout to start ticking again at 10 seconds
1756	ev_timer_again (&mytimer);	2135	ev_timer_again (&mytimer);
1757		2136
…		…
1783		2162
1784	As with timers, the callback is guaranteed to be invoked only when the	2163	As with timers, the callback is guaranteed to be invoked only when the
1785	point in time where it is supposed to trigger has passed. If multiple	2164	point in time where it is supposed to trigger has passed. If multiple
1786	timers become ready during the same loop iteration then the ones with	2165	timers become ready during the same loop iteration then the ones with
1787	earlier time-out values are invoked before ones with later time-out values	2166	earlier time-out values are invoked before ones with later time-out values
1788	(but this is no longer true when a callback calls C<ev_loop> recursively).	2167	(but this is no longer true when a callback calls C<ev_run> recursively).
1789		2168
1790	=head3 Watcher-Specific Functions and Data Members	2169	=head3 Watcher-Specific Functions and Data Members
1791		2170
1792	=over 4	2171	=over 4
1793		2172
…		…
1921	Example: Call a callback every hour, or, more precisely, whenever the	2300	Example: Call a callback every hour, or, more precisely, whenever the
1922	system time is divisible by 3600. The callback invocation times have	2301	system time is divisible by 3600. The callback invocation times have
1923	potentially a lot of jitter, but good long-term stability.	2302	potentially a lot of jitter, but good long-term stability.
1924		2303
1925	static void	2304	static void
1926	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2305	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1927	{	2306	{
1928	... its now a full hour (UTC, or TAI or whatever your clock follows)	2307	... its now a full hour (UTC, or TAI or whatever your clock follows)
1929	}	2308	}
1930		2309
1931	ev_periodic hourly_tick;	2310	ev_periodic hourly_tick;
…		…
1954		2333
1955	=head2 C<ev_signal> - signal me when a signal gets signalled!	2334	=head2 C<ev_signal> - signal me when a signal gets signalled!
1956		2335
1957	Signal watchers will trigger an event when the process receives a specific	2336	Signal watchers will trigger an event when the process receives a specific
1958	signal one or more times. Even though signals are very asynchronous, libev	2337	signal one or more times. Even though signals are very asynchronous, libev
1959	will try it's best to deliver signals synchronously, i.e. as part of the	2338	will try its best to deliver signals synchronously, i.e. as part of the
1960	normal event processing, like any other event.	2339	normal event processing, like any other event.
1961		2340
1962	If you want signals asynchronously, just use C<sigaction> as you would	2341	If you want signals to be delivered truly asynchronously, just use
1963	do without libev and forget about sharing the signal. You can even use	2342	C<sigaction> as you would do without libev and forget about sharing
1964	C<ev_async> from a signal handler to synchronously wake up an event loop.	2343	the signal. You can even use C<ev_async> from a signal handler to
		2344	synchronously wake up an event loop.
1965		2345
1966	You can configure as many watchers as you like per signal. Only when the	2346	You can configure as many watchers as you like for the same signal, but
		2347	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2348	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2349	C<SIGINT> in both the default loop and another loop at the same time. At
		2350	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2351
1967	first watcher gets started will libev actually register a signal handler	2352	When the first watcher gets started will libev actually register something
1968	with the kernel (thus it coexists with your own signal handlers as long as	2353	with the kernel (thus it coexists with your own signal handlers as long as
1969	you don't register any with libev for the same signal). Similarly, when	2354	you don't register any with libev for the same signal).
1970	the last signal watcher for a signal is stopped, libev will reset the
1971	signal handler to SIG_DFL (regardless of what it was set to before).
1972		2355
1973	If possible and supported, libev will install its handlers with	2356	If possible and supported, libev will install its handlers with
1974	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2357	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1975	interrupted. If you have a problem with system calls getting interrupted by	2358	not be unduly interrupted. If you have a problem with system calls getting
1976	signals you can block all signals in an C<ev_check> watcher and unblock	2359	interrupted by signals you can block all signals in an C<ev_check> watcher
1977	them in an C<ev_prepare> watcher.	2360	and unblock them in an C<ev_prepare> watcher.
		2361
		2362	=head3 The special problem of inheritance over fork/execve/pthread_create
		2363
		2364	Both the signal mask (C<sigprocmask>) and the signal disposition
		2365	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2366	stopping it again), that is, libev might or might not block the signal,
		2367	and might or might not set or restore the installed signal handler.
		2368
		2369	While this does not matter for the signal disposition (libev never
		2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2371	C<execve>), this matters for the signal mask: many programs do not expect
		2372	certain signals to be blocked.
		2373
		2374	This means that before calling C<exec> (from the child) you should reset
		2375	the signal mask to whatever "default" you expect (all clear is a good
		2376	choice usually).
		2377
		2378	The simplest way to ensure that the signal mask is reset in the child is
		2379	to install a fork handler with C<pthread_atfork> that resets it. That will
		2380	catch fork calls done by libraries (such as the libc) as well.
		2381
		2382	In current versions of libev, the signal will not be blocked indefinitely
		2383	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2384	the window of opportunity for problems, it will not go away, as libev
		2385	I<has> to modify the signal mask, at least temporarily.
		2386
		2387	So I can't stress this enough: I<If you do not reset your signal mask when
		2388	you expect it to be empty, you have a race condition in your code>. This
		2389	is not a libev-specific thing, this is true for most event libraries.
		2390
		2391	=head3 The special problem of threads signal handling
		2392
		2393	POSIX threads has problematic signal handling semantics, specifically,
		2394	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2395	threads in a process block signals, which is hard to achieve.
		2396
		2397	When you want to use sigwait (or mix libev signal handling with your own
		2398	for the same signals), you can tackle this problem by globally blocking
		2399	all signals before creating any threads (or creating them with a fully set
		2400	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2401	loops. Then designate one thread as "signal receiver thread" which handles
		2402	these signals. You can pass on any signals that libev might be interested
		2403	in by calling C<ev_feed_signal>.
1978		2404
1979	=head3 Watcher-Specific Functions and Data Members	2405	=head3 Watcher-Specific Functions and Data Members
1980		2406
1981	=over 4	2407	=over 4
1982		2408
…		…
1998	Example: Try to exit cleanly on SIGINT.	2424	Example: Try to exit cleanly on SIGINT.
1999		2425
2000	static void	2426	static void
2001	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2427	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2002	{	2428	{
2003	ev_unloop (loop, EVUNLOOP_ALL);	2429	ev_break (loop, EVBREAK_ALL);
2004	}	2430	}
2005		2431
2006	ev_signal signal_watcher;	2432	ev_signal signal_watcher;
2007	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2433	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2008	ev_signal_start (loop, &signal_watcher);	2434	ev_signal_start (loop, &signal_watcher);
…		…
2020	in the next callback invocation is not.	2446	in the next callback invocation is not.
2021		2447
2022	Only the default event loop is capable of handling signals, and therefore	2448	Only the default event loop is capable of handling signals, and therefore
2023	you can only register child watchers in the default event loop.	2449	you can only register child watchers in the default event loop.
2024		2450
		2451	Due to some design glitches inside libev, child watchers will always be
		2452	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2453	libev)
		2454
2025	=head3 Process Interaction	2455	=head3 Process Interaction
2026		2456
2027	Libev grabs C<SIGCHLD> as soon as the default event loop is	2457	Libev grabs C<SIGCHLD> as soon as the default event loop is
2028	initialised. This is necessary to guarantee proper behaviour even if	2458	initialised. This is necessary to guarantee proper behaviour even if the
2029	the first child watcher is started after the child exits. The occurrence	2459	first child watcher is started after the child exits. The occurrence
2030	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2460	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2031	synchronously as part of the event loop processing. Libev always reaps all	2461	synchronously as part of the event loop processing. Libev always reaps all
2032	children, even ones not watched.	2462	children, even ones not watched.
2033		2463
2034	=head3 Overriding the Built-In Processing	2464	=head3 Overriding the Built-In Processing
…		…
2044	=head3 Stopping the Child Watcher	2474	=head3 Stopping the Child Watcher
2045		2475
2046	Currently, the child watcher never gets stopped, even when the	2476	Currently, the child watcher never gets stopped, even when the
2047	child terminates, so normally one needs to stop the watcher in the	2477	child terminates, so normally one needs to stop the watcher in the
2048	callback. Future versions of libev might stop the watcher automatically	2478	callback. Future versions of libev might stop the watcher automatically
2049	when a child exit is detected.	2479	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2480	problem).
2050		2481
2051	=head3 Watcher-Specific Functions and Data Members	2482	=head3 Watcher-Specific Functions and Data Members
2052		2483
2053	=over 4	2484	=over 4
2054		2485
…		…
2389		2820
2390	Prepare and check watchers are usually (but not always) used in pairs:	2821	Prepare and check watchers are usually (but not always) used in pairs:
2391	prepare watchers get invoked before the process blocks and check watchers	2822	prepare watchers get invoked before the process blocks and check watchers
2392	afterwards.	2823	afterwards.
2393		2824
2394	You I<must not> call C<ev_loop> or similar functions that enter	2825	You I<must not> call C<ev_run> or similar functions that enter
2395	the current event loop from either C<ev_prepare> or C<ev_check>	2826	the current event loop from either C<ev_prepare> or C<ev_check>
2396	watchers. Other loops than the current one are fine, however. The	2827	watchers. Other loops than the current one are fine, however. The
2397	rationale behind this is that you do not need to check for recursion in	2828	rationale behind this is that you do not need to check for recursion in
2398	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2829	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2399	C<ev_check> so if you have one watcher of each kind they will always be	2830	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2567		2998
2568	if (timeout >= 0)	2999	if (timeout >= 0)
2569	// create/start timer	3000	// create/start timer
2570		3001
2571	// poll	3002	// poll
2572	ev_loop (EV_A_ 0);	3003	ev_run (EV_A_ 0);
2573		3004
2574	// stop timer again	3005	// stop timer again
2575	if (timeout >= 0)	3006	if (timeout >= 0)
2576	ev_timer_stop (EV_A_ &to);	3007	ev_timer_stop (EV_A_ &to);
2577		3008
…		…
2655	if you do not want that, you need to temporarily stop the embed watcher).	3086	if you do not want that, you need to temporarily stop the embed watcher).
2656		3087
2657	=item ev_embed_sweep (loop, ev_embed *)	3088	=item ev_embed_sweep (loop, ev_embed *)
2658		3089
2659	Make a single, non-blocking sweep over the embedded loop. This works	3090	Make a single, non-blocking sweep over the embedded loop. This works
2660	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3091	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2661	appropriate way for embedded loops.	3092	appropriate way for embedded loops.
2662		3093
2663	=item struct ev_loop *other [read-only]	3094	=item struct ev_loop *other [read-only]
2664		3095
2665	The embedded event loop.	3096	The embedded event loop.
…		…
2725	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3156	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2726	handlers will be invoked, too, of course.	3157	handlers will be invoked, too, of course.
2727		3158
2728	=head3 The special problem of life after fork - how is it possible?	3159	=head3 The special problem of life after fork - how is it possible?
2729		3160
2730	Most uses of C<fork()> consist of forking, then some simple calls to ste	3161	Most uses of C<fork()> consist of forking, then some simple calls to set
2731	up/change the process environment, followed by a call to C<exec()>. This	3162	up/change the process environment, followed by a call to C<exec()>. This
2732	sequence should be handled by libev without any problems.	3163	sequence should be handled by libev without any problems.
2733		3164
2734	This changes when the application actually wants to do event handling	3165	This changes when the application actually wants to do event handling
2735	in the child, or both parent in child, in effect "continuing" after the	3166	in the child, or both parent in child, in effect "continuing" after the
…		…
2751	disadvantage of having to use multiple event loops (which do not support	3182	disadvantage of having to use multiple event loops (which do not support
2752	signal watchers).	3183	signal watchers).
2753		3184
2754	When this is not possible, or you want to use the default loop for	3185	When this is not possible, or you want to use the default loop for
2755	other reasons, then in the process that wants to start "fresh", call	3186	other reasons, then in the process that wants to start "fresh", call
2756	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3187	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2757	the default loop will "orphan" (not stop) all registered watchers, so you	3188	Destroying the default loop will "orphan" (not stop) all registered
2758	have to be careful not to execute code that modifies those watchers. Note	3189	watchers, so you have to be careful not to execute code that modifies
2759	also that in that case, you have to re-register any signal watchers.	3190	those watchers. Note also that in that case, you have to re-register any
		3191	signal watchers.
2760		3192
2761	=head3 Watcher-Specific Functions and Data Members	3193	=head3 Watcher-Specific Functions and Data Members
2762		3194
2763	=over 4	3195	=over 4
2764		3196
2765	=item ev_fork_init (ev_signal *, callback)	3197	=item ev_fork_init (ev_fork *, callback)
2766		3198
2767	Initialises and configures the fork watcher - it has no parameters of any	3199	Initialises and configures the fork watcher - it has no parameters of any
2768	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3200	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2769	believe me.	3201	really.
2770		3202
2771	=back	3203	=back
2772		3204
2773		3205
		3206	=head2 C<ev_cleanup> - even the best things end
		3207
		3208	Cleanup watchers are called just before the event loop is being destroyed
		3209	by a call to C<ev_loop_destroy>.
		3210
		3211	While there is no guarantee that the event loop gets destroyed, cleanup
		3212	watchers provide a convenient method to install cleanup hooks for your
		3213	program, worker threads and so on - you just to make sure to destroy the
		3214	loop when you want them to be invoked.
		3215
		3216	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3217	all other watchers, they do not keep a reference to the event loop (which
		3218	makes a lot of sense if you think about it). Like all other watchers, you
		3219	can call libev functions in the callback, except C<ev_cleanup_start>.
		3220
		3221	=head3 Watcher-Specific Functions and Data Members
		3222
		3223	=over 4
		3224
		3225	=item ev_cleanup_init (ev_cleanup *, callback)
		3226
		3227	Initialises and configures the cleanup watcher - it has no parameters of
		3228	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3229	pointless, I assure you.
		3230
		3231	=back
		3232
		3233	Example: Register an atexit handler to destroy the default loop, so any
		3234	cleanup functions are called.
		3235
		3236	static void
		3237	program_exits (void)
		3238	{
		3239	ev_loop_destroy (EV_DEFAULT_UC);
		3240	}
		3241
		3242	...
		3243	atexit (program_exits);
		3244
		3245
2774	=head2 C<ev_async> - how to wake up another event loop	3246	=head2 C<ev_async> - how to wake up an event loop
2775		3247
2776	In general, you cannot use an C<ev_loop> from multiple threads or other	3248	In general, you cannot use an C<ev_run> from multiple threads or other
2777	asynchronous sources such as signal handlers (as opposed to multiple event	3249	asynchronous sources such as signal handlers (as opposed to multiple event
2778	loops - those are of course safe to use in different threads).	3250	loops - those are of course safe to use in different threads).
2779		3251
2780	Sometimes, however, you need to wake up another event loop you do not	3252	Sometimes, however, you need to wake up an event loop you do not control,
2781	control, for example because it belongs to another thread. This is what	3253	for example because it belongs to another thread. This is what C<ev_async>
2782	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3254	watchers do: as long as the C<ev_async> watcher is active, you can signal
2783	can signal it by calling C<ev_async_send>, which is thread- and signal	3255	it by calling C<ev_async_send>, which is thread- and signal safe.
2784	safe.
2785		3256
2786	This functionality is very similar to C<ev_signal> watchers, as signals,	3257	This functionality is very similar to C<ev_signal> watchers, as signals,
2787	too, are asynchronous in nature, and signals, too, will be compressed	3258	too, are asynchronous in nature, and signals, too, will be compressed
2788	(i.e. the number of callback invocations may be less than the number of	3259	(i.e. the number of callback invocations may be less than the number of
2789	C<ev_async_sent> calls).	3260	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3261	of "global async watchers" by using a watcher on an otherwise unused
		3262	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3263	even without knowing which loop owns the signal.
2790		3264
2791	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3265	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2792	just the default loop.	3266	just the default loop.
2793		3267
2794	=head3 Queueing	3268	=head3 Queueing
2795		3269
2796	C<ev_async> does not support queueing of data in any way. The reason	3270	C<ev_async> does not support queueing of data in any way. The reason
2797	is that the author does not know of a simple (or any) algorithm for a	3271	is that the author does not know of a simple (or any) algorithm for a
2798	multiple-writer-single-reader queue that works in all cases and doesn't	3272	multiple-writer-single-reader queue that works in all cases and doesn't
2799	need elaborate support such as pthreads.	3273	need elaborate support such as pthreads or unportable memory access
		3274	semantics.
2800		3275
2801	That means that if you want to queue data, you have to provide your own	3276	That means that if you want to queue data, you have to provide your own
2802	queue. But at least I can tell you how to implement locking around your	3277	queue. But at least I can tell you how to implement locking around your
2803	queue:	3278	queue:
2804		3279
…		…
2943		3418
2944	If C<timeout> is less than 0, then no timeout watcher will be	3419	If C<timeout> is less than 0, then no timeout watcher will be
2945	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3420	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2946	repeat = 0) will be started. C<0> is a valid timeout.	3421	repeat = 0) will be started. C<0> is a valid timeout.
2947		3422
2948	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3423	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2949	passed an C<revents> set like normal event callbacks (a combination of	3424	passed an C<revents> set like normal event callbacks (a combination of
2950	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3425	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2951	value passed to C<ev_once>. Note that it is possible to receive I<both>	3426	value passed to C<ev_once>. Note that it is possible to receive I<both>
2952	a timeout and an io event at the same time - you probably should give io	3427	a timeout and an io event at the same time - you probably should give io
2953	events precedence.	3428	events precedence.
2954		3429
2955	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3430	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2956		3431
2957	static void stdin_ready (int revents, void *arg)	3432	static void stdin_ready (int revents, void *arg)
2958	{	3433	{
2959	if (revents & EV_READ)	3434	if (revents & EV_READ)
2960	/* stdin might have data for us, joy! */;	3435	/* stdin might have data for us, joy! */;
2961	else if (revents & EV_TIMEOUT)	3436	else if (revents & EV_TIMER)
2962	/* doh, nothing entered */;	3437	/* doh, nothing entered */;
2963	}	3438	}
2964		3439
2965	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3440	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2966		3441
2967	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2968
2969	Feeds the given event set into the event loop, as if the specified event
2970	had happened for the specified watcher (which must be a pointer to an
2971	initialised but not necessarily started event watcher).
2972
2973	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3442	=item ev_feed_fd_event (loop, int fd, int revents)
2974		3443
2975	Feed an event on the given fd, as if a file descriptor backend detected	3444	Feed an event on the given fd, as if a file descriptor backend detected
2976	the given events it.	3445	the given events it.
2977		3446
2978	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3447	=item ev_feed_signal_event (loop, int signum)
2979		3448
2980	Feed an event as if the given signal occurred (C<loop> must be the default	3449	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2981	loop!).	3450	which is async-safe.
2982		3451
2983	=back	3452	=back
		3453
		3454
		3455	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3456
		3457	This section explains some common idioms that are not immediately
		3458	obvious. Note that examples are sprinkled over the whole manual, and this
		3459	section only contains stuff that wouldn't fit anywhere else.
		3460
		3461	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3462
		3463	Often (especially in GUI toolkits) there are places where you have
		3464	I<modal> interaction, which is most easily implemented by recursively
		3465	invoking C<ev_run>.
		3466
		3467	This brings the problem of exiting - a callback might want to finish the
		3468	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3469	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3470	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3471	other combination: In these cases, C<ev_break> will not work alone.
		3472
		3473	The solution is to maintain "break this loop" variable for each C<ev_run>
		3474	invocation, and use a loop around C<ev_run> until the condition is
		3475	triggered, using C<EVRUN_ONCE>:
		3476
		3477	// main loop
		3478	int exit_main_loop = 0;
		3479
		3480	while (!exit_main_loop)
		3481	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3482
		3483	// in a model watcher
		3484	int exit_nested_loop = 0;
		3485
		3486	while (!exit_nested_loop)
		3487	ev_run (EV_A_ EVRUN_ONCE);
		3488
		3489	To exit from any of these loops, just set the corresponding exit variable:
		3490
		3491	// exit modal loop
		3492	exit_nested_loop = 1;
		3493
		3494	// exit main program, after modal loop is finished
		3495	exit_main_loop = 1;
		3496
		3497	// exit both
		3498	exit_main_loop = exit_nested_loop = 1;
		3499
		3500	=head2 THREAD LOCKING EXAMPLE
		3501
		3502	Here is a fictitious example of how to run an event loop in a different
		3503	thread than where callbacks are being invoked and watchers are
		3504	created/added/removed.
		3505
		3506	For a real-world example, see the C<EV::Loop::Async> perl module,
		3507	which uses exactly this technique (which is suited for many high-level
		3508	languages).
		3509
		3510	The example uses a pthread mutex to protect the loop data, a condition
		3511	variable to wait for callback invocations, an async watcher to notify the
		3512	event loop thread and an unspecified mechanism to wake up the main thread.
		3513
		3514	First, you need to associate some data with the event loop:
		3515
		3516	typedef struct {
		3517	mutex_t lock; /* global loop lock */
		3518	ev_async async_w;
		3519	thread_t tid;
		3520	cond_t invoke_cv;
		3521	} userdata;
		3522
		3523	void prepare_loop (EV_P)
		3524	{
		3525	// for simplicity, we use a static userdata struct.
		3526	static userdata u;
		3527
		3528	ev_async_init (&u->async_w, async_cb);
		3529	ev_async_start (EV_A_ &u->async_w);
		3530
		3531	pthread_mutex_init (&u->lock, 0);
		3532	pthread_cond_init (&u->invoke_cv, 0);
		3533
		3534	// now associate this with the loop
		3535	ev_set_userdata (EV_A_ u);
		3536	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3537	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3538
		3539	// then create the thread running ev_loop
		3540	pthread_create (&u->tid, 0, l_run, EV_A);
		3541	}
		3542
		3543	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3544	solely to wake up the event loop so it takes notice of any new watchers
		3545	that might have been added:
		3546
		3547	static void
		3548	async_cb (EV_P_ ev_async *w, int revents)
		3549	{
		3550	// just used for the side effects
		3551	}
		3552
		3553	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3554	protecting the loop data, respectively.
		3555
		3556	static void
		3557	l_release (EV_P)
		3558	{
		3559	userdata *u = ev_userdata (EV_A);
		3560	pthread_mutex_unlock (&u->lock);
		3561	}
		3562
		3563	static void
		3564	l_acquire (EV_P)
		3565	{
		3566	userdata *u = ev_userdata (EV_A);
		3567	pthread_mutex_lock (&u->lock);
		3568	}
		3569
		3570	The event loop thread first acquires the mutex, and then jumps straight
		3571	into C<ev_run>:
		3572
		3573	void *
		3574	l_run (void *thr_arg)
		3575	{
		3576	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3577
		3578	l_acquire (EV_A);
		3579	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3580	ev_run (EV_A_ 0);
		3581	l_release (EV_A);
		3582
		3583	return 0;
		3584	}
		3585
		3586	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3587	signal the main thread via some unspecified mechanism (signals? pipe
		3588	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3589	have been called (in a while loop because a) spurious wakeups are possible
		3590	and b) skipping inter-thread-communication when there are no pending
		3591	watchers is very beneficial):
		3592
		3593	static void
		3594	l_invoke (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597
		3598	while (ev_pending_count (EV_A))
		3599	{
		3600	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3601	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3602	}
		3603	}
		3604
		3605	Now, whenever the main thread gets told to invoke pending watchers, it
		3606	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3607	thread to continue:
		3608
		3609	static void
		3610	real_invoke_pending (EV_P)
		3611	{
		3612	userdata *u = ev_userdata (EV_A);
		3613
		3614	pthread_mutex_lock (&u->lock);
		3615	ev_invoke_pending (EV_A);
		3616	pthread_cond_signal (&u->invoke_cv);
		3617	pthread_mutex_unlock (&u->lock);
		3618	}
		3619
		3620	Whenever you want to start/stop a watcher or do other modifications to an
		3621	event loop, you will now have to lock:
		3622
		3623	ev_timer timeout_watcher;
		3624	userdata *u = ev_userdata (EV_A);
		3625
		3626	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3627
		3628	pthread_mutex_lock (&u->lock);
		3629	ev_timer_start (EV_A_ &timeout_watcher);
		3630	ev_async_send (EV_A_ &u->async_w);
		3631	pthread_mutex_unlock (&u->lock);
		3632
		3633	Note that sending the C<ev_async> watcher is required because otherwise
		3634	an event loop currently blocking in the kernel will have no knowledge
		3635	about the newly added timer. By waking up the loop it will pick up any new
		3636	watchers in the next event loop iteration.
2984		3637
2985		3638
2986	=head1 LIBEVENT EMULATION	3639	=head1 LIBEVENT EMULATION
2987		3640
2988	Libev offers a compatibility emulation layer for libevent. It cannot	3641	Libev offers a compatibility emulation layer for libevent. It cannot
2989	emulate the internals of libevent, so here are some usage hints:	3642	emulate the internals of libevent, so here are some usage hints:
2990		3643
2991	=over 4	3644	=over 4
		3645
		3646	=item * Only the libevent-1.4.1-beta API is being emulated.
		3647
		3648	This was the newest libevent version available when libev was implemented,
		3649	and is still mostly unchanged in 2010.
2992		3650
2993	=item * Use it by including <event.h>, as usual.	3651	=item * Use it by including <event.h>, as usual.
2994		3652
2995	=item * The following members are fully supported: ev_base, ev_callback,	3653	=item * The following members are fully supported: ev_base, ev_callback,
2996	ev_arg, ev_fd, ev_res, ev_events.	3654	ev_arg, ev_fd, ev_res, ev_events.
…		…
3002	=item * Priorities are not currently supported. Initialising priorities	3660	=item * Priorities are not currently supported. Initialising priorities
3003	will fail and all watchers will have the same priority, even though there	3661	will fail and all watchers will have the same priority, even though there
3004	is an ev_pri field.	3662	is an ev_pri field.
3005		3663
3006	=item * In libevent, the last base created gets the signals, in libev, the	3664	=item * In libevent, the last base created gets the signals, in libev, the
3007	first base created (== the default loop) gets the signals.	3665	base that registered the signal gets the signals.
3008		3666
3009	=item * Other members are not supported.	3667	=item * Other members are not supported.
3010		3668
3011	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3669	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3012	to use the libev header file and library.	3670	to use the libev header file and library.
…		…
3031	Care has been taken to keep the overhead low. The only data member the C++	3689	Care has been taken to keep the overhead low. The only data member the C++
3032	classes add (compared to plain C-style watchers) is the event loop pointer	3690	classes add (compared to plain C-style watchers) is the event loop pointer
3033	that the watcher is associated with (or no additional members at all if	3691	that the watcher is associated with (or no additional members at all if
3034	you disable C<EV_MULTIPLICITY> when embedding libev).	3692	you disable C<EV_MULTIPLICITY> when embedding libev).
3035		3693
3036	Currently, functions, and static and non-static member functions can be	3694	Currently, functions, static and non-static member functions and classes
3037	used as callbacks. Other types should be easy to add as long as they only	3695	with C<operator ()> can be used as callbacks. Other types should be easy
3038	need one additional pointer for context. If you need support for other	3696	to add as long as they only need one additional pointer for context. If
3039	types of functors please contact the author (preferably after implementing	3697	you need support for other types of functors please contact the author
3040	it).	3698	(preferably after implementing it).
3041		3699
3042	Here is a list of things available in the C<ev> namespace:	3700	Here is a list of things available in the C<ev> namespace:
3043		3701
3044	=over 4	3702	=over 4
3045		3703
…		…
3063		3721
3064	=over 4	3722	=over 4
3065		3723
3066	=item ev::TYPE::TYPE ()	3724	=item ev::TYPE::TYPE ()
3067		3725
3068	=item ev::TYPE::TYPE (struct ev_loop *)	3726	=item ev::TYPE::TYPE (loop)
3069		3727
3070	=item ev::TYPE::~TYPE	3728	=item ev::TYPE::~TYPE
3071		3729
3072	The constructor (optionally) takes an event loop to associate the watcher	3730	The constructor (optionally) takes an event loop to associate the watcher
3073	with. If it is omitted, it will use C<EV_DEFAULT>.	3731	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3106	myclass obj;	3764	myclass obj;
3107	ev::io iow;	3765	ev::io iow;
3108	iow.set <myclass, &myclass::io_cb> (&obj);	3766	iow.set <myclass, &myclass::io_cb> (&obj);
3109		3767
3110	=item w->set (object *)	3768	=item w->set (object *)
3111
3112	This is an B<experimental> feature that might go away in a future version.
3113		3769
3114	This is a variation of a method callback - leaving out the method to call	3770	This is a variation of a method callback - leaving out the method to call
3115	will default the method to C<operator ()>, which makes it possible to use	3771	will default the method to C<operator ()>, which makes it possible to use
3116	functor objects without having to manually specify the C<operator ()> all	3772	functor objects without having to manually specify the C<operator ()> all
3117	the time. Incidentally, you can then also leave out the template argument	3773	the time. Incidentally, you can then also leave out the template argument
…		…
3150	Example: Use a plain function as callback.	3806	Example: Use a plain function as callback.
3151		3807
3152	static void io_cb (ev::io &w, int revents) { }	3808	static void io_cb (ev::io &w, int revents) { }
3153	iow.set <io_cb> ();	3809	iow.set <io_cb> ();
3154		3810
3155	=item w->set (struct ev_loop *)	3811	=item w->set (loop)
3156		3812
3157	Associates a different C<struct ev_loop> with this watcher. You can only	3813	Associates a different C<struct ev_loop> with this watcher. You can only
3158	do this when the watcher is inactive (and not pending either).	3814	do this when the watcher is inactive (and not pending either).
3159		3815
3160	=item w->set ([arguments])	3816	=item w->set ([arguments])
3161		3817
3162	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3818	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3163	called at least once. Unlike the C counterpart, an active watcher gets	3819	method or a suitable start method must be called at least once. Unlike the
3164	automatically stopped and restarted when reconfiguring it with this	3820	C counterpart, an active watcher gets automatically stopped and restarted
3165	method.	3821	when reconfiguring it with this method.
3166		3822
3167	=item w->start ()	3823	=item w->start ()
3168		3824
3169	Starts the watcher. Note that there is no C<loop> argument, as the	3825	Starts the watcher. Note that there is no C<loop> argument, as the
3170	constructor already stores the event loop.	3826	constructor already stores the event loop.
3171		3827
		3828	=item w->start ([arguments])
		3829
		3830	Instead of calling C<set> and C<start> methods separately, it is often
		3831	convenient to wrap them in one call. Uses the same type of arguments as
		3832	the configure C<set> method of the watcher.
		3833
3172	=item w->stop ()	3834	=item w->stop ()
3173		3835
3174	Stops the watcher if it is active. Again, no C<loop> argument.	3836	Stops the watcher if it is active. Again, no C<loop> argument.
3175		3837
3176	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3838	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3188		3850
3189	=back	3851	=back
3190		3852
3191	=back	3853	=back
3192		3854
3193	Example: Define a class with an IO and idle watcher, start one of them in	3855	Example: Define a class with two I/O and idle watchers, start the I/O
3194	the constructor.	3856	watchers in the constructor.
3195		3857
3196	class myclass	3858	class myclass
3197	{	3859	{
3198	ev::io io ; void io_cb (ev::io &w, int revents);	3860	ev::io io ; void io_cb (ev::io &w, int revents);
		3861	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3199	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3862	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3200		3863
3201	myclass (int fd)	3864	myclass (int fd)
3202	{	3865	{
3203	io .set <myclass, &myclass::io_cb > (this);	3866	io .set <myclass, &myclass::io_cb > (this);
		3867	io2 .set <myclass, &myclass::io2_cb > (this);
3204	idle.set <myclass, &myclass::idle_cb> (this);	3868	idle.set <myclass, &myclass::idle_cb> (this);
3205		3869
3206	io.start (fd, ev::READ);	3870	io.set (fd, ev::WRITE); // configure the watcher
		3871	io.start (); // start it whenever convenient
		3872
		3873	io2.start (fd, ev::READ); // set + start in one call
3207	}	3874	}
3208	};	3875	};
3209		3876
3210		3877
3211	=head1 OTHER LANGUAGE BINDINGS	3878	=head1 OTHER LANGUAGE BINDINGS
…		…
3257	=item Ocaml	3924	=item Ocaml
3258		3925
3259	Erkki Seppala has written Ocaml bindings for libev, to be found at	3926	Erkki Seppala has written Ocaml bindings for libev, to be found at
3260	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3927	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3261		3928
		3929	=item Lua
		3930
		3931	Brian Maher has written a partial interface to libev for lua (at the
		3932	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3933	L<http://github.com/brimworks/lua-ev>.
		3934
3262	=back	3935	=back
3263		3936
3264		3937
3265	=head1 MACRO MAGIC	3938	=head1 MACRO MAGIC
3266		3939
…		…
3279	loop argument"). The C<EV_A> form is used when this is the sole argument,	3952	loop argument"). The C<EV_A> form is used when this is the sole argument,
3280	C<EV_A_> is used when other arguments are following. Example:	3953	C<EV_A_> is used when other arguments are following. Example:
3281		3954
3282	ev_unref (EV_A);	3955	ev_unref (EV_A);
3283	ev_timer_add (EV_A_ watcher);	3956	ev_timer_add (EV_A_ watcher);
3284	ev_loop (EV_A_ 0);	3957	ev_run (EV_A_ 0);
3285		3958
3286	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3959	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3287	which is often provided by the following macro.	3960	which is often provided by the following macro.
3288		3961
3289	=item C<EV_P>, C<EV_P_>	3962	=item C<EV_P>, C<EV_P_>
…		…
3329	}	4002	}
3330		4003
3331	ev_check check;	4004	ev_check check;
3332	ev_check_init (&check, check_cb);	4005	ev_check_init (&check, check_cb);
3333	ev_check_start (EV_DEFAULT_ &check);	4006	ev_check_start (EV_DEFAULT_ &check);
3334	ev_loop (EV_DEFAULT_ 0);	4007	ev_run (EV_DEFAULT_ 0);
3335		4008
3336	=head1 EMBEDDING	4009	=head1 EMBEDDING
3337		4010
3338	Libev can (and often is) directly embedded into host	4011	Libev can (and often is) directly embedded into host
3339	applications. Examples of applications that embed it include the Deliantra	4012	applications. Examples of applications that embed it include the Deliantra
…		…
3419	libev.m4	4092	libev.m4
3420		4093
3421	=head2 PREPROCESSOR SYMBOLS/MACROS	4094	=head2 PREPROCESSOR SYMBOLS/MACROS
3422		4095
3423	Libev can be configured via a variety of preprocessor symbols you have to	4096	Libev can be configured via a variety of preprocessor symbols you have to
3424	define before including any of its files. The default in the absence of	4097	define before including (or compiling) any of its files. The default in
3425	autoconf is documented for every option.	4098	the absence of autoconf is documented for every option.
		4099
		4100	Symbols marked with "(h)" do not change the ABI, and can have different
		4101	values when compiling libev vs. including F<ev.h>, so it is permissible
		4102	to redefine them before including F<ev.h> without breaking compatibility
		4103	to a compiled library. All other symbols change the ABI, which means all
		4104	users of libev and the libev code itself must be compiled with compatible
		4105	settings.
3426		4106
3427	=over 4	4107	=over 4
3428		4108
		4109	=item EV_COMPAT3 (h)
		4110
		4111	Backwards compatibility is a major concern for libev. This is why this
		4112	release of libev comes with wrappers for the functions and symbols that
		4113	have been renamed between libev version 3 and 4.
		4114
		4115	You can disable these wrappers (to test compatibility with future
		4116	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4117	sources. This has the additional advantage that you can drop the C<struct>
		4118	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4119	typedef in that case.
		4120
		4121	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4122	and in some even more future version the compatibility code will be
		4123	removed completely.
		4124
3429	=item EV_STANDALONE	4125	=item EV_STANDALONE (h)
3430		4126
3431	Must always be C<1> if you do not use autoconf configuration, which	4127	Must always be C<1> if you do not use autoconf configuration, which
3432	keeps libev from including F<config.h>, and it also defines dummy	4128	keeps libev from including F<config.h>, and it also defines dummy
3433	implementations for some libevent functions (such as logging, which is not	4129	implementations for some libevent functions (such as logging, which is not
3434	supported). It will also not define any of the structs usually found in	4130	supported). It will also not define any of the structs usually found in
3435	F<event.h> that are not directly supported by the libev core alone.	4131	F<event.h> that are not directly supported by the libev core alone.
3436		4132
3437	In stanbdalone mode, libev will still try to automatically deduce the	4133	In standalone mode, libev will still try to automatically deduce the
3438	configuration, but has to be more conservative.	4134	configuration, but has to be more conservative.
3439		4135
3440	=item EV_USE_MONOTONIC	4136	=item EV_USE_MONOTONIC
3441		4137
3442	If defined to be C<1>, libev will try to detect the availability of the	4138	If defined to be C<1>, libev will try to detect the availability of the
…		…
3507	be used is the winsock select). This means that it will call	4203	be used is the winsock select). This means that it will call
3508	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4204	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3509	it is assumed that all these functions actually work on fds, even	4205	it is assumed that all these functions actually work on fds, even
3510	on win32. Should not be defined on non-win32 platforms.	4206	on win32. Should not be defined on non-win32 platforms.
3511		4207
3512	=item EV_FD_TO_WIN32_HANDLE	4208	=item EV_FD_TO_WIN32_HANDLE(fd)
3513		4209
3514	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4210	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3515	file descriptors to socket handles. When not defining this symbol (the	4211	file descriptors to socket handles. When not defining this symbol (the
3516	default), then libev will call C<_get_osfhandle>, which is usually	4212	default), then libev will call C<_get_osfhandle>, which is usually
3517	correct. In some cases, programs use their own file descriptor management,	4213	correct. In some cases, programs use their own file descriptor management,
3518	in which case they can provide this function to map fds to socket handles.	4214	in which case they can provide this function to map fds to socket handles.
		4215
		4216	=item EV_WIN32_HANDLE_TO_FD(handle)
		4217
		4218	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4219	using the standard C<_open_osfhandle> function. For programs implementing
		4220	their own fd to handle mapping, overwriting this function makes it easier
		4221	to do so. This can be done by defining this macro to an appropriate value.
		4222
		4223	=item EV_WIN32_CLOSE_FD(fd)
		4224
		4225	If programs implement their own fd to handle mapping on win32, then this
		4226	macro can be used to override the C<close> function, useful to unregister
		4227	file descriptors again. Note that the replacement function has to close
		4228	the underlying OS handle.
3519		4229
3520	=item EV_USE_POLL	4230	=item EV_USE_POLL
3521		4231
3522	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4232	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3523	backend. Otherwise it will be enabled on non-win32 platforms. It	4233	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3570	as well as for signal and thread safety in C<ev_async> watchers.	4280	as well as for signal and thread safety in C<ev_async> watchers.
3571		4281
3572	In the absence of this define, libev will use C<sig_atomic_t volatile>	4282	In the absence of this define, libev will use C<sig_atomic_t volatile>
3573	(from F<signal.h>), which is usually good enough on most platforms.	4283	(from F<signal.h>), which is usually good enough on most platforms.
3574		4284
3575	=item EV_H	4285	=item EV_H (h)
3576		4286
3577	The name of the F<ev.h> header file used to include it. The default if	4287	The name of the F<ev.h> header file used to include it. The default if
3578	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4288	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3579	used to virtually rename the F<ev.h> header file in case of conflicts.	4289	used to virtually rename the F<ev.h> header file in case of conflicts.
3580		4290
3581	=item EV_CONFIG_H	4291	=item EV_CONFIG_H (h)
3582		4292
3583	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4293	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3584	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4294	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3585	C<EV_H>, above.	4295	C<EV_H>, above.
3586		4296
3587	=item EV_EVENT_H	4297	=item EV_EVENT_H (h)
3588		4298
3589	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4299	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3590	of how the F<event.h> header can be found, the default is C<"event.h">.	4300	of how the F<event.h> header can be found, the default is C<"event.h">.
3591		4301
3592	=item EV_PROTOTYPES	4302	=item EV_PROTOTYPES (h)
3593		4303
3594	If defined to be C<0>, then F<ev.h> will not define any function	4304	If defined to be C<0>, then F<ev.h> will not define any function
3595	prototypes, but still define all the structs and other symbols. This is	4305	prototypes, but still define all the structs and other symbols. This is
3596	occasionally useful if you want to provide your own wrapper functions	4306	occasionally useful if you want to provide your own wrapper functions
3597	around libev functions.	4307	around libev functions.
…		…
3619	fine.	4329	fine.
3620		4330
3621	If your embedding application does not need any priorities, defining these	4331	If your embedding application does not need any priorities, defining these
3622	both to C<0> will save some memory and CPU.	4332	both to C<0> will save some memory and CPU.
3623		4333
3624	=item EV_PERIODIC_ENABLE	4334	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4335	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4336	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3625		4337
3626	If undefined or defined to be C<1>, then periodic timers are supported. If	4338	If undefined or defined to be C<1> (and the platform supports it), then
3627	defined to be C<0>, then they are not. Disabling them saves a few kB of	4339	the respective watcher type is supported. If defined to be C<0>, then it
3628	code.	4340	is not. Disabling watcher types mainly saves code size.
3629		4341
3630	=item EV_IDLE_ENABLE	4342	=item EV_FEATURES
3631
3632	If undefined or defined to be C<1>, then idle watchers are supported. If
3633	defined to be C<0>, then they are not. Disabling them saves a few kB of
3634	code.
3635
3636	=item EV_EMBED_ENABLE
3637
3638	If undefined or defined to be C<1>, then embed watchers are supported. If
3639	defined to be C<0>, then they are not. Embed watchers rely on most other
3640	watcher types, which therefore must not be disabled.
3641
3642	=item EV_STAT_ENABLE
3643
3644	If undefined or defined to be C<1>, then stat watchers are supported. If
3645	defined to be C<0>, then they are not.
3646
3647	=item EV_FORK_ENABLE
3648
3649	If undefined or defined to be C<1>, then fork watchers are supported. If
3650	defined to be C<0>, then they are not.
3651
3652	=item EV_ASYNC_ENABLE
3653
3654	If undefined or defined to be C<1>, then async watchers are supported. If
3655	defined to be C<0>, then they are not.
3656
3657	=item EV_MINIMAL
3658		4343
3659	If you need to shave off some kilobytes of code at the expense of some	4344	If you need to shave off some kilobytes of code at the expense of some
3660	speed, define this symbol to C<1>. Currently this is used to override some	4345	speed (but with the full API), you can define this symbol to request
3661	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4346	certain subsets of functionality. The default is to enable all features
3662	much smaller 2-heap for timer management over the default 4-heap.	4347	that can be enabled on the platform.
		4348
		4349	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4350	with some broad features you want) and then selectively re-enable
		4351	additional parts you want, for example if you want everything minimal,
		4352	but multiple event loop support, async and child watchers and the poll
		4353	backend, use this:
		4354
		4355	#define EV_FEATURES 0
		4356	#define EV_MULTIPLICITY 1
		4357	#define EV_USE_POLL 1
		4358	#define EV_CHILD_ENABLE 1
		4359	#define EV_ASYNC_ENABLE 1
		4360
		4361	The actual value is a bitset, it can be a combination of the following
		4362	values:
		4363
		4364	=over 4
		4365
		4366	=item C<1> - faster/larger code
		4367
		4368	Use larger code to speed up some operations.
		4369
		4370	Currently this is used to override some inlining decisions (enlarging the
		4371	code size by roughly 30% on amd64).
		4372
		4373	When optimising for size, use of compiler flags such as C<-Os> with
		4374	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4375	assertions.
		4376
		4377	=item C<2> - faster/larger data structures
		4378
		4379	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4380	hash table sizes and so on. This will usually further increase code size
		4381	and can additionally have an effect on the size of data structures at
		4382	runtime.
		4383
		4384	=item C<4> - full API configuration
		4385
		4386	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4387	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4388
		4389	=item C<8> - full API
		4390
		4391	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4392	details on which parts of the API are still available without this
		4393	feature, and do not complain if this subset changes over time.
		4394
		4395	=item C<16> - enable all optional watcher types
		4396
		4397	Enables all optional watcher types. If you want to selectively enable
		4398	only some watcher types other than I/O and timers (e.g. prepare,
		4399	embed, async, child...) you can enable them manually by defining
		4400	C<EV_watchertype_ENABLE> to C<1> instead.
		4401
		4402	=item C<32> - enable all backends
		4403
		4404	This enables all backends - without this feature, you need to enable at
		4405	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4406
		4407	=item C<64> - enable OS-specific "helper" APIs
		4408
		4409	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4410	default.
		4411
		4412	=back
		4413
		4414	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4415	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4416	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4417	watchers, timers and monotonic clock support.
		4418
		4419	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4420	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4421	your program might be left out as well - a binary starting a timer and an
		4422	I/O watcher then might come out at only 5Kb.
		4423
		4424	=item EV_AVOID_STDIO
		4425
		4426	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4427	functions (printf, scanf, perror etc.). This will increase the code size
		4428	somewhat, but if your program doesn't otherwise depend on stdio and your
		4429	libc allows it, this avoids linking in the stdio library which is quite
		4430	big.
		4431
		4432	Note that error messages might become less precise when this option is
		4433	enabled.
		4434
		4435	=item EV_NSIG
		4436
		4437	The highest supported signal number, +1 (or, the number of
		4438	signals): Normally, libev tries to deduce the maximum number of signals
		4439	automatically, but sometimes this fails, in which case it can be
		4440	specified. Also, using a lower number than detected (C<32> should be
		4441	good for about any system in existence) can save some memory, as libev
		4442	statically allocates some 12-24 bytes per signal number.
3663		4443
3664	=item EV_PID_HASHSIZE	4444	=item EV_PID_HASHSIZE
3665		4445
3666	C<ev_child> watchers use a small hash table to distribute workload by	4446	C<ev_child> watchers use a small hash table to distribute workload by
3667	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4447	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3668	than enough. If you need to manage thousands of children you might want to	4448	usually more than enough. If you need to manage thousands of children you
3669	increase this value (I<must> be a power of two).	4449	might want to increase this value (I<must> be a power of two).
3670		4450
3671	=item EV_INOTIFY_HASHSIZE	4451	=item EV_INOTIFY_HASHSIZE
3672		4452
3673	C<ev_stat> watchers use a small hash table to distribute workload by	4453	C<ev_stat> watchers use a small hash table to distribute workload by
3674	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4454	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3675	usually more than enough. If you need to manage thousands of C<ev_stat>	4455	disabled), usually more than enough. If you need to manage thousands of
3676	watchers you might want to increase this value (I<must> be a power of	4456	C<ev_stat> watchers you might want to increase this value (I<must> be a
3677	two).	4457	power of two).
3678		4458
3679	=item EV_USE_4HEAP	4459	=item EV_USE_4HEAP
3680		4460
3681	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4461	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3682	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4462	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3683	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4463	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3684	faster performance with many (thousands) of watchers.	4464	faster performance with many (thousands) of watchers.
3685		4465
3686	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4466	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3687	(disabled).	4467	will be C<0>.
3688		4468
3689	=item EV_HEAP_CACHE_AT	4469	=item EV_HEAP_CACHE_AT
3690		4470
3691	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4471	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3692	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4472	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3693	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4473	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3694	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4474	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3695	but avoids random read accesses on heap changes. This improves performance	4475	but avoids random read accesses on heap changes. This improves performance
3696	noticeably with many (hundreds) of watchers.	4476	noticeably with many (hundreds) of watchers.
3697		4477
3698	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4478	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3699	(disabled).	4479	will be C<0>.
3700		4480
3701	=item EV_VERIFY	4481	=item EV_VERIFY
3702		4482
3703	Controls how much internal verification (see C<ev_loop_verify ()>) will	4483	Controls how much internal verification (see C<ev_verify ()>) will
3704	be done: If set to C<0>, no internal verification code will be compiled	4484	be done: If set to C<0>, no internal verification code will be compiled
3705	in. If set to C<1>, then verification code will be compiled in, but not	4485	in. If set to C<1>, then verification code will be compiled in, but not
3706	called. If set to C<2>, then the internal verification code will be	4486	called. If set to C<2>, then the internal verification code will be
3707	called once per loop, which can slow down libev. If set to C<3>, then the	4487	called once per loop, which can slow down libev. If set to C<3>, then the
3708	verification code will be called very frequently, which will slow down	4488	verification code will be called very frequently, which will slow down
3709	libev considerably.	4489	libev considerably.
3710		4490
3711	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4491	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3712	C<0>.	4492	will be C<0>.
3713		4493
3714	=item EV_COMMON	4494	=item EV_COMMON
3715		4495
3716	By default, all watchers have a C<void *data> member. By redefining	4496	By default, all watchers have a C<void *data> member. By redefining
3717	this macro to a something else you can include more and other types of	4497	this macro to something else you can include more and other types of
3718	members. You have to define it each time you include one of the files,	4498	members. You have to define it each time you include one of the files,
3719	though, and it must be identical each time.	4499	though, and it must be identical each time.
3720		4500
3721	For example, the perl EV module uses something like this:	4501	For example, the perl EV module uses something like this:
3722		4502
…		…
3775	file.	4555	file.
3776		4556
3777	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4557	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3778	that everybody includes and which overrides some configure choices:	4558	that everybody includes and which overrides some configure choices:
3779		4559
3780	#define EV_MINIMAL 1	4560	#define EV_FEATURES 8
3781	#define EV_USE_POLL 0	4561	#define EV_USE_SELECT 1
3782	#define EV_MULTIPLICITY 0
3783	#define EV_PERIODIC_ENABLE 0	4562	#define EV_PREPARE_ENABLE 1
		4563	#define EV_IDLE_ENABLE 1
3784	#define EV_STAT_ENABLE 0	4564	#define EV_SIGNAL_ENABLE 1
3785	#define EV_FORK_ENABLE 0	4565	#define EV_CHILD_ENABLE 1
		4566	#define EV_USE_STDEXCEPT 0
3786	#define EV_CONFIG_H <config.h>	4567	#define EV_CONFIG_H <config.h>
3787	#define EV_MINPRI 0
3788	#define EV_MAXPRI 0
3789		4568
3790	#include "ev++.h"	4569	#include "ev++.h"
3791		4570
3792	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4571	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3793		4572
3794	#include "ev_cpp.h"	4573	#include "ev_cpp.h"
3795	#include "ev.c"	4574	#include "ev.c"
3796		4575
3797	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4576	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3798		4577
3799	=head2 THREADS AND COROUTINES	4578	=head2 THREADS AND COROUTINES
3800		4579
3801	=head3 THREADS	4580	=head3 THREADS
3802		4581
…		…
3853	default loop and triggering an C<ev_async> watcher from the default loop	4632	default loop and triggering an C<ev_async> watcher from the default loop
3854	watcher callback into the event loop interested in the signal.	4633	watcher callback into the event loop interested in the signal.
3855		4634
3856	=back	4635	=back
3857		4636
		4637	See also L<THREAD LOCKING EXAMPLE>.
		4638
3858	=head3 COROUTINES	4639	=head3 COROUTINES
3859		4640
3860	Libev is very accommodating to coroutines ("cooperative threads"):	4641	Libev is very accommodating to coroutines ("cooperative threads"):
3861	libev fully supports nesting calls to its functions from different	4642	libev fully supports nesting calls to its functions from different
3862	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4643	coroutines (e.g. you can call C<ev_run> on the same loop from two
3863	different coroutines, and switch freely between both coroutines running the	4644	different coroutines, and switch freely between both coroutines running
3864	loop, as long as you don't confuse yourself). The only exception is that	4645	the loop, as long as you don't confuse yourself). The only exception is
3865	you must not do this from C<ev_periodic> reschedule callbacks.	4646	that you must not do this from C<ev_periodic> reschedule callbacks.
3866		4647
3867	Care has been taken to ensure that libev does not keep local state inside	4648	Care has been taken to ensure that libev does not keep local state inside
3868	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4649	C<ev_run>, and other calls do not usually allow for coroutine switches as
3869	they do not call any callbacks.	4650	they do not call any callbacks.
3870		4651
3871	=head2 COMPILER WARNINGS	4652	=head2 COMPILER WARNINGS
3872		4653
3873	Depending on your compiler and compiler settings, you might get no or a	4654	Depending on your compiler and compiler settings, you might get no or a
…		…
3884	maintainable.	4665	maintainable.
3885		4666
3886	And of course, some compiler warnings are just plain stupid, or simply	4667	And of course, some compiler warnings are just plain stupid, or simply
3887	wrong (because they don't actually warn about the condition their message	4668	wrong (because they don't actually warn about the condition their message
3888	seems to warn about). For example, certain older gcc versions had some	4669	seems to warn about). For example, certain older gcc versions had some
3889	warnings that resulted an extreme number of false positives. These have	4670	warnings that resulted in an extreme number of false positives. These have
3890	been fixed, but some people still insist on making code warn-free with	4671	been fixed, but some people still insist on making code warn-free with
3891	such buggy versions.	4672	such buggy versions.
3892		4673
3893	While libev is written to generate as few warnings as possible,	4674	While libev is written to generate as few warnings as possible,
3894	"warn-free" code is not a goal, and it is recommended not to build libev	4675	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3930	I suggest using suppression lists.	4711	I suggest using suppression lists.
3931		4712
3932		4713
3933	=head1 PORTABILITY NOTES	4714	=head1 PORTABILITY NOTES
3934		4715
		4716	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4717
		4718	GNU/Linux is the only common platform that supports 64 bit file/large file
		4719	interfaces but I<disables> them by default.
		4720
		4721	That means that libev compiled in the default environment doesn't support
		4722	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4723
		4724	Unfortunately, many programs try to work around this GNU/Linux issue
		4725	by enabling the large file API, which makes them incompatible with the
		4726	standard libev compiled for their system.
		4727
		4728	Likewise, libev cannot enable the large file API itself as this would
		4729	suddenly make it incompatible to the default compile time environment,
		4730	i.e. all programs not using special compile switches.
		4731
		4732	=head2 OS/X AND DARWIN BUGS
		4733
		4734	The whole thing is a bug if you ask me - basically any system interface
		4735	you touch is broken, whether it is locales, poll, kqueue or even the
		4736	OpenGL drivers.
		4737
		4738	=head3 C<kqueue> is buggy
		4739
		4740	The kqueue syscall is broken in all known versions - most versions support
		4741	only sockets, many support pipes.
		4742
		4743	Libev tries to work around this by not using C<kqueue> by default on this
		4744	rotten platform, but of course you can still ask for it when creating a
		4745	loop - embedding a socket-only kqueue loop into a select-based one is
		4746	probably going to work well.
		4747
		4748	=head3 C<poll> is buggy
		4749
		4750	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4751	implementation by something calling C<kqueue> internally around the 10.5.6
		4752	release, so now C<kqueue> I<and> C<poll> are broken.
		4753
		4754	Libev tries to work around this by not using C<poll> by default on
		4755	this rotten platform, but of course you can still ask for it when creating
		4756	a loop.
		4757
		4758	=head3 C<select> is buggy
		4759
		4760	All that's left is C<select>, and of course Apple found a way to fuck this
		4761	one up as well: On OS/X, C<select> actively limits the number of file
		4762	descriptors you can pass in to 1024 - your program suddenly crashes when
		4763	you use more.
		4764
		4765	There is an undocumented "workaround" for this - defining
		4766	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4767	work on OS/X.
		4768
		4769	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4770
		4771	=head3 C<errno> reentrancy
		4772
		4773	The default compile environment on Solaris is unfortunately so
		4774	thread-unsafe that you can't even use components/libraries compiled
		4775	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4776	defined by default. A valid, if stupid, implementation choice.
		4777
		4778	If you want to use libev in threaded environments you have to make sure
		4779	it's compiled with C<_REENTRANT> defined.
		4780
		4781	=head3 Event port backend
		4782
		4783	The scalable event interface for Solaris is called "event
		4784	ports". Unfortunately, this mechanism is very buggy in all major
		4785	releases. If you run into high CPU usage, your program freezes or you get
		4786	a large number of spurious wakeups, make sure you have all the relevant
		4787	and latest kernel patches applied. No, I don't know which ones, but there
		4788	are multiple ones to apply, and afterwards, event ports actually work
		4789	great.
		4790
		4791	If you can't get it to work, you can try running the program by setting
		4792	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4793	C<select> backends.
		4794
		4795	=head2 AIX POLL BUG
		4796
		4797	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4798	this by trying to avoid the poll backend altogether (i.e. it's not even
		4799	compiled in), which normally isn't a big problem as C<select> works fine
		4800	with large bitsets on AIX, and AIX is dead anyway.
		4801
3935	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4802	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4803
		4804	=head3 General issues
3936		4805
3937	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4806	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3938	requires, and its I/O model is fundamentally incompatible with the POSIX	4807	requires, and its I/O model is fundamentally incompatible with the POSIX
3939	model. Libev still offers limited functionality on this platform in	4808	model. Libev still offers limited functionality on this platform in
3940	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4809	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3941	descriptors. This only applies when using Win32 natively, not when using	4810	descriptors. This only applies when using Win32 natively, not when using
3942	e.g. cygwin.	4811	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4812	as every compielr comes with a slightly differently broken/incompatible
		4813	environment.
3943		4814
3944	Lifting these limitations would basically require the full	4815	Lifting these limitations would basically require the full
3945	re-implementation of the I/O system. If you are into these kinds of	4816	re-implementation of the I/O system. If you are into this kind of thing,
3946	things, then note that glib does exactly that for you in a very portable	4817	then note that glib does exactly that for you in a very portable way (note
3947	way (note also that glib is the slowest event library known to man).	4818	also that glib is the slowest event library known to man).
3948		4819
3949	There is no supported compilation method available on windows except	4820	There is no supported compilation method available on windows except
3950	embedding it into other applications.	4821	embedding it into other applications.
3951		4822
3952	Sensible signal handling is officially unsupported by Microsoft - libev	4823	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
3980	you do I<not> compile the F<ev.c> or any other embedded source files!):	4851	you do I<not> compile the F<ev.c> or any other embedded source files!):
3981		4852
3982	#include "evwrap.h"	4853	#include "evwrap.h"
3983	#include "ev.c"	4854	#include "ev.c"
3984		4855
3985	=over 4
3986
3987	=item The winsocket select function	4856	=head3 The winsocket C<select> function
3988		4857
3989	The winsocket C<select> function doesn't follow POSIX in that it	4858	The winsocket C<select> function doesn't follow POSIX in that it
3990	requires socket I<handles> and not socket I<file descriptors> (it is	4859	requires socket I<handles> and not socket I<file descriptors> (it is
3991	also extremely buggy). This makes select very inefficient, and also	4860	also extremely buggy). This makes select very inefficient, and also
3992	requires a mapping from file descriptors to socket handles (the Microsoft	4861	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4001	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4870	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4002		4871
4003	Note that winsockets handling of fd sets is O(n), so you can easily get a	4872	Note that winsockets handling of fd sets is O(n), so you can easily get a
4004	complexity in the O(n²) range when using win32.	4873	complexity in the O(n²) range when using win32.
4005		4874
4006	=item Limited number of file descriptors	4875	=head3 Limited number of file descriptors
4007		4876
4008	Windows has numerous arbitrary (and low) limits on things.	4877	Windows has numerous arbitrary (and low) limits on things.
4009		4878
4010	Early versions of winsocket's select only supported waiting for a maximum	4879	Early versions of winsocket's select only supported waiting for a maximum
4011	of C<64> handles (probably owning to the fact that all windows kernels	4880	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4026	runtime libraries. This might get you to about C<512> or C<2048> sockets	4895	runtime libraries. This might get you to about C<512> or C<2048> sockets
4027	(depending on windows version and/or the phase of the moon). To get more,	4896	(depending on windows version and/or the phase of the moon). To get more,
4028	you need to wrap all I/O functions and provide your own fd management, but	4897	you need to wrap all I/O functions and provide your own fd management, but
4029	the cost of calling select (O(n²)) will likely make this unworkable.	4898	the cost of calling select (O(n²)) will likely make this unworkable.
4030		4899
4031	=back
4032
4033	=head2 PORTABILITY REQUIREMENTS	4900	=head2 PORTABILITY REQUIREMENTS
4034		4901
4035	In addition to a working ISO-C implementation and of course the	4902	In addition to a working ISO-C implementation and of course the
4036	backend-specific APIs, libev relies on a few additional extensions:	4903	backend-specific APIs, libev relies on a few additional extensions:
4037		4904
…		…
4043	Libev assumes not only that all watcher pointers have the same internal	4910	Libev assumes not only that all watcher pointers have the same internal
4044	structure (guaranteed by POSIX but not by ISO C for example), but it also	4911	structure (guaranteed by POSIX but not by ISO C for example), but it also
4045	assumes that the same (machine) code can be used to call any watcher	4912	assumes that the same (machine) code can be used to call any watcher
4046	callback: The watcher callbacks have different type signatures, but libev	4913	callback: The watcher callbacks have different type signatures, but libev
4047	calls them using an C<ev_watcher *> internally.	4914	calls them using an C<ev_watcher *> internally.
		4915
		4916	=item pointer accesses must be thread-atomic
		4917
		4918	Accessing a pointer value must be atomic, it must both be readable and
		4919	writable in one piece - this is the case on all current architectures.
4048		4920
4049	=item C<sig_atomic_t volatile> must be thread-atomic as well	4921	=item C<sig_atomic_t volatile> must be thread-atomic as well
4050		4922
4051	The type C<sig_atomic_t volatile> (or whatever is defined as	4923	The type C<sig_atomic_t volatile> (or whatever is defined as
4052	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4924	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4075	watchers.	4947	watchers.
4076		4948
4077	=item C<double> must hold a time value in seconds with enough accuracy	4949	=item C<double> must hold a time value in seconds with enough accuracy
4078		4950
4079	The type C<double> is used to represent timestamps. It is required to	4951	The type C<double> is used to represent timestamps. It is required to
4080	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4952	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4081	enough for at least into the year 4000. This requirement is fulfilled by	4953	good enough for at least into the year 4000 with millisecond accuracy
		4954	(the design goal for libev). This requirement is overfulfilled by
4082	implementations implementing IEEE 754, which is basically all existing	4955	implementations using IEEE 754, which is basically all existing ones. With
4083	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	4956	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4084	2200.
4085		4957
4086	=back	4958	=back
4087		4959
4088	If you know of other additional requirements drop me a note.	4960	If you know of other additional requirements drop me a note.
4089		4961
…		…
4157	involves iterating over all running async watchers or all signal numbers.	5029	involves iterating over all running async watchers or all signal numbers.
4158		5030
4159	=back	5031	=back
4160		5032
4161		5033
		5034	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5035
		5036	The major version 4 introduced some incompatible changes to the API.
		5037
		5038	At the moment, the C<ev.h> header file provides compatibility definitions
		5039	for all changes, so most programs should still compile. The compatibility
		5040	layer might be removed in later versions of libev, so better update to the
		5041	new API early than late.
		5042
		5043	=over 4
		5044
		5045	=item C<EV_COMPAT3> backwards compatibility mechanism
		5046
		5047	The backward compatibility mechanism can be controlled by
		5048	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5049	section.
		5050
		5051	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5052
		5053	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5054
		5055	ev_loop_destroy (EV_DEFAULT_UC);
		5056	ev_loop_fork (EV_DEFAULT);
		5057
		5058	=item function/symbol renames
		5059
		5060	A number of functions and symbols have been renamed:
		5061
		5062	ev_loop => ev_run
		5063	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5064	EVLOOP_ONESHOT => EVRUN_ONCE
		5065
		5066	ev_unloop => ev_break
		5067	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5068	EVUNLOOP_ONE => EVBREAK_ONE
		5069	EVUNLOOP_ALL => EVBREAK_ALL
		5070
		5071	EV_TIMEOUT => EV_TIMER
		5072
		5073	ev_loop_count => ev_iteration
		5074	ev_loop_depth => ev_depth
		5075	ev_loop_verify => ev_verify
		5076
		5077	Most functions working on C<struct ev_loop> objects don't have an
		5078	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5079	associated constants have been renamed to not collide with the C<struct
		5080	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5081	as all other watcher types. Note that C<ev_loop_fork> is still called
		5082	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5083	typedef.
		5084
		5085	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5086
		5087	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5088	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5089	and work, but the library code will of course be larger.
		5090
		5091	=back
		5092
		5093
4162	=head1 GLOSSARY	5094	=head1 GLOSSARY
4163		5095
4164	=over 4	5096	=over 4
4165		5097
4166	=item active	5098	=item active
4167		5099
4168	A watcher is active as long as it has been started (has been attached to	5100	A watcher is active as long as it has been started and not yet stopped.
4169	an event loop) but not yet stopped (disassociated from the event loop).	5101	See L<WATCHER STATES> for details.
4170		5102
4171	=item application	5103	=item application
4172		5104
4173	In this document, an application is whatever is using libev.	5105	In this document, an application is whatever is using libev.
		5106
		5107	=item backend
		5108
		5109	The part of the code dealing with the operating system interfaces.
4174		5110
4175	=item callback	5111	=item callback
4176		5112
4177	The address of a function that is called when some event has been	5113	The address of a function that is called when some event has been
4178	detected. Callbacks are being passed the event loop, the watcher that	5114	detected. Callbacks are being passed the event loop, the watcher that
4179	received the event, and the actual event bitset.	5115	received the event, and the actual event bitset.
4180		5116
4181	=item callback invocation	5117	=item callback/watcher invocation
4182		5118
4183	The act of calling the callback associated with a watcher.	5119	The act of calling the callback associated with a watcher.
4184		5120
4185	=item event	5121	=item event
4186		5122
4187	A change of state of some external event, such as data now being available	5123	A change of state of some external event, such as data now being available
4188	for reading on a file descriptor, time having passed or simply not having	5124	for reading on a file descriptor, time having passed or simply not having
4189	any other events happening anymore.	5125	any other events happening anymore.
4190		5126
4191	In libev, events are represented as single bits (such as C<EV_READ> or	5127	In libev, events are represented as single bits (such as C<EV_READ> or
4192	C<EV_TIMEOUT>).	5128	C<EV_TIMER>).
4193		5129
4194	=item event library	5130	=item event library
4195		5131
4196	A software package implementing an event model and loop.	5132	A software package implementing an event model and loop.
4197		5133
…		…
4205	The model used to describe how an event loop handles and processes	5141	The model used to describe how an event loop handles and processes
4206	watchers and events.	5142	watchers and events.
4207		5143
4208	=item pending	5144	=item pending
4209		5145
4210	A watcher is pending as soon as the corresponding event has been detected,	5146	A watcher is pending as soon as the corresponding event has been
4211	and stops being pending as soon as the watcher will be invoked or its	5147	detected. See L<WATCHER STATES> for details.
4212	pending status is explicitly cleared by the application.
4213
4214	A watcher can be pending, but not active. Stopping a watcher also clears
4215	its pending status.
4216		5148
4217	=item real time	5149	=item real time
4218		5150
4219	The physical time that is observed. It is apparently strictly monotonic :)	5151	The physical time that is observed. It is apparently strictly monotonic :)
4220		5152
…		…
4227	=item watcher	5159	=item watcher
4228		5160
4229	A data structure that describes interest in certain events. Watchers need	5161	A data structure that describes interest in certain events. Watchers need
4230	to be started (attached to an event loop) before they can receive events.	5162	to be started (attached to an event loop) before they can receive events.
4231		5163
4232	=item watcher invocation
4233
4234	The act of calling the callback associated with a watcher.
4235
4236	=back	5164	=back
4237		5165
4238	=head1 AUTHOR	5166	=head1 AUTHOR
4239		5167
4240	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5168	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5169	Magnusson and Emanuele Giaquinta.
4241		5170

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