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Revision 1.352 by root, Mon Jan 10 14:30:15 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.
421		512
422	While stopping, setting and starting an I/O watcher in the same iteration	513	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	514	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	515	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	516	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	582	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		583
493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	584	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)).	585	it's really slow, but it still scales very well (O(active_fds)).
495		586
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	587	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	588	file descriptor per loop iteration. For small and medium numbers of file
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	589	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	590	might perform better.
504		591
505	On the positive side, with the exception of the spurious readiness	592	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	593	specification in all tests and is fully embeddable, which is a rare feat
508	OS-specific backends (I vastly prefer correctness over speed hacks).	594	among the OS-specific backends (I vastly prefer correctness over speed
		595	hacks).
		596
		597	On the negative side, the interface is I<bizarre> - so bizarre that
		598	even sun itself gets it wrong in their code examples: The event polling
		599	function sometimes returning events to the caller even though an error
		600	occured, but with no indication whether it has done so or not (yes, it's
		601	even documented that way) - deadly for edge-triggered interfaces where
		602	you absolutely have to know whether an event occured or not because you
		603	have to re-arm the watcher.
		604
		605	Fortunately libev seems to be able to work around these idiocies.
509		606
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	607	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	608	C<EVBACKEND_POLL>.
512		609
513	=item C<EVBACKEND_ALL>	610	=item C<EVBACKEND_ALL>
514		611
515	Try all backends (even potentially broken ones that wouldn't be tried	612	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	613	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	614	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		615
519	It is definitely not recommended to use this flag.	616	It is definitely not recommended to use this flag, use whatever
		617	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		618	at all.
		619
		620	=item C<EVBACKEND_MASK>
		621
		622	Not a backend at all, but a mask to select all backend bits from a
		623	C<flags> value, in case you want to mask out any backends from a flags
		624	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
520		625
521	=back	626	=back
522		627
523	If one or more of these are or'ed into the flags value, then only these	628	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	629	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.	630	here). If none are specified, all backends in C<ev_recommended_backends
526		631	()> 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		632
555	Example: Try to create a event loop that uses epoll and nothing else.	633	Example: Try to create a event loop that uses epoll and nothing else.
556		634
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	635	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	636	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	637	fatal ("no epoll found here, maybe it hides under your chair");
560		638
		639	Example: Use whatever libev has to offer, but make sure that kqueue is
		640	used if available.
		641
		642	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		643
561	=item ev_default_destroy ()	644	=item ev_loop_destroy (loop)
562		645
563	Destroys the default loop again (frees all memory and kernel state	646	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	647	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	648	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>	649	responsibility to either stop all watchers cleanly yourself I<before>
567	calling this function, or cope with the fact afterwards (which is usually	650	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	651	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
570		653
571	Note that certain global state, such as signal state (and installed signal	654	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	655	handlers), will not be freed by this function, and related watchers (such
573	as signal and child watchers) would need to be stopped manually.	656	as signal and child watchers) would need to be stopped manually.
574		657
575	In general it is not advisable to call this function except in the	658	This function is normally used on loop objects allocated by
576	rare occasion where you really need to free e.g. the signal handling	659	C<ev_loop_new>, but it can also be used on the default loop returned by
		660	C<ev_default_loop>, in which case it is not thread-safe.
		661
		662	Note that it is not advisable to call this function on the default loop
		663	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	664	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>).	665	and C<ev_loop_destroy>.
579		666
580	=item ev_loop_destroy (loop)	667	=item ev_loop_fork (loop)
581		668
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	669	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	670	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	671	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	672	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	673	child before resuming or calling C<ev_run>.
592	functions, and it will only take effect at the next C<ev_loop> iteration.	674
		675	Again, you I<have> to call it on I<any> loop that you want to re-use after
		676	a fork, I<even if you do not plan to use the loop in the parent>. This is
		677	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		678	during fork.
593		679
594	On the other hand, you only need to call this function in the child	680	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	681	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.	682	you just fork+exec or create a new loop in the child, you don't have to
		683	call it at all (in fact, C<epoll> is so badly broken that it makes a
		684	difference, but libev will usually detect this case on its own and do a
		685	costly reset of the backend).
597		686
598	The function itself is quite fast and it's usually not a problem to call	687	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	688	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		689
		690	Example: Automate calling C<ev_loop_fork> on the default loop when
		691	using pthreads.
		692
		693	static void
		694	post_fork_child (void)
		695	{
		696	ev_loop_fork (EV_DEFAULT);
		697	}
		698
		699	...
602	pthread_atfork (0, 0, ev_default_fork);	700	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		701
611	=item int ev_is_default_loop (loop)	702	=item int ev_is_default_loop (loop)
612		703
613	Returns true when the given loop is, in fact, the default loop, and false	704	Returns true when the given loop is, in fact, the default loop, and false
614	otherwise.	705	otherwise.
615		706
616	=item unsigned int ev_loop_count (loop)	707	=item unsigned int ev_iteration (loop)
617		708
618	Returns the count of loop iterations for the loop, which is identical to	709	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	710	to the number of times libev did poll for new events. It starts at C<0>
620	happily wraps around with enough iterations.	711	and happily wraps around with enough iterations.
621		712
622	This value can sometimes be useful as a generation counter of sorts (it	713	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	714	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	715	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		716	prepare and check phases.
625		717
626	=item unsigned int ev_loop_depth (loop)	718	=item unsigned int ev_depth (loop)
627		719
628	Returns the number of times C<ev_loop> was entered minus the number of	720	Returns the number of times C<ev_run> was entered minus the number of
629	times C<ev_loop> was exited, in other words, the recursion depth.	721	times C<ev_run> was exited normally, in other words, the recursion depth.
630		722
631	Outside C<ev_loop>, this number is zero. In a callback, this number is	723	Outside C<ev_run>, this number is zero. In a callback, this number is
632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	724	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
633	in which case it is higher.	725	in which case it is higher.
634		726
635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	727	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
636	etc.), doesn't count as exit.	728	throwing an exception etc.), doesn't count as "exit" - consider this
		729	as a hint to avoid such ungentleman-like behaviour unless it's really
		730	convenient, in which case it is fully supported.
637		731
638	=item unsigned int ev_backend (loop)	732	=item unsigned int ev_backend (loop)
639		733
640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	734	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
641	use.	735	use.
…		…
650		744
651	=item ev_now_update (loop)	745	=item ev_now_update (loop)
652		746
653	Establishes the current time by querying the kernel, updating the time	747	Establishes the current time by querying the kernel, updating the time
654	returned by C<ev_now ()> in the progress. This is a costly operation and	748	returned by C<ev_now ()> in the progress. This is a costly operation and
655	is usually done automatically within C<ev_loop ()>.	749	is usually done automatically within C<ev_run ()>.
656		750
657	This function is rarely useful, but when some event callback runs for a	751	This function is rarely useful, but when some event callback runs for a
658	very long time without entering the event loop, updating libev's idea of	752	very long time without entering the event loop, updating libev's idea of
659	the current time is a good idea.	753	the current time is a good idea.
660		754
…		…
662		756
663	=item ev_suspend (loop)	757	=item ev_suspend (loop)
664		758
665	=item ev_resume (loop)	759	=item ev_resume (loop)
666		760
667	These two functions suspend and resume a loop, for use when the loop is	761	These two functions suspend and resume an event loop, for use when the
668	not used for a while and timeouts should not be processed.	762	loop is not used for a while and timeouts should not be processed.
669		763
670	A typical use case would be an interactive program such as a game: When	764	A typical use case would be an interactive program such as a game: When
671	the user presses C<^Z> to suspend the game and resumes it an hour later it	765	the user presses C<^Z> to suspend the game and resumes it an hour later it
672	would be best to handle timeouts as if no time had actually passed while	766	would be best to handle timeouts as if no time had actually passed while
673	the program was suspended. This can be achieved by calling C<ev_suspend>	767	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
675	C<ev_resume> directly afterwards to resume timer processing.	769	C<ev_resume> directly afterwards to resume timer processing.
676		770
677	Effectively, all C<ev_timer> watchers will be delayed by the time spend	771	Effectively, all C<ev_timer> watchers will be delayed by the time spend
678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	772	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
679	will be rescheduled (that is, they will lose any events that would have	773	will be rescheduled (that is, they will lose any events that would have
680	occured while suspended).	774	occurred while suspended).
681		775
682	After calling C<ev_suspend> you B<must not> call I<any> function on the	776	After calling C<ev_suspend> you B<must not> call I<any> function on the
683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	777	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
684	without a previous call to C<ev_suspend>.	778	without a previous call to C<ev_suspend>.
685		779
686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	780	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
687	event loop time (see C<ev_now_update>).	781	event loop time (see C<ev_now_update>).
688		782
689	=item ev_loop (loop, int flags)	783	=item ev_run (loop, int flags)
690		784
691	Finally, this is it, the event handler. This function usually is called	785	Finally, this is it, the event handler. This function usually is called
692	after you initialised all your watchers and you want to start handling	786	after you have initialised all your watchers and you want to start
693	events.	787	handling events. It will ask the operating system for any new events, call
		788	the watcher callbacks, an then repeat the whole process indefinitely: This
		789	is why event loops are called I<loops>.
694		790
695	If the flags argument is specified as C<0>, it will not return until	791	If the flags argument is specified as C<0>, it will keep handling events
696	either no event watchers are active anymore or C<ev_unloop> was called.	792	until either no event watchers are active anymore or C<ev_break> was
		793	called.
697		794
698	Please note that an explicit C<ev_unloop> is usually better than	795	Please note that an explicit C<ev_break> is usually better than
699	relying on all watchers to be stopped when deciding when a program has	796	relying on all watchers to be stopped when deciding when a program has
700	finished (especially in interactive programs), but having a program	797	finished (especially in interactive programs), but having a program
701	that automatically loops as long as it has to and no longer by virtue	798	that automatically loops as long as it has to and no longer by virtue
702	of relying on its watchers stopping correctly, that is truly a thing of	799	of relying on its watchers stopping correctly, that is truly a thing of
703	beauty.	800	beauty.
704		801
		802	This function is also I<mostly> exception-safe - you can break out of
		803	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		804	exception and so on. This does not decrement the C<ev_depth> value, nor
		805	will it clear any outstanding C<EVBREAK_ONE> breaks.
		806
705	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	807	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
706	those events and any already outstanding ones, but will not block your	808	those events and any already outstanding ones, but will not wait and
707	process in case there are no events and will return after one iteration of	809	block your process in case there are no events and will return after one
708	the loop.	810	iteration of the loop. This is sometimes useful to poll and handle new
		811	events while doing lengthy calculations, to keep the program responsive.
709		812
710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	813	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
711	necessary) and will handle those and any already outstanding ones. It	814	necessary) and will handle those and any already outstanding ones. It
712	will block your process until at least one new event arrives (which could	815	will block your process until at least one new event arrives (which could
713	be an event internal to libev itself, so there is no guarantee that a	816	be an event internal to libev itself, so there is no guarantee that a
714	user-registered callback will be called), and will return after one	817	user-registered callback will be called), and will return after one
715	iteration of the loop.	818	iteration of the loop.
716		819
717	This is useful if you are waiting for some external event in conjunction	820	This is useful if you are waiting for some external event in conjunction
718	with something not expressible using other libev watchers (i.e. "roll your	821	with something not expressible using other libev watchers (i.e. "roll your
719	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	822	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
720	usually a better approach for this kind of thing.	823	usually a better approach for this kind of thing.
721		824
722	Here are the gory details of what C<ev_loop> does:	825	Here are the gory details of what C<ev_run> does:
723		826
		827	- Increment loop depth.
		828	- Reset the ev_break status.
724	- Before the first iteration, call any pending watchers.	829	- Before the first iteration, call any pending watchers.
		830	LOOP:
725	* If EVFLAG_FORKCHECK was used, check for a fork.	831	- If EVFLAG_FORKCHECK was used, check for a fork.
726	- If a fork was detected (by any means), queue and call all fork watchers.	832	- If a fork was detected (by any means), queue and call all fork watchers.
727	- Queue and call all prepare watchers.	833	- Queue and call all prepare watchers.
		834	- If ev_break was called, goto FINISH.
728	- If we have been forked, detach and recreate the kernel state	835	- If we have been forked, detach and recreate the kernel state
729	as to not disturb the other process.	836	as to not disturb the other process.
730	- Update the kernel state with all outstanding changes.	837	- Update the kernel state with all outstanding changes.
731	- Update the "event loop time" (ev_now ()).	838	- Update the "event loop time" (ev_now ()).
732	- Calculate for how long to sleep or block, if at all	839	- Calculate for how long to sleep or block, if at all
733	(active idle watchers, EVLOOP_NONBLOCK or not having	840	(active idle watchers, EVRUN_NOWAIT or not having
734	any active watchers at all will result in not sleeping).	841	any active watchers at all will result in not sleeping).
735	- Sleep if the I/O and timer collect interval say so.	842	- Sleep if the I/O and timer collect interval say so.
		843	- Increment loop iteration counter.
736	- Block the process, waiting for any events.	844	- Block the process, waiting for any events.
737	- Queue all outstanding I/O (fd) events.	845	- Queue all outstanding I/O (fd) events.
738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	846	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
739	- Queue all expired timers.	847	- Queue all expired timers.
740	- Queue all expired periodics.	848	- Queue all expired periodics.
741	- Unless any events are pending now, queue all idle watchers.	849	- Queue all idle watchers with priority higher than that of pending events.
742	- Queue all check watchers.	850	- Queue all check watchers.
743	- Call all queued watchers in reverse order (i.e. check watchers first).	851	- Call all queued watchers in reverse order (i.e. check watchers first).
744	Signals and child watchers are implemented as I/O watchers, and will	852	Signals and child watchers are implemented as I/O watchers, and will
745	be handled here by queueing them when their watcher gets executed.	853	be handled here by queueing them when their watcher gets executed.
746	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	854	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
747	were used, or there are no active watchers, return, otherwise	855	were used, or there are no active watchers, goto FINISH, otherwise
748	continue with step *.	856	continue with step LOOP.
		857	FINISH:
		858	- Reset the ev_break status iff it was EVBREAK_ONE.
		859	- Decrement the loop depth.
		860	- Return.
749		861
750	Example: Queue some jobs and then loop until no events are outstanding	862	Example: Queue some jobs and then loop until no events are outstanding
751	anymore.	863	anymore.
752		864
753	... queue jobs here, make sure they register event watchers as long	865	... queue jobs here, make sure they register event watchers as long
754	... as they still have work to do (even an idle watcher will do..)	866	... as they still have work to do (even an idle watcher will do..)
755	ev_loop (my_loop, 0);	867	ev_run (my_loop, 0);
756	... jobs done or somebody called unloop. yeah!	868	... jobs done or somebody called unloop. yeah!
757		869
758	=item ev_unloop (loop, how)	870	=item ev_break (loop, how)
759		871
760	Can be used to make a call to C<ev_loop> return early (but only after it	872	Can be used to make a call to C<ev_run> return early (but only after it
761	has processed all outstanding events). The C<how> argument must be either	873	has processed all outstanding events). The C<how> argument must be either
762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	874	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	875	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
764		876
765	This "unloop state" will be cleared when entering C<ev_loop> again.	877	This "break state" will be cleared on the next call to C<ev_run>.
766		878
767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	879	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		880	which case it will have no effect.
768		881
769	=item ev_ref (loop)	882	=item ev_ref (loop)
770		883
771	=item ev_unref (loop)	884	=item ev_unref (loop)
772		885
773	Ref/unref can be used to add or remove a reference count on the event	886	Ref/unref can be used to add or remove a reference count on the event
774	loop: Every watcher keeps one reference, and as long as the reference	887	loop: Every watcher keeps one reference, and as long as the reference
775	count is nonzero, C<ev_loop> will not return on its own.	888	count is nonzero, C<ev_run> will not return on its own.
776		889
777	If you have a watcher you never unregister that should not keep C<ev_loop>	890	This is useful when you have a watcher that you never intend to
778	from returning, call ev_unref() after starting, and ev_ref() before	891	unregister, but that nevertheless should not keep C<ev_run> from
		892	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
779	stopping it.	893	before stopping it.
780		894
781	As an example, libev itself uses this for its internal signal pipe: It	895	As an example, libev itself uses this for its internal signal pipe: It
782	is not visible to the libev user and should not keep C<ev_loop> from	896	is not visible to the libev user and should not keep C<ev_run> from
783	exiting if no event watchers registered by it are active. It is also an	897	exiting if no event watchers registered by it are active. It is also an
784	excellent way to do this for generic recurring timers or from within	898	excellent way to do this for generic recurring timers or from within
785	third-party libraries. Just remember to I<unref after start> and I<ref	899	third-party libraries. Just remember to I<unref after start> and I<ref
786	before stop> (but only if the watcher wasn't active before, or was active	900	before stop> (but only if the watcher wasn't active before, or was active
787	before, respectively. Note also that libev might stop watchers itself	901	before, respectively. Note also that libev might stop watchers itself
788	(e.g. non-repeating timers) in which case you have to C<ev_ref>	902	(e.g. non-repeating timers) in which case you have to C<ev_ref>
789	in the callback).	903	in the callback).
790		904
791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	905	Example: Create a signal watcher, but keep it from keeping C<ev_run>
792	running when nothing else is active.	906	running when nothing else is active.
793		907
794	ev_signal exitsig;	908	ev_signal exitsig;
795	ev_signal_init (&exitsig, sig_cb, SIGINT);	909	ev_signal_init (&exitsig, sig_cb, SIGINT);
796	ev_signal_start (loop, &exitsig);	910	ev_signal_start (loop, &exitsig);
797	evf_unref (loop);	911	ev_unref (loop);
798		912
799	Example: For some weird reason, unregister the above signal handler again.	913	Example: For some weird reason, unregister the above signal handler again.
800		914
801	ev_ref (loop);	915	ev_ref (loop);
802	ev_signal_stop (loop, &exitsig);	916	ev_signal_stop (loop, &exitsig);
…		…
841	usually doesn't make much sense to set it to a lower value than C<0.01>,	955	usually doesn't make much sense to set it to a lower value than C<0.01>,
842	as this approaches the timing granularity of most systems. Note that if	956	as this approaches the timing granularity of most systems. Note that if
843	you do transactions with the outside world and you can't increase the	957	you do transactions with the outside world and you can't increase the
844	parallelity, then this setting will limit your transaction rate (if you	958	parallelity, then this setting will limit your transaction rate (if you
845	need to poll once per transaction and the I/O collect interval is 0.01,	959	need to poll once per transaction and the I/O collect interval is 0.01,
846	then you can't do more than 100 transations per second).	960	then you can't do more than 100 transactions per second).
847		961
848	Setting the I<timeout collect interval> can improve the opportunity for	962	Setting the I<timeout collect interval> can improve the opportunity for
849	saving power, as the program will "bundle" timer callback invocations that	963	saving power, as the program will "bundle" timer callback invocations that
850	are "near" in time together, by delaying some, thus reducing the number of	964	are "near" in time together, by delaying some, thus reducing the number of
851	times the process sleeps and wakes up again. Another useful technique to	965	times the process sleeps and wakes up again. Another useful technique to
…		…
856	more often than 100 times per second:	970	more often than 100 times per second:
857		971
858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	972	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	973	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		974
		975	=item ev_invoke_pending (loop)
		976
		977	This call will simply invoke all pending watchers while resetting their
		978	pending state. Normally, C<ev_run> does this automatically when required,
		979	but when overriding the invoke callback this call comes handy. This
		980	function can be invoked from a watcher - this can be useful for example
		981	when you want to do some lengthy calculation and want to pass further
		982	event handling to another thread (you still have to make sure only one
		983	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		984
		985	=item int ev_pending_count (loop)
		986
		987	Returns the number of pending watchers - zero indicates that no watchers
		988	are pending.
		989
		990	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		991
		992	This overrides the invoke pending functionality of the loop: Instead of
		993	invoking all pending watchers when there are any, C<ev_run> will call
		994	this callback instead. This is useful, for example, when you want to
		995	invoke the actual watchers inside another context (another thread etc.).
		996
		997	If you want to reset the callback, use C<ev_invoke_pending> as new
		998	callback.
		999
		1000	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1001
		1002	Sometimes you want to share the same loop between multiple threads. This
		1003	can be done relatively simply by putting mutex_lock/unlock calls around
		1004	each call to a libev function.
		1005
		1006	However, C<ev_run> can run an indefinite time, so it is not feasible
		1007	to wait for it to return. One way around this is to wake up the event
		1008	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1009	I<release> and I<acquire> callbacks on the loop.
		1010
		1011	When set, then C<release> will be called just before the thread is
		1012	suspended waiting for new events, and C<acquire> is called just
		1013	afterwards.
		1014
		1015	Ideally, C<release> will just call your mutex_unlock function, and
		1016	C<acquire> will just call the mutex_lock function again.
		1017
		1018	While event loop modifications are allowed between invocations of
		1019	C<release> and C<acquire> (that's their only purpose after all), no
		1020	modifications done will affect the event loop, i.e. adding watchers will
		1021	have no effect on the set of file descriptors being watched, or the time
		1022	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1023	to take note of any changes you made.
		1024
		1025	In theory, threads executing C<ev_run> will be async-cancel safe between
		1026	invocations of C<release> and C<acquire>.
		1027
		1028	See also the locking example in the C<THREADS> section later in this
		1029	document.
		1030
		1031	=item ev_set_userdata (loop, void *data)
		1032
		1033	=item void *ev_userdata (loop)
		1034
		1035	Set and retrieve a single C<void *> associated with a loop. When
		1036	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1037	C<0>.
		1038
		1039	These two functions can be used to associate arbitrary data with a loop,
		1040	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1041	C<acquire> callbacks described above, but of course can be (ab-)used for
		1042	any other purpose as well.
		1043
861	=item ev_loop_verify (loop)	1044	=item ev_verify (loop)
862		1045
863	This function only does something when C<EV_VERIFY> support has been	1046	This function only does something when C<EV_VERIFY> support has been
864	compiled in, which is the default for non-minimal builds. It tries to go	1047	compiled in, which is the default for non-minimal builds. It tries to go
865	through all internal structures and checks them for validity. If anything	1048	through all internal structures and checks them for validity. If anything
866	is found to be inconsistent, it will print an error message to standard	1049	is found to be inconsistent, it will print an error message to standard
…		…
877		1060
878	In the following description, uppercase C<TYPE> in names stands for the	1061	In the following description, uppercase C<TYPE> in names stands for the
879	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1062	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
880	watchers and C<ev_io_start> for I/O watchers.	1063	watchers and C<ev_io_start> for I/O watchers.
881		1064
882	A watcher is a structure that you create and register to record your	1065	A watcher is an opaque structure that you allocate and register to record
883	interest in some event. For instance, if you want to wait for STDIN to	1066	your interest in some event. To make a concrete example, imagine you want
884	become readable, you would create an C<ev_io> watcher for that:	1067	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1068	for that:
885		1069
886	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1070	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
887	{	1071	{
888	ev_io_stop (w);	1072	ev_io_stop (w);
889	ev_unloop (loop, EVUNLOOP_ALL);	1073	ev_break (loop, EVBREAK_ALL);
890	}	1074	}
891		1075
892	struct ev_loop *loop = ev_default_loop (0);	1076	struct ev_loop *loop = ev_default_loop (0);
893		1077
894	ev_io stdin_watcher;	1078	ev_io stdin_watcher;
895		1079
896	ev_init (&stdin_watcher, my_cb);	1080	ev_init (&stdin_watcher, my_cb);
897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1081	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
898	ev_io_start (loop, &stdin_watcher);	1082	ev_io_start (loop, &stdin_watcher);
899		1083
900	ev_loop (loop, 0);	1084	ev_run (loop, 0);
901		1085
902	As you can see, you are responsible for allocating the memory for your	1086	As you can see, you are responsible for allocating the memory for your
903	watcher structures (and it is I<usually> a bad idea to do this on the	1087	watcher structures (and it is I<usually> a bad idea to do this on the
904	stack).	1088	stack).
905		1089
906	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1090	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
907	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1091	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
908		1092
909	Each watcher structure must be initialised by a call to C<ev_init	1093	Each watcher structure must be initialised by a call to C<ev_init (watcher
910	(watcher *, callback)>, which expects a callback to be provided. This	1094	*, callback)>, which expects a callback to be provided. This callback is
911	callback gets invoked each time the event occurs (or, in the case of I/O	1095	invoked each time the event occurs (or, in the case of I/O watchers, each
912	watchers, each time the event loop detects that the file descriptor given	1096	time the event loop detects that the file descriptor given is readable
913	is readable and/or writable).	1097	and/or writable).
914		1098
915	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1099	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
916	macro to configure it, with arguments specific to the watcher type. There	1100	macro to configure it, with arguments specific to the watcher type. There
917	is also a macro to combine initialisation and setting in one call: C<<	1101	is also a macro to combine initialisation and setting in one call: C<<
918	ev_TYPE_init (watcher *, callback, ...) >>.	1102	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
941	=item C<EV_WRITE>	1125	=item C<EV_WRITE>
942		1126
943	The file descriptor in the C<ev_io> watcher has become readable and/or	1127	The file descriptor in the C<ev_io> watcher has become readable and/or
944	writable.	1128	writable.
945		1129
946	=item C<EV_TIMEOUT>	1130	=item C<EV_TIMER>
947		1131
948	The C<ev_timer> watcher has timed out.	1132	The C<ev_timer> watcher has timed out.
949		1133
950	=item C<EV_PERIODIC>	1134	=item C<EV_PERIODIC>
951		1135
…		…
969		1153
970	=item C<EV_PREPARE>	1154	=item C<EV_PREPARE>
971		1155
972	=item C<EV_CHECK>	1156	=item C<EV_CHECK>
973		1157
974	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1158	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
975	to gather new events, and all C<ev_check> watchers are invoked just after	1159	to gather new events, and all C<ev_check> watchers are invoked just after
976	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1160	C<ev_run> has gathered them, but before it invokes any callbacks for any
977	received events. Callbacks of both watcher types can start and stop as	1161	received events. Callbacks of both watcher types can start and stop as
978	many watchers as they want, and all of them will be taken into account	1162	many watchers as they want, and all of them will be taken into account
979	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1163	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
980	C<ev_loop> from blocking).	1164	C<ev_run> from blocking).
981		1165
982	=item C<EV_EMBED>	1166	=item C<EV_EMBED>
983		1167
984	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1168	The embedded event loop specified in the C<ev_embed> watcher needs attention.
985		1169
986	=item C<EV_FORK>	1170	=item C<EV_FORK>
987		1171
988	The event loop has been resumed in the child process after fork (see	1172	The event loop has been resumed in the child process after fork (see
989	C<ev_fork>).	1173	C<ev_fork>).
		1174
		1175	=item C<EV_CLEANUP>
		1176
		1177	The event loop is about to be destroyed (see C<ev_cleanup>).
990		1178
991	=item C<EV_ASYNC>	1179	=item C<EV_ASYNC>
992		1180
993	The given async watcher has been asynchronously notified (see C<ev_async>).	1181	The given async watcher has been asynchronously notified (see C<ev_async>).
994		1182
…		…
1041		1229
1042	ev_io w;	1230	ev_io w;
1043	ev_init (&w, my_cb);	1231	ev_init (&w, my_cb);
1044	ev_io_set (&w, STDIN_FILENO, EV_READ);	1232	ev_io_set (&w, STDIN_FILENO, EV_READ);
1045		1233
1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1234	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1047		1235
1048	This macro initialises the type-specific parts of a watcher. You need to	1236	This macro initialises the type-specific parts of a watcher. You need to
1049	call C<ev_init> at least once before you call this macro, but you can	1237	call C<ev_init> at least once before you call this macro, but you can
1050	call C<ev_TYPE_set> any number of times. You must not, however, call this	1238	call C<ev_TYPE_set> any number of times. You must not, however, call this
1051	macro on a watcher that is active (it can be pending, however, which is a	1239	macro on a watcher that is active (it can be pending, however, which is a
…		…
1064		1252
1065	Example: Initialise and set an C<ev_io> watcher in one step.	1253	Example: Initialise and set an C<ev_io> watcher in one step.
1066		1254
1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1255	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1068		1256
1069	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1257	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1070		1258
1071	Starts (activates) the given watcher. Only active watchers will receive	1259	Starts (activates) the given watcher. Only active watchers will receive
1072	events. If the watcher is already active nothing will happen.	1260	events. If the watcher is already active nothing will happen.
1073		1261
1074	Example: Start the C<ev_io> watcher that is being abused as example in this	1262	Example: Start the C<ev_io> watcher that is being abused as example in this
1075	whole section.	1263	whole section.
1076		1264
1077	ev_io_start (EV_DEFAULT_UC, &w);	1265	ev_io_start (EV_DEFAULT_UC, &w);
1078		1266
1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1267	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1080		1268
1081	Stops the given watcher if active, and clears the pending status (whether	1269	Stops the given watcher if active, and clears the pending status (whether
1082	the watcher was active or not).	1270	the watcher was active or not).
1083		1271
1084	It is possible that stopped watchers are pending - for example,	1272	It is possible that stopped watchers are pending - for example,
…		…
1109	=item ev_cb_set (ev_TYPE *watcher, callback)	1297	=item ev_cb_set (ev_TYPE *watcher, callback)
1110		1298
1111	Change the callback. You can change the callback at virtually any time	1299	Change the callback. You can change the callback at virtually any time
1112	(modulo threads).	1300	(modulo threads).
1113		1301
1114	=item ev_set_priority (ev_TYPE *watcher, priority)	1302	=item ev_set_priority (ev_TYPE *watcher, int priority)
1115		1303
1116	=item int ev_priority (ev_TYPE *watcher)	1304	=item int ev_priority (ev_TYPE *watcher)
1117		1305
1118	Set and query the priority of the watcher. The priority is a small	1306	Set and query the priority of the watcher. The priority is a small
1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1307	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1151	watcher isn't pending it does nothing and returns C<0>.	1339	watcher isn't pending it does nothing and returns C<0>.
1152		1340
1153	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1341	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1154	callback to be invoked, which can be accomplished with this function.	1342	callback to be invoked, which can be accomplished with this function.
1155		1343
		1344	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1345
		1346	Feeds the given event set into the event loop, as if the specified event
		1347	had happened for the specified watcher (which must be a pointer to an
		1348	initialised but not necessarily started event watcher). Obviously you must
		1349	not free the watcher as long as it has pending events.
		1350
		1351	Stopping the watcher, letting libev invoke it, or calling
		1352	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1353	not started in the first place.
		1354
		1355	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1356	functions that do not need a watcher.
		1357
1156	=back	1358	=back
1157
1158		1359
1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1360	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1160		1361
1161	Each watcher has, by default, a member C<void *data> that you can change	1362	Each watcher has, by default, a member C<void *data> that you can change
1162	and read at any time: libev will completely ignore it. This can be used	1363	and read at any time: libev will completely ignore it. This can be used
…		…
1218	t2_cb (EV_P_ ev_timer *w, int revents)	1419	t2_cb (EV_P_ ev_timer *w, int revents)
1219	{	1420	{
1220	struct my_biggy big = (struct my_biggy *)	1421	struct my_biggy big = (struct my_biggy *)
1221	(((char *)w) - offsetof (struct my_biggy, t2));	1422	(((char *)w) - offsetof (struct my_biggy, t2));
1222	}	1423	}
		1424
		1425	=head2 WATCHER STATES
		1426
		1427	There are various watcher states mentioned throughout this manual -
		1428	active, pending and so on. In this section these states and the rules to
		1429	transition between them will be described in more detail - and while these
		1430	rules might look complicated, they usually do "the right thing".
		1431
		1432	=over 4
		1433
		1434	=item initialiased
		1435
		1436	Before a watcher can be registered with the event looop it has to be
		1437	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1438	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1439
		1440	In this state it is simply some block of memory that is suitable for use
		1441	in an event loop. It can be moved around, freed, reused etc. at will.
		1442
		1443	=item started/running/active
		1444
		1445	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1446	property of the event loop, and is actively waiting for events. While in
		1447	this state it cannot be accessed (except in a few documented ways), moved,
		1448	freed or anything else - the only legal thing is to keep a pointer to it,
		1449	and call libev functions on it that are documented to work on active watchers.
		1450
		1451	=item pending
		1452
		1453	If a watcher is active and libev determines that an event it is interested
		1454	in has occurred (such as a timer expiring), it will become pending. It will
		1455	stay in this pending state until either it is stopped or its callback is
		1456	about to be invoked, so it is not normally pending inside the watcher
		1457	callback.
		1458
		1459	The watcher might or might not be active while it is pending (for example,
		1460	an expired non-repeating timer can be pending but no longer active). If it
		1461	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1462	but it is still property of the event loop at this time, so cannot be
		1463	moved, freed or reused. And if it is active the rules described in the
		1464	previous item still apply.
		1465
		1466	It is also possible to feed an event on a watcher that is not active (e.g.
		1467	via C<ev_feed_event>), in which case it becomes pending without being
		1468	active.
		1469
		1470	=item stopped
		1471
		1472	A watcher can be stopped implicitly by libev (in which case it might still
		1473	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1474	latter will clear any pending state the watcher might be in, regardless
		1475	of whether it was active or not, so stopping a watcher explicitly before
		1476	freeing it is often a good idea.
		1477
		1478	While stopped (and not pending) the watcher is essentially in the
		1479	initialised state, that is it can be reused, moved, modified in any way
		1480	you wish.
		1481
		1482	=back
1223		1483
1224	=head2 WATCHER PRIORITY MODELS	1484	=head2 WATCHER PRIORITY MODELS
1225		1485
1226	Many event loops support I<watcher priorities>, which are usually small	1486	Many event loops support I<watcher priorities>, which are usually small
1227	integers that influence the ordering of event callback invocation	1487	integers that influence the ordering of event callback invocation
…		…
1270		1530
1271	For example, to emulate how many other event libraries handle priorities,	1531	For example, to emulate how many other event libraries handle priorities,
1272	you can associate an C<ev_idle> watcher to each such watcher, and in	1532	you can associate an C<ev_idle> watcher to each such watcher, and in
1273	the normal watcher callback, you just start the idle watcher. The real	1533	the normal watcher callback, you just start the idle watcher. The real
1274	processing is done in the idle watcher callback. This causes libev to	1534	processing is done in the idle watcher callback. This causes libev to
1275	continously poll and process kernel event data for the watcher, but when	1535	continuously poll and process kernel event data for the watcher, but when
1276	the lock-out case is known to be rare (which in turn is rare :), this is	1536	the lock-out case is known to be rare (which in turn is rare :), this is
1277	workable.	1537	workable.
1278		1538
1279	Usually, however, the lock-out model implemented that way will perform	1539	Usually, however, the lock-out model implemented that way will perform
1280	miserably under the type of load it was designed to handle. In that case,	1540	miserably under the type of load it was designed to handle. In that case,
…		…
1294	{	1554	{
1295	// stop the I/O watcher, we received the event, but	1555	// stop the I/O watcher, we received the event, but
1296	// are not yet ready to handle it.	1556	// are not yet ready to handle it.
1297	ev_io_stop (EV_A_ w);	1557	ev_io_stop (EV_A_ w);
1298		1558
1299	// start the idle watcher to ahndle the actual event.	1559	// start the idle watcher to handle the actual event.
1300	// it will not be executed as long as other watchers	1560	// it will not be executed as long as other watchers
1301	// with the default priority are receiving events.	1561	// with the default priority are receiving events.
1302	ev_idle_start (EV_A_ &idle);	1562	ev_idle_start (EV_A_ &idle);
1303	}	1563	}
1304		1564
…		…
1358		1618
1359	If you cannot use non-blocking mode, then force the use of a	1619	If you cannot use non-blocking mode, then force the use of a
1360	known-to-be-good backend (at the time of this writing, this includes only	1620	known-to-be-good backend (at the time of this writing, this includes only
1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file	1621	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1362	descriptors for which non-blocking operation makes no sense (such as	1622	descriptors for which non-blocking operation makes no sense (such as
1363	files) - libev doesn't guarentee any specific behaviour in that case.	1623	files) - libev doesn't guarantee any specific behaviour in that case.
1364		1624
1365	Another thing you have to watch out for is that it is quite easy to	1625	Another thing you have to watch out for is that it is quite easy to
1366	receive "spurious" readiness notifications, that is your callback might	1626	receive "spurious" readiness notifications, that is your callback might
1367	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1627	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1368	because there is no data. Not only are some backends known to create a	1628	because there is no data. Not only are some backends known to create a
…		…
1433		1693
1434	So when you encounter spurious, unexplained daemon exits, make sure you	1694	So when you encounter spurious, unexplained daemon exits, make sure you
1435	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1695	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1436	somewhere, as that would have given you a big clue).	1696	somewhere, as that would have given you a big clue).
1437		1697
		1698	=head3 The special problem of accept()ing when you can't
		1699
		1700	Many implementations of the POSIX C<accept> function (for example,
		1701	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1702	connection from the pending queue in all error cases.
		1703
		1704	For example, larger servers often run out of file descriptors (because
		1705	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1706	rejecting the connection, leading to libev signalling readiness on
		1707	the next iteration again (the connection still exists after all), and
		1708	typically causing the program to loop at 100% CPU usage.
		1709
		1710	Unfortunately, the set of errors that cause this issue differs between
		1711	operating systems, there is usually little the app can do to remedy the
		1712	situation, and no known thread-safe method of removing the connection to
		1713	cope with overload is known (to me).
		1714
		1715	One of the easiest ways to handle this situation is to just ignore it
		1716	- when the program encounters an overload, it will just loop until the
		1717	situation is over. While this is a form of busy waiting, no OS offers an
		1718	event-based way to handle this situation, so it's the best one can do.
		1719
		1720	A better way to handle the situation is to log any errors other than
		1721	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1722	messages, and continue as usual, which at least gives the user an idea of
		1723	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1724	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1725	usage.
		1726
		1727	If your program is single-threaded, then you could also keep a dummy file
		1728	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1729	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1730	close that fd, and create a new dummy fd. This will gracefully refuse
		1731	clients under typical overload conditions.
		1732
		1733	The last way to handle it is to simply log the error and C<exit>, as
		1734	is often done with C<malloc> failures, but this results in an easy
		1735	opportunity for a DoS attack.
1438		1736
1439	=head3 Watcher-Specific Functions	1737	=head3 Watcher-Specific Functions
1440		1738
1441	=over 4	1739	=over 4
1442		1740
…		…
1474	...	1772	...
1475	struct ev_loop *loop = ev_default_init (0);	1773	struct ev_loop *loop = ev_default_init (0);
1476	ev_io stdin_readable;	1774	ev_io stdin_readable;
1477	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1775	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1478	ev_io_start (loop, &stdin_readable);	1776	ev_io_start (loop, &stdin_readable);
1479	ev_loop (loop, 0);	1777	ev_run (loop, 0);
1480		1778
1481		1779
1482	=head2 C<ev_timer> - relative and optionally repeating timeouts	1780	=head2 C<ev_timer> - relative and optionally repeating timeouts
1483		1781
1484	Timer watchers are simple relative timers that generate an event after a	1782	Timer watchers are simple relative timers that generate an event after a
…		…
1493	The callback is guaranteed to be invoked only I<after> its timeout has	1791	The callback is guaranteed to be invoked only I<after> its timeout has
1494	passed (not I<at>, so on systems with very low-resolution clocks this	1792	passed (not I<at>, so on systems with very low-resolution clocks this
1495	might introduce a small delay). If multiple timers become ready during the	1793	might introduce a small delay). If multiple timers become ready during the
1496	same loop iteration then the ones with earlier time-out values are invoked	1794	same loop iteration then the ones with earlier time-out values are invoked
1497	before ones of the same priority with later time-out values (but this is	1795	before ones of the same priority with later time-out values (but this is
1498	no longer true when a callback calls C<ev_loop> recursively).	1796	no longer true when a callback calls C<ev_run> recursively).
1499		1797
1500	=head3 Be smart about timeouts	1798	=head3 Be smart about timeouts
1501		1799
1502	Many real-world problems involve some kind of timeout, usually for error	1800	Many real-world problems involve some kind of timeout, usually for error
1503	recovery. A typical example is an HTTP request - if the other side hangs,	1801	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1589	ev_tstamp timeout = last_activity + 60.;	1887	ev_tstamp timeout = last_activity + 60.;
1590		1888
1591	// if last_activity + 60. is older than now, we did time out	1889	// if last_activity + 60. is older than now, we did time out
1592	if (timeout < now)	1890	if (timeout < now)
1593	{	1891	{
1594	// timeout occured, take action	1892	// timeout occurred, take action
1595	}	1893	}
1596	else	1894	else
1597	{	1895	{
1598	// callback was invoked, but there was some activity, re-arm	1896	// callback was invoked, but there was some activity, re-arm
1599	// the watcher to fire in last_activity + 60, which is	1897	// the watcher to fire in last_activity + 60, which is
…		…
1621	to the current time (meaning we just have some activity :), then call the	1919	to the current time (meaning we just have some activity :), then call the
1622	callback, which will "do the right thing" and start the timer:	1920	callback, which will "do the right thing" and start the timer:
1623		1921
1624	ev_init (timer, callback);	1922	ev_init (timer, callback);
1625	last_activity = ev_now (loop);	1923	last_activity = ev_now (loop);
1626	callback (loop, timer, EV_TIMEOUT);	1924	callback (loop, timer, EV_TIMER);
1627		1925
1628	And when there is some activity, simply store the current time in	1926	And when there is some activity, simply store the current time in
1629	C<last_activity>, no libev calls at all:	1927	C<last_activity>, no libev calls at all:
1630		1928
1631	last_actiivty = ev_now (loop);	1929	last_activity = ev_now (loop);
1632		1930
1633	This technique is slightly more complex, but in most cases where the	1931	This technique is slightly more complex, but in most cases where the
1634	time-out is unlikely to be triggered, much more efficient.	1932	time-out is unlikely to be triggered, much more efficient.
1635		1933
1636	Changing the timeout is trivial as well (if it isn't hard-coded in the	1934	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1674		1972
1675	=head3 The special problem of time updates	1973	=head3 The special problem of time updates
1676		1974
1677	Establishing the current time is a costly operation (it usually takes at	1975	Establishing the current time is a costly operation (it usually takes at
1678	least two system calls): EV therefore updates its idea of the current	1976	least two system calls): EV therefore updates its idea of the current
1679	time only before and after C<ev_loop> collects new events, which causes a	1977	time only before and after C<ev_run> collects new events, which causes a
1680	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1978	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1681	lots of events in one iteration.	1979	lots of events in one iteration.
1682		1980
1683	The relative timeouts are calculated relative to the C<ev_now ()>	1981	The relative timeouts are calculated relative to the C<ev_now ()>
1684	time. This is usually the right thing as this timestamp refers to the time	1982	time. This is usually the right thing as this timestamp refers to the time
…		…
1690		1988
1691	If the event loop is suspended for a long time, you can also force an	1989	If the event loop is suspended for a long time, you can also force an
1692	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1990	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1693	()>.	1991	()>.
1694		1992
		1993	=head3 The special problems of suspended animation
		1994
		1995	When you leave the server world it is quite customary to hit machines that
		1996	can suspend/hibernate - what happens to the clocks during such a suspend?
		1997
		1998	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1999	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2000	to run until the system is suspended, but they will not advance while the
		2001	system is suspended. That means, on resume, it will be as if the program
		2002	was frozen for a few seconds, but the suspend time will not be counted
		2003	towards C<ev_timer> when a monotonic clock source is used. The real time
		2004	clock advanced as expected, but if it is used as sole clocksource, then a
		2005	long suspend would be detected as a time jump by libev, and timers would
		2006	be adjusted accordingly.
		2007
		2008	I would not be surprised to see different behaviour in different between
		2009	operating systems, OS versions or even different hardware.
		2010
		2011	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2012	time jump in the monotonic clocks and the realtime clock. If the program
		2013	is suspended for a very long time, and monotonic clock sources are in use,
		2014	then you can expect C<ev_timer>s to expire as the full suspension time
		2015	will be counted towards the timers. When no monotonic clock source is in
		2016	use, then libev will again assume a timejump and adjust accordingly.
		2017
		2018	It might be beneficial for this latter case to call C<ev_suspend>
		2019	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2020	deterministic behaviour in this case (you can do nothing against
		2021	C<SIGSTOP>).
		2022
1695	=head3 Watcher-Specific Functions and Data Members	2023	=head3 Watcher-Specific Functions and Data Members
1696		2024
1697	=over 4	2025	=over 4
1698		2026
1699	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2027	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1725	C<repeat> value), or reset the running timer to the C<repeat> value.	2053	C<repeat> value), or reset the running timer to the C<repeat> value.
1726		2054
1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2055	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1728	usage example.	2056	usage example.
1729		2057
		2058	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2059
		2060	Returns the remaining time until a timer fires. If the timer is active,
		2061	then this time is relative to the current event loop time, otherwise it's
		2062	the timeout value currently configured.
		2063
		2064	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2065	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2066	will return C<4>. When the timer expires and is restarted, it will return
		2067	roughly C<7> (likely slightly less as callback invocation takes some time,
		2068	too), and so on.
		2069
1730	=item ev_tstamp repeat [read-write]	2070	=item ev_tstamp repeat [read-write]
1731		2071
1732	The current C<repeat> value. Will be used each time the watcher times out	2072	The current C<repeat> value. Will be used each time the watcher times out
1733	or C<ev_timer_again> is called, and determines the next timeout (if any),	2073	or C<ev_timer_again> is called, and determines the next timeout (if any),
1734	which is also when any modifications are taken into account.	2074	which is also when any modifications are taken into account.
…		…
1759	}	2099	}
1760		2100
1761	ev_timer mytimer;	2101	ev_timer mytimer;
1762	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2102	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1763	ev_timer_again (&mytimer); /* start timer */	2103	ev_timer_again (&mytimer); /* start timer */
1764	ev_loop (loop, 0);	2104	ev_run (loop, 0);
1765		2105
1766	// and in some piece of code that gets executed on any "activity":	2106	// and in some piece of code that gets executed on any "activity":
1767	// reset the timeout to start ticking again at 10 seconds	2107	// reset the timeout to start ticking again at 10 seconds
1768	ev_timer_again (&mytimer);	2108	ev_timer_again (&mytimer);
1769		2109
…		…
1795		2135
1796	As with timers, the callback is guaranteed to be invoked only when the	2136	As with timers, the callback is guaranteed to be invoked only when the
1797	point in time where it is supposed to trigger has passed. If multiple	2137	point in time where it is supposed to trigger has passed. If multiple
1798	timers become ready during the same loop iteration then the ones with	2138	timers become ready during the same loop iteration then the ones with
1799	earlier time-out values are invoked before ones with later time-out values	2139	earlier time-out values are invoked before ones with later time-out values
1800	(but this is no longer true when a callback calls C<ev_loop> recursively).	2140	(but this is no longer true when a callback calls C<ev_run> recursively).
1801		2141
1802	=head3 Watcher-Specific Functions and Data Members	2142	=head3 Watcher-Specific Functions and Data Members
1803		2143
1804	=over 4	2144	=over 4
1805		2145
…		…
1933	Example: Call a callback every hour, or, more precisely, whenever the	2273	Example: Call a callback every hour, or, more precisely, whenever the
1934	system time is divisible by 3600. The callback invocation times have	2274	system time is divisible by 3600. The callback invocation times have
1935	potentially a lot of jitter, but good long-term stability.	2275	potentially a lot of jitter, but good long-term stability.
1936		2276
1937	static void	2277	static void
1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2278	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1939	{	2279	{
1940	... its now a full hour (UTC, or TAI or whatever your clock follows)	2280	... its now a full hour (UTC, or TAI or whatever your clock follows)
1941	}	2281	}
1942		2282
1943	ev_periodic hourly_tick;	2283	ev_periodic hourly_tick;
…		…
1966		2306
1967	=head2 C<ev_signal> - signal me when a signal gets signalled!	2307	=head2 C<ev_signal> - signal me when a signal gets signalled!
1968		2308
1969	Signal watchers will trigger an event when the process receives a specific	2309	Signal watchers will trigger an event when the process receives a specific
1970	signal one or more times. Even though signals are very asynchronous, libev	2310	signal one or more times. Even though signals are very asynchronous, libev
1971	will try it's best to deliver signals synchronously, i.e. as part of the	2311	will try its best to deliver signals synchronously, i.e. as part of the
1972	normal event processing, like any other event.	2312	normal event processing, like any other event.
1973		2313
1974	If you want signals asynchronously, just use C<sigaction> as you would	2314	If you want signals to be delivered truly asynchronously, just use
1975	do without libev and forget about sharing the signal. You can even use	2315	C<sigaction> as you would do without libev and forget about sharing
1976	C<ev_async> from a signal handler to synchronously wake up an event loop.	2316	the signal. You can even use C<ev_async> from a signal handler to
		2317	synchronously wake up an event loop.
1977		2318
1978	You can configure as many watchers as you like per signal. Only when the	2319	You can configure as many watchers as you like for the same signal, but
		2320	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2321	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2322	C<SIGINT> in both the default loop and another loop at the same time. At
		2323	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2324
1979	first watcher gets started will libev actually register a signal handler	2325	When the first watcher gets started will libev actually register something
1980	with the kernel (thus it coexists with your own signal handlers as long as	2326	with the kernel (thus it coexists with your own signal handlers as long as
1981	you don't register any with libev for the same signal). Similarly, when	2327	you don't register any with libev for the same signal).
1982	the last signal watcher for a signal is stopped, libev will reset the
1983	signal handler to SIG_DFL (regardless of what it was set to before).
1984		2328
1985	If possible and supported, libev will install its handlers with	2329	If possible and supported, libev will install its handlers with
1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2330	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1987	interrupted. If you have a problem with system calls getting interrupted by	2331	not be unduly interrupted. If you have a problem with system calls getting
1988	signals you can block all signals in an C<ev_check> watcher and unblock	2332	interrupted by signals you can block all signals in an C<ev_check> watcher
1989	them in an C<ev_prepare> watcher.	2333	and unblock them in an C<ev_prepare> watcher.
		2334
		2335	=head3 The special problem of inheritance over fork/execve/pthread_create
		2336
		2337	Both the signal mask (C<sigprocmask>) and the signal disposition
		2338	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2339	stopping it again), that is, libev might or might not block the signal,
		2340	and might or might not set or restore the installed signal handler.
		2341
		2342	While this does not matter for the signal disposition (libev never
		2343	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2344	C<execve>), this matters for the signal mask: many programs do not expect
		2345	certain signals to be blocked.
		2346
		2347	This means that before calling C<exec> (from the child) you should reset
		2348	the signal mask to whatever "default" you expect (all clear is a good
		2349	choice usually).
		2350
		2351	The simplest way to ensure that the signal mask is reset in the child is
		2352	to install a fork handler with C<pthread_atfork> that resets it. That will
		2353	catch fork calls done by libraries (such as the libc) as well.
		2354
		2355	In current versions of libev, the signal will not be blocked indefinitely
		2356	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2357	the window of opportunity for problems, it will not go away, as libev
		2358	I<has> to modify the signal mask, at least temporarily.
		2359
		2360	So I can't stress this enough: I<If you do not reset your signal mask when
		2361	you expect it to be empty, you have a race condition in your code>. This
		2362	is not a libev-specific thing, this is true for most event libraries.
		2363
		2364	=head3 The special problem of threads signal handling
		2365
		2366	POSIX threads has problematic signal handling semantics, specifically,
		2367	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2368	threads in a process block signals, which is hard to achieve.
		2369
		2370	When you want to use sigwait (or mix libev signal handling with your own
		2371	for the same signals), you can tackle this problem by globally blocking
		2372	all signals before creating any threads (or creating them with a fully set
		2373	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2374	loops. Then designate one thread as "signal receiver thread" which handles
		2375	these signals. You can pass on any signals that libev might be interested
		2376	in by calling C<ev_feed_signal>.
1990		2377
1991	=head3 Watcher-Specific Functions and Data Members	2378	=head3 Watcher-Specific Functions and Data Members
1992		2379
1993	=over 4	2380	=over 4
1994		2381
…		…
2010	Example: Try to exit cleanly on SIGINT.	2397	Example: Try to exit cleanly on SIGINT.
2011		2398
2012	static void	2399	static void
2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2400	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2014	{	2401	{
2015	ev_unloop (loop, EVUNLOOP_ALL);	2402	ev_break (loop, EVBREAK_ALL);
2016	}	2403	}
2017		2404
2018	ev_signal signal_watcher;	2405	ev_signal signal_watcher;
2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2406	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2020	ev_signal_start (loop, &signal_watcher);	2407	ev_signal_start (loop, &signal_watcher);
…		…
2033		2420
2034	Only the default event loop is capable of handling signals, and therefore	2421	Only the default event loop is capable of handling signals, and therefore
2035	you can only register child watchers in the default event loop.	2422	you can only register child watchers in the default event loop.
2036		2423
2037	Due to some design glitches inside libev, child watchers will always be	2424	Due to some design glitches inside libev, child watchers will always be
2038	handled at maximum priority (their priority is set to EV_MAXPRI by libev)	2425	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2426	libev)
2039		2427
2040	=head3 Process Interaction	2428	=head3 Process Interaction
2041		2429
2042	Libev grabs C<SIGCHLD> as soon as the default event loop is	2430	Libev grabs C<SIGCHLD> as soon as the default event loop is
2043	initialised. This is necessary to guarantee proper behaviour even if	2431	initialised. This is necessary to guarantee proper behaviour even if the
2044	the first child watcher is started after the child exits. The occurrence	2432	first child watcher is started after the child exits. The occurrence
2045	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2433	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2046	synchronously as part of the event loop processing. Libev always reaps all	2434	synchronously as part of the event loop processing. Libev always reaps all
2047	children, even ones not watched.	2435	children, even ones not watched.
2048		2436
2049	=head3 Overriding the Built-In Processing	2437	=head3 Overriding the Built-In Processing
…		…
2059	=head3 Stopping the Child Watcher	2447	=head3 Stopping the Child Watcher
2060		2448
2061	Currently, the child watcher never gets stopped, even when the	2449	Currently, the child watcher never gets stopped, even when the
2062	child terminates, so normally one needs to stop the watcher in the	2450	child terminates, so normally one needs to stop the watcher in the
2063	callback. Future versions of libev might stop the watcher automatically	2451	callback. Future versions of libev might stop the watcher automatically
2064	when a child exit is detected.	2452	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2453	problem).
2065		2454
2066	=head3 Watcher-Specific Functions and Data Members	2455	=head3 Watcher-Specific Functions and Data Members
2067		2456
2068	=over 4	2457	=over 4
2069		2458
…		…
2404		2793
2405	Prepare and check watchers are usually (but not always) used in pairs:	2794	Prepare and check watchers are usually (but not always) used in pairs:
2406	prepare watchers get invoked before the process blocks and check watchers	2795	prepare watchers get invoked before the process blocks and check watchers
2407	afterwards.	2796	afterwards.
2408		2797
2409	You I<must not> call C<ev_loop> or similar functions that enter	2798	You I<must not> call C<ev_run> or similar functions that enter
2410	the current event loop from either C<ev_prepare> or C<ev_check>	2799	the current event loop from either C<ev_prepare> or C<ev_check>
2411	watchers. Other loops than the current one are fine, however. The	2800	watchers. Other loops than the current one are fine, however. The
2412	rationale behind this is that you do not need to check for recursion in	2801	rationale behind this is that you do not need to check for recursion in
2413	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2802	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2414	C<ev_check> so if you have one watcher of each kind they will always be	2803	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2582		2971
2583	if (timeout >= 0)	2972	if (timeout >= 0)
2584	// create/start timer	2973	// create/start timer
2585		2974
2586	// poll	2975	// poll
2587	ev_loop (EV_A_ 0);	2976	ev_run (EV_A_ 0);
2588		2977
2589	// stop timer again	2978	// stop timer again
2590	if (timeout >= 0)	2979	if (timeout >= 0)
2591	ev_timer_stop (EV_A_ &to);	2980	ev_timer_stop (EV_A_ &to);
2592		2981
…		…
2670	if you do not want that, you need to temporarily stop the embed watcher).	3059	if you do not want that, you need to temporarily stop the embed watcher).
2671		3060
2672	=item ev_embed_sweep (loop, ev_embed *)	3061	=item ev_embed_sweep (loop, ev_embed *)
2673		3062
2674	Make a single, non-blocking sweep over the embedded loop. This works	3063	Make a single, non-blocking sweep over the embedded loop. This works
2675	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3064	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2676	appropriate way for embedded loops.	3065	appropriate way for embedded loops.
2677		3066
2678	=item struct ev_loop *other [read-only]	3067	=item struct ev_loop *other [read-only]
2679		3068
2680	The embedded event loop.	3069	The embedded event loop.
…		…
2740	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3129	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2741	handlers will be invoked, too, of course.	3130	handlers will be invoked, too, of course.
2742		3131
2743	=head3 The special problem of life after fork - how is it possible?	3132	=head3 The special problem of life after fork - how is it possible?
2744		3133
2745	Most uses of C<fork()> consist of forking, then some simple calls to ste	3134	Most uses of C<fork()> consist of forking, then some simple calls to set
2746	up/change the process environment, followed by a call to C<exec()>. This	3135	up/change the process environment, followed by a call to C<exec()>. This
2747	sequence should be handled by libev without any problems.	3136	sequence should be handled by libev without any problems.
2748		3137
2749	This changes when the application actually wants to do event handling	3138	This changes when the application actually wants to do event handling
2750	in the child, or both parent in child, in effect "continuing" after the	3139	in the child, or both parent in child, in effect "continuing" after the
…		…
2766	disadvantage of having to use multiple event loops (which do not support	3155	disadvantage of having to use multiple event loops (which do not support
2767	signal watchers).	3156	signal watchers).
2768		3157
2769	When this is not possible, or you want to use the default loop for	3158	When this is not possible, or you want to use the default loop for
2770	other reasons, then in the process that wants to start "fresh", call	3159	other reasons, then in the process that wants to start "fresh", call
2771	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3160	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2772	the default loop will "orphan" (not stop) all registered watchers, so you	3161	Destroying the default loop will "orphan" (not stop) all registered
2773	have to be careful not to execute code that modifies those watchers. Note	3162	watchers, so you have to be careful not to execute code that modifies
2774	also that in that case, you have to re-register any signal watchers.	3163	those watchers. Note also that in that case, you have to re-register any
		3164	signal watchers.
2775		3165
2776	=head3 Watcher-Specific Functions and Data Members	3166	=head3 Watcher-Specific Functions and Data Members
2777		3167
2778	=over 4	3168	=over 4
2779		3169
2780	=item ev_fork_init (ev_signal *, callback)	3170	=item ev_fork_init (ev_fork *, callback)
2781		3171
2782	Initialises and configures the fork watcher - it has no parameters of any	3172	Initialises and configures the fork watcher - it has no parameters of any
2783	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3173	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2784	believe me.	3174	really.
2785		3175
2786	=back	3176	=back
2787		3177
2788		3178
		3179	=head2 C<ev_cleanup> - even the best things end
		3180
		3181	Cleanup watchers are called just before the event loop is being destroyed
		3182	by a call to C<ev_loop_destroy>.
		3183
		3184	While there is no guarantee that the event loop gets destroyed, cleanup
		3185	watchers provide a convenient method to install cleanup hooks for your
		3186	program, worker threads and so on - you just to make sure to destroy the
		3187	loop when you want them to be invoked.
		3188
		3189	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3190	all other watchers, they do not keep a reference to the event loop (which
		3191	makes a lot of sense if you think about it). Like all other watchers, you
		3192	can call libev functions in the callback, except C<ev_cleanup_start>.
		3193
		3194	=head3 Watcher-Specific Functions and Data Members
		3195
		3196	=over 4
		3197
		3198	=item ev_cleanup_init (ev_cleanup *, callback)
		3199
		3200	Initialises and configures the cleanup watcher - it has no parameters of
		3201	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3202	pointless, I assure you.
		3203
		3204	=back
		3205
		3206	Example: Register an atexit handler to destroy the default loop, so any
		3207	cleanup functions are called.
		3208
		3209	static void
		3210	program_exits (void)
		3211	{
		3212	ev_loop_destroy (EV_DEFAULT_UC);
		3213	}
		3214
		3215	...
		3216	atexit (program_exits);
		3217
		3218
2789	=head2 C<ev_async> - how to wake up another event loop	3219	=head2 C<ev_async> - how to wake up an event loop
2790		3220
2791	In general, you cannot use an C<ev_loop> from multiple threads or other	3221	In general, you cannot use an C<ev_run> from multiple threads or other
2792	asynchronous sources such as signal handlers (as opposed to multiple event	3222	asynchronous sources such as signal handlers (as opposed to multiple event
2793	loops - those are of course safe to use in different threads).	3223	loops - those are of course safe to use in different threads).
2794		3224
2795	Sometimes, however, you need to wake up another event loop you do not	3225	Sometimes, however, you need to wake up an event loop you do not control,
2796	control, for example because it belongs to another thread. This is what	3226	for example because it belongs to another thread. This is what C<ev_async>
2797	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3227	watchers do: as long as the C<ev_async> watcher is active, you can signal
2798	can signal it by calling C<ev_async_send>, which is thread- and signal	3228	it by calling C<ev_async_send>, which is thread- and signal safe.
2799	safe.
2800		3229
2801	This functionality is very similar to C<ev_signal> watchers, as signals,	3230	This functionality is very similar to C<ev_signal> watchers, as signals,
2802	too, are asynchronous in nature, and signals, too, will be compressed	3231	too, are asynchronous in nature, and signals, too, will be compressed
2803	(i.e. the number of callback invocations may be less than the number of	3232	(i.e. the number of callback invocations may be less than the number of
2804	C<ev_async_sent> calls).	3233	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3234	of "global async watchers" by using a watcher on an otherwise unused
		3235	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3236	even without knowing which loop owns the signal.
2805		3237
2806	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3238	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2807	just the default loop.	3239	just the default loop.
2808		3240
2809	=head3 Queueing	3241	=head3 Queueing
2810		3242
2811	C<ev_async> does not support queueing of data in any way. The reason	3243	C<ev_async> does not support queueing of data in any way. The reason
2812	is that the author does not know of a simple (or any) algorithm for a	3244	is that the author does not know of a simple (or any) algorithm for a
2813	multiple-writer-single-reader queue that works in all cases and doesn't	3245	multiple-writer-single-reader queue that works in all cases and doesn't
2814	need elaborate support such as pthreads.	3246	need elaborate support such as pthreads or unportable memory access
		3247	semantics.
2815		3248
2816	That means that if you want to queue data, you have to provide your own	3249	That means that if you want to queue data, you have to provide your own
2817	queue. But at least I can tell you how to implement locking around your	3250	queue. But at least I can tell you how to implement locking around your
2818	queue:	3251	queue:
2819		3252
…		…
2958		3391
2959	If C<timeout> is less than 0, then no timeout watcher will be	3392	If C<timeout> is less than 0, then no timeout watcher will be
2960	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3393	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2961	repeat = 0) will be started. C<0> is a valid timeout.	3394	repeat = 0) will be started. C<0> is a valid timeout.
2962		3395
2963	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3396	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2964	passed an C<revents> set like normal event callbacks (a combination of	3397	passed an C<revents> set like normal event callbacks (a combination of
2965	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3398	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2966	value passed to C<ev_once>. Note that it is possible to receive I<both>	3399	value passed to C<ev_once>. Note that it is possible to receive I<both>
2967	a timeout and an io event at the same time - you probably should give io	3400	a timeout and an io event at the same time - you probably should give io
2968	events precedence.	3401	events precedence.
2969		3402
2970	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3403	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2971		3404
2972	static void stdin_ready (int revents, void *arg)	3405	static void stdin_ready (int revents, void *arg)
2973	{	3406	{
2974	if (revents & EV_READ)	3407	if (revents & EV_READ)
2975	/* stdin might have data for us, joy! */;	3408	/* stdin might have data for us, joy! */;
2976	else if (revents & EV_TIMEOUT)	3409	else if (revents & EV_TIMER)
2977	/* doh, nothing entered */;	3410	/* doh, nothing entered */;
2978	}	3411	}
2979		3412
2980	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3413	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2981		3414
2982	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2983
2984	Feeds the given event set into the event loop, as if the specified event
2985	had happened for the specified watcher (which must be a pointer to an
2986	initialised but not necessarily started event watcher).
2987
2988	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3415	=item ev_feed_fd_event (loop, int fd, int revents)
2989		3416
2990	Feed an event on the given fd, as if a file descriptor backend detected	3417	Feed an event on the given fd, as if a file descriptor backend detected
2991	the given events it.	3418	the given events it.
2992		3419
2993	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3420	=item ev_feed_signal_event (loop, int signum)
2994		3421
2995	Feed an event as if the given signal occurred (C<loop> must be the default	3422	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2996	loop!).	3423	which is async-safe.
		3424
		3425	=back
		3426
		3427
		3428	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3429
		3430	This section explains some common idioms that are not immediately
		3431	obvious. Note that examples are sprinkled over the whole manual, and this
		3432	section only contains stuff that wouldn't fit anywhere else.
		3433
		3434	=over 4
		3435
		3436	=item Model/nested event loop invocations and exit conditions.
		3437
		3438	Often (especially in GUI toolkits) there are places where you have
		3439	I<modal> interaction, which is most easily implemented by recursively
		3440	invoking C<ev_run>.
		3441
		3442	This brings the problem of exiting - a callback might want to finish the
		3443	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3444	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3445	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3446	other combination: In these cases, C<ev_break> will not work alone.
		3447
		3448	The solution is to maintain "break this loop" variable for each C<ev_run>
		3449	invocation, and use a loop around C<ev_run> until the condition is
		3450	triggered, using C<EVRUN_ONCE>:
		3451
		3452	// main loop
		3453	int exit_main_loop = 0;
		3454
		3455	while (!exit_main_loop)
		3456	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3457
		3458	// in a model watcher
		3459	int exit_nested_loop = 0;
		3460
		3461	while (!exit_nested_loop)
		3462	ev_run (EV_A_ EVRUN_ONCE);
		3463
		3464	To exit from any of these loops, just set the corresponding exit variable:
		3465
		3466	// exit modal loop
		3467	exit_nested_loop = 1;
		3468
		3469	// exit main program, after modal loop is finished
		3470	exit_main_loop = 1;
		3471
		3472	// exit both
		3473	exit_main_loop = exit_nested_loop = 1;
2997		3474
2998	=back	3475	=back
2999		3476
3000		3477
3001	=head1 LIBEVENT EMULATION	3478	=head1 LIBEVENT EMULATION
3002		3479
3003	Libev offers a compatibility emulation layer for libevent. It cannot	3480	Libev offers a compatibility emulation layer for libevent. It cannot
3004	emulate the internals of libevent, so here are some usage hints:	3481	emulate the internals of libevent, so here are some usage hints:
3005		3482
3006	=over 4	3483	=over 4
		3484
		3485	=item * Only the libevent-1.4.1-beta API is being emulated.
		3486
		3487	This was the newest libevent version available when libev was implemented,
		3488	and is still mostly unchanged in 2010.
3007		3489
3008	=item * Use it by including <event.h>, as usual.	3490	=item * Use it by including <event.h>, as usual.
3009		3491
3010	=item * The following members are fully supported: ev_base, ev_callback,	3492	=item * The following members are fully supported: ev_base, ev_callback,
3011	ev_arg, ev_fd, ev_res, ev_events.	3493	ev_arg, ev_fd, ev_res, ev_events.
…		…
3017	=item * Priorities are not currently supported. Initialising priorities	3499	=item * Priorities are not currently supported. Initialising priorities
3018	will fail and all watchers will have the same priority, even though there	3500	will fail and all watchers will have the same priority, even though there
3019	is an ev_pri field.	3501	is an ev_pri field.
3020		3502
3021	=item * In libevent, the last base created gets the signals, in libev, the	3503	=item * In libevent, the last base created gets the signals, in libev, the
3022	first base created (== the default loop) gets the signals.	3504	base that registered the signal gets the signals.
3023		3505
3024	=item * Other members are not supported.	3506	=item * Other members are not supported.
3025		3507
3026	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3508	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3027	to use the libev header file and library.	3509	to use the libev header file and library.
…		…
3046	Care has been taken to keep the overhead low. The only data member the C++	3528	Care has been taken to keep the overhead low. The only data member the C++
3047	classes add (compared to plain C-style watchers) is the event loop pointer	3529	classes add (compared to plain C-style watchers) is the event loop pointer
3048	that the watcher is associated with (or no additional members at all if	3530	that the watcher is associated with (or no additional members at all if
3049	you disable C<EV_MULTIPLICITY> when embedding libev).	3531	you disable C<EV_MULTIPLICITY> when embedding libev).
3050		3532
3051	Currently, functions, and static and non-static member functions can be	3533	Currently, functions, static and non-static member functions and classes
3052	used as callbacks. Other types should be easy to add as long as they only	3534	with C<operator ()> can be used as callbacks. Other types should be easy
3053	need one additional pointer for context. If you need support for other	3535	to add as long as they only need one additional pointer for context. If
3054	types of functors please contact the author (preferably after implementing	3536	you need support for other types of functors please contact the author
3055	it).	3537	(preferably after implementing it).
3056		3538
3057	Here is a list of things available in the C<ev> namespace:	3539	Here is a list of things available in the C<ev> namespace:
3058		3540
3059	=over 4	3541	=over 4
3060		3542
…		…
3078		3560
3079	=over 4	3561	=over 4
3080		3562
3081	=item ev::TYPE::TYPE ()	3563	=item ev::TYPE::TYPE ()
3082		3564
3083	=item ev::TYPE::TYPE (struct ev_loop *)	3565	=item ev::TYPE::TYPE (loop)
3084		3566
3085	=item ev::TYPE::~TYPE	3567	=item ev::TYPE::~TYPE
3086		3568
3087	The constructor (optionally) takes an event loop to associate the watcher	3569	The constructor (optionally) takes an event loop to associate the watcher
3088	with. If it is omitted, it will use C<EV_DEFAULT>.	3570	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3121	myclass obj;	3603	myclass obj;
3122	ev::io iow;	3604	ev::io iow;
3123	iow.set <myclass, &myclass::io_cb> (&obj);	3605	iow.set <myclass, &myclass::io_cb> (&obj);
3124		3606
3125	=item w->set (object *)	3607	=item w->set (object *)
3126
3127	This is an B<experimental> feature that might go away in a future version.
3128		3608
3129	This is a variation of a method callback - leaving out the method to call	3609	This is a variation of a method callback - leaving out the method to call
3130	will default the method to C<operator ()>, which makes it possible to use	3610	will default the method to C<operator ()>, which makes it possible to use
3131	functor objects without having to manually specify the C<operator ()> all	3611	functor objects without having to manually specify the C<operator ()> all
3132	the time. Incidentally, you can then also leave out the template argument	3612	the time. Incidentally, you can then also leave out the template argument
…		…
3165	Example: Use a plain function as callback.	3645	Example: Use a plain function as callback.
3166		3646
3167	static void io_cb (ev::io &w, int revents) { }	3647	static void io_cb (ev::io &w, int revents) { }
3168	iow.set <io_cb> ();	3648	iow.set <io_cb> ();
3169		3649
3170	=item w->set (struct ev_loop *)	3650	=item w->set (loop)
3171		3651
3172	Associates a different C<struct ev_loop> with this watcher. You can only	3652	Associates a different C<struct ev_loop> with this watcher. You can only
3173	do this when the watcher is inactive (and not pending either).	3653	do this when the watcher is inactive (and not pending either).
3174		3654
3175	=item w->set ([arguments])	3655	=item w->set ([arguments])
3176		3656
3177	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3657	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3178	called at least once. Unlike the C counterpart, an active watcher gets	3658	method or a suitable start method must be called at least once. Unlike the
3179	automatically stopped and restarted when reconfiguring it with this	3659	C counterpart, an active watcher gets automatically stopped and restarted
3180	method.	3660	when reconfiguring it with this method.
3181		3661
3182	=item w->start ()	3662	=item w->start ()
3183		3663
3184	Starts the watcher. Note that there is no C<loop> argument, as the	3664	Starts the watcher. Note that there is no C<loop> argument, as the
3185	constructor already stores the event loop.	3665	constructor already stores the event loop.
3186		3666
		3667	=item w->start ([arguments])
		3668
		3669	Instead of calling C<set> and C<start> methods separately, it is often
		3670	convenient to wrap them in one call. Uses the same type of arguments as
		3671	the configure C<set> method of the watcher.
		3672
3187	=item w->stop ()	3673	=item w->stop ()
3188		3674
3189	Stops the watcher if it is active. Again, no C<loop> argument.	3675	Stops the watcher if it is active. Again, no C<loop> argument.
3190		3676
3191	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3677	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3203		3689
3204	=back	3690	=back
3205		3691
3206	=back	3692	=back
3207		3693
3208	Example: Define a class with an IO and idle watcher, start one of them in	3694	Example: Define a class with two I/O and idle watchers, start the I/O
3209	the constructor.	3695	watchers in the constructor.
3210		3696
3211	class myclass	3697	class myclass
3212	{	3698	{
3213	ev::io io ; void io_cb (ev::io &w, int revents);	3699	ev::io io ; void io_cb (ev::io &w, int revents);
		3700	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3214	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3701	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3215		3702
3216	myclass (int fd)	3703	myclass (int fd)
3217	{	3704	{
3218	io .set <myclass, &myclass::io_cb > (this);	3705	io .set <myclass, &myclass::io_cb > (this);
		3706	io2 .set <myclass, &myclass::io2_cb > (this);
3219	idle.set <myclass, &myclass::idle_cb> (this);	3707	idle.set <myclass, &myclass::idle_cb> (this);
3220		3708
3221	io.start (fd, ev::READ);	3709	io.set (fd, ev::WRITE); // configure the watcher
		3710	io.start (); // start it whenever convenient
		3711
		3712	io2.start (fd, ev::READ); // set + start in one call
3222	}	3713	}
3223	};	3714	};
3224		3715
3225		3716
3226	=head1 OTHER LANGUAGE BINDINGS	3717	=head1 OTHER LANGUAGE BINDINGS
…		…
3272	=item Ocaml	3763	=item Ocaml
3273		3764
3274	Erkki Seppala has written Ocaml bindings for libev, to be found at	3765	Erkki Seppala has written Ocaml bindings for libev, to be found at
3275	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3766	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3276		3767
		3768	=item Lua
		3769
		3770	Brian Maher has written a partial interface to libev for lua (at the
		3771	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3772	L<http://github.com/brimworks/lua-ev>.
		3773
3277	=back	3774	=back
3278		3775
3279		3776
3280	=head1 MACRO MAGIC	3777	=head1 MACRO MAGIC
3281		3778
…		…
3294	loop argument"). The C<EV_A> form is used when this is the sole argument,	3791	loop argument"). The C<EV_A> form is used when this is the sole argument,
3295	C<EV_A_> is used when other arguments are following. Example:	3792	C<EV_A_> is used when other arguments are following. Example:
3296		3793
3297	ev_unref (EV_A);	3794	ev_unref (EV_A);
3298	ev_timer_add (EV_A_ watcher);	3795	ev_timer_add (EV_A_ watcher);
3299	ev_loop (EV_A_ 0);	3796	ev_run (EV_A_ 0);
3300		3797
3301	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3798	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3302	which is often provided by the following macro.	3799	which is often provided by the following macro.
3303		3800
3304	=item C<EV_P>, C<EV_P_>	3801	=item C<EV_P>, C<EV_P_>
…		…
3344	}	3841	}
3345		3842
3346	ev_check check;	3843	ev_check check;
3347	ev_check_init (&check, check_cb);	3844	ev_check_init (&check, check_cb);
3348	ev_check_start (EV_DEFAULT_ &check);	3845	ev_check_start (EV_DEFAULT_ &check);
3349	ev_loop (EV_DEFAULT_ 0);	3846	ev_run (EV_DEFAULT_ 0);
3350		3847
3351	=head1 EMBEDDING	3848	=head1 EMBEDDING
3352		3849
3353	Libev can (and often is) directly embedded into host	3850	Libev can (and often is) directly embedded into host
3354	applications. Examples of applications that embed it include the Deliantra	3851	applications. Examples of applications that embed it include the Deliantra
…		…
3434	libev.m4	3931	libev.m4
3435		3932
3436	=head2 PREPROCESSOR SYMBOLS/MACROS	3933	=head2 PREPROCESSOR SYMBOLS/MACROS
3437		3934
3438	Libev can be configured via a variety of preprocessor symbols you have to	3935	Libev can be configured via a variety of preprocessor symbols you have to
3439	define before including any of its files. The default in the absence of	3936	define before including (or compiling) any of its files. The default in
3440	autoconf is documented for every option.	3937	the absence of autoconf is documented for every option.
		3938
		3939	Symbols marked with "(h)" do not change the ABI, and can have different
		3940	values when compiling libev vs. including F<ev.h>, so it is permissible
		3941	to redefine them before including F<ev.h> without breaking compatibility
		3942	to a compiled library. All other symbols change the ABI, which means all
		3943	users of libev and the libev code itself must be compiled with compatible
		3944	settings.
3441		3945
3442	=over 4	3946	=over 4
3443		3947
		3948	=item EV_COMPAT3 (h)
		3949
		3950	Backwards compatibility is a major concern for libev. This is why this
		3951	release of libev comes with wrappers for the functions and symbols that
		3952	have been renamed between libev version 3 and 4.
		3953
		3954	You can disable these wrappers (to test compatibility with future
		3955	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3956	sources. This has the additional advantage that you can drop the C<struct>
		3957	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3958	typedef in that case.
		3959
		3960	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3961	and in some even more future version the compatibility code will be
		3962	removed completely.
		3963
3444	=item EV_STANDALONE	3964	=item EV_STANDALONE (h)
3445		3965
3446	Must always be C<1> if you do not use autoconf configuration, which	3966	Must always be C<1> if you do not use autoconf configuration, which
3447	keeps libev from including F<config.h>, and it also defines dummy	3967	keeps libev from including F<config.h>, and it also defines dummy
3448	implementations for some libevent functions (such as logging, which is not	3968	implementations for some libevent functions (such as logging, which is not
3449	supported). It will also not define any of the structs usually found in	3969	supported). It will also not define any of the structs usually found in
3450	F<event.h> that are not directly supported by the libev core alone.	3970	F<event.h> that are not directly supported by the libev core alone.
3451		3971
3452	In stanbdalone mode, libev will still try to automatically deduce the	3972	In standalone mode, libev will still try to automatically deduce the
3453	configuration, but has to be more conservative.	3973	configuration, but has to be more conservative.
3454		3974
3455	=item EV_USE_MONOTONIC	3975	=item EV_USE_MONOTONIC
3456		3976
3457	If defined to be C<1>, libev will try to detect the availability of the	3977	If defined to be C<1>, libev will try to detect the availability of the
…		…
3522	be used is the winsock select). This means that it will call	4042	be used is the winsock select). This means that it will call
3523	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4043	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3524	it is assumed that all these functions actually work on fds, even	4044	it is assumed that all these functions actually work on fds, even
3525	on win32. Should not be defined on non-win32 platforms.	4045	on win32. Should not be defined on non-win32 platforms.
3526		4046
3527	=item EV_FD_TO_WIN32_HANDLE	4047	=item EV_FD_TO_WIN32_HANDLE(fd)
3528		4048
3529	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4049	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3530	file descriptors to socket handles. When not defining this symbol (the	4050	file descriptors to socket handles. When not defining this symbol (the
3531	default), then libev will call C<_get_osfhandle>, which is usually	4051	default), then libev will call C<_get_osfhandle>, which is usually
3532	correct. In some cases, programs use their own file descriptor management,	4052	correct. In some cases, programs use their own file descriptor management,
3533	in which case they can provide this function to map fds to socket handles.	4053	in which case they can provide this function to map fds to socket handles.
		4054
		4055	=item EV_WIN32_HANDLE_TO_FD(handle)
		4056
		4057	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4058	using the standard C<_open_osfhandle> function. For programs implementing
		4059	their own fd to handle mapping, overwriting this function makes it easier
		4060	to do so. This can be done by defining this macro to an appropriate value.
		4061
		4062	=item EV_WIN32_CLOSE_FD(fd)
		4063
		4064	If programs implement their own fd to handle mapping on win32, then this
		4065	macro can be used to override the C<close> function, useful to unregister
		4066	file descriptors again. Note that the replacement function has to close
		4067	the underlying OS handle.
3534		4068
3535	=item EV_USE_POLL	4069	=item EV_USE_POLL
3536		4070
3537	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4071	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3538	backend. Otherwise it will be enabled on non-win32 platforms. It	4072	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3585	as well as for signal and thread safety in C<ev_async> watchers.	4119	as well as for signal and thread safety in C<ev_async> watchers.
3586		4120
3587	In the absence of this define, libev will use C<sig_atomic_t volatile>	4121	In the absence of this define, libev will use C<sig_atomic_t volatile>
3588	(from F<signal.h>), which is usually good enough on most platforms.	4122	(from F<signal.h>), which is usually good enough on most platforms.
3589		4123
3590	=item EV_H	4124	=item EV_H (h)
3591		4125
3592	The name of the F<ev.h> header file used to include it. The default if	4126	The name of the F<ev.h> header file used to include it. The default if
3593	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4127	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3594	used to virtually rename the F<ev.h> header file in case of conflicts.	4128	used to virtually rename the F<ev.h> header file in case of conflicts.
3595		4129
3596	=item EV_CONFIG_H	4130	=item EV_CONFIG_H (h)
3597		4131
3598	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4132	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3599	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4133	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3600	C<EV_H>, above.	4134	C<EV_H>, above.
3601		4135
3602	=item EV_EVENT_H	4136	=item EV_EVENT_H (h)
3603		4137
3604	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4138	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3605	of how the F<event.h> header can be found, the default is C<"event.h">.	4139	of how the F<event.h> header can be found, the default is C<"event.h">.
3606		4140
3607	=item EV_PROTOTYPES	4141	=item EV_PROTOTYPES (h)
3608		4142
3609	If defined to be C<0>, then F<ev.h> will not define any function	4143	If defined to be C<0>, then F<ev.h> will not define any function
3610	prototypes, but still define all the structs and other symbols. This is	4144	prototypes, but still define all the structs and other symbols. This is
3611	occasionally useful if you want to provide your own wrapper functions	4145	occasionally useful if you want to provide your own wrapper functions
3612	around libev functions.	4146	around libev functions.
…		…
3634	fine.	4168	fine.
3635		4169
3636	If your embedding application does not need any priorities, defining these	4170	If your embedding application does not need any priorities, defining these
3637	both to C<0> will save some memory and CPU.	4171	both to C<0> will save some memory and CPU.
3638		4172
3639	=item EV_PERIODIC_ENABLE	4173	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4174	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4175	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3640		4176
3641	If undefined or defined to be C<1>, then periodic timers are supported. If	4177	If undefined or defined to be C<1> (and the platform supports it), then
3642	defined to be C<0>, then they are not. Disabling them saves a few kB of	4178	the respective watcher type is supported. If defined to be C<0>, then it
3643	code.	4179	is not. Disabling watcher types mainly saves code size.
3644		4180
3645	=item EV_IDLE_ENABLE	4181	=item EV_FEATURES
3646
3647	If undefined or defined to be C<1>, then idle watchers are supported. If
3648	defined to be C<0>, then they are not. Disabling them saves a few kB of
3649	code.
3650
3651	=item EV_EMBED_ENABLE
3652
3653	If undefined or defined to be C<1>, then embed watchers are supported. If
3654	defined to be C<0>, then they are not. Embed watchers rely on most other
3655	watcher types, which therefore must not be disabled.
3656
3657	=item EV_STAT_ENABLE
3658
3659	If undefined or defined to be C<1>, then stat watchers are supported. If
3660	defined to be C<0>, then they are not.
3661
3662	=item EV_FORK_ENABLE
3663
3664	If undefined or defined to be C<1>, then fork watchers are supported. If
3665	defined to be C<0>, then they are not.
3666
3667	=item EV_ASYNC_ENABLE
3668
3669	If undefined or defined to be C<1>, then async watchers are supported. If
3670	defined to be C<0>, then they are not.
3671
3672	=item EV_MINIMAL
3673		4182
3674	If you need to shave off some kilobytes of code at the expense of some	4183	If you need to shave off some kilobytes of code at the expense of some
3675	speed, define this symbol to C<1>. Currently this is used to override some	4184	speed (but with the full API), you can define this symbol to request
3676	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4185	certain subsets of functionality. The default is to enable all features
3677	much smaller 2-heap for timer management over the default 4-heap.	4186	that can be enabled on the platform.
		4187
		4188	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4189	with some broad features you want) and then selectively re-enable
		4190	additional parts you want, for example if you want everything minimal,
		4191	but multiple event loop support, async and child watchers and the poll
		4192	backend, use this:
		4193
		4194	#define EV_FEATURES 0
		4195	#define EV_MULTIPLICITY 1
		4196	#define EV_USE_POLL 1
		4197	#define EV_CHILD_ENABLE 1
		4198	#define EV_ASYNC_ENABLE 1
		4199
		4200	The actual value is a bitset, it can be a combination of the following
		4201	values:
		4202
		4203	=over 4
		4204
		4205	=item C<1> - faster/larger code
		4206
		4207	Use larger code to speed up some operations.
		4208
		4209	Currently this is used to override some inlining decisions (enlarging the
		4210	code size by roughly 30% on amd64).
		4211
		4212	When optimising for size, use of compiler flags such as C<-Os> with
		4213	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4214	assertions.
		4215
		4216	=item C<2> - faster/larger data structures
		4217
		4218	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4219	hash table sizes and so on. This will usually further increase code size
		4220	and can additionally have an effect on the size of data structures at
		4221	runtime.
		4222
		4223	=item C<4> - full API configuration
		4224
		4225	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4226	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4227
		4228	=item C<8> - full API
		4229
		4230	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4231	details on which parts of the API are still available without this
		4232	feature, and do not complain if this subset changes over time.
		4233
		4234	=item C<16> - enable all optional watcher types
		4235
		4236	Enables all optional watcher types. If you want to selectively enable
		4237	only some watcher types other than I/O and timers (e.g. prepare,
		4238	embed, async, child...) you can enable them manually by defining
		4239	C<EV_watchertype_ENABLE> to C<1> instead.
		4240
		4241	=item C<32> - enable all backends
		4242
		4243	This enables all backends - without this feature, you need to enable at
		4244	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4245
		4246	=item C<64> - enable OS-specific "helper" APIs
		4247
		4248	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4249	default.
		4250
		4251	=back
		4252
		4253	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4254	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4255	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4256	watchers, timers and monotonic clock support.
		4257
		4258	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4259	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4260	your program might be left out as well - a binary starting a timer and an
		4261	I/O watcher then might come out at only 5Kb.
		4262
		4263	=item EV_AVOID_STDIO
		4264
		4265	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4266	functions (printf, scanf, perror etc.). This will increase the code size
		4267	somewhat, but if your program doesn't otherwise depend on stdio and your
		4268	libc allows it, this avoids linking in the stdio library which is quite
		4269	big.
		4270
		4271	Note that error messages might become less precise when this option is
		4272	enabled.
		4273
		4274	=item EV_NSIG
		4275
		4276	The highest supported signal number, +1 (or, the number of
		4277	signals): Normally, libev tries to deduce the maximum number of signals
		4278	automatically, but sometimes this fails, in which case it can be
		4279	specified. Also, using a lower number than detected (C<32> should be
		4280	good for about any system in existence) can save some memory, as libev
		4281	statically allocates some 12-24 bytes per signal number.
3678		4282
3679	=item EV_PID_HASHSIZE	4283	=item EV_PID_HASHSIZE
3680		4284
3681	C<ev_child> watchers use a small hash table to distribute workload by	4285	C<ev_child> watchers use a small hash table to distribute workload by
3682	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4286	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3683	than enough. If you need to manage thousands of children you might want to	4287	usually more than enough. If you need to manage thousands of children you
3684	increase this value (I<must> be a power of two).	4288	might want to increase this value (I<must> be a power of two).
3685		4289
3686	=item EV_INOTIFY_HASHSIZE	4290	=item EV_INOTIFY_HASHSIZE
3687		4291
3688	C<ev_stat> watchers use a small hash table to distribute workload by	4292	C<ev_stat> watchers use a small hash table to distribute workload by
3689	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4293	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3690	usually more than enough. If you need to manage thousands of C<ev_stat>	4294	disabled), usually more than enough. If you need to manage thousands of
3691	watchers you might want to increase this value (I<must> be a power of	4295	C<ev_stat> watchers you might want to increase this value (I<must> be a
3692	two).	4296	power of two).
3693		4297
3694	=item EV_USE_4HEAP	4298	=item EV_USE_4HEAP
3695		4299
3696	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4300	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3697	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4301	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3698	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4302	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3699	faster performance with many (thousands) of watchers.	4303	faster performance with many (thousands) of watchers.
3700		4304
3701	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4305	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3702	(disabled).	4306	will be C<0>.
3703		4307
3704	=item EV_HEAP_CACHE_AT	4308	=item EV_HEAP_CACHE_AT
3705		4309
3706	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4310	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3707	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4311	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3708	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4312	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3709	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4313	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3710	but avoids random read accesses on heap changes. This improves performance	4314	but avoids random read accesses on heap changes. This improves performance
3711	noticeably with many (hundreds) of watchers.	4315	noticeably with many (hundreds) of watchers.
3712		4316
3713	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4317	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3714	(disabled).	4318	will be C<0>.
3715		4319
3716	=item EV_VERIFY	4320	=item EV_VERIFY
3717		4321
3718	Controls how much internal verification (see C<ev_loop_verify ()>) will	4322	Controls how much internal verification (see C<ev_verify ()>) will
3719	be done: If set to C<0>, no internal verification code will be compiled	4323	be done: If set to C<0>, no internal verification code will be compiled
3720	in. If set to C<1>, then verification code will be compiled in, but not	4324	in. If set to C<1>, then verification code will be compiled in, but not
3721	called. If set to C<2>, then the internal verification code will be	4325	called. If set to C<2>, then the internal verification code will be
3722	called once per loop, which can slow down libev. If set to C<3>, then the	4326	called once per loop, which can slow down libev. If set to C<3>, then the
3723	verification code will be called very frequently, which will slow down	4327	verification code will be called very frequently, which will slow down
3724	libev considerably.	4328	libev considerably.
3725		4329
3726	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4330	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3727	C<0>.	4331	will be C<0>.
3728		4332
3729	=item EV_COMMON	4333	=item EV_COMMON
3730		4334
3731	By default, all watchers have a C<void *data> member. By redefining	4335	By default, all watchers have a C<void *data> member. By redefining
3732	this macro to a something else you can include more and other types of	4336	this macro to something else you can include more and other types of
3733	members. You have to define it each time you include one of the files,	4337	members. You have to define it each time you include one of the files,
3734	though, and it must be identical each time.	4338	though, and it must be identical each time.
3735		4339
3736	For example, the perl EV module uses something like this:	4340	For example, the perl EV module uses something like this:
3737		4341
…		…
3790	file.	4394	file.
3791		4395
3792	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4396	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3793	that everybody includes and which overrides some configure choices:	4397	that everybody includes and which overrides some configure choices:
3794		4398
3795	#define EV_MINIMAL 1	4399	#define EV_FEATURES 8
3796	#define EV_USE_POLL 0	4400	#define EV_USE_SELECT 1
3797	#define EV_MULTIPLICITY 0
3798	#define EV_PERIODIC_ENABLE 0	4401	#define EV_PREPARE_ENABLE 1
		4402	#define EV_IDLE_ENABLE 1
3799	#define EV_STAT_ENABLE 0	4403	#define EV_SIGNAL_ENABLE 1
3800	#define EV_FORK_ENABLE 0	4404	#define EV_CHILD_ENABLE 1
		4405	#define EV_USE_STDEXCEPT 0
3801	#define EV_CONFIG_H <config.h>	4406	#define EV_CONFIG_H <config.h>
3802	#define EV_MINPRI 0
3803	#define EV_MAXPRI 0
3804		4407
3805	#include "ev++.h"	4408	#include "ev++.h"
3806		4409
3807	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4410	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3808		4411
…		…
3868	default loop and triggering an C<ev_async> watcher from the default loop	4471	default loop and triggering an C<ev_async> watcher from the default loop
3869	watcher callback into the event loop interested in the signal.	4472	watcher callback into the event loop interested in the signal.
3870		4473
3871	=back	4474	=back
3872		4475
		4476	=head4 THREAD LOCKING EXAMPLE
		4477
		4478	Here is a fictitious example of how to run an event loop in a different
		4479	thread than where callbacks are being invoked and watchers are
		4480	created/added/removed.
		4481
		4482	For a real-world example, see the C<EV::Loop::Async> perl module,
		4483	which uses exactly this technique (which is suited for many high-level
		4484	languages).
		4485
		4486	The example uses a pthread mutex to protect the loop data, a condition
		4487	variable to wait for callback invocations, an async watcher to notify the
		4488	event loop thread and an unspecified mechanism to wake up the main thread.
		4489
		4490	First, you need to associate some data with the event loop:
		4491
		4492	typedef struct {
		4493	mutex_t lock; /* global loop lock */
		4494	ev_async async_w;
		4495	thread_t tid;
		4496	cond_t invoke_cv;
		4497	} userdata;
		4498
		4499	void prepare_loop (EV_P)
		4500	{
		4501	// for simplicity, we use a static userdata struct.
		4502	static userdata u;
		4503
		4504	ev_async_init (&u->async_w, async_cb);
		4505	ev_async_start (EV_A_ &u->async_w);
		4506
		4507	pthread_mutex_init (&u->lock, 0);
		4508	pthread_cond_init (&u->invoke_cv, 0);
		4509
		4510	// now associate this with the loop
		4511	ev_set_userdata (EV_A_ u);
		4512	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4513	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4514
		4515	// then create the thread running ev_loop
		4516	pthread_create (&u->tid, 0, l_run, EV_A);
		4517	}
		4518
		4519	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4520	solely to wake up the event loop so it takes notice of any new watchers
		4521	that might have been added:
		4522
		4523	static void
		4524	async_cb (EV_P_ ev_async *w, int revents)
		4525	{
		4526	// just used for the side effects
		4527	}
		4528
		4529	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4530	protecting the loop data, respectively.
		4531
		4532	static void
		4533	l_release (EV_P)
		4534	{
		4535	userdata *u = ev_userdata (EV_A);
		4536	pthread_mutex_unlock (&u->lock);
		4537	}
		4538
		4539	static void
		4540	l_acquire (EV_P)
		4541	{
		4542	userdata *u = ev_userdata (EV_A);
		4543	pthread_mutex_lock (&u->lock);
		4544	}
		4545
		4546	The event loop thread first acquires the mutex, and then jumps straight
		4547	into C<ev_run>:
		4548
		4549	void *
		4550	l_run (void *thr_arg)
		4551	{
		4552	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4553
		4554	l_acquire (EV_A);
		4555	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4556	ev_run (EV_A_ 0);
		4557	l_release (EV_A);
		4558
		4559	return 0;
		4560	}
		4561
		4562	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4563	signal the main thread via some unspecified mechanism (signals? pipe
		4564	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4565	have been called (in a while loop because a) spurious wakeups are possible
		4566	and b) skipping inter-thread-communication when there are no pending
		4567	watchers is very beneficial):
		4568
		4569	static void
		4570	l_invoke (EV_P)
		4571	{
		4572	userdata *u = ev_userdata (EV_A);
		4573
		4574	while (ev_pending_count (EV_A))
		4575	{
		4576	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4577	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4578	}
		4579	}
		4580
		4581	Now, whenever the main thread gets told to invoke pending watchers, it
		4582	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4583	thread to continue:
		4584
		4585	static void
		4586	real_invoke_pending (EV_P)
		4587	{
		4588	userdata *u = ev_userdata (EV_A);
		4589
		4590	pthread_mutex_lock (&u->lock);
		4591	ev_invoke_pending (EV_A);
		4592	pthread_cond_signal (&u->invoke_cv);
		4593	pthread_mutex_unlock (&u->lock);
		4594	}
		4595
		4596	Whenever you want to start/stop a watcher or do other modifications to an
		4597	event loop, you will now have to lock:
		4598
		4599	ev_timer timeout_watcher;
		4600	userdata *u = ev_userdata (EV_A);
		4601
		4602	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4603
		4604	pthread_mutex_lock (&u->lock);
		4605	ev_timer_start (EV_A_ &timeout_watcher);
		4606	ev_async_send (EV_A_ &u->async_w);
		4607	pthread_mutex_unlock (&u->lock);
		4608
		4609	Note that sending the C<ev_async> watcher is required because otherwise
		4610	an event loop currently blocking in the kernel will have no knowledge
		4611	about the newly added timer. By waking up the loop it will pick up any new
		4612	watchers in the next event loop iteration.
		4613
3873	=head3 COROUTINES	4614	=head3 COROUTINES
3874		4615
3875	Libev is very accommodating to coroutines ("cooperative threads"):	4616	Libev is very accommodating to coroutines ("cooperative threads"):
3876	libev fully supports nesting calls to its functions from different	4617	libev fully supports nesting calls to its functions from different
3877	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4618	coroutines (e.g. you can call C<ev_run> on the same loop from two
3878	different coroutines, and switch freely between both coroutines running the	4619	different coroutines, and switch freely between both coroutines running
3879	loop, as long as you don't confuse yourself). The only exception is that	4620	the loop, as long as you don't confuse yourself). The only exception is
3880	you must not do this from C<ev_periodic> reschedule callbacks.	4621	that you must not do this from C<ev_periodic> reschedule callbacks.
3881		4622
3882	Care has been taken to ensure that libev does not keep local state inside	4623	Care has been taken to ensure that libev does not keep local state inside
3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4624	C<ev_run>, and other calls do not usually allow for coroutine switches as
3884	they do not call any callbacks.	4625	they do not call any callbacks.
3885		4626
3886	=head2 COMPILER WARNINGS	4627	=head2 COMPILER WARNINGS
3887		4628
3888	Depending on your compiler and compiler settings, you might get no or a	4629	Depending on your compiler and compiler settings, you might get no or a
…		…
3899	maintainable.	4640	maintainable.
3900		4641
3901	And of course, some compiler warnings are just plain stupid, or simply	4642	And of course, some compiler warnings are just plain stupid, or simply
3902	wrong (because they don't actually warn about the condition their message	4643	wrong (because they don't actually warn about the condition their message
3903	seems to warn about). For example, certain older gcc versions had some	4644	seems to warn about). For example, certain older gcc versions had some
3904	warnings that resulted an extreme number of false positives. These have	4645	warnings that resulted in an extreme number of false positives. These have
3905	been fixed, but some people still insist on making code warn-free with	4646	been fixed, but some people still insist on making code warn-free with
3906	such buggy versions.	4647	such buggy versions.
3907		4648
3908	While libev is written to generate as few warnings as possible,	4649	While libev is written to generate as few warnings as possible,
3909	"warn-free" code is not a goal, and it is recommended not to build libev	4650	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3945	I suggest using suppression lists.	4686	I suggest using suppression lists.
3946		4687
3947		4688
3948	=head1 PORTABILITY NOTES	4689	=head1 PORTABILITY NOTES
3949		4690
		4691	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4692
		4693	GNU/Linux is the only common platform that supports 64 bit file/large file
		4694	interfaces but I<disables> them by default.
		4695
		4696	That means that libev compiled in the default environment doesn't support
		4697	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4698
		4699	Unfortunately, many programs try to work around this GNU/Linux issue
		4700	by enabling the large file API, which makes them incompatible with the
		4701	standard libev compiled for their system.
		4702
		4703	Likewise, libev cannot enable the large file API itself as this would
		4704	suddenly make it incompatible to the default compile time environment,
		4705	i.e. all programs not using special compile switches.
		4706
		4707	=head2 OS/X AND DARWIN BUGS
		4708
		4709	The whole thing is a bug if you ask me - basically any system interface
		4710	you touch is broken, whether it is locales, poll, kqueue or even the
		4711	OpenGL drivers.
		4712
		4713	=head3 C<kqueue> is buggy
		4714
		4715	The kqueue syscall is broken in all known versions - most versions support
		4716	only sockets, many support pipes.
		4717
		4718	Libev tries to work around this by not using C<kqueue> by default on this
		4719	rotten platform, but of course you can still ask for it when creating a
		4720	loop - embedding a socket-only kqueue loop into a select-based one is
		4721	probably going to work well.
		4722
		4723	=head3 C<poll> is buggy
		4724
		4725	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4726	implementation by something calling C<kqueue> internally around the 10.5.6
		4727	release, so now C<kqueue> I<and> C<poll> are broken.
		4728
		4729	Libev tries to work around this by not using C<poll> by default on
		4730	this rotten platform, but of course you can still ask for it when creating
		4731	a loop.
		4732
		4733	=head3 C<select> is buggy
		4734
		4735	All that's left is C<select>, and of course Apple found a way to fuck this
		4736	one up as well: On OS/X, C<select> actively limits the number of file
		4737	descriptors you can pass in to 1024 - your program suddenly crashes when
		4738	you use more.
		4739
		4740	There is an undocumented "workaround" for this - defining
		4741	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4742	work on OS/X.
		4743
		4744	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4745
		4746	=head3 C<errno> reentrancy
		4747
		4748	The default compile environment on Solaris is unfortunately so
		4749	thread-unsafe that you can't even use components/libraries compiled
		4750	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4751	defined by default. A valid, if stupid, implementation choice.
		4752
		4753	If you want to use libev in threaded environments you have to make sure
		4754	it's compiled with C<_REENTRANT> defined.
		4755
		4756	=head3 Event port backend
		4757
		4758	The scalable event interface for Solaris is called "event
		4759	ports". Unfortunately, this mechanism is very buggy in all major
		4760	releases. If you run into high CPU usage, your program freezes or you get
		4761	a large number of spurious wakeups, make sure you have all the relevant
		4762	and latest kernel patches applied. No, I don't know which ones, but there
		4763	are multiple ones to apply, and afterwards, event ports actually work
		4764	great.
		4765
		4766	If you can't get it to work, you can try running the program by setting
		4767	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4768	C<select> backends.
		4769
		4770	=head2 AIX POLL BUG
		4771
		4772	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4773	this by trying to avoid the poll backend altogether (i.e. it's not even
		4774	compiled in), which normally isn't a big problem as C<select> works fine
		4775	with large bitsets on AIX, and AIX is dead anyway.
		4776
3950	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4777	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4778
		4779	=head3 General issues
3951		4780
3952	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4781	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3953	requires, and its I/O model is fundamentally incompatible with the POSIX	4782	requires, and its I/O model is fundamentally incompatible with the POSIX
3954	model. Libev still offers limited functionality on this platform in	4783	model. Libev still offers limited functionality on this platform in
3955	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4784	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3956	descriptors. This only applies when using Win32 natively, not when using	4785	descriptors. This only applies when using Win32 natively, not when using
3957	e.g. cygwin.	4786	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4787	as every compielr comes with a slightly differently broken/incompatible
		4788	environment.
3958		4789
3959	Lifting these limitations would basically require the full	4790	Lifting these limitations would basically require the full
3960	re-implementation of the I/O system. If you are into these kinds of	4791	re-implementation of the I/O system. If you are into this kind of thing,
3961	things, then note that glib does exactly that for you in a very portable	4792	then note that glib does exactly that for you in a very portable way (note
3962	way (note also that glib is the slowest event library known to man).	4793	also that glib is the slowest event library known to man).
3963		4794
3964	There is no supported compilation method available on windows except	4795	There is no supported compilation method available on windows except
3965	embedding it into other applications.	4796	embedding it into other applications.
3966		4797
3967	Sensible signal handling is officially unsupported by Microsoft - libev	4798	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
3995	you do I<not> compile the F<ev.c> or any other embedded source files!):	4826	you do I<not> compile the F<ev.c> or any other embedded source files!):
3996		4827
3997	#include "evwrap.h"	4828	#include "evwrap.h"
3998	#include "ev.c"	4829	#include "ev.c"
3999		4830
4000	=over 4
4001
4002	=item The winsocket select function	4831	=head3 The winsocket C<select> function
4003		4832
4004	The winsocket C<select> function doesn't follow POSIX in that it	4833	The winsocket C<select> function doesn't follow POSIX in that it
4005	requires socket I<handles> and not socket I<file descriptors> (it is	4834	requires socket I<handles> and not socket I<file descriptors> (it is
4006	also extremely buggy). This makes select very inefficient, and also	4835	also extremely buggy). This makes select very inefficient, and also
4007	requires a mapping from file descriptors to socket handles (the Microsoft	4836	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4016	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4845	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4017		4846
4018	Note that winsockets handling of fd sets is O(n), so you can easily get a	4847	Note that winsockets handling of fd sets is O(n), so you can easily get a
4019	complexity in the O(n²) range when using win32.	4848	complexity in the O(n²) range when using win32.
4020		4849
4021	=item Limited number of file descriptors	4850	=head3 Limited number of file descriptors
4022		4851
4023	Windows has numerous arbitrary (and low) limits on things.	4852	Windows has numerous arbitrary (and low) limits on things.
4024		4853
4025	Early versions of winsocket's select only supported waiting for a maximum	4854	Early versions of winsocket's select only supported waiting for a maximum
4026	of C<64> handles (probably owning to the fact that all windows kernels	4855	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4041	runtime libraries. This might get you to about C<512> or C<2048> sockets	4870	runtime libraries. This might get you to about C<512> or C<2048> sockets
4042	(depending on windows version and/or the phase of the moon). To get more,	4871	(depending on windows version and/or the phase of the moon). To get more,
4043	you need to wrap all I/O functions and provide your own fd management, but	4872	you need to wrap all I/O functions and provide your own fd management, but
4044	the cost of calling select (O(n²)) will likely make this unworkable.	4873	the cost of calling select (O(n²)) will likely make this unworkable.
4045		4874
4046	=back
4047
4048	=head2 PORTABILITY REQUIREMENTS	4875	=head2 PORTABILITY REQUIREMENTS
4049		4876
4050	In addition to a working ISO-C implementation and of course the	4877	In addition to a working ISO-C implementation and of course the
4051	backend-specific APIs, libev relies on a few additional extensions:	4878	backend-specific APIs, libev relies on a few additional extensions:
4052		4879
…		…
4058	Libev assumes not only that all watcher pointers have the same internal	4885	Libev assumes not only that all watcher pointers have the same internal
4059	structure (guaranteed by POSIX but not by ISO C for example), but it also	4886	structure (guaranteed by POSIX but not by ISO C for example), but it also
4060	assumes that the same (machine) code can be used to call any watcher	4887	assumes that the same (machine) code can be used to call any watcher
4061	callback: The watcher callbacks have different type signatures, but libev	4888	callback: The watcher callbacks have different type signatures, but libev
4062	calls them using an C<ev_watcher *> internally.	4889	calls them using an C<ev_watcher *> internally.
		4890
		4891	=item pointer accesses must be thread-atomic
		4892
		4893	Accessing a pointer value must be atomic, it must both be readable and
		4894	writable in one piece - this is the case on all current architectures.
4063		4895
4064	=item C<sig_atomic_t volatile> must be thread-atomic as well	4896	=item C<sig_atomic_t volatile> must be thread-atomic as well
4065		4897
4066	The type C<sig_atomic_t volatile> (or whatever is defined as	4898	The type C<sig_atomic_t volatile> (or whatever is defined as
4067	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4899	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4090	watchers.	4922	watchers.
4091		4923
4092	=item C<double> must hold a time value in seconds with enough accuracy	4924	=item C<double> must hold a time value in seconds with enough accuracy
4093		4925
4094	The type C<double> is used to represent timestamps. It is required to	4926	The type C<double> is used to represent timestamps. It is required to
4095	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4927	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4096	enough for at least into the year 4000. This requirement is fulfilled by	4928	good enough for at least into the year 4000 with millisecond accuracy
		4929	(the design goal for libev). This requirement is overfulfilled by
4097	implementations implementing IEEE 754, which is basically all existing	4930	implementations using IEEE 754, which is basically all existing ones. With
4098	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	4931	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4099	2200.
4100		4932
4101	=back	4933	=back
4102		4934
4103	If you know of other additional requirements drop me a note.	4935	If you know of other additional requirements drop me a note.
4104		4936
…		…
4172	involves iterating over all running async watchers or all signal numbers.	5004	involves iterating over all running async watchers or all signal numbers.
4173		5005
4174	=back	5006	=back
4175		5007
4176		5008
		5009	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5010
		5011	The major version 4 introduced some incompatible changes to the API.
		5012
		5013	At the moment, the C<ev.h> header file provides compatibility definitions
		5014	for all changes, so most programs should still compile. The compatibility
		5015	layer might be removed in later versions of libev, so better update to the
		5016	new API early than late.
		5017
		5018	=over 4
		5019
		5020	=item C<EV_COMPAT3> backwards compatibility mechanism
		5021
		5022	The backward compatibility mechanism can be controlled by
		5023	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5024	section.
		5025
		5026	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5027
		5028	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5029
		5030	ev_loop_destroy (EV_DEFAULT_UC);
		5031	ev_loop_fork (EV_DEFAULT);
		5032
		5033	=item function/symbol renames
		5034
		5035	A number of functions and symbols have been renamed:
		5036
		5037	ev_loop => ev_run
		5038	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5039	EVLOOP_ONESHOT => EVRUN_ONCE
		5040
		5041	ev_unloop => ev_break
		5042	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5043	EVUNLOOP_ONE => EVBREAK_ONE
		5044	EVUNLOOP_ALL => EVBREAK_ALL
		5045
		5046	EV_TIMEOUT => EV_TIMER
		5047
		5048	ev_loop_count => ev_iteration
		5049	ev_loop_depth => ev_depth
		5050	ev_loop_verify => ev_verify
		5051
		5052	Most functions working on C<struct ev_loop> objects don't have an
		5053	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5054	associated constants have been renamed to not collide with the C<struct
		5055	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5056	as all other watcher types. Note that C<ev_loop_fork> is still called
		5057	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5058	typedef.
		5059
		5060	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5061
		5062	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5063	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5064	and work, but the library code will of course be larger.
		5065
		5066	=back
		5067
		5068
4177	=head1 GLOSSARY	5069	=head1 GLOSSARY
4178		5070
4179	=over 4	5071	=over 4
4180		5072
4181	=item active	5073	=item active
4182		5074
4183	A watcher is active as long as it has been started (has been attached to	5075	A watcher is active as long as it has been started and not yet stopped.
4184	an event loop) but not yet stopped (disassociated from the event loop).	5076	See L<WATCHER STATES> for details.
4185		5077
4186	=item application	5078	=item application
4187		5079
4188	In this document, an application is whatever is using libev.	5080	In this document, an application is whatever is using libev.
		5081
		5082	=item backend
		5083
		5084	The part of the code dealing with the operating system interfaces.
4189		5085
4190	=item callback	5086	=item callback
4191		5087
4192	The address of a function that is called when some event has been	5088	The address of a function that is called when some event has been
4193	detected. Callbacks are being passed the event loop, the watcher that	5089	detected. Callbacks are being passed the event loop, the watcher that
4194	received the event, and the actual event bitset.	5090	received the event, and the actual event bitset.
4195		5091
4196	=item callback invocation	5092	=item callback/watcher invocation
4197		5093
4198	The act of calling the callback associated with a watcher.	5094	The act of calling the callback associated with a watcher.
4199		5095
4200	=item event	5096	=item event
4201		5097
4202	A change of state of some external event, such as data now being available	5098	A change of state of some external event, such as data now being available
4203	for reading on a file descriptor, time having passed or simply not having	5099	for reading on a file descriptor, time having passed or simply not having
4204	any other events happening anymore.	5100	any other events happening anymore.
4205		5101
4206	In libev, events are represented as single bits (such as C<EV_READ> or	5102	In libev, events are represented as single bits (such as C<EV_READ> or
4207	C<EV_TIMEOUT>).	5103	C<EV_TIMER>).
4208		5104
4209	=item event library	5105	=item event library
4210		5106
4211	A software package implementing an event model and loop.	5107	A software package implementing an event model and loop.
4212		5108
…		…
4220	The model used to describe how an event loop handles and processes	5116	The model used to describe how an event loop handles and processes
4221	watchers and events.	5117	watchers and events.
4222		5118
4223	=item pending	5119	=item pending
4224		5120
4225	A watcher is pending as soon as the corresponding event has been detected,	5121	A watcher is pending as soon as the corresponding event has been
4226	and stops being pending as soon as the watcher will be invoked or its	5122	detected. See L<WATCHER STATES> for details.
4227	pending status is explicitly cleared by the application.
4228
4229	A watcher can be pending, but not active. Stopping a watcher also clears
4230	its pending status.
4231		5123
4232	=item real time	5124	=item real time
4233		5125
4234	The physical time that is observed. It is apparently strictly monotonic :)	5126	The physical time that is observed. It is apparently strictly monotonic :)
4235		5127
…		…
4242	=item watcher	5134	=item watcher
4243		5135
4244	A data structure that describes interest in certain events. Watchers need	5136	A data structure that describes interest in certain events. Watchers need
4245	to be started (attached to an event loop) before they can receive events.	5137	to be started (attached to an event loop) before they can receive events.
4246		5138
4247	=item watcher invocation
4248
4249	The act of calling the callback associated with a watcher.
4250
4251	=back	5139	=back
4252		5140
4253	=head1 AUTHOR	5141	=head1 AUTHOR
4254		5142
4255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5143	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5144	Magnusson and Emanuele Giaquinta.
4256		5145

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