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Revision 1.369 by root, Mon May 30 18:34:28 2011 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
98	=head2 FEATURES	106	=head2 FEATURES
99		107
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
108	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
109	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
110		119
111	It also is quite fast (see this	120	It also is quite fast (see this
112	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
113	for example).	122	for example).
114		123
…		…
117	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
118	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
120	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
121	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
122	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
123	this argument.	132	this argument.
124		133
125	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
126		135
127	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
128	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
129	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
130	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
131	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
132	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
133	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
134	throughout libev.	144	time differences (e.g. delays) throughout libev.
135		145
136	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
137		147
138	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
139	and internal errors (bugs).	149	and internal errors (bugs).
…		…
163		173
164	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
165		175
166	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
167	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
168	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
169		180
170	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
171		182
172	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
173	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
190	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
191	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
192	not a problem.	203	not a problem.
193		204
194	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
195	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
196		208
197	assert (("libev version mismatch",	209	assert (("libev version mismatch",
198	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
199	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
200		212
…		…
211	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
212	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
213		225
214	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
215		227
216	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
217	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
218	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
219	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
220	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
221	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
222		235
223	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
224		237
225	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
226	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
227	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
229	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
230		243
231	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
232		245
233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
234		247
235	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
237	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
238	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
264	}	277	}
265		278
266	...	279	...
267	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
268		281
269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
270		283
271	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
272	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
273	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
274	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
286	}	299	}
287		300
288	...	301	...
289	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
290		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
291	=back	317	=back
292		318
293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
294		320
295	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
296	is I<not> optional in this case, as there is also an C<ev_loop>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
297	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
298		324
299	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
300	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
301	not.	327	do not.
302		328
303	=over 4	329	=over 4
304		330
305	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
306		332
307	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
308	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
309	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
310	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
311		343
312	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
313	function.	345	function (or via the C<EV_DEFAULT> macro).
314		346
315	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
316	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
317	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
318		351
319	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
320	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
321	for C<SIGCHLD>. If this is a problem for your application you can either	354	a problem for your application you can either create a dynamic loop with
322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
324	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
325		376
326	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
327	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
328		379
329	The following flags are supported:	380	The following flags are supported:
…		…
344	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
345	around bugs.	396	around bugs.
346		397
347	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
348		399
349	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
350	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
351	enabling this flag.
352		402
353	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
354	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
355	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
356	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
362	flag.	412	flag.
363		413
364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365	environment variable.	415	environment variable.
366		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
		451
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		453
369	This is your standard select(2) backend. Not I<completely> standard, as	454	This is your standard select(2) backend. Not I<completely> standard, as
370	libev tries to roll its own fd_set with no limits on the number of fds,	455	libev tries to roll its own fd_set with no limits on the number of fds,
371	but if that fails, expect a fairly low limit on the number of fds when	456	but if that fails, expect a fairly low limit on the number of fds when
…		…
395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	480	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	481	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
397		482
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	483	=item C<EVBACKEND_EPOLL> (value 4, Linux)
399		484
		485	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		486	kernels).
		487
400	For few fds, this backend is a bit little slower than poll and select,	488	For few fds, this backend is a bit little slower than poll and select, but
401	but it scales phenomenally better. While poll and select usually scale	489	it scales phenomenally better. While poll and select usually scale like
402	like O(total_fds) where n is the total number of fds (or the highest fd),	490	O(total_fds) where total_fds is the total number of fds (or the highest
403	epoll scales either O(1) or O(active_fds).	491	fd), epoll scales either O(1) or O(active_fds).
404		492
405	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
406	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
407	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
408	descriptor (and unnecessary guessing of parameters), problems with dup and	496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(and only giving 5ms accuracy while select on the same platform gives
409	so on. The biggest issue is fork races, however - if a program forks then	499	0.1ms) and so on. The biggest issue is fork races, however - if a program
410	I<both> parent and child process have to recreate the epoll set, which can	500	forks then I<both> parent and child process have to recreate the epoll
411	take considerable time (one syscall per file descriptor) and is of course	501	set, which can take considerable time (one syscall per file descriptor)
412	hard to detect.	502	and is of course hard to detect.
413		503
414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
415	of course I<doesn't>, and epoll just loves to report events for totally	505	of course I<doesn't>, and epoll just loves to report events for totally
416	I<different> file descriptors (even already closed ones, so one cannot	506	I<different> file descriptors (even already closed ones, so one cannot
417	even remove them from the set) than registered in the set (especially	507	even remove them from the set) than registered in the set (especially
418	on SMP systems). Libev tries to counter these spurious notifications by	508	on SMP systems). Libev tries to counter these spurious notifications by
419	employing an additional generation counter and comparing that against the	509	employing an additional generation counter and comparing that against the
420	events to filter out spurious ones, recreating the set when required.	510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
421		517
422	While stopping, setting and starting an I/O watcher in the same iteration	518	While stopping, setting and starting an I/O watcher in the same iteration
423	will result in some caching, there is still a system call per such	519	will result in some caching, there is still a system call per such
424	incident (because the same I<file descriptor> could point to a different	520	incident (because the same I<file descriptor> could point to a different
425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		588
493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
494	it's really slow, but it still scales very well (O(active_fds)).	590	it's really slow, but it still scales very well (O(active_fds)).
495		591
496	Please note that Solaris event ports can deliver a lot of spurious
497	notifications, so you need to use non-blocking I/O or other means to avoid
498	blocking when no data (or space) is available.
499
500	While this backend scales well, it requires one system call per active	592	While this backend scales well, it requires one system call per active
501	file descriptor per loop iteration. For small and medium numbers of file	593	file descriptor per loop iteration. For small and medium numbers of file
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	595	might perform better.
504		596
505	On the positive side, with the exception of the spurious readiness	597	On the positive side, this backend actually performed fully to
506	notifications, this backend actually performed fully to specification
507	in all tests and is fully embeddable, which is a rare feat among the	598	specification in all tests and is fully embeddable, which is a rare feat
508	OS-specific backends (I vastly prefer correctness over speed hacks).	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
509		611
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
512		614
513	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
514		616
515	Try all backends (even potentially broken ones that wouldn't be tried	617	Try all backends (even potentially broken ones that wouldn't be tried
516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		620
519	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
520		630
521	=back	631	=back
522		632
523	If one or more of these are or'ed into the flags value, then only these	633	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	634	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	635	here). If none are specified, all backends in C<ev_recommended_backends
526		636	()> will be tried.
527	Example: This is the most typical usage.
528
529	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
531
532	Example: Restrict libev to the select and poll backends, and do not allow
533	environment settings to be taken into account:
534
535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
536
537	Example: Use whatever libev has to offer, but make sure that kqueue is
538	used if available (warning, breaks stuff, best use only with your own
539	private event loop and only if you know the OS supports your types of
540	fds):
541
542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
543
544	=item struct ev_loop *ev_loop_new (unsigned int flags)
545
546	Similar to C<ev_default_loop>, but always creates a new event loop that is
547	always distinct from the default loop. Unlike the default loop, it cannot
548	handle signal and child watchers, and attempts to do so will be greeted by
549	undefined behaviour (or a failed assertion if assertions are enabled).
550
551	Note that this function I<is> thread-safe, and the recommended way to use
552	libev with threads is indeed to create one loop per thread, and using the
553	default loop in the "main" or "initial" thread.
554		637
555	Example: Try to create a event loop that uses epoll and nothing else.	638	Example: Try to create a event loop that uses epoll and nothing else.
556		639
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	641	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
560		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
561	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
562		650
563	Destroys the default loop again (frees all memory and kernel state	651	Destroys an event loop object (frees all memory and kernel state
564	etc.). None of the active event watchers will be stopped in the normal	652	etc.). None of the active event watchers will be stopped in the normal
565	sense, so e.g. C<ev_is_active> might still return true. It is your	653	sense, so e.g. C<ev_is_active> might still return true. It is your
566	responsibility to either stop all watchers cleanly yourself I<before>	654	responsibility to either stop all watchers cleanly yourself I<before>
567	calling this function, or cope with the fact afterwards (which is usually	655	calling this function, or cope with the fact afterwards (which is usually
568	the easiest thing, you can just ignore the watchers and/or C<free ()> them	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
570		658
571	Note that certain global state, such as signal state (and installed signal	659	Note that certain global state, such as signal state (and installed signal
572	handlers), will not be freed by this function, and related watchers (such	660	handlers), will not be freed by this function, and related watchers (such
573	as signal and child watchers) would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
574		662
575	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
576	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	except in the rare occasion where you really need to free its resources.
577	pipe fds. If you need dynamically allocated loops it is better to use	669	If you need dynamically allocated loops it is better to use C<ev_loop_new>
578	C<ev_loop_new> and C<ev_loop_destroy>).	670	and C<ev_loop_destroy>.
579		671
580	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
581		673
582	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.
584
585	=item ev_default_fork ()
586
587	This function sets a flag that causes subsequent C<ev_loop> iterations	674	This function sets a flag that causes subsequent C<ev_run> iterations to
588	to reinitialise the kernel state for backends that have one. Despite the	675	reinitialise the kernel state for backends that have one. Despite the
589	name, you can call it anytime, but it makes most sense after forking, in	676	name, you can call it anytime, but it makes most sense after forking, in
590	the child process (or both child and parent, but that again makes little	677	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
591	sense). You I<must> call it in the child before using any of the libev	678	child before resuming or calling C<ev_run>.
592	functions, and it will only take effect at the next C<ev_loop> iteration.	679
		680	Again, you I<have> to call it on I<any> loop that you want to re-use after
		681	a fork, I<even if you do not plan to use the loop in the parent>. This is
		682	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		683	during fork.
593		684
594	On the other hand, you only need to call this function in the child	685	On the other hand, you only need to call this function in the child
595	process if and only if you want to use the event library in the child. If	686	process if and only if you want to use the event loop in the child. If
596	you just fork+exec, you don't have to call it at all.	687	you just fork+exec or create a new loop in the child, you don't have to
		688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
597		691
598	The function itself is quite fast and it's usually not a problem to call	692	The function itself is quite fast and it's usually not a problem to call
599	it just in case after a fork. To make this easy, the function will fit in	693	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
602	pthread_atfork (0, 0, ev_default_fork);	705	pthread_atfork (0, 0, post_fork_child);
603
604	=item ev_loop_fork (loop)
605
606	Like C<ev_default_fork>, but acts on an event loop created by
607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
608	after fork that you want to re-use in the child, and how you do this is
609	entirely your own problem.
610		706
611	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
612		708
613	Returns true when the given loop is, in fact, the default loop, and false	709	Returns true when the given loop is, in fact, the default loop, and false
614	otherwise.	710	otherwise.
615		711
616	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
617		713
618	Returns the count of loop iterations for the loop, which is identical to	714	Returns the current iteration count for the event loop, which is identical
619	the number of times libev did poll for new events. It starts at C<0> and	715	to the number of times libev did poll for new events. It starts at C<0>
620	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
621		717
622	This value can sometimes be useful as a generation counter of sorts (it	718	This value can sometimes be useful as a generation counter of sorts (it
623	"ticks" the number of loop iterations), as it roughly corresponds with	719	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		721	prepare and check phases.
		722
		723	=item unsigned int ev_depth (loop)
		724
		725	Returns the number of times C<ev_run> was entered minus the number of
		726	times C<ev_run> was exited normally, in other words, the recursion depth.
		727
		728	Outside C<ev_run>, this number is zero. In a callback, this number is
		729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		730	in which case it is higher.
		731
		732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		733	throwing an exception etc.), doesn't count as "exit" - consider this
		734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
625		736
626	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
627		738
628	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
629	use.	740	use.
…		…
638		749
639	=item ev_now_update (loop)	750	=item ev_now_update (loop)
640		751
641	Establishes the current time by querying the kernel, updating the time	752	Establishes the current time by querying the kernel, updating the time
642	returned by C<ev_now ()> in the progress. This is a costly operation and	753	returned by C<ev_now ()> in the progress. This is a costly operation and
643	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
644		755
645	This function is rarely useful, but when some event callback runs for a	756	This function is rarely useful, but when some event callback runs for a
646	very long time without entering the event loop, updating libev's idea of	757	very long time without entering the event loop, updating libev's idea of
647	the current time is a good idea.	758	the current time is a good idea.
648		759
…		…
650		761
651	=item ev_suspend (loop)	762	=item ev_suspend (loop)
652		763
653	=item ev_resume (loop)	764	=item ev_resume (loop)
654		765
655	These two functions suspend and resume a loop, for use when the loop is	766	These two functions suspend and resume an event loop, for use when the
656	not used for a while and timeouts should not be processed.	767	loop is not used for a while and timeouts should not be processed.
657		768
658	A typical use case would be an interactive program such as a game: When	769	A typical use case would be an interactive program such as a game: When
659	the user presses C<^Z> to suspend the game and resumes it an hour later it	770	the user presses C<^Z> to suspend the game and resumes it an hour later it
660	would be best to handle timeouts as if no time had actually passed while	771	would be best to handle timeouts as if no time had actually passed while
661	the program was suspended. This can be achieved by calling C<ev_suspend>	772	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
663	C<ev_resume> directly afterwards to resume timer processing.	774	C<ev_resume> directly afterwards to resume timer processing.
664		775
665	Effectively, all C<ev_timer> watchers will be delayed by the time spend	776	Effectively, all C<ev_timer> watchers will be delayed by the time spend
666	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	777	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
667	will be rescheduled (that is, they will lose any events that would have	778	will be rescheduled (that is, they will lose any events that would have
668	occured while suspended).	779	occurred while suspended).
669		780
670	After calling C<ev_suspend> you B<must not> call I<any> function on the	781	After calling C<ev_suspend> you B<must not> call I<any> function on the
671	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	782	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
672	without a previous call to C<ev_suspend>.	783	without a previous call to C<ev_suspend>.
673		784
674	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
675	event loop time (see C<ev_now_update>).	786	event loop time (see C<ev_now_update>).
676		787
677	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
678		789
679	Finally, this is it, the event handler. This function usually is called	790	Finally, this is it, the event handler. This function usually is called
680	after you initialised all your watchers and you want to start handling	791	after you have initialised all your watchers and you want to start
681	events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
682		795
683	If the flags argument is specified as C<0>, it will not return until	796	If the flags argument is specified as C<0>, it will keep handling events
684	either no event watchers are active anymore or C<ev_unloop> was called.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
685		799
686	Please note that an explicit C<ev_unloop> is usually better than	800	Please note that an explicit C<ev_break> is usually better than
687	relying on all watchers to be stopped when deciding when a program has	801	relying on all watchers to be stopped when deciding when a program has
688	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
689	that automatically loops as long as it has to and no longer by virtue	803	that automatically loops as long as it has to and no longer by virtue
690	of relying on its watchers stopping correctly, that is truly a thing of	804	of relying on its watchers stopping correctly, that is truly a thing of
691	beauty.	805	beauty.
692		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
693	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
694	those events and any already outstanding ones, but will not block your	813	those events and any already outstanding ones, but will not wait and
695	process in case there are no events and will return after one iteration of	814	block your process in case there are no events and will return after one
696	the loop.	815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
697		817
698	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
699	necessary) and will handle those and any already outstanding ones. It	819	necessary) and will handle those and any already outstanding ones. It
700	will block your process until at least one new event arrives (which could	820	will block your process until at least one new event arrives (which could
701	be an event internal to libev itself, so there is no guarantee that a	821	be an event internal to libev itself, so there is no guarantee that a
702	user-registered callback will be called), and will return after one	822	user-registered callback will be called), and will return after one
703	iteration of the loop.	823	iteration of the loop.
704		824
705	This is useful if you are waiting for some external event in conjunction	825	This is useful if you are waiting for some external event in conjunction
706	with something not expressible using other libev watchers (i.e. "roll your	826	with something not expressible using other libev watchers (i.e. "roll your
707	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	827	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
708	usually a better approach for this kind of thing.	828	usually a better approach for this kind of thing.
709		829
710	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does (this is for your
		831	understanding, not a guarantee that things will work exactly like this in
		832	future versions):
711		833
		834	- Increment loop depth.
		835	- Reset the ev_break status.
712	- Before the first iteration, call any pending watchers.	836	- Before the first iteration, call any pending watchers.
		837	LOOP:
713	* If EVFLAG_FORKCHECK was used, check for a fork.	838	- If EVFLAG_FORKCHECK was used, check for a fork.
714	- If a fork was detected (by any means), queue and call all fork watchers.	839	- If a fork was detected (by any means), queue and call all fork watchers.
715	- Queue and call all prepare watchers.	840	- Queue and call all prepare watchers.
		841	- If ev_break was called, goto FINISH.
716	- If we have been forked, detach and recreate the kernel state	842	- If we have been forked, detach and recreate the kernel state
717	as to not disturb the other process.	843	as to not disturb the other process.
718	- Update the kernel state with all outstanding changes.	844	- Update the kernel state with all outstanding changes.
719	- Update the "event loop time" (ev_now ()).	845	- Update the "event loop time" (ev_now ()).
720	- Calculate for how long to sleep or block, if at all	846	- Calculate for how long to sleep or block, if at all
721	(active idle watchers, EVLOOP_NONBLOCK or not having	847	(active idle watchers, EVRUN_NOWAIT or not having
722	any active watchers at all will result in not sleeping).	848	any active watchers at all will result in not sleeping).
723	- Sleep if the I/O and timer collect interval say so.	849	- Sleep if the I/O and timer collect interval say so.
		850	- Increment loop iteration counter.
724	- Block the process, waiting for any events.	851	- Block the process, waiting for any events.
725	- Queue all outstanding I/O (fd) events.	852	- Queue all outstanding I/O (fd) events.
726	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	853	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
727	- Queue all expired timers.	854	- Queue all expired timers.
728	- Queue all expired periodics.	855	- Queue all expired periodics.
729	- Unless any events are pending now, queue all idle watchers.	856	- Queue all idle watchers with priority higher than that of pending events.
730	- Queue all check watchers.	857	- Queue all check watchers.
731	- Call all queued watchers in reverse order (i.e. check watchers first).	858	- Call all queued watchers in reverse order (i.e. check watchers first).
732	Signals and child watchers are implemented as I/O watchers, and will	859	Signals and child watchers are implemented as I/O watchers, and will
733	be handled here by queueing them when their watcher gets executed.	860	be handled here by queueing them when their watcher gets executed.
734	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	861	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
735	were used, or there are no active watchers, return, otherwise	862	were used, or there are no active watchers, goto FINISH, otherwise
736	continue with step *.	863	continue with step LOOP.
		864	FINISH:
		865	- Reset the ev_break status iff it was EVBREAK_ONE.
		866	- Decrement the loop depth.
		867	- Return.
737		868
738	Example: Queue some jobs and then loop until no events are outstanding	869	Example: Queue some jobs and then loop until no events are outstanding
739	anymore.	870	anymore.
740		871
741	... queue jobs here, make sure they register event watchers as long	872	... queue jobs here, make sure they register event watchers as long
742	... as they still have work to do (even an idle watcher will do..)	873	... as they still have work to do (even an idle watcher will do..)
743	ev_loop (my_loop, 0);	874	ev_run (my_loop, 0);
744	... jobs done or somebody called unloop. yeah!	875	... jobs done or somebody called break. yeah!
745		876
746	=item ev_unloop (loop, how)	877	=item ev_break (loop, how)
747		878
748	Can be used to make a call to C<ev_loop> return early (but only after it	879	Can be used to make a call to C<ev_run> return early (but only after it
749	has processed all outstanding events). The C<how> argument must be either	880	has processed all outstanding events). The C<how> argument must be either
750	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	881	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
751	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	882	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
752		883
753	This "unloop state" will be cleared when entering C<ev_loop> again.	884	This "break state" will be cleared on the next call to C<ev_run>.
754		885
755	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	886	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		887	which case it will have no effect.
756		888
757	=item ev_ref (loop)	889	=item ev_ref (loop)
758		890
759	=item ev_unref (loop)	891	=item ev_unref (loop)
760		892
761	Ref/unref can be used to add or remove a reference count on the event	893	Ref/unref can be used to add or remove a reference count on the event
762	loop: Every watcher keeps one reference, and as long as the reference	894	loop: Every watcher keeps one reference, and as long as the reference
763	count is nonzero, C<ev_loop> will not return on its own.	895	count is nonzero, C<ev_run> will not return on its own.
764		896
765	If you have a watcher you never unregister that should not keep C<ev_loop>	897	This is useful when you have a watcher that you never intend to
766	from returning, call ev_unref() after starting, and ev_ref() before	898	unregister, but that nevertheless should not keep C<ev_run> from
		899	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
767	stopping it.	900	before stopping it.
768		901
769	As an example, libev itself uses this for its internal signal pipe: It	902	As an example, libev itself uses this for its internal signal pipe: It
770	is not visible to the libev user and should not keep C<ev_loop> from	903	is not visible to the libev user and should not keep C<ev_run> from
771	exiting if no event watchers registered by it are active. It is also an	904	exiting if no event watchers registered by it are active. It is also an
772	excellent way to do this for generic recurring timers or from within	905	excellent way to do this for generic recurring timers or from within
773	third-party libraries. Just remember to I<unref after start> and I<ref	906	third-party libraries. Just remember to I<unref after start> and I<ref
774	before stop> (but only if the watcher wasn't active before, or was active	907	before stop> (but only if the watcher wasn't active before, or was active
775	before, respectively. Note also that libev might stop watchers itself	908	before, respectively. Note also that libev might stop watchers itself
776	(e.g. non-repeating timers) in which case you have to C<ev_ref>	909	(e.g. non-repeating timers) in which case you have to C<ev_ref>
777	in the callback).	910	in the callback).
778		911
779	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	912	Example: Create a signal watcher, but keep it from keeping C<ev_run>
780	running when nothing else is active.	913	running when nothing else is active.
781		914
782	ev_signal exitsig;	915	ev_signal exitsig;
783	ev_signal_init (&exitsig, sig_cb, SIGINT);	916	ev_signal_init (&exitsig, sig_cb, SIGINT);
784	ev_signal_start (loop, &exitsig);	917	ev_signal_start (loop, &exitsig);
785	evf_unref (loop);	918	ev_unref (loop);
786		919
787	Example: For some weird reason, unregister the above signal handler again.	920	Example: For some weird reason, unregister the above signal handler again.
788		921
789	ev_ref (loop);	922	ev_ref (loop);
790	ev_signal_stop (loop, &exitsig);	923	ev_signal_stop (loop, &exitsig);
…		…
829	usually doesn't make much sense to set it to a lower value than C<0.01>,	962	usually doesn't make much sense to set it to a lower value than C<0.01>,
830	as this approaches the timing granularity of most systems. Note that if	963	as this approaches the timing granularity of most systems. Note that if
831	you do transactions with the outside world and you can't increase the	964	you do transactions with the outside world and you can't increase the
832	parallelity, then this setting will limit your transaction rate (if you	965	parallelity, then this setting will limit your transaction rate (if you
833	need to poll once per transaction and the I/O collect interval is 0.01,	966	need to poll once per transaction and the I/O collect interval is 0.01,
834	then you can't do more than 100 transations per second).	967	then you can't do more than 100 transactions per second).
835		968
836	Setting the I<timeout collect interval> can improve the opportunity for	969	Setting the I<timeout collect interval> can improve the opportunity for
837	saving power, as the program will "bundle" timer callback invocations that	970	saving power, as the program will "bundle" timer callback invocations that
838	are "near" in time together, by delaying some, thus reducing the number of	971	are "near" in time together, by delaying some, thus reducing the number of
839	times the process sleeps and wakes up again. Another useful technique to	972	times the process sleeps and wakes up again. Another useful technique to
…		…
844	more often than 100 times per second:	977	more often than 100 times per second:
845		978
846	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	979	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
847	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	980	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
848		981
		982	=item ev_invoke_pending (loop)
		983
		984	This call will simply invoke all pending watchers while resetting their
		985	pending state. Normally, C<ev_run> does this automatically when required,
		986	but when overriding the invoke callback this call comes handy. This
		987	function can be invoked from a watcher - this can be useful for example
		988	when you want to do some lengthy calculation and want to pass further
		989	event handling to another thread (you still have to make sure only one
		990	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		991
		992	=item int ev_pending_count (loop)
		993
		994	Returns the number of pending watchers - zero indicates that no watchers
		995	are pending.
		996
		997	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		998
		999	This overrides the invoke pending functionality of the loop: Instead of
		1000	invoking all pending watchers when there are any, C<ev_run> will call
		1001	this callback instead. This is useful, for example, when you want to
		1002	invoke the actual watchers inside another context (another thread etc.).
		1003
		1004	If you want to reset the callback, use C<ev_invoke_pending> as new
		1005	callback.
		1006
		1007	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1008
		1009	Sometimes you want to share the same loop between multiple threads. This
		1010	can be done relatively simply by putting mutex_lock/unlock calls around
		1011	each call to a libev function.
		1012
		1013	However, C<ev_run> can run an indefinite time, so it is not feasible
		1014	to wait for it to return. One way around this is to wake up the event
		1015	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1016	I<release> and I<acquire> callbacks on the loop.
		1017
		1018	When set, then C<release> will be called just before the thread is
		1019	suspended waiting for new events, and C<acquire> is called just
		1020	afterwards.
		1021
		1022	Ideally, C<release> will just call your mutex_unlock function, and
		1023	C<acquire> will just call the mutex_lock function again.
		1024
		1025	While event loop modifications are allowed between invocations of
		1026	C<release> and C<acquire> (that's their only purpose after all), no
		1027	modifications done will affect the event loop, i.e. adding watchers will
		1028	have no effect on the set of file descriptors being watched, or the time
		1029	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1030	to take note of any changes you made.
		1031
		1032	In theory, threads executing C<ev_run> will be async-cancel safe between
		1033	invocations of C<release> and C<acquire>.
		1034
		1035	See also the locking example in the C<THREADS> section later in this
		1036	document.
		1037
		1038	=item ev_set_userdata (loop, void *data)
		1039
		1040	=item void *ev_userdata (loop)
		1041
		1042	Set and retrieve a single C<void *> associated with a loop. When
		1043	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1044	C<0>.
		1045
		1046	These two functions can be used to associate arbitrary data with a loop,
		1047	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1048	C<acquire> callbacks described above, but of course can be (ab-)used for
		1049	any other purpose as well.
		1050
849	=item ev_loop_verify (loop)	1051	=item ev_verify (loop)
850		1052
851	This function only does something when C<EV_VERIFY> support has been	1053	This function only does something when C<EV_VERIFY> support has been
852	compiled in, which is the default for non-minimal builds. It tries to go	1054	compiled in, which is the default for non-minimal builds. It tries to go
853	through all internal structures and checks them for validity. If anything	1055	through all internal structures and checks them for validity. If anything
854	is found to be inconsistent, it will print an error message to standard	1056	is found to be inconsistent, it will print an error message to standard
…		…
865		1067
866	In the following description, uppercase C<TYPE> in names stands for the	1068	In the following description, uppercase C<TYPE> in names stands for the
867	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1069	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
868	watchers and C<ev_io_start> for I/O watchers.	1070	watchers and C<ev_io_start> for I/O watchers.
869		1071
870	A watcher is a structure that you create and register to record your	1072	A watcher is an opaque structure that you allocate and register to record
871	interest in some event. For instance, if you want to wait for STDIN to	1073	your interest in some event. To make a concrete example, imagine you want
872	become readable, you would create an C<ev_io> watcher for that:	1074	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1075	for that:
873		1076
874	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1077	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
875	{	1078	{
876	ev_io_stop (w);	1079	ev_io_stop (w);
877	ev_unloop (loop, EVUNLOOP_ALL);	1080	ev_break (loop, EVBREAK_ALL);
878	}	1081	}
879		1082
880	struct ev_loop *loop = ev_default_loop (0);	1083	struct ev_loop *loop = ev_default_loop (0);
881		1084
882	ev_io stdin_watcher;	1085	ev_io stdin_watcher;
883		1086
884	ev_init (&stdin_watcher, my_cb);	1087	ev_init (&stdin_watcher, my_cb);
885	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1088	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
886	ev_io_start (loop, &stdin_watcher);	1089	ev_io_start (loop, &stdin_watcher);
887		1090
888	ev_loop (loop, 0);	1091	ev_run (loop, 0);
889		1092
890	As you can see, you are responsible for allocating the memory for your	1093	As you can see, you are responsible for allocating the memory for your
891	watcher structures (and it is I<usually> a bad idea to do this on the	1094	watcher structures (and it is I<usually> a bad idea to do this on the
892	stack).	1095	stack).
893		1096
894	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1097	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
895	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1098	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
896		1099
897	Each watcher structure must be initialised by a call to C<ev_init	1100	Each watcher structure must be initialised by a call to C<ev_init (watcher
898	(watcher *, callback)>, which expects a callback to be provided. This	1101	*, callback)>, which expects a callback to be provided. This callback is
899	callback gets invoked each time the event occurs (or, in the case of I/O	1102	invoked each time the event occurs (or, in the case of I/O watchers, each
900	watchers, each time the event loop detects that the file descriptor given	1103	time the event loop detects that the file descriptor given is readable
901	is readable and/or writable).	1104	and/or writable).
902		1105
903	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1106	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
904	macro to configure it, with arguments specific to the watcher type. There	1107	macro to configure it, with arguments specific to the watcher type. There
905	is also a macro to combine initialisation and setting in one call: C<<	1108	is also a macro to combine initialisation and setting in one call: C<<
906	ev_TYPE_init (watcher *, callback, ...) >>.	1109	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
929	=item C<EV_WRITE>	1132	=item C<EV_WRITE>
930		1133
931	The file descriptor in the C<ev_io> watcher has become readable and/or	1134	The file descriptor in the C<ev_io> watcher has become readable and/or
932	writable.	1135	writable.
933		1136
934	=item C<EV_TIMEOUT>	1137	=item C<EV_TIMER>
935		1138
936	The C<ev_timer> watcher has timed out.	1139	The C<ev_timer> watcher has timed out.
937		1140
938	=item C<EV_PERIODIC>	1141	=item C<EV_PERIODIC>
939		1142
…		…
957		1160
958	=item C<EV_PREPARE>	1161	=item C<EV_PREPARE>
959		1162
960	=item C<EV_CHECK>	1163	=item C<EV_CHECK>
961		1164
962	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1165	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
963	to gather new events, and all C<ev_check> watchers are invoked just after	1166	to gather new events, and all C<ev_check> watchers are invoked just after
964	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1167	C<ev_run> has gathered them, but before it invokes any callbacks for any
965	received events. Callbacks of both watcher types can start and stop as	1168	received events. Callbacks of both watcher types can start and stop as
966	many watchers as they want, and all of them will be taken into account	1169	many watchers as they want, and all of them will be taken into account
967	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1170	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
968	C<ev_loop> from blocking).	1171	C<ev_run> from blocking).
969		1172
970	=item C<EV_EMBED>	1173	=item C<EV_EMBED>
971		1174
972	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1175	The embedded event loop specified in the C<ev_embed> watcher needs attention.
973		1176
974	=item C<EV_FORK>	1177	=item C<EV_FORK>
975		1178
976	The event loop has been resumed in the child process after fork (see	1179	The event loop has been resumed in the child process after fork (see
977	C<ev_fork>).	1180	C<ev_fork>).
		1181
		1182	=item C<EV_CLEANUP>
		1183
		1184	The event loop is about to be destroyed (see C<ev_cleanup>).
978		1185
979	=item C<EV_ASYNC>	1186	=item C<EV_ASYNC>
980		1187
981	The given async watcher has been asynchronously notified (see C<ev_async>).	1188	The given async watcher has been asynchronously notified (see C<ev_async>).
982		1189
…		…
1029		1236
1030	ev_io w;	1237	ev_io w;
1031	ev_init (&w, my_cb);	1238	ev_init (&w, my_cb);
1032	ev_io_set (&w, STDIN_FILENO, EV_READ);	1239	ev_io_set (&w, STDIN_FILENO, EV_READ);
1033		1240
1034	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1241	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1035		1242
1036	This macro initialises the type-specific parts of a watcher. You need to	1243	This macro initialises the type-specific parts of a watcher. You need to
1037	call C<ev_init> at least once before you call this macro, but you can	1244	call C<ev_init> at least once before you call this macro, but you can
1038	call C<ev_TYPE_set> any number of times. You must not, however, call this	1245	call C<ev_TYPE_set> any number of times. You must not, however, call this
1039	macro on a watcher that is active (it can be pending, however, which is a	1246	macro on a watcher that is active (it can be pending, however, which is a
…		…
1052		1259
1053	Example: Initialise and set an C<ev_io> watcher in one step.	1260	Example: Initialise and set an C<ev_io> watcher in one step.
1054		1261
1055	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1262	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1056		1263
1057	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1264	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1058		1265
1059	Starts (activates) the given watcher. Only active watchers will receive	1266	Starts (activates) the given watcher. Only active watchers will receive
1060	events. If the watcher is already active nothing will happen.	1267	events. If the watcher is already active nothing will happen.
1061		1268
1062	Example: Start the C<ev_io> watcher that is being abused as example in this	1269	Example: Start the C<ev_io> watcher that is being abused as example in this
1063	whole section.	1270	whole section.
1064		1271
1065	ev_io_start (EV_DEFAULT_UC, &w);	1272	ev_io_start (EV_DEFAULT_UC, &w);
1066		1273
1067	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1068		1275
1069	Stops the given watcher if active, and clears the pending status (whether	1276	Stops the given watcher if active, and clears the pending status (whether
1070	the watcher was active or not).	1277	the watcher was active or not).
1071		1278
1072	It is possible that stopped watchers are pending - for example,	1279	It is possible that stopped watchers are pending - for example,
…		…
1097	=item ev_cb_set (ev_TYPE *watcher, callback)	1304	=item ev_cb_set (ev_TYPE *watcher, callback)
1098		1305
1099	Change the callback. You can change the callback at virtually any time	1306	Change the callback. You can change the callback at virtually any time
1100	(modulo threads).	1307	(modulo threads).
1101		1308
1102	=item ev_set_priority (ev_TYPE *watcher, priority)	1309	=item ev_set_priority (ev_TYPE *watcher, int priority)
1103		1310
1104	=item int ev_priority (ev_TYPE *watcher)	1311	=item int ev_priority (ev_TYPE *watcher)
1105		1312
1106	Set and query the priority of the watcher. The priority is a small	1313	Set and query the priority of the watcher. The priority is a small
1107	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1314	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1139	watcher isn't pending it does nothing and returns C<0>.	1346	watcher isn't pending it does nothing and returns C<0>.
1140		1347
1141	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1348	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1142	callback to be invoked, which can be accomplished with this function.	1349	callback to be invoked, which can be accomplished with this function.
1143		1350
		1351	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1352
		1353	Feeds the given event set into the event loop, as if the specified event
		1354	had happened for the specified watcher (which must be a pointer to an
		1355	initialised but not necessarily started event watcher). Obviously you must
		1356	not free the watcher as long as it has pending events.
		1357
		1358	Stopping the watcher, letting libev invoke it, or calling
		1359	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1360	not started in the first place.
		1361
		1362	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1363	functions that do not need a watcher.
		1364
1144	=back	1365	=back
1145		1366
		1367	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1368	OWN COMPOSITE WATCHERS> idioms.
1146		1369
1147	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1370	=head2 WATCHER STATES
1148		1371
1149	Each watcher has, by default, a member C<void *data> that you can change	1372	There are various watcher states mentioned throughout this manual -
1150	and read at any time: libev will completely ignore it. This can be used	1373	active, pending and so on. In this section these states and the rules to
1151	to associate arbitrary data with your watcher. If you need more data and	1374	transition between them will be described in more detail - and while these
1152	don't want to allocate memory and store a pointer to it in that data	1375	rules might look complicated, they usually do "the right thing".
1153	member, you can also "subclass" the watcher type and provide your own
1154	data:
1155		1376
1156	struct my_io	1377	=over 4
1157	{
1158	ev_io io;
1159	int otherfd;
1160	void *somedata;
1161	struct whatever *mostinteresting;
1162	};
1163		1378
1164	...	1379	=item initialiased
1165	struct my_io w;
1166	ev_io_init (&w.io, my_cb, fd, EV_READ);
1167		1380
1168	And since your callback will be called with a pointer to the watcher, you	1381	Before a watcher can be registered with the event looop it has to be
1169	can cast it back to your own type:	1382	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1383	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1170		1384
1171	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1385	In this state it is simply some block of memory that is suitable for
1172	{	1386	use in an event loop. It can be moved around, freed, reused etc. at
1173	struct my_io *w = (struct my_io *)w_;	1387	will - as long as you either keep the memory contents intact, or call
1174	...	1388	C<ev_TYPE_init> again.
1175	}
1176		1389
1177	More interesting and less C-conformant ways of casting your callback type	1390	=item started/running/active
1178	instead have been omitted.
1179		1391
1180	Another common scenario is to use some data structure with multiple	1392	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1181	embedded watchers:	1393	property of the event loop, and is actively waiting for events. While in
		1394	this state it cannot be accessed (except in a few documented ways), moved,
		1395	freed or anything else - the only legal thing is to keep a pointer to it,
		1396	and call libev functions on it that are documented to work on active watchers.
1182		1397
1183	struct my_biggy	1398	=item pending
1184	{
1185	int some_data;
1186	ev_timer t1;
1187	ev_timer t2;
1188	}
1189		1399
1190	In this case getting the pointer to C<my_biggy> is a bit more	1400	If a watcher is active and libev determines that an event it is interested
1191	complicated: Either you store the address of your C<my_biggy> struct	1401	in has occurred (such as a timer expiring), it will become pending. It will
1192	in the C<data> member of the watcher (for woozies), or you need to use	1402	stay in this pending state until either it is stopped or its callback is
1193	some pointer arithmetic using C<offsetof> inside your watchers (for real	1403	about to be invoked, so it is not normally pending inside the watcher
1194	programmers):	1404	callback.
1195		1405
1196	#include <stddef.h>	1406	The watcher might or might not be active while it is pending (for example,
		1407	an expired non-repeating timer can be pending but no longer active). If it
		1408	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1409	but it is still property of the event loop at this time, so cannot be
		1410	moved, freed or reused. And if it is active the rules described in the
		1411	previous item still apply.
1197		1412
1198	static void	1413	It is also possible to feed an event on a watcher that is not active (e.g.
1199	t1_cb (EV_P_ ev_timer *w, int revents)	1414	via C<ev_feed_event>), in which case it becomes pending without being
1200	{	1415	active.
1201	struct my_biggy big = (struct my_biggy *)
1202	(((char *)w) - offsetof (struct my_biggy, t1));
1203	}
1204		1416
1205	static void	1417	=item stopped
1206	t2_cb (EV_P_ ev_timer *w, int revents)	1418
1207	{	1419	A watcher can be stopped implicitly by libev (in which case it might still
1208	struct my_biggy big = (struct my_biggy *)	1420	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1209	(((char *)w) - offsetof (struct my_biggy, t2));	1421	latter will clear any pending state the watcher might be in, regardless
1210	}	1422	of whether it was active or not, so stopping a watcher explicitly before
		1423	freeing it is often a good idea.
		1424
		1425	While stopped (and not pending) the watcher is essentially in the
		1426	initialised state, that is, it can be reused, moved, modified in any way
		1427	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1428	it again).
		1429
		1430	=back
1211		1431
1212	=head2 WATCHER PRIORITY MODELS	1432	=head2 WATCHER PRIORITY MODELS
1213		1433
1214	Many event loops support I<watcher priorities>, which are usually small	1434	Many event loops support I<watcher priorities>, which are usually small
1215	integers that influence the ordering of event callback invocation	1435	integers that influence the ordering of event callback invocation
…		…
1258		1478
1259	For example, to emulate how many other event libraries handle priorities,	1479	For example, to emulate how many other event libraries handle priorities,
1260	you can associate an C<ev_idle> watcher to each such watcher, and in	1480	you can associate an C<ev_idle> watcher to each such watcher, and in
1261	the normal watcher callback, you just start the idle watcher. The real	1481	the normal watcher callback, you just start the idle watcher. The real
1262	processing is done in the idle watcher callback. This causes libev to	1482	processing is done in the idle watcher callback. This causes libev to
1263	continously poll and process kernel event data for the watcher, but when	1483	continuously poll and process kernel event data for the watcher, but when
1264	the lock-out case is known to be rare (which in turn is rare :), this is	1484	the lock-out case is known to be rare (which in turn is rare :), this is
1265	workable.	1485	workable.
1266		1486
1267	Usually, however, the lock-out model implemented that way will perform	1487	Usually, however, the lock-out model implemented that way will perform
1268	miserably under the type of load it was designed to handle. In that case,	1488	miserably under the type of load it was designed to handle. In that case,
…		…
1282	{	1502	{
1283	// stop the I/O watcher, we received the event, but	1503	// stop the I/O watcher, we received the event, but
1284	// are not yet ready to handle it.	1504	// are not yet ready to handle it.
1285	ev_io_stop (EV_A_ w);	1505	ev_io_stop (EV_A_ w);
1286		1506
1287	// start the idle watcher to ahndle the actual event.	1507	// start the idle watcher to handle the actual event.
1288	// it will not be executed as long as other watchers	1508	// it will not be executed as long as other watchers
1289	// with the default priority are receiving events.	1509	// with the default priority are receiving events.
1290	ev_idle_start (EV_A_ &idle);	1510	ev_idle_start (EV_A_ &idle);
1291	}	1511	}
1292		1512
…		…
1342	In general you can register as many read and/or write event watchers per	1562	In general you can register as many read and/or write event watchers per
1343	fd as you want (as long as you don't confuse yourself). Setting all file	1563	fd as you want (as long as you don't confuse yourself). Setting all file
1344	descriptors to non-blocking mode is also usually a good idea (but not	1564	descriptors to non-blocking mode is also usually a good idea (but not
1345	required if you know what you are doing).	1565	required if you know what you are doing).
1346		1566
1347	If you cannot use non-blocking mode, then force the use of a
1348	known-to-be-good backend (at the time of this writing, this includes only
1349	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1350	descriptors for which non-blocking operation makes no sense (such as
1351	files) - libev doesn't guarentee any specific behaviour in that case.
1352
1353	Another thing you have to watch out for is that it is quite easy to	1567	Another thing you have to watch out for is that it is quite easy to
1354	receive "spurious" readiness notifications, that is your callback might	1568	receive "spurious" readiness notifications, that is, your callback might
1355	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1569	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1356	because there is no data. Not only are some backends known to create a	1570	because there is no data. It is very easy to get into this situation even
1357	lot of those (for example Solaris ports), it is very easy to get into	1571	with a relatively standard program structure. Thus it is best to always
1358	this situation even with a relatively standard program structure. Thus	1572	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1359	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1360	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1573	preferable to a program hanging until some data arrives.
1361		1574
1362	If you cannot run the fd in non-blocking mode (for example you should	1575	If you cannot run the fd in non-blocking mode (for example you should
1363	not play around with an Xlib connection), then you have to separately	1576	not play around with an Xlib connection), then you have to separately
1364	re-test whether a file descriptor is really ready with a known-to-be good	1577	re-test whether a file descriptor is really ready with a known-to-be good
1365	interface such as poll (fortunately in our Xlib example, Xlib already	1578	interface such as poll (fortunately in the case of Xlib, it already does
1366	does this on its own, so its quite safe to use). Some people additionally	1579	this on its own, so its quite safe to use). Some people additionally
1367	use C<SIGALRM> and an interval timer, just to be sure you won't block	1580	use C<SIGALRM> and an interval timer, just to be sure you won't block
1368	indefinitely.	1581	indefinitely.
1369		1582
1370	But really, best use non-blocking mode.	1583	But really, best use non-blocking mode.
1371		1584
…		…
1399		1612
1400	There is no workaround possible except not registering events	1613	There is no workaround possible except not registering events
1401	for potentially C<dup ()>'ed file descriptors, or to resort to	1614	for potentially C<dup ()>'ed file descriptors, or to resort to
1402	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1615	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1403		1616
		1617	=head3 The special problem of files
		1618
		1619	Many people try to use C<select> (or libev) on file descriptors
		1620	representing files, and expect it to become ready when their program
		1621	doesn't block on disk accesses (which can take a long time on their own).
		1622
		1623	However, this cannot ever work in the "expected" way - you get a readiness
		1624	notification as soon as the kernel knows whether and how much data is
		1625	there, and in the case of open files, that's always the case, so you
		1626	always get a readiness notification instantly, and your read (or possibly
		1627	write) will still block on the disk I/O.
		1628
		1629	Another way to view it is that in the case of sockets, pipes, character
		1630	devices and so on, there is another party (the sender) that delivers data
		1631	on its own, but in the case of files, there is no such thing: the disk
		1632	will not send data on its own, simply because it doesn't know what you
		1633	wish to read - you would first have to request some data.
		1634
		1635	Since files are typically not-so-well supported by advanced notification
		1636	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1637	to files, even though you should not use it. The reason for this is
		1638	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1639	usually a tty, often a pipe, but also sometimes files or special devices
		1640	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1641	F</dev/urandom>), and even though the file might better be served with
		1642	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1643	it "just works" instead of freezing.
		1644
		1645	So avoid file descriptors pointing to files when you know it (e.g. use
		1646	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1647	when you rarely read from a file instead of from a socket, and want to
		1648	reuse the same code path.
		1649
1404	=head3 The special problem of fork	1650	=head3 The special problem of fork
1405		1651
1406	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1652	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1407	useless behaviour. Libev fully supports fork, but needs to be told about	1653	useless behaviour. Libev fully supports fork, but needs to be told about
1408	it in the child.	1654	it in the child if you want to continue to use it in the child.
1409		1655
1410	To support fork in your programs, you either have to call	1656	To support fork in your child processes, you have to call C<ev_loop_fork
1411	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1657	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1412	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1658	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1413	C<EVBACKEND_POLL>.
1414		1659
1415	=head3 The special problem of SIGPIPE	1660	=head3 The special problem of SIGPIPE
1416		1661
1417	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1662	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1418	when writing to a pipe whose other end has been closed, your program gets	1663	when writing to a pipe whose other end has been closed, your program gets
…		…
1421		1666
1422	So when you encounter spurious, unexplained daemon exits, make sure you	1667	So when you encounter spurious, unexplained daemon exits, make sure you
1423	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1668	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1424	somewhere, as that would have given you a big clue).	1669	somewhere, as that would have given you a big clue).
1425		1670
		1671	=head3 The special problem of accept()ing when you can't
		1672
		1673	Many implementations of the POSIX C<accept> function (for example,
		1674	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1675	connection from the pending queue in all error cases.
		1676
		1677	For example, larger servers often run out of file descriptors (because
		1678	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1679	rejecting the connection, leading to libev signalling readiness on
		1680	the next iteration again (the connection still exists after all), and
		1681	typically causing the program to loop at 100% CPU usage.
		1682
		1683	Unfortunately, the set of errors that cause this issue differs between
		1684	operating systems, there is usually little the app can do to remedy the
		1685	situation, and no known thread-safe method of removing the connection to
		1686	cope with overload is known (to me).
		1687
		1688	One of the easiest ways to handle this situation is to just ignore it
		1689	- when the program encounters an overload, it will just loop until the
		1690	situation is over. While this is a form of busy waiting, no OS offers an
		1691	event-based way to handle this situation, so it's the best one can do.
		1692
		1693	A better way to handle the situation is to log any errors other than
		1694	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1695	messages, and continue as usual, which at least gives the user an idea of
		1696	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1697	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1698	usage.
		1699
		1700	If your program is single-threaded, then you could also keep a dummy file
		1701	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1702	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1703	close that fd, and create a new dummy fd. This will gracefully refuse
		1704	clients under typical overload conditions.
		1705
		1706	The last way to handle it is to simply log the error and C<exit>, as
		1707	is often done with C<malloc> failures, but this results in an easy
		1708	opportunity for a DoS attack.
1426		1709
1427	=head3 Watcher-Specific Functions	1710	=head3 Watcher-Specific Functions
1428		1711
1429	=over 4	1712	=over 4
1430		1713
…		…
1462	...	1745	...
1463	struct ev_loop *loop = ev_default_init (0);	1746	struct ev_loop *loop = ev_default_init (0);
1464	ev_io stdin_readable;	1747	ev_io stdin_readable;
1465	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1748	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1466	ev_io_start (loop, &stdin_readable);	1749	ev_io_start (loop, &stdin_readable);
1467	ev_loop (loop, 0);	1750	ev_run (loop, 0);
1468		1751
1469		1752
1470	=head2 C<ev_timer> - relative and optionally repeating timeouts	1753	=head2 C<ev_timer> - relative and optionally repeating timeouts
1471		1754
1472	Timer watchers are simple relative timers that generate an event after a	1755	Timer watchers are simple relative timers that generate an event after a
…		…
1480		1763
1481	The callback is guaranteed to be invoked only I<after> its timeout has	1764	The callback is guaranteed to be invoked only I<after> its timeout has
1482	passed (not I<at>, so on systems with very low-resolution clocks this	1765	passed (not I<at>, so on systems with very low-resolution clocks this
1483	might introduce a small delay). If multiple timers become ready during the	1766	might introduce a small delay). If multiple timers become ready during the
1484	same loop iteration then the ones with earlier time-out values are invoked	1767	same loop iteration then the ones with earlier time-out values are invoked
1485	before ones with later time-out values (but this is no longer true when a	1768	before ones of the same priority with later time-out values (but this is
1486	callback calls C<ev_loop> recursively).	1769	no longer true when a callback calls C<ev_run> recursively).
1487		1770
1488	=head3 Be smart about timeouts	1771	=head3 Be smart about timeouts
1489		1772
1490	Many real-world problems involve some kind of timeout, usually for error	1773	Many real-world problems involve some kind of timeout, usually for error
1491	recovery. A typical example is an HTTP request - if the other side hangs,	1774	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1577	ev_tstamp timeout = last_activity + 60.;	1860	ev_tstamp timeout = last_activity + 60.;
1578		1861
1579	// if last_activity + 60. is older than now, we did time out	1862	// if last_activity + 60. is older than now, we did time out
1580	if (timeout < now)	1863	if (timeout < now)
1581	{	1864	{
1582	// timeout occured, take action	1865	// timeout occurred, take action
1583	}	1866	}
1584	else	1867	else
1585	{	1868	{
1586	// callback was invoked, but there was some activity, re-arm	1869	// callback was invoked, but there was some activity, re-arm
1587	// the watcher to fire in last_activity + 60, which is	1870	// the watcher to fire in last_activity + 60, which is
…		…
1609	to the current time (meaning we just have some activity :), then call the	1892	to the current time (meaning we just have some activity :), then call the
1610	callback, which will "do the right thing" and start the timer:	1893	callback, which will "do the right thing" and start the timer:
1611		1894
1612	ev_init (timer, callback);	1895	ev_init (timer, callback);
1613	last_activity = ev_now (loop);	1896	last_activity = ev_now (loop);
1614	callback (loop, timer, EV_TIMEOUT);	1897	callback (loop, timer, EV_TIMER);
1615		1898
1616	And when there is some activity, simply store the current time in	1899	And when there is some activity, simply store the current time in
1617	C<last_activity>, no libev calls at all:	1900	C<last_activity>, no libev calls at all:
1618		1901
1619	last_actiivty = ev_now (loop);	1902	last_activity = ev_now (loop);
1620		1903
1621	This technique is slightly more complex, but in most cases where the	1904	This technique is slightly more complex, but in most cases where the
1622	time-out is unlikely to be triggered, much more efficient.	1905	time-out is unlikely to be triggered, much more efficient.
1623		1906
1624	Changing the timeout is trivial as well (if it isn't hard-coded in the	1907	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1662		1945
1663	=head3 The special problem of time updates	1946	=head3 The special problem of time updates
1664		1947
1665	Establishing the current time is a costly operation (it usually takes at	1948	Establishing the current time is a costly operation (it usually takes at
1666	least two system calls): EV therefore updates its idea of the current	1949	least two system calls): EV therefore updates its idea of the current
1667	time only before and after C<ev_loop> collects new events, which causes a	1950	time only before and after C<ev_run> collects new events, which causes a
1668	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1951	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1669	lots of events in one iteration.	1952	lots of events in one iteration.
1670		1953
1671	The relative timeouts are calculated relative to the C<ev_now ()>	1954	The relative timeouts are calculated relative to the C<ev_now ()>
1672	time. This is usually the right thing as this timestamp refers to the time	1955	time. This is usually the right thing as this timestamp refers to the time
…		…
1678		1961
1679	If the event loop is suspended for a long time, you can also force an	1962	If the event loop is suspended for a long time, you can also force an
1680	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1963	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1681	()>.	1964	()>.
1682		1965
		1966	=head3 The special problems of suspended animation
		1967
		1968	When you leave the server world it is quite customary to hit machines that
		1969	can suspend/hibernate - what happens to the clocks during such a suspend?
		1970
		1971	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1972	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1973	to run until the system is suspended, but they will not advance while the
		1974	system is suspended. That means, on resume, it will be as if the program
		1975	was frozen for a few seconds, but the suspend time will not be counted
		1976	towards C<ev_timer> when a monotonic clock source is used. The real time
		1977	clock advanced as expected, but if it is used as sole clocksource, then a
		1978	long suspend would be detected as a time jump by libev, and timers would
		1979	be adjusted accordingly.
		1980
		1981	I would not be surprised to see different behaviour in different between
		1982	operating systems, OS versions or even different hardware.
		1983
		1984	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1985	time jump in the monotonic clocks and the realtime clock. If the program
		1986	is suspended for a very long time, and monotonic clock sources are in use,
		1987	then you can expect C<ev_timer>s to expire as the full suspension time
		1988	will be counted towards the timers. When no monotonic clock source is in
		1989	use, then libev will again assume a timejump and adjust accordingly.
		1990
		1991	It might be beneficial for this latter case to call C<ev_suspend>
		1992	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1993	deterministic behaviour in this case (you can do nothing against
		1994	C<SIGSTOP>).
		1995
1683	=head3 Watcher-Specific Functions and Data Members	1996	=head3 Watcher-Specific Functions and Data Members
1684		1997
1685	=over 4	1998	=over 4
1686		1999
1687	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2000	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1713	C<repeat> value), or reset the running timer to the C<repeat> value.	2026	C<repeat> value), or reset the running timer to the C<repeat> value.
1714		2027
1715	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2028	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1716	usage example.	2029	usage example.
1717		2030
		2031	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2032
		2033	Returns the remaining time until a timer fires. If the timer is active,
		2034	then this time is relative to the current event loop time, otherwise it's
		2035	the timeout value currently configured.
		2036
		2037	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2038	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2039	will return C<4>. When the timer expires and is restarted, it will return
		2040	roughly C<7> (likely slightly less as callback invocation takes some time,
		2041	too), and so on.
		2042
1718	=item ev_tstamp repeat [read-write]	2043	=item ev_tstamp repeat [read-write]
1719		2044
1720	The current C<repeat> value. Will be used each time the watcher times out	2045	The current C<repeat> value. Will be used each time the watcher times out
1721	or C<ev_timer_again> is called, and determines the next timeout (if any),	2046	or C<ev_timer_again> is called, and determines the next timeout (if any),
1722	which is also when any modifications are taken into account.	2047	which is also when any modifications are taken into account.
…		…
1747	}	2072	}
1748		2073
1749	ev_timer mytimer;	2074	ev_timer mytimer;
1750	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2075	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1751	ev_timer_again (&mytimer); /* start timer */	2076	ev_timer_again (&mytimer); /* start timer */
1752	ev_loop (loop, 0);	2077	ev_run (loop, 0);
1753		2078
1754	// and in some piece of code that gets executed on any "activity":	2079	// and in some piece of code that gets executed on any "activity":
1755	// reset the timeout to start ticking again at 10 seconds	2080	// reset the timeout to start ticking again at 10 seconds
1756	ev_timer_again (&mytimer);	2081	ev_timer_again (&mytimer);
1757		2082
…		…
1783		2108
1784	As with timers, the callback is guaranteed to be invoked only when the	2109	As with timers, the callback is guaranteed to be invoked only when the
1785	point in time where it is supposed to trigger has passed. If multiple	2110	point in time where it is supposed to trigger has passed. If multiple
1786	timers become ready during the same loop iteration then the ones with	2111	timers become ready during the same loop iteration then the ones with
1787	earlier time-out values are invoked before ones with later time-out values	2112	earlier time-out values are invoked before ones with later time-out values
1788	(but this is no longer true when a callback calls C<ev_loop> recursively).	2113	(but this is no longer true when a callback calls C<ev_run> recursively).
1789		2114
1790	=head3 Watcher-Specific Functions and Data Members	2115	=head3 Watcher-Specific Functions and Data Members
1791		2116
1792	=over 4	2117	=over 4
1793		2118
…		…
1828		2153
1829	Another way to think about it (for the mathematically inclined) is that	2154	Another way to think about it (for the mathematically inclined) is that
1830	C<ev_periodic> will try to run the callback in this mode at the next possible	2155	C<ev_periodic> will try to run the callback in this mode at the next possible
1831	time where C<time = offset (mod interval)>, regardless of any time jumps.	2156	time where C<time = offset (mod interval)>, regardless of any time jumps.
1832		2157
1833	For numerical stability it is preferable that the C<offset> value is near	2158	The C<interval> I<MUST> be positive, and for numerical stability, the
1834	C<ev_now ()> (the current time), but there is no range requirement for	2159	interval value should be higher than C<1/8192> (which is around 100
1835	this value, and in fact is often specified as zero.	2160	microseconds) and C<offset> should be higher than C<0> and should have
		2161	at most a similar magnitude as the current time (say, within a factor of
		2162	ten). Typical values for offset are, in fact, C<0> or something between
		2163	C<0> and C<interval>, which is also the recommended range.
1836		2164
1837	Note also that there is an upper limit to how often a timer can fire (CPU	2165	Note also that there is an upper limit to how often a timer can fire (CPU
1838	speed for example), so if C<interval> is very small then timing stability	2166	speed for example), so if C<interval> is very small then timing stability
1839	will of course deteriorate. Libev itself tries to be exact to be about one	2167	will of course deteriorate. Libev itself tries to be exact to be about one
1840	millisecond (if the OS supports it and the machine is fast enough).	2168	millisecond (if the OS supports it and the machine is fast enough).
…		…
1921	Example: Call a callback every hour, or, more precisely, whenever the	2249	Example: Call a callback every hour, or, more precisely, whenever the
1922	system time is divisible by 3600. The callback invocation times have	2250	system time is divisible by 3600. The callback invocation times have
1923	potentially a lot of jitter, but good long-term stability.	2251	potentially a lot of jitter, but good long-term stability.
1924		2252
1925	static void	2253	static void
1926	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2254	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1927	{	2255	{
1928	... its now a full hour (UTC, or TAI or whatever your clock follows)	2256	... its now a full hour (UTC, or TAI or whatever your clock follows)
1929	}	2257	}
1930		2258
1931	ev_periodic hourly_tick;	2259	ev_periodic hourly_tick;
…		…
1954		2282
1955	=head2 C<ev_signal> - signal me when a signal gets signalled!	2283	=head2 C<ev_signal> - signal me when a signal gets signalled!
1956		2284
1957	Signal watchers will trigger an event when the process receives a specific	2285	Signal watchers will trigger an event when the process receives a specific
1958	signal one or more times. Even though signals are very asynchronous, libev	2286	signal one or more times. Even though signals are very asynchronous, libev
1959	will try it's best to deliver signals synchronously, i.e. as part of the	2287	will try its best to deliver signals synchronously, i.e. as part of the
1960	normal event processing, like any other event.	2288	normal event processing, like any other event.
1961		2289
1962	If you want signals asynchronously, just use C<sigaction> as you would	2290	If you want signals to be delivered truly asynchronously, just use
1963	do without libev and forget about sharing the signal. You can even use	2291	C<sigaction> as you would do without libev and forget about sharing
1964	C<ev_async> from a signal handler to synchronously wake up an event loop.	2292	the signal. You can even use C<ev_async> from a signal handler to
		2293	synchronously wake up an event loop.
1965		2294
1966	You can configure as many watchers as you like per signal. Only when the	2295	You can configure as many watchers as you like for the same signal, but
		2296	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2297	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2298	C<SIGINT> in both the default loop and another loop at the same time. At
		2299	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2300
1967	first watcher gets started will libev actually register a signal handler	2301	When the first watcher gets started will libev actually register something
1968	with the kernel (thus it coexists with your own signal handlers as long as	2302	with the kernel (thus it coexists with your own signal handlers as long as
1969	you don't register any with libev for the same signal). Similarly, when	2303	you don't register any with libev for the same signal).
1970	the last signal watcher for a signal is stopped, libev will reset the
1971	signal handler to SIG_DFL (regardless of what it was set to before).
1972		2304
1973	If possible and supported, libev will install its handlers with	2305	If possible and supported, libev will install its handlers with
1974	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2306	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1975	interrupted. If you have a problem with system calls getting interrupted by	2307	not be unduly interrupted. If you have a problem with system calls getting
1976	signals you can block all signals in an C<ev_check> watcher and unblock	2308	interrupted by signals you can block all signals in an C<ev_check> watcher
1977	them in an C<ev_prepare> watcher.	2309	and unblock them in an C<ev_prepare> watcher.
		2310
		2311	=head3 The special problem of inheritance over fork/execve/pthread_create
		2312
		2313	Both the signal mask (C<sigprocmask>) and the signal disposition
		2314	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2315	stopping it again), that is, libev might or might not block the signal,
		2316	and might or might not set or restore the installed signal handler (but
		2317	see C<EVFLAG_NOSIGMASK>).
		2318
		2319	While this does not matter for the signal disposition (libev never
		2320	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2321	C<execve>), this matters for the signal mask: many programs do not expect
		2322	certain signals to be blocked.
		2323
		2324	This means that before calling C<exec> (from the child) you should reset
		2325	the signal mask to whatever "default" you expect (all clear is a good
		2326	choice usually).
		2327
		2328	The simplest way to ensure that the signal mask is reset in the child is
		2329	to install a fork handler with C<pthread_atfork> that resets it. That will
		2330	catch fork calls done by libraries (such as the libc) as well.
		2331
		2332	In current versions of libev, the signal will not be blocked indefinitely
		2333	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2334	the window of opportunity for problems, it will not go away, as libev
		2335	I<has> to modify the signal mask, at least temporarily.
		2336
		2337	So I can't stress this enough: I<If you do not reset your signal mask when
		2338	you expect it to be empty, you have a race condition in your code>. This
		2339	is not a libev-specific thing, this is true for most event libraries.
		2340
		2341	=head3 The special problem of threads signal handling
		2342
		2343	POSIX threads has problematic signal handling semantics, specifically,
		2344	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2345	threads in a process block signals, which is hard to achieve.
		2346
		2347	When you want to use sigwait (or mix libev signal handling with your own
		2348	for the same signals), you can tackle this problem by globally blocking
		2349	all signals before creating any threads (or creating them with a fully set
		2350	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2351	loops. Then designate one thread as "signal receiver thread" which handles
		2352	these signals. You can pass on any signals that libev might be interested
		2353	in by calling C<ev_feed_signal>.
1978		2354
1979	=head3 Watcher-Specific Functions and Data Members	2355	=head3 Watcher-Specific Functions and Data Members
1980		2356
1981	=over 4	2357	=over 4
1982		2358
…		…
1998	Example: Try to exit cleanly on SIGINT.	2374	Example: Try to exit cleanly on SIGINT.
1999		2375
2000	static void	2376	static void
2001	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2377	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2002	{	2378	{
2003	ev_unloop (loop, EVUNLOOP_ALL);	2379	ev_break (loop, EVBREAK_ALL);
2004	}	2380	}
2005		2381
2006	ev_signal signal_watcher;	2382	ev_signal signal_watcher;
2007	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2383	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2008	ev_signal_start (loop, &signal_watcher);	2384	ev_signal_start (loop, &signal_watcher);
…		…
2020	in the next callback invocation is not.	2396	in the next callback invocation is not.
2021		2397
2022	Only the default event loop is capable of handling signals, and therefore	2398	Only the default event loop is capable of handling signals, and therefore
2023	you can only register child watchers in the default event loop.	2399	you can only register child watchers in the default event loop.
2024		2400
		2401	Due to some design glitches inside libev, child watchers will always be
		2402	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2403	libev)
		2404
2025	=head3 Process Interaction	2405	=head3 Process Interaction
2026		2406
2027	Libev grabs C<SIGCHLD> as soon as the default event loop is	2407	Libev grabs C<SIGCHLD> as soon as the default event loop is
2028	initialised. This is necessary to guarantee proper behaviour even if	2408	initialised. This is necessary to guarantee proper behaviour even if the
2029	the first child watcher is started after the child exits. The occurrence	2409	first child watcher is started after the child exits. The occurrence
2030	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2410	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2031	synchronously as part of the event loop processing. Libev always reaps all	2411	synchronously as part of the event loop processing. Libev always reaps all
2032	children, even ones not watched.	2412	children, even ones not watched.
2033		2413
2034	=head3 Overriding the Built-In Processing	2414	=head3 Overriding the Built-In Processing
…		…
2044	=head3 Stopping the Child Watcher	2424	=head3 Stopping the Child Watcher
2045		2425
2046	Currently, the child watcher never gets stopped, even when the	2426	Currently, the child watcher never gets stopped, even when the
2047	child terminates, so normally one needs to stop the watcher in the	2427	child terminates, so normally one needs to stop the watcher in the
2048	callback. Future versions of libev might stop the watcher automatically	2428	callback. Future versions of libev might stop the watcher automatically
2049	when a child exit is detected.	2429	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2430	problem).
2050		2431
2051	=head3 Watcher-Specific Functions and Data Members	2432	=head3 Watcher-Specific Functions and Data Members
2052		2433
2053	=over 4	2434	=over 4
2054		2435
…		…
2389		2770
2390	Prepare and check watchers are usually (but not always) used in pairs:	2771	Prepare and check watchers are usually (but not always) used in pairs:
2391	prepare watchers get invoked before the process blocks and check watchers	2772	prepare watchers get invoked before the process blocks and check watchers
2392	afterwards.	2773	afterwards.
2393		2774
2394	You I<must not> call C<ev_loop> or similar functions that enter	2775	You I<must not> call C<ev_run> or similar functions that enter
2395	the current event loop from either C<ev_prepare> or C<ev_check>	2776	the current event loop from either C<ev_prepare> or C<ev_check>
2396	watchers. Other loops than the current one are fine, however. The	2777	watchers. Other loops than the current one are fine, however. The
2397	rationale behind this is that you do not need to check for recursion in	2778	rationale behind this is that you do not need to check for recursion in
2398	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2779	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2399	C<ev_check> so if you have one watcher of each kind they will always be	2780	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2567		2948
2568	if (timeout >= 0)	2949	if (timeout >= 0)
2569	// create/start timer	2950	// create/start timer
2570		2951
2571	// poll	2952	// poll
2572	ev_loop (EV_A_ 0);	2953	ev_run (EV_A_ 0);
2573		2954
2574	// stop timer again	2955	// stop timer again
2575	if (timeout >= 0)	2956	if (timeout >= 0)
2576	ev_timer_stop (EV_A_ &to);	2957	ev_timer_stop (EV_A_ &to);
2577		2958
…		…
2655	if you do not want that, you need to temporarily stop the embed watcher).	3036	if you do not want that, you need to temporarily stop the embed watcher).
2656		3037
2657	=item ev_embed_sweep (loop, ev_embed *)	3038	=item ev_embed_sweep (loop, ev_embed *)
2658		3039
2659	Make a single, non-blocking sweep over the embedded loop. This works	3040	Make a single, non-blocking sweep over the embedded loop. This works
2660	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3041	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2661	appropriate way for embedded loops.	3042	appropriate way for embedded loops.
2662		3043
2663	=item struct ev_loop *other [read-only]	3044	=item struct ev_loop *other [read-only]
2664		3045
2665	The embedded event loop.	3046	The embedded event loop.
…		…
2725	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3106	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2726	handlers will be invoked, too, of course.	3107	handlers will be invoked, too, of course.
2727		3108
2728	=head3 The special problem of life after fork - how is it possible?	3109	=head3 The special problem of life after fork - how is it possible?
2729		3110
2730	Most uses of C<fork()> consist of forking, then some simple calls to ste	3111	Most uses of C<fork()> consist of forking, then some simple calls to set
2731	up/change the process environment, followed by a call to C<exec()>. This	3112	up/change the process environment, followed by a call to C<exec()>. This
2732	sequence should be handled by libev without any problems.	3113	sequence should be handled by libev without any problems.
2733		3114
2734	This changes when the application actually wants to do event handling	3115	This changes when the application actually wants to do event handling
2735	in the child, or both parent in child, in effect "continuing" after the	3116	in the child, or both parent in child, in effect "continuing" after the
…		…
2751	disadvantage of having to use multiple event loops (which do not support	3132	disadvantage of having to use multiple event loops (which do not support
2752	signal watchers).	3133	signal watchers).
2753		3134
2754	When this is not possible, or you want to use the default loop for	3135	When this is not possible, or you want to use the default loop for
2755	other reasons, then in the process that wants to start "fresh", call	3136	other reasons, then in the process that wants to start "fresh", call
2756	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3137	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2757	the default loop will "orphan" (not stop) all registered watchers, so you	3138	Destroying the default loop will "orphan" (not stop) all registered
2758	have to be careful not to execute code that modifies those watchers. Note	3139	watchers, so you have to be careful not to execute code that modifies
2759	also that in that case, you have to re-register any signal watchers.	3140	those watchers. Note also that in that case, you have to re-register any
		3141	signal watchers.
2760		3142
2761	=head3 Watcher-Specific Functions and Data Members	3143	=head3 Watcher-Specific Functions and Data Members
2762		3144
2763	=over 4	3145	=over 4
2764		3146
2765	=item ev_fork_init (ev_signal *, callback)	3147	=item ev_fork_init (ev_fork *, callback)
2766		3148
2767	Initialises and configures the fork watcher - it has no parameters of any	3149	Initialises and configures the fork watcher - it has no parameters of any
2768	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3150	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2769	believe me.	3151	really.
2770		3152
2771	=back	3153	=back
2772		3154
2773		3155
		3156	=head2 C<ev_cleanup> - even the best things end
		3157
		3158	Cleanup watchers are called just before the event loop is being destroyed
		3159	by a call to C<ev_loop_destroy>.
		3160
		3161	While there is no guarantee that the event loop gets destroyed, cleanup
		3162	watchers provide a convenient method to install cleanup hooks for your
		3163	program, worker threads and so on - you just to make sure to destroy the
		3164	loop when you want them to be invoked.
		3165
		3166	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3167	all other watchers, they do not keep a reference to the event loop (which
		3168	makes a lot of sense if you think about it). Like all other watchers, you
		3169	can call libev functions in the callback, except C<ev_cleanup_start>.
		3170
		3171	=head3 Watcher-Specific Functions and Data Members
		3172
		3173	=over 4
		3174
		3175	=item ev_cleanup_init (ev_cleanup *, callback)
		3176
		3177	Initialises and configures the cleanup watcher - it has no parameters of
		3178	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3179	pointless, I assure you.
		3180
		3181	=back
		3182
		3183	Example: Register an atexit handler to destroy the default loop, so any
		3184	cleanup functions are called.
		3185
		3186	static void
		3187	program_exits (void)
		3188	{
		3189	ev_loop_destroy (EV_DEFAULT_UC);
		3190	}
		3191
		3192	...
		3193	atexit (program_exits);
		3194
		3195
2774	=head2 C<ev_async> - how to wake up another event loop	3196	=head2 C<ev_async> - how to wake up an event loop
2775		3197
2776	In general, you cannot use an C<ev_loop> from multiple threads or other	3198	In general, you cannot use an C<ev_loop> from multiple threads or other
2777	asynchronous sources such as signal handlers (as opposed to multiple event	3199	asynchronous sources such as signal handlers (as opposed to multiple event
2778	loops - those are of course safe to use in different threads).	3200	loops - those are of course safe to use in different threads).
2779		3201
2780	Sometimes, however, you need to wake up another event loop you do not	3202	Sometimes, however, you need to wake up an event loop you do not control,
2781	control, for example because it belongs to another thread. This is what	3203	for example because it belongs to another thread. This is what C<ev_async>
2782	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3204	watchers do: as long as the C<ev_async> watcher is active, you can signal
2783	can signal it by calling C<ev_async_send>, which is thread- and signal	3205	it by calling C<ev_async_send>, which is thread- and signal safe.
2784	safe.
2785		3206
2786	This functionality is very similar to C<ev_signal> watchers, as signals,	3207	This functionality is very similar to C<ev_signal> watchers, as signals,
2787	too, are asynchronous in nature, and signals, too, will be compressed	3208	too, are asynchronous in nature, and signals, too, will be compressed
2788	(i.e. the number of callback invocations may be less than the number of	3209	(i.e. the number of callback invocations may be less than the number of
2789	C<ev_async_sent> calls).	3210	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3211	of "global async watchers" by using a watcher on an otherwise unused
		3212	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3213	even without knowing which loop owns the signal.
2790		3214
2791	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3215	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2792	just the default loop.	3216	just the default loop.
2793		3217
2794	=head3 Queueing	3218	=head3 Queueing
2795		3219
2796	C<ev_async> does not support queueing of data in any way. The reason	3220	C<ev_async> does not support queueing of data in any way. The reason
2797	is that the author does not know of a simple (or any) algorithm for a	3221	is that the author does not know of a simple (or any) algorithm for a
2798	multiple-writer-single-reader queue that works in all cases and doesn't	3222	multiple-writer-single-reader queue that works in all cases and doesn't
2799	need elaborate support such as pthreads.	3223	need elaborate support such as pthreads or unportable memory access
		3224	semantics.
2800		3225
2801	That means that if you want to queue data, you have to provide your own	3226	That means that if you want to queue data, you have to provide your own
2802	queue. But at least I can tell you how to implement locking around your	3227	queue. But at least I can tell you how to implement locking around your
2803	queue:	3228	queue:
2804		3229
…		…
2888	trust me.	3313	trust me.
2889		3314
2890	=item ev_async_send (loop, ev_async *)	3315	=item ev_async_send (loop, ev_async *)
2891		3316
2892	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3317	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2893	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3318	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3319	returns.
		3320
2894	C<ev_feed_event>, this call is safe to do from other threads, signal or	3321	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2895	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3322	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2896	section below on what exactly this means).	3323	embedding section below on what exactly this means).
2897		3324
2898	Note that, as with other watchers in libev, multiple events might get	3325	Note that, as with other watchers in libev, multiple events might get
2899	compressed into a single callback invocation (another way to look at this	3326	compressed into a single callback invocation (another way to look at this
2900	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3327	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
2901	reset when the event loop detects that).	3328	reset when the event loop detects that).
…		…
2943		3370
2944	If C<timeout> is less than 0, then no timeout watcher will be	3371	If C<timeout> is less than 0, then no timeout watcher will be
2945	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3372	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2946	repeat = 0) will be started. C<0> is a valid timeout.	3373	repeat = 0) will be started. C<0> is a valid timeout.
2947		3374
2948	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3375	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2949	passed an C<revents> set like normal event callbacks (a combination of	3376	passed an C<revents> set like normal event callbacks (a combination of
2950	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3377	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2951	value passed to C<ev_once>. Note that it is possible to receive I<both>	3378	value passed to C<ev_once>. Note that it is possible to receive I<both>
2952	a timeout and an io event at the same time - you probably should give io	3379	a timeout and an io event at the same time - you probably should give io
2953	events precedence.	3380	events precedence.
2954		3381
2955	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3382	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2956		3383
2957	static void stdin_ready (int revents, void *arg)	3384	static void stdin_ready (int revents, void *arg)
2958	{	3385	{
2959	if (revents & EV_READ)	3386	if (revents & EV_READ)
2960	/* stdin might have data for us, joy! */;	3387	/* stdin might have data for us, joy! */;
2961	else if (revents & EV_TIMEOUT)	3388	else if (revents & EV_TIMER)
2962	/* doh, nothing entered */;	3389	/* doh, nothing entered */;
2963	}	3390	}
2964		3391
2965	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3392	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2966		3393
2967	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2968
2969	Feeds the given event set into the event loop, as if the specified event
2970	had happened for the specified watcher (which must be a pointer to an
2971	initialised but not necessarily started event watcher).
2972
2973	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3394	=item ev_feed_fd_event (loop, int fd, int revents)
2974		3395
2975	Feed an event on the given fd, as if a file descriptor backend detected	3396	Feed an event on the given fd, as if a file descriptor backend detected
2976	the given events it.	3397	the given events it.
2977		3398
2978	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3399	=item ev_feed_signal_event (loop, int signum)
2979		3400
2980	Feed an event as if the given signal occurred (C<loop> must be the default	3401	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2981	loop!).	3402	which is async-safe.
2982		3403
2983	=back	3404	=back
		3405
		3406
		3407	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3408
		3409	This section explains some common idioms that are not immediately
		3410	obvious. Note that examples are sprinkled over the whole manual, and this
		3411	section only contains stuff that wouldn't fit anywhere else.
		3412
		3413	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3414
		3415	Each watcher has, by default, a C<void *data> member that you can read
		3416	or modify at any time: libev will completely ignore it. This can be used
		3417	to associate arbitrary data with your watcher. If you need more data and
		3418	don't want to allocate memory separately and store a pointer to it in that
		3419	data member, you can also "subclass" the watcher type and provide your own
		3420	data:
		3421
		3422	struct my_io
		3423	{
		3424	ev_io io;
		3425	int otherfd;
		3426	void *somedata;
		3427	struct whatever *mostinteresting;
		3428	};
		3429
		3430	...
		3431	struct my_io w;
		3432	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3433
		3434	And since your callback will be called with a pointer to the watcher, you
		3435	can cast it back to your own type:
		3436
		3437	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3438	{
		3439	struct my_io *w = (struct my_io *)w_;
		3440	...
		3441	}
		3442
		3443	More interesting and less C-conformant ways of casting your callback
		3444	function type instead have been omitted.
		3445
		3446	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3447
		3448	Another common scenario is to use some data structure with multiple
		3449	embedded watchers, in effect creating your own watcher that combines
		3450	multiple libev event sources into one "super-watcher":
		3451
		3452	struct my_biggy
		3453	{
		3454	int some_data;
		3455	ev_timer t1;
		3456	ev_timer t2;
		3457	}
		3458
		3459	In this case getting the pointer to C<my_biggy> is a bit more
		3460	complicated: Either you store the address of your C<my_biggy> struct in
		3461	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3462	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3463	real programmers):
		3464
		3465	#include <stddef.h>
		3466
		3467	static void
		3468	t1_cb (EV_P_ ev_timer *w, int revents)
		3469	{
		3470	struct my_biggy big = (struct my_biggy *)
		3471	(((char *)w) - offsetof (struct my_biggy, t1));
		3472	}
		3473
		3474	static void
		3475	t2_cb (EV_P_ ev_timer *w, int revents)
		3476	{
		3477	struct my_biggy big = (struct my_biggy *)
		3478	(((char *)w) - offsetof (struct my_biggy, t2));
		3479	}
		3480
		3481	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3482
		3483	Often (especially in GUI toolkits) there are places where you have
		3484	I<modal> interaction, which is most easily implemented by recursively
		3485	invoking C<ev_run>.
		3486
		3487	This brings the problem of exiting - a callback might want to finish the
		3488	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3489	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3490	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3491	other combination: In these cases, C<ev_break> will not work alone.
		3492
		3493	The solution is to maintain "break this loop" variable for each C<ev_run>
		3494	invocation, and use a loop around C<ev_run> until the condition is
		3495	triggered, using C<EVRUN_ONCE>:
		3496
		3497	// main loop
		3498	int exit_main_loop = 0;
		3499
		3500	while (!exit_main_loop)
		3501	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3502
		3503	// in a model watcher
		3504	int exit_nested_loop = 0;
		3505
		3506	while (!exit_nested_loop)
		3507	ev_run (EV_A_ EVRUN_ONCE);
		3508
		3509	To exit from any of these loops, just set the corresponding exit variable:
		3510
		3511	// exit modal loop
		3512	exit_nested_loop = 1;
		3513
		3514	// exit main program, after modal loop is finished
		3515	exit_main_loop = 1;
		3516
		3517	// exit both
		3518	exit_main_loop = exit_nested_loop = 1;
		3519
		3520	=head2 THREAD LOCKING EXAMPLE
		3521
		3522	Here is a fictitious example of how to run an event loop in a different
		3523	thread from where callbacks are being invoked and watchers are
		3524	created/added/removed.
		3525
		3526	For a real-world example, see the C<EV::Loop::Async> perl module,
		3527	which uses exactly this technique (which is suited for many high-level
		3528	languages).
		3529
		3530	The example uses a pthread mutex to protect the loop data, a condition
		3531	variable to wait for callback invocations, an async watcher to notify the
		3532	event loop thread and an unspecified mechanism to wake up the main thread.
		3533
		3534	First, you need to associate some data with the event loop:
		3535
		3536	typedef struct {
		3537	mutex_t lock; /* global loop lock */
		3538	ev_async async_w;
		3539	thread_t tid;
		3540	cond_t invoke_cv;
		3541	} userdata;
		3542
		3543	void prepare_loop (EV_P)
		3544	{
		3545	// for simplicity, we use a static userdata struct.
		3546	static userdata u;
		3547
		3548	ev_async_init (&u->async_w, async_cb);
		3549	ev_async_start (EV_A_ &u->async_w);
		3550
		3551	pthread_mutex_init (&u->lock, 0);
		3552	pthread_cond_init (&u->invoke_cv, 0);
		3553
		3554	// now associate this with the loop
		3555	ev_set_userdata (EV_A_ u);
		3556	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3557	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3558
		3559	// then create the thread running ev_run
		3560	pthread_create (&u->tid, 0, l_run, EV_A);
		3561	}
		3562
		3563	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3564	solely to wake up the event loop so it takes notice of any new watchers
		3565	that might have been added:
		3566
		3567	static void
		3568	async_cb (EV_P_ ev_async *w, int revents)
		3569	{
		3570	// just used for the side effects
		3571	}
		3572
		3573	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3574	protecting the loop data, respectively.
		3575
		3576	static void
		3577	l_release (EV_P)
		3578	{
		3579	userdata *u = ev_userdata (EV_A);
		3580	pthread_mutex_unlock (&u->lock);
		3581	}
		3582
		3583	static void
		3584	l_acquire (EV_P)
		3585	{
		3586	userdata *u = ev_userdata (EV_A);
		3587	pthread_mutex_lock (&u->lock);
		3588	}
		3589
		3590	The event loop thread first acquires the mutex, and then jumps straight
		3591	into C<ev_run>:
		3592
		3593	void *
		3594	l_run (void *thr_arg)
		3595	{
		3596	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3597
		3598	l_acquire (EV_A);
		3599	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3600	ev_run (EV_A_ 0);
		3601	l_release (EV_A);
		3602
		3603	return 0;
		3604	}
		3605
		3606	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3607	signal the main thread via some unspecified mechanism (signals? pipe
		3608	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3609	have been called (in a while loop because a) spurious wakeups are possible
		3610	and b) skipping inter-thread-communication when there are no pending
		3611	watchers is very beneficial):
		3612
		3613	static void
		3614	l_invoke (EV_P)
		3615	{
		3616	userdata *u = ev_userdata (EV_A);
		3617
		3618	while (ev_pending_count (EV_A))
		3619	{
		3620	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3621	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3622	}
		3623	}
		3624
		3625	Now, whenever the main thread gets told to invoke pending watchers, it
		3626	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3627	thread to continue:
		3628
		3629	static void
		3630	real_invoke_pending (EV_P)
		3631	{
		3632	userdata *u = ev_userdata (EV_A);
		3633
		3634	pthread_mutex_lock (&u->lock);
		3635	ev_invoke_pending (EV_A);
		3636	pthread_cond_signal (&u->invoke_cv);
		3637	pthread_mutex_unlock (&u->lock);
		3638	}
		3639
		3640	Whenever you want to start/stop a watcher or do other modifications to an
		3641	event loop, you will now have to lock:
		3642
		3643	ev_timer timeout_watcher;
		3644	userdata *u = ev_userdata (EV_A);
		3645
		3646	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3647
		3648	pthread_mutex_lock (&u->lock);
		3649	ev_timer_start (EV_A_ &timeout_watcher);
		3650	ev_async_send (EV_A_ &u->async_w);
		3651	pthread_mutex_unlock (&u->lock);
		3652
		3653	Note that sending the C<ev_async> watcher is required because otherwise
		3654	an event loop currently blocking in the kernel will have no knowledge
		3655	about the newly added timer. By waking up the loop it will pick up any new
		3656	watchers in the next event loop iteration.
		3657
		3658	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3659
		3660	While the overhead of a callback that e.g. schedules a thread is small, it
		3661	is still an overhead. If you embed libev, and your main usage is with some
		3662	kind of threads or coroutines, you might want to customise libev so that
		3663	doesn't need callbacks anymore.
		3664
		3665	Imagine you have coroutines that you can switch to using a function
		3666	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3667	and that due to some magic, the currently active coroutine is stored in a
		3668	global called C<current_coro>. Then you can build your own "wait for libev
		3669	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3670	the differing C<;> conventions):
		3671
		3672	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3673	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3674
		3675	That means instead of having a C callback function, you store the
		3676	coroutine to switch to in each watcher, and instead of having libev call
		3677	your callback, you instead have it switch to that coroutine.
		3678
		3679	A coroutine might now wait for an event with a function called
		3680	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3681	matter when, or whether the watcher is active or not when this function is
		3682	called):
		3683
		3684	void
		3685	wait_for_event (ev_watcher *w)
		3686	{
		3687	ev_cb_set (w) = current_coro;
		3688	switch_to (libev_coro);
		3689	}
		3690
		3691	That basically suspends the coroutine inside C<wait_for_event> and
		3692	continues the libev coroutine, which, when appropriate, switches back to
		3693	this or any other coroutine. I am sure if you sue this your own :)
		3694
		3695	You can do similar tricks if you have, say, threads with an event queue -
		3696	instead of storing a coroutine, you store the queue object and instead of
		3697	switching to a coroutine, you push the watcher onto the queue and notify
		3698	any waiters.
		3699
		3700	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3701	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3702
		3703	// my_ev.h
		3704	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3705	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3706	#include "../libev/ev.h"
		3707
		3708	// my_ev.c
		3709	#define EV_H "my_ev.h"
		3710	#include "../libev/ev.c"
		3711
		3712	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3713	F<my_ev.c> into your project. When properly specifying include paths, you
		3714	can even use F<ev.h> as header file name directly.
2984		3715
2985		3716
2986	=head1 LIBEVENT EMULATION	3717	=head1 LIBEVENT EMULATION
2987		3718
2988	Libev offers a compatibility emulation layer for libevent. It cannot	3719	Libev offers a compatibility emulation layer for libevent. It cannot
2989	emulate the internals of libevent, so here are some usage hints:	3720	emulate the internals of libevent, so here are some usage hints:
2990		3721
2991	=over 4	3722	=over 4
		3723
		3724	=item * Only the libevent-1.4.1-beta API is being emulated.
		3725
		3726	This was the newest libevent version available when libev was implemented,
		3727	and is still mostly unchanged in 2010.
2992		3728
2993	=item * Use it by including <event.h>, as usual.	3729	=item * Use it by including <event.h>, as usual.
2994		3730
2995	=item * The following members are fully supported: ev_base, ev_callback,	3731	=item * The following members are fully supported: ev_base, ev_callback,
2996	ev_arg, ev_fd, ev_res, ev_events.	3732	ev_arg, ev_fd, ev_res, ev_events.
…		…
3002	=item * Priorities are not currently supported. Initialising priorities	3738	=item * Priorities are not currently supported. Initialising priorities
3003	will fail and all watchers will have the same priority, even though there	3739	will fail and all watchers will have the same priority, even though there
3004	is an ev_pri field.	3740	is an ev_pri field.
3005		3741
3006	=item * In libevent, the last base created gets the signals, in libev, the	3742	=item * In libevent, the last base created gets the signals, in libev, the
3007	first base created (== the default loop) gets the signals.	3743	base that registered the signal gets the signals.
3008		3744
3009	=item * Other members are not supported.	3745	=item * Other members are not supported.
3010		3746
3011	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3747	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3012	to use the libev header file and library.	3748	to use the libev header file and library.
…		…
3031	Care has been taken to keep the overhead low. The only data member the C++	3767	Care has been taken to keep the overhead low. The only data member the C++
3032	classes add (compared to plain C-style watchers) is the event loop pointer	3768	classes add (compared to plain C-style watchers) is the event loop pointer
3033	that the watcher is associated with (or no additional members at all if	3769	that the watcher is associated with (or no additional members at all if
3034	you disable C<EV_MULTIPLICITY> when embedding libev).	3770	you disable C<EV_MULTIPLICITY> when embedding libev).
3035		3771
3036	Currently, functions, and static and non-static member functions can be	3772	Currently, functions, static and non-static member functions and classes
3037	used as callbacks. Other types should be easy to add as long as they only	3773	with C<operator ()> can be used as callbacks. Other types should be easy
3038	need one additional pointer for context. If you need support for other	3774	to add as long as they only need one additional pointer for context. If
3039	types of functors please contact the author (preferably after implementing	3775	you need support for other types of functors please contact the author
3040	it).	3776	(preferably after implementing it).
3041		3777
3042	Here is a list of things available in the C<ev> namespace:	3778	Here is a list of things available in the C<ev> namespace:
3043		3779
3044	=over 4	3780	=over 4
3045		3781
…		…
3063		3799
3064	=over 4	3800	=over 4
3065		3801
3066	=item ev::TYPE::TYPE ()	3802	=item ev::TYPE::TYPE ()
3067		3803
3068	=item ev::TYPE::TYPE (struct ev_loop *)	3804	=item ev::TYPE::TYPE (loop)
3069		3805
3070	=item ev::TYPE::~TYPE	3806	=item ev::TYPE::~TYPE
3071		3807
3072	The constructor (optionally) takes an event loop to associate the watcher	3808	The constructor (optionally) takes an event loop to associate the watcher
3073	with. If it is omitted, it will use C<EV_DEFAULT>.	3809	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3106	myclass obj;	3842	myclass obj;
3107	ev::io iow;	3843	ev::io iow;
3108	iow.set <myclass, &myclass::io_cb> (&obj);	3844	iow.set <myclass, &myclass::io_cb> (&obj);
3109		3845
3110	=item w->set (object *)	3846	=item w->set (object *)
3111
3112	This is an B<experimental> feature that might go away in a future version.
3113		3847
3114	This is a variation of a method callback - leaving out the method to call	3848	This is a variation of a method callback - leaving out the method to call
3115	will default the method to C<operator ()>, which makes it possible to use	3849	will default the method to C<operator ()>, which makes it possible to use
3116	functor objects without having to manually specify the C<operator ()> all	3850	functor objects without having to manually specify the C<operator ()> all
3117	the time. Incidentally, you can then also leave out the template argument	3851	the time. Incidentally, you can then also leave out the template argument
…		…
3150	Example: Use a plain function as callback.	3884	Example: Use a plain function as callback.
3151		3885
3152	static void io_cb (ev::io &w, int revents) { }	3886	static void io_cb (ev::io &w, int revents) { }
3153	iow.set <io_cb> ();	3887	iow.set <io_cb> ();
3154		3888
3155	=item w->set (struct ev_loop *)	3889	=item w->set (loop)
3156		3890
3157	Associates a different C<struct ev_loop> with this watcher. You can only	3891	Associates a different C<struct ev_loop> with this watcher. You can only
3158	do this when the watcher is inactive (and not pending either).	3892	do this when the watcher is inactive (and not pending either).
3159		3893
3160	=item w->set ([arguments])	3894	=item w->set ([arguments])
3161		3895
3162	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3896	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3163	called at least once. Unlike the C counterpart, an active watcher gets	3897	method or a suitable start method must be called at least once. Unlike the
3164	automatically stopped and restarted when reconfiguring it with this	3898	C counterpart, an active watcher gets automatically stopped and restarted
3165	method.	3899	when reconfiguring it with this method.
3166		3900
3167	=item w->start ()	3901	=item w->start ()
3168		3902
3169	Starts the watcher. Note that there is no C<loop> argument, as the	3903	Starts the watcher. Note that there is no C<loop> argument, as the
3170	constructor already stores the event loop.	3904	constructor already stores the event loop.
3171		3905
		3906	=item w->start ([arguments])
		3907
		3908	Instead of calling C<set> and C<start> methods separately, it is often
		3909	convenient to wrap them in one call. Uses the same type of arguments as
		3910	the configure C<set> method of the watcher.
		3911
3172	=item w->stop ()	3912	=item w->stop ()
3173		3913
3174	Stops the watcher if it is active. Again, no C<loop> argument.	3914	Stops the watcher if it is active. Again, no C<loop> argument.
3175		3915
3176	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3916	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3188		3928
3189	=back	3929	=back
3190		3930
3191	=back	3931	=back
3192		3932
3193	Example: Define a class with an IO and idle watcher, start one of them in	3933	Example: Define a class with two I/O and idle watchers, start the I/O
3194	the constructor.	3934	watchers in the constructor.
3195		3935
3196	class myclass	3936	class myclass
3197	{	3937	{
3198	ev::io io ; void io_cb (ev::io &w, int revents);	3938	ev::io io ; void io_cb (ev::io &w, int revents);
		3939	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3199	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3940	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3200		3941
3201	myclass (int fd)	3942	myclass (int fd)
3202	{	3943	{
3203	io .set <myclass, &myclass::io_cb > (this);	3944	io .set <myclass, &myclass::io_cb > (this);
		3945	io2 .set <myclass, &myclass::io2_cb > (this);
3204	idle.set <myclass, &myclass::idle_cb> (this);	3946	idle.set <myclass, &myclass::idle_cb> (this);
3205		3947
3206	io.start (fd, ev::READ);	3948	io.set (fd, ev::WRITE); // configure the watcher
		3949	io.start (); // start it whenever convenient
		3950
		3951	io2.start (fd, ev::READ); // set + start in one call
3207	}	3952	}
3208	};	3953	};
3209		3954
3210		3955
3211	=head1 OTHER LANGUAGE BINDINGS	3956	=head1 OTHER LANGUAGE BINDINGS
…		…
3257	=item Ocaml	4002	=item Ocaml
3258		4003
3259	Erkki Seppala has written Ocaml bindings for libev, to be found at	4004	Erkki Seppala has written Ocaml bindings for libev, to be found at
3260	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4005	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3261		4006
		4007	=item Lua
		4008
		4009	Brian Maher has written a partial interface to libev for lua (at the
		4010	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4011	L<http://github.com/brimworks/lua-ev>.
		4012
3262	=back	4013	=back
3263		4014
3264		4015
3265	=head1 MACRO MAGIC	4016	=head1 MACRO MAGIC
3266		4017
…		…
3279	loop argument"). The C<EV_A> form is used when this is the sole argument,	4030	loop argument"). The C<EV_A> form is used when this is the sole argument,
3280	C<EV_A_> is used when other arguments are following. Example:	4031	C<EV_A_> is used when other arguments are following. Example:
3281		4032
3282	ev_unref (EV_A);	4033	ev_unref (EV_A);
3283	ev_timer_add (EV_A_ watcher);	4034	ev_timer_add (EV_A_ watcher);
3284	ev_loop (EV_A_ 0);	4035	ev_run (EV_A_ 0);
3285		4036
3286	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4037	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3287	which is often provided by the following macro.	4038	which is often provided by the following macro.
3288		4039
3289	=item C<EV_P>, C<EV_P_>	4040	=item C<EV_P>, C<EV_P_>
…		…
3329	}	4080	}
3330		4081
3331	ev_check check;	4082	ev_check check;
3332	ev_check_init (&check, check_cb);	4083	ev_check_init (&check, check_cb);
3333	ev_check_start (EV_DEFAULT_ &check);	4084	ev_check_start (EV_DEFAULT_ &check);
3334	ev_loop (EV_DEFAULT_ 0);	4085	ev_run (EV_DEFAULT_ 0);
3335		4086
3336	=head1 EMBEDDING	4087	=head1 EMBEDDING
3337		4088
3338	Libev can (and often is) directly embedded into host	4089	Libev can (and often is) directly embedded into host
3339	applications. Examples of applications that embed it include the Deliantra	4090	applications. Examples of applications that embed it include the Deliantra
…		…
3419	libev.m4	4170	libev.m4
3420		4171
3421	=head2 PREPROCESSOR SYMBOLS/MACROS	4172	=head2 PREPROCESSOR SYMBOLS/MACROS
3422		4173
3423	Libev can be configured via a variety of preprocessor symbols you have to	4174	Libev can be configured via a variety of preprocessor symbols you have to
3424	define before including any of its files. The default in the absence of	4175	define before including (or compiling) any of its files. The default in
3425	autoconf is documented for every option.	4176	the absence of autoconf is documented for every option.
		4177
		4178	Symbols marked with "(h)" do not change the ABI, and can have different
		4179	values when compiling libev vs. including F<ev.h>, so it is permissible
		4180	to redefine them before including F<ev.h> without breaking compatibility
		4181	to a compiled library. All other symbols change the ABI, which means all
		4182	users of libev and the libev code itself must be compiled with compatible
		4183	settings.
3426		4184
3427	=over 4	4185	=over 4
3428		4186
		4187	=item EV_COMPAT3 (h)
		4188
		4189	Backwards compatibility is a major concern for libev. This is why this
		4190	release of libev comes with wrappers for the functions and symbols that
		4191	have been renamed between libev version 3 and 4.
		4192
		4193	You can disable these wrappers (to test compatibility with future
		4194	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4195	sources. This has the additional advantage that you can drop the C<struct>
		4196	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4197	typedef in that case.
		4198
		4199	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4200	and in some even more future version the compatibility code will be
		4201	removed completely.
		4202
3429	=item EV_STANDALONE	4203	=item EV_STANDALONE (h)
3430		4204
3431	Must always be C<1> if you do not use autoconf configuration, which	4205	Must always be C<1> if you do not use autoconf configuration, which
3432	keeps libev from including F<config.h>, and it also defines dummy	4206	keeps libev from including F<config.h>, and it also defines dummy
3433	implementations for some libevent functions (such as logging, which is not	4207	implementations for some libevent functions (such as logging, which is not
3434	supported). It will also not define any of the structs usually found in	4208	supported). It will also not define any of the structs usually found in
3435	F<event.h> that are not directly supported by the libev core alone.	4209	F<event.h> that are not directly supported by the libev core alone.
3436		4210
3437	In stanbdalone mode, libev will still try to automatically deduce the	4211	In standalone mode, libev will still try to automatically deduce the
3438	configuration, but has to be more conservative.	4212	configuration, but has to be more conservative.
		4213
		4214	=item EV_USE_FLOOR
		4215
		4216	If defined to be C<1>, libev will use the C<floor ()> function for its
		4217	periodic reschedule calculations, otherwise libev will fall back on a
		4218	portable (slower) implementation. If you enable this, you usually have to
		4219	link against libm or something equivalent. Enabling this when the C<floor>
		4220	function is not available will fail, so the safe default is to not enable
		4221	this.
3439		4222
3440	=item EV_USE_MONOTONIC	4223	=item EV_USE_MONOTONIC
3441		4224
3442	If defined to be C<1>, libev will try to detect the availability of the	4225	If defined to be C<1>, libev will try to detect the availability of the
3443	monotonic clock option at both compile time and runtime. Otherwise no	4226	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3507	be used is the winsock select). This means that it will call	4290	be used is the winsock select). This means that it will call
3508	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4291	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3509	it is assumed that all these functions actually work on fds, even	4292	it is assumed that all these functions actually work on fds, even
3510	on win32. Should not be defined on non-win32 platforms.	4293	on win32. Should not be defined on non-win32 platforms.
3511		4294
3512	=item EV_FD_TO_WIN32_HANDLE	4295	=item EV_FD_TO_WIN32_HANDLE(fd)
3513		4296
3514	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4297	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3515	file descriptors to socket handles. When not defining this symbol (the	4298	file descriptors to socket handles. When not defining this symbol (the
3516	default), then libev will call C<_get_osfhandle>, which is usually	4299	default), then libev will call C<_get_osfhandle>, which is usually
3517	correct. In some cases, programs use their own file descriptor management,	4300	correct. In some cases, programs use their own file descriptor management,
3518	in which case they can provide this function to map fds to socket handles.	4301	in which case they can provide this function to map fds to socket handles.
		4302
		4303	=item EV_WIN32_HANDLE_TO_FD(handle)
		4304
		4305	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4306	using the standard C<_open_osfhandle> function. For programs implementing
		4307	their own fd to handle mapping, overwriting this function makes it easier
		4308	to do so. This can be done by defining this macro to an appropriate value.
		4309
		4310	=item EV_WIN32_CLOSE_FD(fd)
		4311
		4312	If programs implement their own fd to handle mapping on win32, then this
		4313	macro can be used to override the C<close> function, useful to unregister
		4314	file descriptors again. Note that the replacement function has to close
		4315	the underlying OS handle.
3519		4316
3520	=item EV_USE_POLL	4317	=item EV_USE_POLL
3521		4318
3522	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4319	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3523	backend. Otherwise it will be enabled on non-win32 platforms. It	4320	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3570	as well as for signal and thread safety in C<ev_async> watchers.	4367	as well as for signal and thread safety in C<ev_async> watchers.
3571		4368
3572	In the absence of this define, libev will use C<sig_atomic_t volatile>	4369	In the absence of this define, libev will use C<sig_atomic_t volatile>
3573	(from F<signal.h>), which is usually good enough on most platforms.	4370	(from F<signal.h>), which is usually good enough on most platforms.
3574		4371
3575	=item EV_H	4372	=item EV_H (h)
3576		4373
3577	The name of the F<ev.h> header file used to include it. The default if	4374	The name of the F<ev.h> header file used to include it. The default if
3578	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4375	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3579	used to virtually rename the F<ev.h> header file in case of conflicts.	4376	used to virtually rename the F<ev.h> header file in case of conflicts.
3580		4377
3581	=item EV_CONFIG_H	4378	=item EV_CONFIG_H (h)
3582		4379
3583	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4380	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3584	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4381	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3585	C<EV_H>, above.	4382	C<EV_H>, above.
3586		4383
3587	=item EV_EVENT_H	4384	=item EV_EVENT_H (h)
3588		4385
3589	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4386	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3590	of how the F<event.h> header can be found, the default is C<"event.h">.	4387	of how the F<event.h> header can be found, the default is C<"event.h">.
3591		4388
3592	=item EV_PROTOTYPES	4389	=item EV_PROTOTYPES (h)
3593		4390
3594	If defined to be C<0>, then F<ev.h> will not define any function	4391	If defined to be C<0>, then F<ev.h> will not define any function
3595	prototypes, but still define all the structs and other symbols. This is	4392	prototypes, but still define all the structs and other symbols. This is
3596	occasionally useful if you want to provide your own wrapper functions	4393	occasionally useful if you want to provide your own wrapper functions
3597	around libev functions.	4394	around libev functions.
…		…
3619	fine.	4416	fine.
3620		4417
3621	If your embedding application does not need any priorities, defining these	4418	If your embedding application does not need any priorities, defining these
3622	both to C<0> will save some memory and CPU.	4419	both to C<0> will save some memory and CPU.
3623		4420
3624	=item EV_PERIODIC_ENABLE	4421	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4422	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4423	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3625		4424
3626	If undefined or defined to be C<1>, then periodic timers are supported. If	4425	If undefined or defined to be C<1> (and the platform supports it), then
3627	defined to be C<0>, then they are not. Disabling them saves a few kB of	4426	the respective watcher type is supported. If defined to be C<0>, then it
3628	code.	4427	is not. Disabling watcher types mainly saves code size.
3629		4428
3630	=item EV_IDLE_ENABLE	4429	=item EV_FEATURES
3631
3632	If undefined or defined to be C<1>, then idle watchers are supported. If
3633	defined to be C<0>, then they are not. Disabling them saves a few kB of
3634	code.
3635
3636	=item EV_EMBED_ENABLE
3637
3638	If undefined or defined to be C<1>, then embed watchers are supported. If
3639	defined to be C<0>, then they are not. Embed watchers rely on most other
3640	watcher types, which therefore must not be disabled.
3641
3642	=item EV_STAT_ENABLE
3643
3644	If undefined or defined to be C<1>, then stat watchers are supported. If
3645	defined to be C<0>, then they are not.
3646
3647	=item EV_FORK_ENABLE
3648
3649	If undefined or defined to be C<1>, then fork watchers are supported. If
3650	defined to be C<0>, then they are not.
3651
3652	=item EV_ASYNC_ENABLE
3653
3654	If undefined or defined to be C<1>, then async watchers are supported. If
3655	defined to be C<0>, then they are not.
3656
3657	=item EV_MINIMAL
3658		4430
3659	If you need to shave off some kilobytes of code at the expense of some	4431	If you need to shave off some kilobytes of code at the expense of some
3660	speed, define this symbol to C<1>. Currently this is used to override some	4432	speed (but with the full API), you can define this symbol to request
3661	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4433	certain subsets of functionality. The default is to enable all features
3662	much smaller 2-heap for timer management over the default 4-heap.	4434	that can be enabled on the platform.
		4435
		4436	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4437	with some broad features you want) and then selectively re-enable
		4438	additional parts you want, for example if you want everything minimal,
		4439	but multiple event loop support, async and child watchers and the poll
		4440	backend, use this:
		4441
		4442	#define EV_FEATURES 0
		4443	#define EV_MULTIPLICITY 1
		4444	#define EV_USE_POLL 1
		4445	#define EV_CHILD_ENABLE 1
		4446	#define EV_ASYNC_ENABLE 1
		4447
		4448	The actual value is a bitset, it can be a combination of the following
		4449	values:
		4450
		4451	=over 4
		4452
		4453	=item C<1> - faster/larger code
		4454
		4455	Use larger code to speed up some operations.
		4456
		4457	Currently this is used to override some inlining decisions (enlarging the
		4458	code size by roughly 30% on amd64).
		4459
		4460	When optimising for size, use of compiler flags such as C<-Os> with
		4461	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4462	assertions.
		4463
		4464	=item C<2> - faster/larger data structures
		4465
		4466	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4467	hash table sizes and so on. This will usually further increase code size
		4468	and can additionally have an effect on the size of data structures at
		4469	runtime.
		4470
		4471	=item C<4> - full API configuration
		4472
		4473	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4474	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4475
		4476	=item C<8> - full API
		4477
		4478	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4479	details on which parts of the API are still available without this
		4480	feature, and do not complain if this subset changes over time.
		4481
		4482	=item C<16> - enable all optional watcher types
		4483
		4484	Enables all optional watcher types. If you want to selectively enable
		4485	only some watcher types other than I/O and timers (e.g. prepare,
		4486	embed, async, child...) you can enable them manually by defining
		4487	C<EV_watchertype_ENABLE> to C<1> instead.
		4488
		4489	=item C<32> - enable all backends
		4490
		4491	This enables all backends - without this feature, you need to enable at
		4492	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4493
		4494	=item C<64> - enable OS-specific "helper" APIs
		4495
		4496	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4497	default.
		4498
		4499	=back
		4500
		4501	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4502	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4503	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4504	watchers, timers and monotonic clock support.
		4505
		4506	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4507	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4508	your program might be left out as well - a binary starting a timer and an
		4509	I/O watcher then might come out at only 5Kb.
		4510
		4511	=item EV_AVOID_STDIO
		4512
		4513	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4514	functions (printf, scanf, perror etc.). This will increase the code size
		4515	somewhat, but if your program doesn't otherwise depend on stdio and your
		4516	libc allows it, this avoids linking in the stdio library which is quite
		4517	big.
		4518
		4519	Note that error messages might become less precise when this option is
		4520	enabled.
		4521
		4522	=item EV_NSIG
		4523
		4524	The highest supported signal number, +1 (or, the number of
		4525	signals): Normally, libev tries to deduce the maximum number of signals
		4526	automatically, but sometimes this fails, in which case it can be
		4527	specified. Also, using a lower number than detected (C<32> should be
		4528	good for about any system in existence) can save some memory, as libev
		4529	statically allocates some 12-24 bytes per signal number.
3663		4530
3664	=item EV_PID_HASHSIZE	4531	=item EV_PID_HASHSIZE
3665		4532
3666	C<ev_child> watchers use a small hash table to distribute workload by	4533	C<ev_child> watchers use a small hash table to distribute workload by
3667	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4534	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3668	than enough. If you need to manage thousands of children you might want to	4535	usually more than enough. If you need to manage thousands of children you
3669	increase this value (I<must> be a power of two).	4536	might want to increase this value (I<must> be a power of two).
3670		4537
3671	=item EV_INOTIFY_HASHSIZE	4538	=item EV_INOTIFY_HASHSIZE
3672		4539
3673	C<ev_stat> watchers use a small hash table to distribute workload by	4540	C<ev_stat> watchers use a small hash table to distribute workload by
3674	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4541	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3675	usually more than enough. If you need to manage thousands of C<ev_stat>	4542	disabled), usually more than enough. If you need to manage thousands of
3676	watchers you might want to increase this value (I<must> be a power of	4543	C<ev_stat> watchers you might want to increase this value (I<must> be a
3677	two).	4544	power of two).
3678		4545
3679	=item EV_USE_4HEAP	4546	=item EV_USE_4HEAP
3680		4547
3681	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4548	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3682	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4549	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3683	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4550	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3684	faster performance with many (thousands) of watchers.	4551	faster performance with many (thousands) of watchers.
3685		4552
3686	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4553	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3687	(disabled).	4554	will be C<0>.
3688		4555
3689	=item EV_HEAP_CACHE_AT	4556	=item EV_HEAP_CACHE_AT
3690		4557
3691	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4558	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3692	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4559	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3693	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4560	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3694	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4561	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3695	but avoids random read accesses on heap changes. This improves performance	4562	but avoids random read accesses on heap changes. This improves performance
3696	noticeably with many (hundreds) of watchers.	4563	noticeably with many (hundreds) of watchers.
3697		4564
3698	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4565	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3699	(disabled).	4566	will be C<0>.
3700		4567
3701	=item EV_VERIFY	4568	=item EV_VERIFY
3702		4569
3703	Controls how much internal verification (see C<ev_loop_verify ()>) will	4570	Controls how much internal verification (see C<ev_verify ()>) will
3704	be done: If set to C<0>, no internal verification code will be compiled	4571	be done: If set to C<0>, no internal verification code will be compiled
3705	in. If set to C<1>, then verification code will be compiled in, but not	4572	in. If set to C<1>, then verification code will be compiled in, but not
3706	called. If set to C<2>, then the internal verification code will be	4573	called. If set to C<2>, then the internal verification code will be
3707	called once per loop, which can slow down libev. If set to C<3>, then the	4574	called once per loop, which can slow down libev. If set to C<3>, then the
3708	verification code will be called very frequently, which will slow down	4575	verification code will be called very frequently, which will slow down
3709	libev considerably.	4576	libev considerably.
3710		4577
3711	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4578	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3712	C<0>.	4579	will be C<0>.
3713		4580
3714	=item EV_COMMON	4581	=item EV_COMMON
3715		4582
3716	By default, all watchers have a C<void *data> member. By redefining	4583	By default, all watchers have a C<void *data> member. By redefining
3717	this macro to a something else you can include more and other types of	4584	this macro to something else you can include more and other types of
3718	members. You have to define it each time you include one of the files,	4585	members. You have to define it each time you include one of the files,
3719	though, and it must be identical each time.	4586	though, and it must be identical each time.
3720		4587
3721	For example, the perl EV module uses something like this:	4588	For example, the perl EV module uses something like this:
3722		4589
…		…
3775	file.	4642	file.
3776		4643
3777	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4644	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3778	that everybody includes and which overrides some configure choices:	4645	that everybody includes and which overrides some configure choices:
3779		4646
3780	#define EV_MINIMAL 1	4647	#define EV_FEATURES 8
3781	#define EV_USE_POLL 0	4648	#define EV_USE_SELECT 1
3782	#define EV_MULTIPLICITY 0
3783	#define EV_PERIODIC_ENABLE 0	4649	#define EV_PREPARE_ENABLE 1
		4650	#define EV_IDLE_ENABLE 1
3784	#define EV_STAT_ENABLE 0	4651	#define EV_SIGNAL_ENABLE 1
3785	#define EV_FORK_ENABLE 0	4652	#define EV_CHILD_ENABLE 1
		4653	#define EV_USE_STDEXCEPT 0
3786	#define EV_CONFIG_H <config.h>	4654	#define EV_CONFIG_H <config.h>
3787	#define EV_MINPRI 0
3788	#define EV_MAXPRI 0
3789		4655
3790	#include "ev++.h"	4656	#include "ev++.h"
3791		4657
3792	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4658	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3793		4659
3794	#include "ev_cpp.h"	4660	#include "ev_cpp.h"
3795	#include "ev.c"	4661	#include "ev.c"
3796		4662
3797	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4663	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3798		4664
3799	=head2 THREADS AND COROUTINES	4665	=head2 THREADS AND COROUTINES
3800		4666
3801	=head3 THREADS	4667	=head3 THREADS
3802		4668
…		…
3853	default loop and triggering an C<ev_async> watcher from the default loop	4719	default loop and triggering an C<ev_async> watcher from the default loop
3854	watcher callback into the event loop interested in the signal.	4720	watcher callback into the event loop interested in the signal.
3855		4721
3856	=back	4722	=back
3857		4723
		4724	See also L<THREAD LOCKING EXAMPLE>.
		4725
3858	=head3 COROUTINES	4726	=head3 COROUTINES
3859		4727
3860	Libev is very accommodating to coroutines ("cooperative threads"):	4728	Libev is very accommodating to coroutines ("cooperative threads"):
3861	libev fully supports nesting calls to its functions from different	4729	libev fully supports nesting calls to its functions from different
3862	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4730	coroutines (e.g. you can call C<ev_run> on the same loop from two
3863	different coroutines, and switch freely between both coroutines running the	4731	different coroutines, and switch freely between both coroutines running
3864	loop, as long as you don't confuse yourself). The only exception is that	4732	the loop, as long as you don't confuse yourself). The only exception is
3865	you must not do this from C<ev_periodic> reschedule callbacks.	4733	that you must not do this from C<ev_periodic> reschedule callbacks.
3866		4734
3867	Care has been taken to ensure that libev does not keep local state inside	4735	Care has been taken to ensure that libev does not keep local state inside
3868	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4736	C<ev_run>, and other calls do not usually allow for coroutine switches as
3869	they do not call any callbacks.	4737	they do not call any callbacks.
3870		4738
3871	=head2 COMPILER WARNINGS	4739	=head2 COMPILER WARNINGS
3872		4740
3873	Depending on your compiler and compiler settings, you might get no or a	4741	Depending on your compiler and compiler settings, you might get no or a
…		…
3884	maintainable.	4752	maintainable.
3885		4753
3886	And of course, some compiler warnings are just plain stupid, or simply	4754	And of course, some compiler warnings are just plain stupid, or simply
3887	wrong (because they don't actually warn about the condition their message	4755	wrong (because they don't actually warn about the condition their message
3888	seems to warn about). For example, certain older gcc versions had some	4756	seems to warn about). For example, certain older gcc versions had some
3889	warnings that resulted an extreme number of false positives. These have	4757	warnings that resulted in an extreme number of false positives. These have
3890	been fixed, but some people still insist on making code warn-free with	4758	been fixed, but some people still insist on making code warn-free with
3891	such buggy versions.	4759	such buggy versions.
3892		4760
3893	While libev is written to generate as few warnings as possible,	4761	While libev is written to generate as few warnings as possible,
3894	"warn-free" code is not a goal, and it is recommended not to build libev	4762	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3930	I suggest using suppression lists.	4798	I suggest using suppression lists.
3931		4799
3932		4800
3933	=head1 PORTABILITY NOTES	4801	=head1 PORTABILITY NOTES
3934		4802
		4803	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4804
		4805	GNU/Linux is the only common platform that supports 64 bit file/large file
		4806	interfaces but I<disables> them by default.
		4807
		4808	That means that libev compiled in the default environment doesn't support
		4809	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4810
		4811	Unfortunately, many programs try to work around this GNU/Linux issue
		4812	by enabling the large file API, which makes them incompatible with the
		4813	standard libev compiled for their system.
		4814
		4815	Likewise, libev cannot enable the large file API itself as this would
		4816	suddenly make it incompatible to the default compile time environment,
		4817	i.e. all programs not using special compile switches.
		4818
		4819	=head2 OS/X AND DARWIN BUGS
		4820
		4821	The whole thing is a bug if you ask me - basically any system interface
		4822	you touch is broken, whether it is locales, poll, kqueue or even the
		4823	OpenGL drivers.
		4824
		4825	=head3 C<kqueue> is buggy
		4826
		4827	The kqueue syscall is broken in all known versions - most versions support
		4828	only sockets, many support pipes.
		4829
		4830	Libev tries to work around this by not using C<kqueue> by default on this
		4831	rotten platform, but of course you can still ask for it when creating a
		4832	loop - embedding a socket-only kqueue loop into a select-based one is
		4833	probably going to work well.
		4834
		4835	=head3 C<poll> is buggy
		4836
		4837	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4838	implementation by something calling C<kqueue> internally around the 10.5.6
		4839	release, so now C<kqueue> I<and> C<poll> are broken.
		4840
		4841	Libev tries to work around this by not using C<poll> by default on
		4842	this rotten platform, but of course you can still ask for it when creating
		4843	a loop.
		4844
		4845	=head3 C<select> is buggy
		4846
		4847	All that's left is C<select>, and of course Apple found a way to fuck this
		4848	one up as well: On OS/X, C<select> actively limits the number of file
		4849	descriptors you can pass in to 1024 - your program suddenly crashes when
		4850	you use more.
		4851
		4852	There is an undocumented "workaround" for this - defining
		4853	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4854	work on OS/X.
		4855
		4856	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4857
		4858	=head3 C<errno> reentrancy
		4859
		4860	The default compile environment on Solaris is unfortunately so
		4861	thread-unsafe that you can't even use components/libraries compiled
		4862	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4863	defined by default. A valid, if stupid, implementation choice.
		4864
		4865	If you want to use libev in threaded environments you have to make sure
		4866	it's compiled with C<_REENTRANT> defined.
		4867
		4868	=head3 Event port backend
		4869
		4870	The scalable event interface for Solaris is called "event
		4871	ports". Unfortunately, this mechanism is very buggy in all major
		4872	releases. If you run into high CPU usage, your program freezes or you get
		4873	a large number of spurious wakeups, make sure you have all the relevant
		4874	and latest kernel patches applied. No, I don't know which ones, but there
		4875	are multiple ones to apply, and afterwards, event ports actually work
		4876	great.
		4877
		4878	If you can't get it to work, you can try running the program by setting
		4879	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4880	C<select> backends.
		4881
		4882	=head2 AIX POLL BUG
		4883
		4884	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4885	this by trying to avoid the poll backend altogether (i.e. it's not even
		4886	compiled in), which normally isn't a big problem as C<select> works fine
		4887	with large bitsets on AIX, and AIX is dead anyway.
		4888
3935	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4889	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4890
		4891	=head3 General issues
3936		4892
3937	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4893	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3938	requires, and its I/O model is fundamentally incompatible with the POSIX	4894	requires, and its I/O model is fundamentally incompatible with the POSIX
3939	model. Libev still offers limited functionality on this platform in	4895	model. Libev still offers limited functionality on this platform in
3940	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4896	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3941	descriptors. This only applies when using Win32 natively, not when using	4897	descriptors. This only applies when using Win32 natively, not when using
3942	e.g. cygwin.	4898	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4899	as every compielr comes with a slightly differently broken/incompatible
		4900	environment.
3943		4901
3944	Lifting these limitations would basically require the full	4902	Lifting these limitations would basically require the full
3945	re-implementation of the I/O system. If you are into these kinds of	4903	re-implementation of the I/O system. If you are into this kind of thing,
3946	things, then note that glib does exactly that for you in a very portable	4904	then note that glib does exactly that for you in a very portable way (note
3947	way (note also that glib is the slowest event library known to man).	4905	also that glib is the slowest event library known to man).
3948		4906
3949	There is no supported compilation method available on windows except	4907	There is no supported compilation method available on windows except
3950	embedding it into other applications.	4908	embedding it into other applications.
3951		4909
3952	Sensible signal handling is officially unsupported by Microsoft - libev	4910	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
3980	you do I<not> compile the F<ev.c> or any other embedded source files!):	4938	you do I<not> compile the F<ev.c> or any other embedded source files!):
3981		4939
3982	#include "evwrap.h"	4940	#include "evwrap.h"
3983	#include "ev.c"	4941	#include "ev.c"
3984		4942
3985	=over 4
3986
3987	=item The winsocket select function	4943	=head3 The winsocket C<select> function
3988		4944
3989	The winsocket C<select> function doesn't follow POSIX in that it	4945	The winsocket C<select> function doesn't follow POSIX in that it
3990	requires socket I<handles> and not socket I<file descriptors> (it is	4946	requires socket I<handles> and not socket I<file descriptors> (it is
3991	also extremely buggy). This makes select very inefficient, and also	4947	also extremely buggy). This makes select very inefficient, and also
3992	requires a mapping from file descriptors to socket handles (the Microsoft	4948	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4001	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4957	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4002		4958
4003	Note that winsockets handling of fd sets is O(n), so you can easily get a	4959	Note that winsockets handling of fd sets is O(n), so you can easily get a
4004	complexity in the O(n²) range when using win32.	4960	complexity in the O(n²) range when using win32.
4005		4961
4006	=item Limited number of file descriptors	4962	=head3 Limited number of file descriptors
4007		4963
4008	Windows has numerous arbitrary (and low) limits on things.	4964	Windows has numerous arbitrary (and low) limits on things.
4009		4965
4010	Early versions of winsocket's select only supported waiting for a maximum	4966	Early versions of winsocket's select only supported waiting for a maximum
4011	of C<64> handles (probably owning to the fact that all windows kernels	4967	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4026	runtime libraries. This might get you to about C<512> or C<2048> sockets	4982	runtime libraries. This might get you to about C<512> or C<2048> sockets
4027	(depending on windows version and/or the phase of the moon). To get more,	4983	(depending on windows version and/or the phase of the moon). To get more,
4028	you need to wrap all I/O functions and provide your own fd management, but	4984	you need to wrap all I/O functions and provide your own fd management, but
4029	the cost of calling select (O(n²)) will likely make this unworkable.	4985	the cost of calling select (O(n²)) will likely make this unworkable.
4030		4986
4031	=back
4032
4033	=head2 PORTABILITY REQUIREMENTS	4987	=head2 PORTABILITY REQUIREMENTS
4034		4988
4035	In addition to a working ISO-C implementation and of course the	4989	In addition to a working ISO-C implementation and of course the
4036	backend-specific APIs, libev relies on a few additional extensions:	4990	backend-specific APIs, libev relies on a few additional extensions:
4037		4991
…		…
4043	Libev assumes not only that all watcher pointers have the same internal	4997	Libev assumes not only that all watcher pointers have the same internal
4044	structure (guaranteed by POSIX but not by ISO C for example), but it also	4998	structure (guaranteed by POSIX but not by ISO C for example), but it also
4045	assumes that the same (machine) code can be used to call any watcher	4999	assumes that the same (machine) code can be used to call any watcher
4046	callback: The watcher callbacks have different type signatures, but libev	5000	callback: The watcher callbacks have different type signatures, but libev
4047	calls them using an C<ev_watcher *> internally.	5001	calls them using an C<ev_watcher *> internally.
		5002
		5003	=item pointer accesses must be thread-atomic
		5004
		5005	Accessing a pointer value must be atomic, it must both be readable and
		5006	writable in one piece - this is the case on all current architectures.
4048		5007
4049	=item C<sig_atomic_t volatile> must be thread-atomic as well	5008	=item C<sig_atomic_t volatile> must be thread-atomic as well
4050		5009
4051	The type C<sig_atomic_t volatile> (or whatever is defined as	5010	The type C<sig_atomic_t volatile> (or whatever is defined as
4052	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5011	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4075	watchers.	5034	watchers.
4076		5035
4077	=item C<double> must hold a time value in seconds with enough accuracy	5036	=item C<double> must hold a time value in seconds with enough accuracy
4078		5037
4079	The type C<double> is used to represent timestamps. It is required to	5038	The type C<double> is used to represent timestamps. It is required to
4080	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5039	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4081	enough for at least into the year 4000. This requirement is fulfilled by	5040	good enough for at least into the year 4000 with millisecond accuracy
		5041	(the design goal for libev). This requirement is overfulfilled by
4082	implementations implementing IEEE 754, which is basically all existing	5042	implementations using IEEE 754, which is basically all existing ones. With
4083	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5043	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4084	2200.
4085		5044
4086	=back	5045	=back
4087		5046
4088	If you know of other additional requirements drop me a note.	5047	If you know of other additional requirements drop me a note.
4089		5048
…		…
4157	involves iterating over all running async watchers or all signal numbers.	5116	involves iterating over all running async watchers or all signal numbers.
4158		5117
4159	=back	5118	=back
4160		5119
4161		5120
		5121	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5122
		5123	The major version 4 introduced some incompatible changes to the API.
		5124
		5125	At the moment, the C<ev.h> header file provides compatibility definitions
		5126	for all changes, so most programs should still compile. The compatibility
		5127	layer might be removed in later versions of libev, so better update to the
		5128	new API early than late.
		5129
		5130	=over 4
		5131
		5132	=item C<EV_COMPAT3> backwards compatibility mechanism
		5133
		5134	The backward compatibility mechanism can be controlled by
		5135	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5136	section.
		5137
		5138	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5139
		5140	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5141
		5142	ev_loop_destroy (EV_DEFAULT_UC);
		5143	ev_loop_fork (EV_DEFAULT);
		5144
		5145	=item function/symbol renames
		5146
		5147	A number of functions and symbols have been renamed:
		5148
		5149	ev_loop => ev_run
		5150	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5151	EVLOOP_ONESHOT => EVRUN_ONCE
		5152
		5153	ev_unloop => ev_break
		5154	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5155	EVUNLOOP_ONE => EVBREAK_ONE
		5156	EVUNLOOP_ALL => EVBREAK_ALL
		5157
		5158	EV_TIMEOUT => EV_TIMER
		5159
		5160	ev_loop_count => ev_iteration
		5161	ev_loop_depth => ev_depth
		5162	ev_loop_verify => ev_verify
		5163
		5164	Most functions working on C<struct ev_loop> objects don't have an
		5165	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5166	associated constants have been renamed to not collide with the C<struct
		5167	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5168	as all other watcher types. Note that C<ev_loop_fork> is still called
		5169	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5170	typedef.
		5171
		5172	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5173
		5174	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5175	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5176	and work, but the library code will of course be larger.
		5177
		5178	=back
		5179
		5180
4162	=head1 GLOSSARY	5181	=head1 GLOSSARY
4163		5182
4164	=over 4	5183	=over 4
4165		5184
4166	=item active	5185	=item active
4167		5186
4168	A watcher is active as long as it has been started (has been attached to	5187	A watcher is active as long as it has been started and not yet stopped.
4169	an event loop) but not yet stopped (disassociated from the event loop).	5188	See L<WATCHER STATES> for details.
4170		5189
4171	=item application	5190	=item application
4172		5191
4173	In this document, an application is whatever is using libev.	5192	In this document, an application is whatever is using libev.
		5193
		5194	=item backend
		5195
		5196	The part of the code dealing with the operating system interfaces.
4174		5197
4175	=item callback	5198	=item callback
4176		5199
4177	The address of a function that is called when some event has been	5200	The address of a function that is called when some event has been
4178	detected. Callbacks are being passed the event loop, the watcher that	5201	detected. Callbacks are being passed the event loop, the watcher that
4179	received the event, and the actual event bitset.	5202	received the event, and the actual event bitset.
4180		5203
4181	=item callback invocation	5204	=item callback/watcher invocation
4182		5205
4183	The act of calling the callback associated with a watcher.	5206	The act of calling the callback associated with a watcher.
4184		5207
4185	=item event	5208	=item event
4186		5209
4187	A change of state of some external event, such as data now being available	5210	A change of state of some external event, such as data now being available
4188	for reading on a file descriptor, time having passed or simply not having	5211	for reading on a file descriptor, time having passed or simply not having
4189	any other events happening anymore.	5212	any other events happening anymore.
4190		5213
4191	In libev, events are represented as single bits (such as C<EV_READ> or	5214	In libev, events are represented as single bits (such as C<EV_READ> or
4192	C<EV_TIMEOUT>).	5215	C<EV_TIMER>).
4193		5216
4194	=item event library	5217	=item event library
4195		5218
4196	A software package implementing an event model and loop.	5219	A software package implementing an event model and loop.
4197		5220
…		…
4205	The model used to describe how an event loop handles and processes	5228	The model used to describe how an event loop handles and processes
4206	watchers and events.	5229	watchers and events.
4207		5230
4208	=item pending	5231	=item pending
4209		5232
4210	A watcher is pending as soon as the corresponding event has been detected,	5233	A watcher is pending as soon as the corresponding event has been
4211	and stops being pending as soon as the watcher will be invoked or its	5234	detected. See L<WATCHER STATES> for details.
4212	pending status is explicitly cleared by the application.
4213
4214	A watcher can be pending, but not active. Stopping a watcher also clears
4215	its pending status.
4216		5235
4217	=item real time	5236	=item real time
4218		5237
4219	The physical time that is observed. It is apparently strictly monotonic :)	5238	The physical time that is observed. It is apparently strictly monotonic :)
4220		5239
4221	=item wall-clock time	5240	=item wall-clock time
4222		5241
4223	The time and date as shown on clocks. Unlike real time, it can actually	5242	The time and date as shown on clocks. Unlike real time, it can actually
4224	be wrong and jump forwards and backwards, e.g. when the you adjust your	5243	be wrong and jump forwards and backwards, e.g. when you adjust your
4225	clock.	5244	clock.
4226		5245
4227	=item watcher	5246	=item watcher
4228		5247
4229	A data structure that describes interest in certain events. Watchers need	5248	A data structure that describes interest in certain events. Watchers need
4230	to be started (attached to an event loop) before they can receive events.	5249	to be started (attached to an event loop) before they can receive events.
4231		5250
4232	=item watcher invocation
4233
4234	The act of calling the callback associated with a watcher.
4235
4236	=back	5251	=back
4237		5252
4238	=head1 AUTHOR	5253	=head1 AUTHOR
4239		5254
4240	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5256	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4241		5257

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