ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.253 by root, Tue Jul 14 18:33:48 2009 UTC vs.
Revision 1.362 by root, Sun Jan 30 21:10:13 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,
401	but it scales phenomenally better. While poll and select usually scale	489	but it scales phenomenally better. While poll and select usually scale
402	like O(total_fds) where n is the total number of fds (or the highest fd),	490	like O(total_fds) where n is the total number of fds (or the highest fd),
403	epoll scales either O(1) or O(active_fds).	491	epoll scales either O(1) or O(active_fds).
404		492
405	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
406	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
407	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
408	descriptor (and unnecessary guessing of parameters), problems with dup and	496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(and only giving 5ms accuracy while select on the same platform gives
409	so on. The biggest issue is fork races, however - if a program forks then	499	0.1ms) and so on. The biggest issue is fork races, however - if a program
410	I<both> parent and child process have to recreate the epoll set, which can	500	forks then I<both> parent and child process have to recreate the epoll
411	take considerable time (one syscall per file descriptor) and is of course	501	set, which can take considerable time (one syscall per file descriptor)
412	hard to detect.	502	and is of course hard to detect.
413		503
414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
415	of course I<doesn't>, and epoll just loves to report events for totally	505	of course I<doesn't>, and epoll just loves to report events for totally
416	I<different> file descriptors (even already closed ones, so one cannot	506	I<different> file descriptors (even already closed ones, so one cannot
417	even remove them from the set) than registered in the set (especially	507	even remove them from the set) than registered in the set (especially
418	on SMP systems). Libev tries to counter these spurious notifications by	508	on SMP systems). Libev tries to counter these spurious notifications by
419	employing an additional generation counter and comparing that against the	509	employing an additional generation counter and comparing that against the
420	events to filter out spurious ones, recreating the set when required.	510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
421		517
422	While stopping, setting and starting an I/O watcher in the same iteration	518	While stopping, setting and starting an I/O watcher in the same iteration
423	will result in some caching, there is still a system call per such	519	will result in some caching, there is still a system call per such
424	incident (because the same I<file descriptor> could point to a different	520	incident (because the same I<file descriptor> could point to a different
425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		588
493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
494	it's really slow, but it still scales very well (O(active_fds)).	590	it's really slow, but it still scales very well (O(active_fds)).
495		591
496	Please note that Solaris event ports can deliver a lot of spurious
497	notifications, so you need to use non-blocking I/O or other means to avoid
498	blocking when no data (or space) is available.
499
500	While this backend scales well, it requires one system call per active	592	While this backend scales well, it requires one system call per active
501	file descriptor per loop iteration. For small and medium numbers of file	593	file descriptor per loop iteration. For small and medium numbers of file
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	595	might perform better.
504		596
505	On the positive side, with the exception of the spurious readiness	597	On the positive side, this backend actually performed fully to
506	notifications, this backend actually performed fully to specification
507	in all tests and is fully embeddable, which is a rare feat among the	598	specification in all tests and is fully embeddable, which is a rare feat
508	OS-specific backends (I vastly prefer correctness over speed hacks).	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
509		611
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
512		614
513	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
514		616
515	Try all backends (even potentially broken ones that wouldn't be tried	617	Try all backends (even potentially broken ones that wouldn't be tried
516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		620
519	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
520		630
521	=back	631	=back
522		632
523	If one or more of these are or'ed into the flags value, then only these	633	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	634	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	635	here). If none are specified, all backends in C<ev_recommended_backends
526		636	()> will be tried.
527	Example: This is the most typical usage.
528
529	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
531
532	Example: Restrict libev to the select and poll backends, and do not allow
533	environment settings to be taken into account:
534
535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
536
537	Example: Use whatever libev has to offer, but make sure that kqueue is
538	used if available (warning, breaks stuff, best use only with your own
539	private event loop and only if you know the OS supports your types of
540	fds):
541
542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
543
544	=item struct ev_loop *ev_loop_new (unsigned int flags)
545
546	Similar to C<ev_default_loop>, but always creates a new event loop that is
547	always distinct from the default loop. Unlike the default loop, it cannot
548	handle signal and child watchers, and attempts to do so will be greeted by
549	undefined behaviour (or a failed assertion if assertions are enabled).
550
551	Note that this function I<is> thread-safe, and the recommended way to use
552	libev with threads is indeed to create one loop per thread, and using the
553	default loop in the "main" or "initial" thread.
554		637
555	Example: Try to create a event loop that uses epoll and nothing else.	638	Example: Try to create a event loop that uses epoll and nothing else.
556		639
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	641	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
560		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
561	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
562		650
563	Destroys the default loop again (frees all memory and kernel state	651	Destroys an event loop object (frees all memory and kernel state
564	etc.). None of the active event watchers will be stopped in the normal	652	etc.). None of the active event watchers will be stopped in the normal
565	sense, so e.g. C<ev_is_active> might still return true. It is your	653	sense, so e.g. C<ev_is_active> might still return true. It is your
566	responsibility to either stop all watchers cleanly yourself I<before>	654	responsibility to either stop all watchers cleanly yourself I<before>
567	calling this function, or cope with the fact afterwards (which is usually	655	calling this function, or cope with the fact afterwards (which is usually
568	the easiest thing, you can just ignore the watchers and/or C<free ()> them	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
570		658
571	Note that certain global state, such as signal state (and installed signal	659	Note that certain global state, such as signal state (and installed signal
572	handlers), will not be freed by this function, and related watchers (such	660	handlers), will not be freed by this function, and related watchers (such
573	as signal and child watchers) would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
574		662
575	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
576	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	except in the rare occasion where you really need to free its resources.
577	pipe fds. If you need dynamically allocated loops it is better to use	669	If you need dynamically allocated loops it is better to use C<ev_loop_new>
578	C<ev_loop_new> and C<ev_loop_destroy>).	670	and C<ev_loop_destroy>.
579		671
580	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
581		673
582	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.
584
585	=item ev_default_fork ()
586
587	This function sets a flag that causes subsequent C<ev_loop> iterations	674	This function sets a flag that causes subsequent C<ev_run> iterations to
588	to reinitialise the kernel state for backends that have one. Despite the	675	reinitialise the kernel state for backends that have one. Despite the
589	name, you can call it anytime, but it makes most sense after forking, in	676	name, you can call it anytime, but it makes most sense after forking, in
590	the child process (or both child and parent, but that again makes little	677	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
591	sense). You I<must> call it in the child before using any of the libev	678	child before resuming or calling C<ev_run>.
592	functions, and it will only take effect at the next C<ev_loop> iteration.	679
		680	Again, you I<have> to call it on I<any> loop that you want to re-use after
		681	a fork, I<even if you do not plan to use the loop in the parent>. This is
		682	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		683	during fork.
593		684
594	On the other hand, you only need to call this function in the child	685	On the other hand, you only need to call this function in the child
595	process if and only if you want to use the event library in the child. If	686	process if and only if you want to use the event loop in the child. If
596	you just fork+exec, you don't have to call it at all.	687	you just fork+exec or create a new loop in the child, you don't have to
		688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
597		691
598	The function itself is quite fast and it's usually not a problem to call	692	The function itself is quite fast and it's usually not a problem to call
599	it just in case after a fork. To make this easy, the function will fit in	693	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
602	pthread_atfork (0, 0, ev_default_fork);	705	pthread_atfork (0, 0, post_fork_child);
603
604	=item ev_loop_fork (loop)
605
606	Like C<ev_default_fork>, but acts on an event loop created by
607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
608	after fork that you want to re-use in the child, and how you do this is
609	entirely your own problem.
610		706
611	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
612		708
613	Returns true when the given loop is, in fact, the default loop, and false	709	Returns true when the given loop is, in fact, the default loop, and false
614	otherwise.	710	otherwise.
615		711
616	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
617		713
618	Returns the count of loop iterations for the loop, which is identical to	714	Returns the current iteration count for the event loop, which is identical
619	the number of times libev did poll for new events. It starts at C<0> and	715	to the number of times libev did poll for new events. It starts at C<0>
620	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
621		717
622	This value can sometimes be useful as a generation counter of sorts (it	718	This value can sometimes be useful as a generation counter of sorts (it
623	"ticks" the number of loop iterations), as it roughly corresponds with	719	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		721	prepare and check phases.
625		722
626	=item unsigned int ev_loop_depth (loop)	723	=item unsigned int ev_depth (loop)
627		724
628	Returns the number of times C<ev_loop> was entered minus the number of	725	Returns the number of times C<ev_run> was entered minus the number of
629	times C<ev_loop> was exited, in other words, the recursion depth.	726	times C<ev_run> was exited normally, in other words, the recursion depth.
630		727
631	Outside C<ev_loop>, this number is zero. In a callback, this number is	728	Outside C<ev_run>, this number is zero. In a callback, this number is
632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
633	in which case it is higher.	730	in which case it is higher.
634		731
635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
636	etc.), doesn't count as exit.	733	throwing an exception etc.), doesn't count as "exit" - consider this
		734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
637		736
638	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
639		738
640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
641	use.	740	use.
…		…
650		749
651	=item ev_now_update (loop)	750	=item ev_now_update (loop)
652		751
653	Establishes the current time by querying the kernel, updating the time	752	Establishes the current time by querying the kernel, updating the time
654	returned by C<ev_now ()> in the progress. This is a costly operation and	753	returned by C<ev_now ()> in the progress. This is a costly operation and
655	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
656		755
657	This function is rarely useful, but when some event callback runs for a	756	This function is rarely useful, but when some event callback runs for a
658	very long time without entering the event loop, updating libev's idea of	757	very long time without entering the event loop, updating libev's idea of
659	the current time is a good idea.	758	the current time is a good idea.
660		759
…		…
662		761
663	=item ev_suspend (loop)	762	=item ev_suspend (loop)
664		763
665	=item ev_resume (loop)	764	=item ev_resume (loop)
666		765
667	These two functions suspend and resume a loop, for use when the loop is	766	These two functions suspend and resume an event loop, for use when the
668	not used for a while and timeouts should not be processed.	767	loop is not used for a while and timeouts should not be processed.
669		768
670	A typical use case would be an interactive program such as a game: When	769	A typical use case would be an interactive program such as a game: When
671	the user presses C<^Z> to suspend the game and resumes it an hour later it	770	the user presses C<^Z> to suspend the game and resumes it an hour later it
672	would be best to handle timeouts as if no time had actually passed while	771	would be best to handle timeouts as if no time had actually passed while
673	the program was suspended. This can be achieved by calling C<ev_suspend>	772	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
675	C<ev_resume> directly afterwards to resume timer processing.	774	C<ev_resume> directly afterwards to resume timer processing.
676		775
677	Effectively, all C<ev_timer> watchers will be delayed by the time spend	776	Effectively, all C<ev_timer> watchers will be delayed by the time spend
678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	777	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
679	will be rescheduled (that is, they will lose any events that would have	778	will be rescheduled (that is, they will lose any events that would have
680	occured while suspended).	779	occurred while suspended).
681		780
682	After calling C<ev_suspend> you B<must not> call I<any> function on the	781	After calling C<ev_suspend> you B<must not> call I<any> function on the
683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	782	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
684	without a previous call to C<ev_suspend>.	783	without a previous call to C<ev_suspend>.
685		784
686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
687	event loop time (see C<ev_now_update>).	786	event loop time (see C<ev_now_update>).
688		787
689	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
690		789
691	Finally, this is it, the event handler. This function usually is called	790	Finally, this is it, the event handler. This function usually is called
692	after you initialised all your watchers and you want to start handling	791	after you have initialised all your watchers and you want to start
693	events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
694		795
695	If the flags argument is specified as C<0>, it will not return until	796	If the flags argument is specified as C<0>, it will keep handling events
696	either no event watchers are active anymore or C<ev_unloop> was called.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
697		799
698	Please note that an explicit C<ev_unloop> is usually better than	800	Please note that an explicit C<ev_break> is usually better than
699	relying on all watchers to be stopped when deciding when a program has	801	relying on all watchers to be stopped when deciding when a program has
700	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
701	that automatically loops as long as it has to and no longer by virtue	803	that automatically loops as long as it has to and no longer by virtue
702	of relying on its watchers stopping correctly, that is truly a thing of	804	of relying on its watchers stopping correctly, that is truly a thing of
703	beauty.	805	beauty.
704		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
705	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
706	those events and any already outstanding ones, but will not block your	813	those events and any already outstanding ones, but will not wait and
707	process in case there are no events and will return after one iteration of	814	block your process in case there are no events and will return after one
708	the loop.	815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
709		817
710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
711	necessary) and will handle those and any already outstanding ones. It	819	necessary) and will handle those and any already outstanding ones. It
712	will block your process until at least one new event arrives (which could	820	will block your process until at least one new event arrives (which could
713	be an event internal to libev itself, so there is no guarantee that a	821	be an event internal to libev itself, so there is no guarantee that a
714	user-registered callback will be called), and will return after one	822	user-registered callback will be called), and will return after one
715	iteration of the loop.	823	iteration of the loop.
716		824
717	This is useful if you are waiting for some external event in conjunction	825	This is useful if you are waiting for some external event in conjunction
718	with something not expressible using other libev watchers (i.e. "roll your	826	with something not expressible using other libev watchers (i.e. "roll your
719	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	827	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
720	usually a better approach for this kind of thing.	828	usually a better approach for this kind of thing.
721		829
722	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does:
723		831
		832	- Increment loop depth.
		833	- Reset the ev_break status.
724	- Before the first iteration, call any pending watchers.	834	- Before the first iteration, call any pending watchers.
		835	LOOP:
725	* If EVFLAG_FORKCHECK was used, check for a fork.	836	- If EVFLAG_FORKCHECK was used, check for a fork.
726	- If a fork was detected (by any means), queue and call all fork watchers.	837	- If a fork was detected (by any means), queue and call all fork watchers.
727	- Queue and call all prepare watchers.	838	- Queue and call all prepare watchers.
		839	- If ev_break was called, goto FINISH.
728	- If we have been forked, detach and recreate the kernel state	840	- If we have been forked, detach and recreate the kernel state
729	as to not disturb the other process.	841	as to not disturb the other process.
730	- Update the kernel state with all outstanding changes.	842	- Update the kernel state with all outstanding changes.
731	- Update the "event loop time" (ev_now ()).	843	- Update the "event loop time" (ev_now ()).
732	- Calculate for how long to sleep or block, if at all	844	- Calculate for how long to sleep or block, if at all
733	(active idle watchers, EVLOOP_NONBLOCK or not having	845	(active idle watchers, EVRUN_NOWAIT or not having
734	any active watchers at all will result in not sleeping).	846	any active watchers at all will result in not sleeping).
735	- Sleep if the I/O and timer collect interval say so.	847	- Sleep if the I/O and timer collect interval say so.
		848	- Increment loop iteration counter.
736	- Block the process, waiting for any events.	849	- Block the process, waiting for any events.
737	- Queue all outstanding I/O (fd) events.	850	- Queue all outstanding I/O (fd) events.
738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	851	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
739	- Queue all expired timers.	852	- Queue all expired timers.
740	- Queue all expired periodics.	853	- Queue all expired periodics.
741	- Unless any events are pending now, queue all idle watchers.	854	- Queue all idle watchers with priority higher than that of pending events.
742	- Queue all check watchers.	855	- Queue all check watchers.
743	- Call all queued watchers in reverse order (i.e. check watchers first).	856	- Call all queued watchers in reverse order (i.e. check watchers first).
744	Signals and child watchers are implemented as I/O watchers, and will	857	Signals and child watchers are implemented as I/O watchers, and will
745	be handled here by queueing them when their watcher gets executed.	858	be handled here by queueing them when their watcher gets executed.
746	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	859	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
747	were used, or there are no active watchers, return, otherwise	860	were used, or there are no active watchers, goto FINISH, otherwise
748	continue with step *.	861	continue with step LOOP.
		862	FINISH:
		863	- Reset the ev_break status iff it was EVBREAK_ONE.
		864	- Decrement the loop depth.
		865	- Return.
749		866
750	Example: Queue some jobs and then loop until no events are outstanding	867	Example: Queue some jobs and then loop until no events are outstanding
751	anymore.	868	anymore.
752		869
753	... queue jobs here, make sure they register event watchers as long	870	... queue jobs here, make sure they register event watchers as long
754	... as they still have work to do (even an idle watcher will do..)	871	... as they still have work to do (even an idle watcher will do..)
755	ev_loop (my_loop, 0);	872	ev_run (my_loop, 0);
756	... jobs done or somebody called unloop. yeah!	873	... jobs done or somebody called break. yeah!
757		874
758	=item ev_unloop (loop, how)	875	=item ev_break (loop, how)
759		876
760	Can be used to make a call to C<ev_loop> return early (but only after it	877	Can be used to make a call to C<ev_run> return early (but only after it
761	has processed all outstanding events). The C<how> argument must be either	878	has processed all outstanding events). The C<how> argument must be either
762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	879	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	880	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
764		881
765	This "unloop state" will be cleared when entering C<ev_loop> again.	882	This "break state" will be cleared on the next call to C<ev_run>.
766		883
767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	884	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		885	which case it will have no effect.
768		886
769	=item ev_ref (loop)	887	=item ev_ref (loop)
770		888
771	=item ev_unref (loop)	889	=item ev_unref (loop)
772		890
773	Ref/unref can be used to add or remove a reference count on the event	891	Ref/unref can be used to add or remove a reference count on the event
774	loop: Every watcher keeps one reference, and as long as the reference	892	loop: Every watcher keeps one reference, and as long as the reference
775	count is nonzero, C<ev_loop> will not return on its own.	893	count is nonzero, C<ev_run> will not return on its own.
776		894
777	If you have a watcher you never unregister that should not keep C<ev_loop>	895	This is useful when you have a watcher that you never intend to
778	from returning, call ev_unref() after starting, and ev_ref() before	896	unregister, but that nevertheless should not keep C<ev_run> from
		897	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
779	stopping it.	898	before stopping it.
780		899
781	As an example, libev itself uses this for its internal signal pipe: It	900	As an example, libev itself uses this for its internal signal pipe: It
782	is not visible to the libev user and should not keep C<ev_loop> from	901	is not visible to the libev user and should not keep C<ev_run> from
783	exiting if no event watchers registered by it are active. It is also an	902	exiting if no event watchers registered by it are active. It is also an
784	excellent way to do this for generic recurring timers or from within	903	excellent way to do this for generic recurring timers or from within
785	third-party libraries. Just remember to I<unref after start> and I<ref	904	third-party libraries. Just remember to I<unref after start> and I<ref
786	before stop> (but only if the watcher wasn't active before, or was active	905	before stop> (but only if the watcher wasn't active before, or was active
787	before, respectively. Note also that libev might stop watchers itself	906	before, respectively. Note also that libev might stop watchers itself
788	(e.g. non-repeating timers) in which case you have to C<ev_ref>	907	(e.g. non-repeating timers) in which case you have to C<ev_ref>
789	in the callback).	908	in the callback).
790		909
791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	910	Example: Create a signal watcher, but keep it from keeping C<ev_run>
792	running when nothing else is active.	911	running when nothing else is active.
793		912
794	ev_signal exitsig;	913	ev_signal exitsig;
795	ev_signal_init (&exitsig, sig_cb, SIGINT);	914	ev_signal_init (&exitsig, sig_cb, SIGINT);
796	ev_signal_start (loop, &exitsig);	915	ev_signal_start (loop, &exitsig);
797	evf_unref (loop);	916	ev_unref (loop);
798		917
799	Example: For some weird reason, unregister the above signal handler again.	918	Example: For some weird reason, unregister the above signal handler again.
800		919
801	ev_ref (loop);	920	ev_ref (loop);
802	ev_signal_stop (loop, &exitsig);	921	ev_signal_stop (loop, &exitsig);
…		…
841	usually doesn't make much sense to set it to a lower value than C<0.01>,	960	usually doesn't make much sense to set it to a lower value than C<0.01>,
842	as this approaches the timing granularity of most systems. Note that if	961	as this approaches the timing granularity of most systems. Note that if
843	you do transactions with the outside world and you can't increase the	962	you do transactions with the outside world and you can't increase the
844	parallelity, then this setting will limit your transaction rate (if you	963	parallelity, then this setting will limit your transaction rate (if you
845	need to poll once per transaction and the I/O collect interval is 0.01,	964	need to poll once per transaction and the I/O collect interval is 0.01,
846	then you can't do more than 100 transations per second).	965	then you can't do more than 100 transactions per second).
847		966
848	Setting the I<timeout collect interval> can improve the opportunity for	967	Setting the I<timeout collect interval> can improve the opportunity for
849	saving power, as the program will "bundle" timer callback invocations that	968	saving power, as the program will "bundle" timer callback invocations that
850	are "near" in time together, by delaying some, thus reducing the number of	969	are "near" in time together, by delaying some, thus reducing the number of
851	times the process sleeps and wakes up again. Another useful technique to	970	times the process sleeps and wakes up again. Another useful technique to
…		…
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	978	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		979
861	=item ev_invoke_pending (loop)	980	=item ev_invoke_pending (loop)
862		981
863	This call will simply invoke all pending watchers while resetting their	982	This call will simply invoke all pending watchers while resetting their
864	pending state. Normally, C<ev_loop> does this automatically when required,	983	pending state. Normally, C<ev_run> does this automatically when required,
865	but when overriding the invoke callback this call comes handy.	984	but when overriding the invoke callback this call comes handy. This
		985	function can be invoked from a watcher - this can be useful for example
		986	when you want to do some lengthy calculation and want to pass further
		987	event handling to another thread (you still have to make sure only one
		988	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		989
		990	=item int ev_pending_count (loop)
		991
		992	Returns the number of pending watchers - zero indicates that no watchers
		993	are pending.
866		994
867	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	995	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
868		996
869	This overrides the invoke pending functionality of the loop: Instead of	997	This overrides the invoke pending functionality of the loop: Instead of
870	invoking all pending watchers when there are any, C<ev_loop> will call	998	invoking all pending watchers when there are any, C<ev_run> will call
871	this callback instead. This is useful, for example, when you want to	999	this callback instead. This is useful, for example, when you want to
872	invoke the actual watchers inside another context (another thread etc.).	1000	invoke the actual watchers inside another context (another thread etc.).
873		1001
874	If you want to reset the callback, use C<ev_invoke_pending> as new	1002	If you want to reset the callback, use C<ev_invoke_pending> as new
875	callback.	1003	callback.
…		…
878		1006
879	Sometimes you want to share the same loop between multiple threads. This	1007	Sometimes you want to share the same loop between multiple threads. This
880	can be done relatively simply by putting mutex_lock/unlock calls around	1008	can be done relatively simply by putting mutex_lock/unlock calls around
881	each call to a libev function.	1009	each call to a libev function.
882		1010
883	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1011	However, C<ev_run> can run an indefinite time, so it is not feasible
884	wait for it to return. One way around this is to wake up the loop via	1012	to wait for it to return. One way around this is to wake up the event
885	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1013	loop via C<ev_break> and C<av_async_send>, another way is to set these
886	and I<acquire> callbacks on the loop.	1014	I<release> and I<acquire> callbacks on the loop.
887		1015
888	When set, then C<release> will be called just before the thread is	1016	When set, then C<release> will be called just before the thread is
889	suspended waiting for new events, and C<acquire> is called just	1017	suspended waiting for new events, and C<acquire> is called just
890	afterwards.	1018	afterwards.
891		1019
892	Ideally, C<release> will just call your mutex_unlock function, and	1020	Ideally, C<release> will just call your mutex_unlock function, and
893	C<acquire> will just call the mutex_lock function again.	1021	C<acquire> will just call the mutex_lock function again.
894		1022
		1023	While event loop modifications are allowed between invocations of
		1024	C<release> and C<acquire> (that's their only purpose after all), no
		1025	modifications done will affect the event loop, i.e. adding watchers will
		1026	have no effect on the set of file descriptors being watched, or the time
		1027	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1028	to take note of any changes you made.
		1029
		1030	In theory, threads executing C<ev_run> will be async-cancel safe between
		1031	invocations of C<release> and C<acquire>.
		1032
		1033	See also the locking example in the C<THREADS> section later in this
		1034	document.
		1035
895	=item ev_set_userdata (loop, void *data)	1036	=item ev_set_userdata (loop, void *data)
896		1037
897	=item ev_userdata (loop)	1038	=item void *ev_userdata (loop)
898		1039
899	Set and retrieve a single C<void *> associated with a loop. When	1040	Set and retrieve a single C<void *> associated with a loop. When
900	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1041	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
901	C<0.>	1042	C<0>.
902		1043
903	These two functions can be used to associate arbitrary data with a loop,	1044	These two functions can be used to associate arbitrary data with a loop,
904	and are intended solely for the C<invoke_pending_cb>, C<release> and	1045	and are intended solely for the C<invoke_pending_cb>, C<release> and
905	C<acquire> callbacks described above, but of course can be (ab-)used for	1046	C<acquire> callbacks described above, but of course can be (ab-)used for
906	any other purpose as well.	1047	any other purpose as well.
907		1048
908	=item ev_loop_verify (loop)	1049	=item ev_verify (loop)
909		1050
910	This function only does something when C<EV_VERIFY> support has been	1051	This function only does something when C<EV_VERIFY> support has been
911	compiled in, which is the default for non-minimal builds. It tries to go	1052	compiled in, which is the default for non-minimal builds. It tries to go
912	through all internal structures and checks them for validity. If anything	1053	through all internal structures and checks them for validity. If anything
913	is found to be inconsistent, it will print an error message to standard	1054	is found to be inconsistent, it will print an error message to standard
…		…
924		1065
925	In the following description, uppercase C<TYPE> in names stands for the	1066	In the following description, uppercase C<TYPE> in names stands for the
926	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1067	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
927	watchers and C<ev_io_start> for I/O watchers.	1068	watchers and C<ev_io_start> for I/O watchers.
928		1069
929	A watcher is a structure that you create and register to record your	1070	A watcher is an opaque structure that you allocate and register to record
930	interest in some event. For instance, if you want to wait for STDIN to	1071	your interest in some event. To make a concrete example, imagine you want
931	become readable, you would create an C<ev_io> watcher for that:	1072	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1073	for that:
932		1074
933	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1075	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
934	{	1076	{
935	ev_io_stop (w);	1077	ev_io_stop (w);
936	ev_unloop (loop, EVUNLOOP_ALL);	1078	ev_break (loop, EVBREAK_ALL);
937	}	1079	}
938		1080
939	struct ev_loop *loop = ev_default_loop (0);	1081	struct ev_loop *loop = ev_default_loop (0);
940		1082
941	ev_io stdin_watcher;	1083	ev_io stdin_watcher;
942		1084
943	ev_init (&stdin_watcher, my_cb);	1085	ev_init (&stdin_watcher, my_cb);
944	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1086	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
945	ev_io_start (loop, &stdin_watcher);	1087	ev_io_start (loop, &stdin_watcher);
946		1088
947	ev_loop (loop, 0);	1089	ev_run (loop, 0);
948		1090
949	As you can see, you are responsible for allocating the memory for your	1091	As you can see, you are responsible for allocating the memory for your
950	watcher structures (and it is I<usually> a bad idea to do this on the	1092	watcher structures (and it is I<usually> a bad idea to do this on the
951	stack).	1093	stack).
952		1094
953	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1095	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
954	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1096	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
955		1097
956	Each watcher structure must be initialised by a call to C<ev_init	1098	Each watcher structure must be initialised by a call to C<ev_init (watcher
957	(watcher *, callback)>, which expects a callback to be provided. This	1099	*, callback)>, which expects a callback to be provided. This callback is
958	callback gets invoked each time the event occurs (or, in the case of I/O	1100	invoked each time the event occurs (or, in the case of I/O watchers, each
959	watchers, each time the event loop detects that the file descriptor given	1101	time the event loop detects that the file descriptor given is readable
960	is readable and/or writable).	1102	and/or writable).
961		1103
962	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1104	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
963	macro to configure it, with arguments specific to the watcher type. There	1105	macro to configure it, with arguments specific to the watcher type. There
964	is also a macro to combine initialisation and setting in one call: C<<	1106	is also a macro to combine initialisation and setting in one call: C<<
965	ev_TYPE_init (watcher *, callback, ...) >>.	1107	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
988	=item C<EV_WRITE>	1130	=item C<EV_WRITE>
989		1131
990	The file descriptor in the C<ev_io> watcher has become readable and/or	1132	The file descriptor in the C<ev_io> watcher has become readable and/or
991	writable.	1133	writable.
992		1134
993	=item C<EV_TIMEOUT>	1135	=item C<EV_TIMER>
994		1136
995	The C<ev_timer> watcher has timed out.	1137	The C<ev_timer> watcher has timed out.
996		1138
997	=item C<EV_PERIODIC>	1139	=item C<EV_PERIODIC>
998		1140
…		…
1016		1158
1017	=item C<EV_PREPARE>	1159	=item C<EV_PREPARE>
1018		1160
1019	=item C<EV_CHECK>	1161	=item C<EV_CHECK>
1020		1162
1021	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1163	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1022	to gather new events, and all C<ev_check> watchers are invoked just after	1164	to gather new events, and all C<ev_check> watchers are invoked just after
1023	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1165	C<ev_run> has gathered them, but before it invokes any callbacks for any
1024	received events. Callbacks of both watcher types can start and stop as	1166	received events. Callbacks of both watcher types can start and stop as
1025	many watchers as they want, and all of them will be taken into account	1167	many watchers as they want, and all of them will be taken into account
1026	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1168	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1027	C<ev_loop> from blocking).	1169	C<ev_run> from blocking).
1028		1170
1029	=item C<EV_EMBED>	1171	=item C<EV_EMBED>
1030		1172
1031	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1173	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1032		1174
1033	=item C<EV_FORK>	1175	=item C<EV_FORK>
1034		1176
1035	The event loop has been resumed in the child process after fork (see	1177	The event loop has been resumed in the child process after fork (see
1036	C<ev_fork>).	1178	C<ev_fork>).
		1179
		1180	=item C<EV_CLEANUP>
		1181
		1182	The event loop is about to be destroyed (see C<ev_cleanup>).
1037		1183
1038	=item C<EV_ASYNC>	1184	=item C<EV_ASYNC>
1039		1185
1040	The given async watcher has been asynchronously notified (see C<ev_async>).	1186	The given async watcher has been asynchronously notified (see C<ev_async>).
1041		1187
…		…
1088		1234
1089	ev_io w;	1235	ev_io w;
1090	ev_init (&w, my_cb);	1236	ev_init (&w, my_cb);
1091	ev_io_set (&w, STDIN_FILENO, EV_READ);	1237	ev_io_set (&w, STDIN_FILENO, EV_READ);
1092		1238
1093	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1239	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1094		1240
1095	This macro initialises the type-specific parts of a watcher. You need to	1241	This macro initialises the type-specific parts of a watcher. You need to
1096	call C<ev_init> at least once before you call this macro, but you can	1242	call C<ev_init> at least once before you call this macro, but you can
1097	call C<ev_TYPE_set> any number of times. You must not, however, call this	1243	call C<ev_TYPE_set> any number of times. You must not, however, call this
1098	macro on a watcher that is active (it can be pending, however, which is a	1244	macro on a watcher that is active (it can be pending, however, which is a
…		…
1111		1257
1112	Example: Initialise and set an C<ev_io> watcher in one step.	1258	Example: Initialise and set an C<ev_io> watcher in one step.
1113		1259
1114	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1260	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1115		1261
1116	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1262	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1117		1263
1118	Starts (activates) the given watcher. Only active watchers will receive	1264	Starts (activates) the given watcher. Only active watchers will receive
1119	events. If the watcher is already active nothing will happen.	1265	events. If the watcher is already active nothing will happen.
1120		1266
1121	Example: Start the C<ev_io> watcher that is being abused as example in this	1267	Example: Start the C<ev_io> watcher that is being abused as example in this
1122	whole section.	1268	whole section.
1123		1269
1124	ev_io_start (EV_DEFAULT_UC, &w);	1270	ev_io_start (EV_DEFAULT_UC, &w);
1125		1271
1126	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1272	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1127		1273
1128	Stops the given watcher if active, and clears the pending status (whether	1274	Stops the given watcher if active, and clears the pending status (whether
1129	the watcher was active or not).	1275	the watcher was active or not).
1130		1276
1131	It is possible that stopped watchers are pending - for example,	1277	It is possible that stopped watchers are pending - for example,
…		…
1156	=item ev_cb_set (ev_TYPE *watcher, callback)	1302	=item ev_cb_set (ev_TYPE *watcher, callback)
1157		1303
1158	Change the callback. You can change the callback at virtually any time	1304	Change the callback. You can change the callback at virtually any time
1159	(modulo threads).	1305	(modulo threads).
1160		1306
1161	=item ev_set_priority (ev_TYPE *watcher, priority)	1307	=item ev_set_priority (ev_TYPE *watcher, int priority)
1162		1308
1163	=item int ev_priority (ev_TYPE *watcher)	1309	=item int ev_priority (ev_TYPE *watcher)
1164		1310
1165	Set and query the priority of the watcher. The priority is a small	1311	Set and query the priority of the watcher. The priority is a small
1166	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1312	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1198	watcher isn't pending it does nothing and returns C<0>.	1344	watcher isn't pending it does nothing and returns C<0>.
1199		1345
1200	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1346	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1201	callback to be invoked, which can be accomplished with this function.	1347	callback to be invoked, which can be accomplished with this function.
1202		1348
		1349	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1350
		1351	Feeds the given event set into the event loop, as if the specified event
		1352	had happened for the specified watcher (which must be a pointer to an
		1353	initialised but not necessarily started event watcher). Obviously you must
		1354	not free the watcher as long as it has pending events.
		1355
		1356	Stopping the watcher, letting libev invoke it, or calling
		1357	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1358	not started in the first place.
		1359
		1360	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1361	functions that do not need a watcher.
		1362
1203	=back	1363	=back
1204		1364
		1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1366	OWN COMPOSITE WATCHERS> idioms.
1205		1367
1206	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1368	=head2 WATCHER STATES
1207		1369
1208	Each watcher has, by default, a member C<void *data> that you can change	1370	There are various watcher states mentioned throughout this manual -
1209	and read at any time: libev will completely ignore it. This can be used	1371	active, pending and so on. In this section these states and the rules to
1210	to associate arbitrary data with your watcher. If you need more data and	1372	transition between them will be described in more detail - and while these
1211	don't want to allocate memory and store a pointer to it in that data	1373	rules might look complicated, they usually do "the right thing".
1212	member, you can also "subclass" the watcher type and provide your own
1213	data:
1214		1374
1215	struct my_io	1375	=over 4
1216	{
1217	ev_io io;
1218	int otherfd;
1219	void *somedata;
1220	struct whatever *mostinteresting;
1221	};
1222		1376
1223	...	1377	=item initialiased
1224	struct my_io w;
1225	ev_io_init (&w.io, my_cb, fd, EV_READ);
1226		1378
1227	And since your callback will be called with a pointer to the watcher, you	1379	Before a watcher can be registered with the event looop it has to be
1228	can cast it back to your own type:	1380	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1381	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1229		1382
1230	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1383	In this state it is simply some block of memory that is suitable for
1231	{	1384	use in an event loop. It can be moved around, freed, reused etc. at
1232	struct my_io *w = (struct my_io *)w_;	1385	will - as long as you either keep the memory contents intact, or call
1233	...	1386	C<ev_TYPE_init> again.
1234	}
1235		1387
1236	More interesting and less C-conformant ways of casting your callback type	1388	=item started/running/active
1237	instead have been omitted.
1238		1389
1239	Another common scenario is to use some data structure with multiple	1390	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1240	embedded watchers:	1391	property of the event loop, and is actively waiting for events. While in
		1392	this state it cannot be accessed (except in a few documented ways), moved,
		1393	freed or anything else - the only legal thing is to keep a pointer to it,
		1394	and call libev functions on it that are documented to work on active watchers.
1241		1395
1242	struct my_biggy	1396	=item pending
1243	{
1244	int some_data;
1245	ev_timer t1;
1246	ev_timer t2;
1247	}
1248		1397
1249	In this case getting the pointer to C<my_biggy> is a bit more	1398	If a watcher is active and libev determines that an event it is interested
1250	complicated: Either you store the address of your C<my_biggy> struct	1399	in has occurred (such as a timer expiring), it will become pending. It will
1251	in the C<data> member of the watcher (for woozies), or you need to use	1400	stay in this pending state until either it is stopped or its callback is
1252	some pointer arithmetic using C<offsetof> inside your watchers (for real	1401	about to be invoked, so it is not normally pending inside the watcher
1253	programmers):	1402	callback.
1254		1403
1255	#include <stddef.h>	1404	The watcher might or might not be active while it is pending (for example,
		1405	an expired non-repeating timer can be pending but no longer active). If it
		1406	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1407	but it is still property of the event loop at this time, so cannot be
		1408	moved, freed or reused. And if it is active the rules described in the
		1409	previous item still apply.
1256		1410
1257	static void	1411	It is also possible to feed an event on a watcher that is not active (e.g.
1258	t1_cb (EV_P_ ev_timer *w, int revents)	1412	via C<ev_feed_event>), in which case it becomes pending without being
1259	{	1413	active.
1260	struct my_biggy big = (struct my_biggy *)
1261	(((char *)w) - offsetof (struct my_biggy, t1));
1262	}
1263		1414
1264	static void	1415	=item stopped
1265	t2_cb (EV_P_ ev_timer *w, int revents)	1416
1266	{	1417	A watcher can be stopped implicitly by libev (in which case it might still
1267	struct my_biggy big = (struct my_biggy *)	1418	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1268	(((char *)w) - offsetof (struct my_biggy, t2));	1419	latter will clear any pending state the watcher might be in, regardless
1269	}	1420	of whether it was active or not, so stopping a watcher explicitly before
		1421	freeing it is often a good idea.
		1422
		1423	While stopped (and not pending) the watcher is essentially in the
		1424	initialised state, that is, it can be reused, moved, modified in any way
		1425	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1426	it again).
		1427
		1428	=back
1270		1429
1271	=head2 WATCHER PRIORITY MODELS	1430	=head2 WATCHER PRIORITY MODELS
1272		1431
1273	Many event loops support I<watcher priorities>, which are usually small	1432	Many event loops support I<watcher priorities>, which are usually small
1274	integers that influence the ordering of event callback invocation	1433	integers that influence the ordering of event callback invocation
…		…
1317		1476
1318	For example, to emulate how many other event libraries handle priorities,	1477	For example, to emulate how many other event libraries handle priorities,
1319	you can associate an C<ev_idle> watcher to each such watcher, and in	1478	you can associate an C<ev_idle> watcher to each such watcher, and in
1320	the normal watcher callback, you just start the idle watcher. The real	1479	the normal watcher callback, you just start the idle watcher. The real
1321	processing is done in the idle watcher callback. This causes libev to	1480	processing is done in the idle watcher callback. This causes libev to
1322	continously poll and process kernel event data for the watcher, but when	1481	continuously poll and process kernel event data for the watcher, but when
1323	the lock-out case is known to be rare (which in turn is rare :), this is	1482	the lock-out case is known to be rare (which in turn is rare :), this is
1324	workable.	1483	workable.
1325		1484
1326	Usually, however, the lock-out model implemented that way will perform	1485	Usually, however, the lock-out model implemented that way will perform
1327	miserably under the type of load it was designed to handle. In that case,	1486	miserably under the type of load it was designed to handle. In that case,
…		…
1341	{	1500	{
1342	// stop the I/O watcher, we received the event, but	1501	// stop the I/O watcher, we received the event, but
1343	// are not yet ready to handle it.	1502	// are not yet ready to handle it.
1344	ev_io_stop (EV_A_ w);	1503	ev_io_stop (EV_A_ w);
1345		1504
1346	// start the idle watcher to ahndle the actual event.	1505	// start the idle watcher to handle the actual event.
1347	// it will not be executed as long as other watchers	1506	// it will not be executed as long as other watchers
1348	// with the default priority are receiving events.	1507	// with the default priority are receiving events.
1349	ev_idle_start (EV_A_ &idle);	1508	ev_idle_start (EV_A_ &idle);
1350	}	1509	}
1351		1510
…		…
1401	In general you can register as many read and/or write event watchers per	1560	In general you can register as many read and/or write event watchers per
1402	fd as you want (as long as you don't confuse yourself). Setting all file	1561	fd as you want (as long as you don't confuse yourself). Setting all file
1403	descriptors to non-blocking mode is also usually a good idea (but not	1562	descriptors to non-blocking mode is also usually a good idea (but not
1404	required if you know what you are doing).	1563	required if you know what you are doing).
1405		1564
1406	If you cannot use non-blocking mode, then force the use of a
1407	known-to-be-good backend (at the time of this writing, this includes only
1408	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1409	descriptors for which non-blocking operation makes no sense (such as
1410	files) - libev doesn't guarentee any specific behaviour in that case.
1411
1412	Another thing you have to watch out for is that it is quite easy to	1565	Another thing you have to watch out for is that it is quite easy to
1413	receive "spurious" readiness notifications, that is your callback might	1566	receive "spurious" readiness notifications, that is, your callback might
1414	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1567	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1415	because there is no data. Not only are some backends known to create a	1568	because there is no data. It is very easy to get into this situation even
1416	lot of those (for example Solaris ports), it is very easy to get into	1569	with a relatively standard program structure. Thus it is best to always
1417	this situation even with a relatively standard program structure. Thus	1570	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1418	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1419	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1571	preferable to a program hanging until some data arrives.
1420		1572
1421	If you cannot run the fd in non-blocking mode (for example you should	1573	If you cannot run the fd in non-blocking mode (for example you should
1422	not play around with an Xlib connection), then you have to separately	1574	not play around with an Xlib connection), then you have to separately
1423	re-test whether a file descriptor is really ready with a known-to-be good	1575	re-test whether a file descriptor is really ready with a known-to-be good
1424	interface such as poll (fortunately in our Xlib example, Xlib already	1576	interface such as poll (fortunately in the case of Xlib, it already does
1425	does this on its own, so its quite safe to use). Some people additionally	1577	this on its own, so its quite safe to use). Some people additionally
1426	use C<SIGALRM> and an interval timer, just to be sure you won't block	1578	use C<SIGALRM> and an interval timer, just to be sure you won't block
1427	indefinitely.	1579	indefinitely.
1428		1580
1429	But really, best use non-blocking mode.	1581	But really, best use non-blocking mode.
1430		1582
…		…
1458		1610
1459	There is no workaround possible except not registering events	1611	There is no workaround possible except not registering events
1460	for potentially C<dup ()>'ed file descriptors, or to resort to	1612	for potentially C<dup ()>'ed file descriptors, or to resort to
1461	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1613	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1462		1614
		1615	=head3 The special problem of files
		1616
		1617	Many people try to use C<select> (or libev) on file descriptors
		1618	representing files, and expect it to become ready when their program
		1619	doesn't block on disk accesses (which can take a long time on their own).
		1620
		1621	However, this cannot ever work in the "expected" way - you get a readiness
		1622	notification as soon as the kernel knows whether and how much data is
		1623	there, and in the case of open files, that's always the case, so you
		1624	always get a readiness notification instantly, and your read (or possibly
		1625	write) will still block on the disk I/O.
		1626
		1627	Another way to view it is that in the case of sockets, pipes, character
		1628	devices and so on, there is another party (the sender) that delivers data
		1629	on its own, but in the case of files, there is no such thing: the disk
		1630	will not send data on its own, simply because it doesn't know what you
		1631	wish to read - you would first have to request some data.
		1632
		1633	Since files are typically not-so-well supported by advanced notification
		1634	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1635	to files, even though you should not use it. The reason for this is
		1636	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1637	usually a tty, often a pipe, but also sometimes files or special devices
		1638	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1639	F</dev/urandom>), and even though the file might better be served with
		1640	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1641	it "just works" instead of freezing.
		1642
		1643	So avoid file descriptors pointing to files when you know it (e.g. use
		1644	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1645	when you rarely read from a file instead of from a socket, and want to
		1646	reuse the same code path.
		1647
1463	=head3 The special problem of fork	1648	=head3 The special problem of fork
1464		1649
1465	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1650	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1466	useless behaviour. Libev fully supports fork, but needs to be told about	1651	useless behaviour. Libev fully supports fork, but needs to be told about
1467	it in the child.	1652	it in the child if you want to continue to use it in the child.
1468		1653
1469	To support fork in your programs, you either have to call	1654	To support fork in your child processes, you have to call C<ev_loop_fork
1470	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1655	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1471	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1656	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1472	C<EVBACKEND_POLL>.
1473		1657
1474	=head3 The special problem of SIGPIPE	1658	=head3 The special problem of SIGPIPE
1475		1659
1476	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1660	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1477	when writing to a pipe whose other end has been closed, your program gets	1661	when writing to a pipe whose other end has been closed, your program gets
…		…
1480		1664
1481	So when you encounter spurious, unexplained daemon exits, make sure you	1665	So when you encounter spurious, unexplained daemon exits, make sure you
1482	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1666	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1483	somewhere, as that would have given you a big clue).	1667	somewhere, as that would have given you a big clue).
1484		1668
		1669	=head3 The special problem of accept()ing when you can't
		1670
		1671	Many implementations of the POSIX C<accept> function (for example,
		1672	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1673	connection from the pending queue in all error cases.
		1674
		1675	For example, larger servers often run out of file descriptors (because
		1676	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1677	rejecting the connection, leading to libev signalling readiness on
		1678	the next iteration again (the connection still exists after all), and
		1679	typically causing the program to loop at 100% CPU usage.
		1680
		1681	Unfortunately, the set of errors that cause this issue differs between
		1682	operating systems, there is usually little the app can do to remedy the
		1683	situation, and no known thread-safe method of removing the connection to
		1684	cope with overload is known (to me).
		1685
		1686	One of the easiest ways to handle this situation is to just ignore it
		1687	- when the program encounters an overload, it will just loop until the
		1688	situation is over. While this is a form of busy waiting, no OS offers an
		1689	event-based way to handle this situation, so it's the best one can do.
		1690
		1691	A better way to handle the situation is to log any errors other than
		1692	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1693	messages, and continue as usual, which at least gives the user an idea of
		1694	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1695	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1696	usage.
		1697
		1698	If your program is single-threaded, then you could also keep a dummy file
		1699	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1700	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1701	close that fd, and create a new dummy fd. This will gracefully refuse
		1702	clients under typical overload conditions.
		1703
		1704	The last way to handle it is to simply log the error and C<exit>, as
		1705	is often done with C<malloc> failures, but this results in an easy
		1706	opportunity for a DoS attack.
1485		1707
1486	=head3 Watcher-Specific Functions	1708	=head3 Watcher-Specific Functions
1487		1709
1488	=over 4	1710	=over 4
1489		1711
…		…
1521	...	1743	...
1522	struct ev_loop *loop = ev_default_init (0);	1744	struct ev_loop *loop = ev_default_init (0);
1523	ev_io stdin_readable;	1745	ev_io stdin_readable;
1524	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1746	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1525	ev_io_start (loop, &stdin_readable);	1747	ev_io_start (loop, &stdin_readable);
1526	ev_loop (loop, 0);	1748	ev_run (loop, 0);
1527		1749
1528		1750
1529	=head2 C<ev_timer> - relative and optionally repeating timeouts	1751	=head2 C<ev_timer> - relative and optionally repeating timeouts
1530		1752
1531	Timer watchers are simple relative timers that generate an event after a	1753	Timer watchers are simple relative timers that generate an event after a
…		…
1540	The callback is guaranteed to be invoked only I<after> its timeout has	1762	The callback is guaranteed to be invoked only I<after> its timeout has
1541	passed (not I<at>, so on systems with very low-resolution clocks this	1763	passed (not I<at>, so on systems with very low-resolution clocks this
1542	might introduce a small delay). If multiple timers become ready during the	1764	might introduce a small delay). If multiple timers become ready during the
1543	same loop iteration then the ones with earlier time-out values are invoked	1765	same loop iteration then the ones with earlier time-out values are invoked
1544	before ones of the same priority with later time-out values (but this is	1766	before ones of the same priority with later time-out values (but this is
1545	no longer true when a callback calls C<ev_loop> recursively).	1767	no longer true when a callback calls C<ev_run> recursively).
1546		1768
1547	=head3 Be smart about timeouts	1769	=head3 Be smart about timeouts
1548		1770
1549	Many real-world problems involve some kind of timeout, usually for error	1771	Many real-world problems involve some kind of timeout, usually for error
1550	recovery. A typical example is an HTTP request - if the other side hangs,	1772	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1636	ev_tstamp timeout = last_activity + 60.;	1858	ev_tstamp timeout = last_activity + 60.;
1637		1859
1638	// if last_activity + 60. is older than now, we did time out	1860	// if last_activity + 60. is older than now, we did time out
1639	if (timeout < now)	1861	if (timeout < now)
1640	{	1862	{
1641	// timeout occured, take action	1863	// timeout occurred, take action
1642	}	1864	}
1643	else	1865	else
1644	{	1866	{
1645	// callback was invoked, but there was some activity, re-arm	1867	// callback was invoked, but there was some activity, re-arm
1646	// the watcher to fire in last_activity + 60, which is	1868	// the watcher to fire in last_activity + 60, which is
…		…
1668	to the current time (meaning we just have some activity :), then call the	1890	to the current time (meaning we just have some activity :), then call the
1669	callback, which will "do the right thing" and start the timer:	1891	callback, which will "do the right thing" and start the timer:
1670		1892
1671	ev_init (timer, callback);	1893	ev_init (timer, callback);
1672	last_activity = ev_now (loop);	1894	last_activity = ev_now (loop);
1673	callback (loop, timer, EV_TIMEOUT);	1895	callback (loop, timer, EV_TIMER);
1674		1896
1675	And when there is some activity, simply store the current time in	1897	And when there is some activity, simply store the current time in
1676	C<last_activity>, no libev calls at all:	1898	C<last_activity>, no libev calls at all:
1677		1899
1678	last_actiivty = ev_now (loop);	1900	last_activity = ev_now (loop);
1679		1901
1680	This technique is slightly more complex, but in most cases where the	1902	This technique is slightly more complex, but in most cases where the
1681	time-out is unlikely to be triggered, much more efficient.	1903	time-out is unlikely to be triggered, much more efficient.
1682		1904
1683	Changing the timeout is trivial as well (if it isn't hard-coded in the	1905	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1721		1943
1722	=head3 The special problem of time updates	1944	=head3 The special problem of time updates
1723		1945
1724	Establishing the current time is a costly operation (it usually takes at	1946	Establishing the current time is a costly operation (it usually takes at
1725	least two system calls): EV therefore updates its idea of the current	1947	least two system calls): EV therefore updates its idea of the current
1726	time only before and after C<ev_loop> collects new events, which causes a	1948	time only before and after C<ev_run> collects new events, which causes a
1727	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1949	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1728	lots of events in one iteration.	1950	lots of events in one iteration.
1729		1951
1730	The relative timeouts are calculated relative to the C<ev_now ()>	1952	The relative timeouts are calculated relative to the C<ev_now ()>
1731	time. This is usually the right thing as this timestamp refers to the time	1953	time. This is usually the right thing as this timestamp refers to the time
…		…
1737		1959
1738	If the event loop is suspended for a long time, you can also force an	1960	If the event loop is suspended for a long time, you can also force an
1739	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1961	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1740	()>.	1962	()>.
1741		1963
		1964	=head3 The special problems of suspended animation
		1965
		1966	When you leave the server world it is quite customary to hit machines that
		1967	can suspend/hibernate - what happens to the clocks during such a suspend?
		1968
		1969	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1970	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1971	to run until the system is suspended, but they will not advance while the
		1972	system is suspended. That means, on resume, it will be as if the program
		1973	was frozen for a few seconds, but the suspend time will not be counted
		1974	towards C<ev_timer> when a monotonic clock source is used. The real time
		1975	clock advanced as expected, but if it is used as sole clocksource, then a
		1976	long suspend would be detected as a time jump by libev, and timers would
		1977	be adjusted accordingly.
		1978
		1979	I would not be surprised to see different behaviour in different between
		1980	operating systems, OS versions or even different hardware.
		1981
		1982	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1983	time jump in the monotonic clocks and the realtime clock. If the program
		1984	is suspended for a very long time, and monotonic clock sources are in use,
		1985	then you can expect C<ev_timer>s to expire as the full suspension time
		1986	will be counted towards the timers. When no monotonic clock source is in
		1987	use, then libev will again assume a timejump and adjust accordingly.
		1988
		1989	It might be beneficial for this latter case to call C<ev_suspend>
		1990	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1991	deterministic behaviour in this case (you can do nothing against
		1992	C<SIGSTOP>).
		1993
1742	=head3 Watcher-Specific Functions and Data Members	1994	=head3 Watcher-Specific Functions and Data Members
1743		1995
1744	=over 4	1996	=over 4
1745		1997
1746	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1998	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1772	C<repeat> value), or reset the running timer to the C<repeat> value.	2024	C<repeat> value), or reset the running timer to the C<repeat> value.
1773		2025
1774	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2026	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1775	usage example.	2027	usage example.
1776		2028
		2029	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2030
		2031	Returns the remaining time until a timer fires. If the timer is active,
		2032	then this time is relative to the current event loop time, otherwise it's
		2033	the timeout value currently configured.
		2034
		2035	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2036	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2037	will return C<4>. When the timer expires and is restarted, it will return
		2038	roughly C<7> (likely slightly less as callback invocation takes some time,
		2039	too), and so on.
		2040
1777	=item ev_tstamp repeat [read-write]	2041	=item ev_tstamp repeat [read-write]
1778		2042
1779	The current C<repeat> value. Will be used each time the watcher times out	2043	The current C<repeat> value. Will be used each time the watcher times out
1780	or C<ev_timer_again> is called, and determines the next timeout (if any),	2044	or C<ev_timer_again> is called, and determines the next timeout (if any),
1781	which is also when any modifications are taken into account.	2045	which is also when any modifications are taken into account.
…		…
1806	}	2070	}
1807		2071
1808	ev_timer mytimer;	2072	ev_timer mytimer;
1809	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2073	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1810	ev_timer_again (&mytimer); /* start timer */	2074	ev_timer_again (&mytimer); /* start timer */
1811	ev_loop (loop, 0);	2075	ev_run (loop, 0);
1812		2076
1813	// and in some piece of code that gets executed on any "activity":	2077	// and in some piece of code that gets executed on any "activity":
1814	// reset the timeout to start ticking again at 10 seconds	2078	// reset the timeout to start ticking again at 10 seconds
1815	ev_timer_again (&mytimer);	2079	ev_timer_again (&mytimer);
1816		2080
…		…
1842		2106
1843	As with timers, the callback is guaranteed to be invoked only when the	2107	As with timers, the callback is guaranteed to be invoked only when the
1844	point in time where it is supposed to trigger has passed. If multiple	2108	point in time where it is supposed to trigger has passed. If multiple
1845	timers become ready during the same loop iteration then the ones with	2109	timers become ready during the same loop iteration then the ones with
1846	earlier time-out values are invoked before ones with later time-out values	2110	earlier time-out values are invoked before ones with later time-out values
1847	(but this is no longer true when a callback calls C<ev_loop> recursively).	2111	(but this is no longer true when a callback calls C<ev_run> recursively).
1848		2112
1849	=head3 Watcher-Specific Functions and Data Members	2113	=head3 Watcher-Specific Functions and Data Members
1850		2114
1851	=over 4	2115	=over 4
1852		2116
…		…
1980	Example: Call a callback every hour, or, more precisely, whenever the	2244	Example: Call a callback every hour, or, more precisely, whenever the
1981	system time is divisible by 3600. The callback invocation times have	2245	system time is divisible by 3600. The callback invocation times have
1982	potentially a lot of jitter, but good long-term stability.	2246	potentially a lot of jitter, but good long-term stability.
1983		2247
1984	static void	2248	static void
1985	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2249	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1986	{	2250	{
1987	... its now a full hour (UTC, or TAI or whatever your clock follows)	2251	... its now a full hour (UTC, or TAI or whatever your clock follows)
1988	}	2252	}
1989		2253
1990	ev_periodic hourly_tick;	2254	ev_periodic hourly_tick;
…		…
2013		2277
2014	=head2 C<ev_signal> - signal me when a signal gets signalled!	2278	=head2 C<ev_signal> - signal me when a signal gets signalled!
2015		2279
2016	Signal watchers will trigger an event when the process receives a specific	2280	Signal watchers will trigger an event when the process receives a specific
2017	signal one or more times. Even though signals are very asynchronous, libev	2281	signal one or more times. Even though signals are very asynchronous, libev
2018	will try it's best to deliver signals synchronously, i.e. as part of the	2282	will try its best to deliver signals synchronously, i.e. as part of the
2019	normal event processing, like any other event.	2283	normal event processing, like any other event.
2020		2284
2021	If you want signals asynchronously, just use C<sigaction> as you would	2285	If you want signals to be delivered truly asynchronously, just use
2022	do without libev and forget about sharing the signal. You can even use	2286	C<sigaction> as you would do without libev and forget about sharing
2023	C<ev_async> from a signal handler to synchronously wake up an event loop.	2287	the signal. You can even use C<ev_async> from a signal handler to
		2288	synchronously wake up an event loop.
2024		2289
2025	You can configure as many watchers as you like per signal. Only when the	2290	You can configure as many watchers as you like for the same signal, but
		2291	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2292	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2293	C<SIGINT> in both the default loop and another loop at the same time. At
		2294	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2295
2026	first watcher gets started will libev actually register a signal handler	2296	When the first watcher gets started will libev actually register something
2027	with the kernel (thus it coexists with your own signal handlers as long as	2297	with the kernel (thus it coexists with your own signal handlers as long as
2028	you don't register any with libev for the same signal). Similarly, when	2298	you don't register any with libev for the same signal).
2029	the last signal watcher for a signal is stopped, libev will reset the
2030	signal handler to SIG_DFL (regardless of what it was set to before).
2031		2299
2032	If possible and supported, libev will install its handlers with	2300	If possible and supported, libev will install its handlers with
2033	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2301	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2034	interrupted. If you have a problem with system calls getting interrupted by	2302	not be unduly interrupted. If you have a problem with system calls getting
2035	signals you can block all signals in an C<ev_check> watcher and unblock	2303	interrupted by signals you can block all signals in an C<ev_check> watcher
2036	them in an C<ev_prepare> watcher.	2304	and unblock them in an C<ev_prepare> watcher.
		2305
		2306	=head3 The special problem of inheritance over fork/execve/pthread_create
		2307
		2308	Both the signal mask (C<sigprocmask>) and the signal disposition
		2309	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2310	stopping it again), that is, libev might or might not block the signal,
		2311	and might or might not set or restore the installed signal handler (but
		2312	see C<EVFLAG_NOSIGMASK>).
		2313
		2314	While this does not matter for the signal disposition (libev never
		2315	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2316	C<execve>), this matters for the signal mask: many programs do not expect
		2317	certain signals to be blocked.
		2318
		2319	This means that before calling C<exec> (from the child) you should reset
		2320	the signal mask to whatever "default" you expect (all clear is a good
		2321	choice usually).
		2322
		2323	The simplest way to ensure that the signal mask is reset in the child is
		2324	to install a fork handler with C<pthread_atfork> that resets it. That will
		2325	catch fork calls done by libraries (such as the libc) as well.
		2326
		2327	In current versions of libev, the signal will not be blocked indefinitely
		2328	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2329	the window of opportunity for problems, it will not go away, as libev
		2330	I<has> to modify the signal mask, at least temporarily.
		2331
		2332	So I can't stress this enough: I<If you do not reset your signal mask when
		2333	you expect it to be empty, you have a race condition in your code>. This
		2334	is not a libev-specific thing, this is true for most event libraries.
		2335
		2336	=head3 The special problem of threads signal handling
		2337
		2338	POSIX threads has problematic signal handling semantics, specifically,
		2339	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2340	threads in a process block signals, which is hard to achieve.
		2341
		2342	When you want to use sigwait (or mix libev signal handling with your own
		2343	for the same signals), you can tackle this problem by globally blocking
		2344	all signals before creating any threads (or creating them with a fully set
		2345	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2346	loops. Then designate one thread as "signal receiver thread" which handles
		2347	these signals. You can pass on any signals that libev might be interested
		2348	in by calling C<ev_feed_signal>.
2037		2349
2038	=head3 Watcher-Specific Functions and Data Members	2350	=head3 Watcher-Specific Functions and Data Members
2039		2351
2040	=over 4	2352	=over 4
2041		2353
…		…
2057	Example: Try to exit cleanly on SIGINT.	2369	Example: Try to exit cleanly on SIGINT.
2058		2370
2059	static void	2371	static void
2060	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2372	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2061	{	2373	{
2062	ev_unloop (loop, EVUNLOOP_ALL);	2374	ev_break (loop, EVBREAK_ALL);
2063	}	2375	}
2064		2376
2065	ev_signal signal_watcher;	2377	ev_signal signal_watcher;
2066	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2378	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2067	ev_signal_start (loop, &signal_watcher);	2379	ev_signal_start (loop, &signal_watcher);
…		…
2086	libev)	2398	libev)
2087		2399
2088	=head3 Process Interaction	2400	=head3 Process Interaction
2089		2401
2090	Libev grabs C<SIGCHLD> as soon as the default event loop is	2402	Libev grabs C<SIGCHLD> as soon as the default event loop is
2091	initialised. This is necessary to guarantee proper behaviour even if	2403	initialised. This is necessary to guarantee proper behaviour even if the
2092	the first child watcher is started after the child exits. The occurrence	2404	first child watcher is started after the child exits. The occurrence
2093	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2405	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2094	synchronously as part of the event loop processing. Libev always reaps all	2406	synchronously as part of the event loop processing. Libev always reaps all
2095	children, even ones not watched.	2407	children, even ones not watched.
2096		2408
2097	=head3 Overriding the Built-In Processing	2409	=head3 Overriding the Built-In Processing
…		…
2107	=head3 Stopping the Child Watcher	2419	=head3 Stopping the Child Watcher
2108		2420
2109	Currently, the child watcher never gets stopped, even when the	2421	Currently, the child watcher never gets stopped, even when the
2110	child terminates, so normally one needs to stop the watcher in the	2422	child terminates, so normally one needs to stop the watcher in the
2111	callback. Future versions of libev might stop the watcher automatically	2423	callback. Future versions of libev might stop the watcher automatically
2112	when a child exit is detected.	2424	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2425	problem).
2113		2426
2114	=head3 Watcher-Specific Functions and Data Members	2427	=head3 Watcher-Specific Functions and Data Members
2115		2428
2116	=over 4	2429	=over 4
2117		2430
…		…
2452		2765
2453	Prepare and check watchers are usually (but not always) used in pairs:	2766	Prepare and check watchers are usually (but not always) used in pairs:
2454	prepare watchers get invoked before the process blocks and check watchers	2767	prepare watchers get invoked before the process blocks and check watchers
2455	afterwards.	2768	afterwards.
2456		2769
2457	You I<must not> call C<ev_loop> or similar functions that enter	2770	You I<must not> call C<ev_run> or similar functions that enter
2458	the current event loop from either C<ev_prepare> or C<ev_check>	2771	the current event loop from either C<ev_prepare> or C<ev_check>
2459	watchers. Other loops than the current one are fine, however. The	2772	watchers. Other loops than the current one are fine, however. The
2460	rationale behind this is that you do not need to check for recursion in	2773	rationale behind this is that you do not need to check for recursion in
2461	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2774	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2462	C<ev_check> so if you have one watcher of each kind they will always be	2775	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2630		2943
2631	if (timeout >= 0)	2944	if (timeout >= 0)
2632	// create/start timer	2945	// create/start timer
2633		2946
2634	// poll	2947	// poll
2635	ev_loop (EV_A_ 0);	2948	ev_run (EV_A_ 0);
2636		2949
2637	// stop timer again	2950	// stop timer again
2638	if (timeout >= 0)	2951	if (timeout >= 0)
2639	ev_timer_stop (EV_A_ &to);	2952	ev_timer_stop (EV_A_ &to);
2640		2953
…		…
2718	if you do not want that, you need to temporarily stop the embed watcher).	3031	if you do not want that, you need to temporarily stop the embed watcher).
2719		3032
2720	=item ev_embed_sweep (loop, ev_embed *)	3033	=item ev_embed_sweep (loop, ev_embed *)
2721		3034
2722	Make a single, non-blocking sweep over the embedded loop. This works	3035	Make a single, non-blocking sweep over the embedded loop. This works
2723	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3036	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2724	appropriate way for embedded loops.	3037	appropriate way for embedded loops.
2725		3038
2726	=item struct ev_loop *other [read-only]	3039	=item struct ev_loop *other [read-only]
2727		3040
2728	The embedded event loop.	3041	The embedded event loop.
…		…
2788	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3101	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2789	handlers will be invoked, too, of course.	3102	handlers will be invoked, too, of course.
2790		3103
2791	=head3 The special problem of life after fork - how is it possible?	3104	=head3 The special problem of life after fork - how is it possible?
2792		3105
2793	Most uses of C<fork()> consist of forking, then some simple calls to ste	3106	Most uses of C<fork()> consist of forking, then some simple calls to set
2794	up/change the process environment, followed by a call to C<exec()>. This	3107	up/change the process environment, followed by a call to C<exec()>. This
2795	sequence should be handled by libev without any problems.	3108	sequence should be handled by libev without any problems.
2796		3109
2797	This changes when the application actually wants to do event handling	3110	This changes when the application actually wants to do event handling
2798	in the child, or both parent in child, in effect "continuing" after the	3111	in the child, or both parent in child, in effect "continuing" after the
…		…
2814	disadvantage of having to use multiple event loops (which do not support	3127	disadvantage of having to use multiple event loops (which do not support
2815	signal watchers).	3128	signal watchers).
2816		3129
2817	When this is not possible, or you want to use the default loop for	3130	When this is not possible, or you want to use the default loop for
2818	other reasons, then in the process that wants to start "fresh", call	3131	other reasons, then in the process that wants to start "fresh", call
2819	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3132	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2820	the default loop will "orphan" (not stop) all registered watchers, so you	3133	Destroying the default loop will "orphan" (not stop) all registered
2821	have to be careful not to execute code that modifies those watchers. Note	3134	watchers, so you have to be careful not to execute code that modifies
2822	also that in that case, you have to re-register any signal watchers.	3135	those watchers. Note also that in that case, you have to re-register any
		3136	signal watchers.
2823		3137
2824	=head3 Watcher-Specific Functions and Data Members	3138	=head3 Watcher-Specific Functions and Data Members
2825		3139
2826	=over 4	3140	=over 4
2827		3141
2828	=item ev_fork_init (ev_signal *, callback)	3142	=item ev_fork_init (ev_fork *, callback)
2829		3143
2830	Initialises and configures the fork watcher - it has no parameters of any	3144	Initialises and configures the fork watcher - it has no parameters of any
2831	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3145	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2832	believe me.	3146	really.
2833		3147
2834	=back	3148	=back
2835		3149
2836		3150
		3151	=head2 C<ev_cleanup> - even the best things end
		3152
		3153	Cleanup watchers are called just before the event loop is being destroyed
		3154	by a call to C<ev_loop_destroy>.
		3155
		3156	While there is no guarantee that the event loop gets destroyed, cleanup
		3157	watchers provide a convenient method to install cleanup hooks for your
		3158	program, worker threads and so on - you just to make sure to destroy the
		3159	loop when you want them to be invoked.
		3160
		3161	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3162	all other watchers, they do not keep a reference to the event loop (which
		3163	makes a lot of sense if you think about it). Like all other watchers, you
		3164	can call libev functions in the callback, except C<ev_cleanup_start>.
		3165
		3166	=head3 Watcher-Specific Functions and Data Members
		3167
		3168	=over 4
		3169
		3170	=item ev_cleanup_init (ev_cleanup *, callback)
		3171
		3172	Initialises and configures the cleanup watcher - it has no parameters of
		3173	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3174	pointless, I assure you.
		3175
		3176	=back
		3177
		3178	Example: Register an atexit handler to destroy the default loop, so any
		3179	cleanup functions are called.
		3180
		3181	static void
		3182	program_exits (void)
		3183	{
		3184	ev_loop_destroy (EV_DEFAULT_UC);
		3185	}
		3186
		3187	...
		3188	atexit (program_exits);
		3189
		3190
2837	=head2 C<ev_async> - how to wake up another event loop	3191	=head2 C<ev_async> - how to wake up an event loop
2838		3192
2839	In general, you cannot use an C<ev_loop> from multiple threads or other	3193	In general, you cannot use an C<ev_run> from multiple threads or other
2840	asynchronous sources such as signal handlers (as opposed to multiple event	3194	asynchronous sources such as signal handlers (as opposed to multiple event
2841	loops - those are of course safe to use in different threads).	3195	loops - those are of course safe to use in different threads).
2842		3196
2843	Sometimes, however, you need to wake up another event loop you do not	3197	Sometimes, however, you need to wake up an event loop you do not control,
2844	control, for example because it belongs to another thread. This is what	3198	for example because it belongs to another thread. This is what C<ev_async>
2845	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3199	watchers do: as long as the C<ev_async> watcher is active, you can signal
2846	can signal it by calling C<ev_async_send>, which is thread- and signal	3200	it by calling C<ev_async_send>, which is thread- and signal safe.
2847	safe.
2848		3201
2849	This functionality is very similar to C<ev_signal> watchers, as signals,	3202	This functionality is very similar to C<ev_signal> watchers, as signals,
2850	too, are asynchronous in nature, and signals, too, will be compressed	3203	too, are asynchronous in nature, and signals, too, will be compressed
2851	(i.e. the number of callback invocations may be less than the number of	3204	(i.e. the number of callback invocations may be less than the number of
2852	C<ev_async_sent> calls).	3205	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3206	of "global async watchers" by using a watcher on an otherwise unused
		3207	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3208	even without knowing which loop owns the signal.
2853		3209
2854	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3210	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2855	just the default loop.	3211	just the default loop.
2856		3212
2857	=head3 Queueing	3213	=head3 Queueing
2858		3214
2859	C<ev_async> does not support queueing of data in any way. The reason	3215	C<ev_async> does not support queueing of data in any way. The reason
2860	is that the author does not know of a simple (or any) algorithm for a	3216	is that the author does not know of a simple (or any) algorithm for a
2861	multiple-writer-single-reader queue that works in all cases and doesn't	3217	multiple-writer-single-reader queue that works in all cases and doesn't
2862	need elaborate support such as pthreads.	3218	need elaborate support such as pthreads or unportable memory access
		3219	semantics.
2863		3220
2864	That means that if you want to queue data, you have to provide your own	3221	That means that if you want to queue data, you have to provide your own
2865	queue. But at least I can tell you how to implement locking around your	3222	queue. But at least I can tell you how to implement locking around your
2866	queue:	3223	queue:
2867		3224
…		…
3006		3363
3007	If C<timeout> is less than 0, then no timeout watcher will be	3364	If C<timeout> is less than 0, then no timeout watcher will be
3008	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3365	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3009	repeat = 0) will be started. C<0> is a valid timeout.	3366	repeat = 0) will be started. C<0> is a valid timeout.
3010		3367
3011	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3368	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3012	passed an C<revents> set like normal event callbacks (a combination of	3369	passed an C<revents> set like normal event callbacks (a combination of
3013	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3370	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3014	value passed to C<ev_once>. Note that it is possible to receive I<both>	3371	value passed to C<ev_once>. Note that it is possible to receive I<both>
3015	a timeout and an io event at the same time - you probably should give io	3372	a timeout and an io event at the same time - you probably should give io
3016	events precedence.	3373	events precedence.
3017		3374
3018	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3375	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3019		3376
3020	static void stdin_ready (int revents, void *arg)	3377	static void stdin_ready (int revents, void *arg)
3021	{	3378	{
3022	if (revents & EV_READ)	3379	if (revents & EV_READ)
3023	/* stdin might have data for us, joy! */;	3380	/* stdin might have data for us, joy! */;
3024	else if (revents & EV_TIMEOUT)	3381	else if (revents & EV_TIMER)
3025	/* doh, nothing entered */;	3382	/* doh, nothing entered */;
3026	}	3383	}
3027		3384
3028	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3385	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3029		3386
3030	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3031
3032	Feeds the given event set into the event loop, as if the specified event
3033	had happened for the specified watcher (which must be a pointer to an
3034	initialised but not necessarily started event watcher).
3035
3036	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3387	=item ev_feed_fd_event (loop, int fd, int revents)
3037		3388
3038	Feed an event on the given fd, as if a file descriptor backend detected	3389	Feed an event on the given fd, as if a file descriptor backend detected
3039	the given events it.	3390	the given events it.
3040		3391
3041	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3392	=item ev_feed_signal_event (loop, int signum)
3042		3393
3043	Feed an event as if the given signal occurred (C<loop> must be the default	3394	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3044	loop!).	3395	which is async-safe.
3045		3396
3046	=back	3397	=back
		3398
		3399
		3400	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3401
		3402	This section explains some common idioms that are not immediately
		3403	obvious. Note that examples are sprinkled over the whole manual, and this
		3404	section only contains stuff that wouldn't fit anywhere else.
		3405
		3406	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3407
		3408	Each watcher has, by default, a C<void *data> member that you can read
		3409	or modify at any time: libev will completely ignore it. This can be used
		3410	to associate arbitrary data with your watcher. If you need more data and
		3411	don't want to allocate memory separately and store a pointer to it in that
		3412	data member, you can also "subclass" the watcher type and provide your own
		3413	data:
		3414
		3415	struct my_io
		3416	{
		3417	ev_io io;
		3418	int otherfd;
		3419	void *somedata;
		3420	struct whatever *mostinteresting;
		3421	};
		3422
		3423	...
		3424	struct my_io w;
		3425	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3426
		3427	And since your callback will be called with a pointer to the watcher, you
		3428	can cast it back to your own type:
		3429
		3430	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3431	{
		3432	struct my_io *w = (struct my_io *)w_;
		3433	...
		3434	}
		3435
		3436	More interesting and less C-conformant ways of casting your callback
		3437	function type instead have been omitted.
		3438
		3439	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3440
		3441	Another common scenario is to use some data structure with multiple
		3442	embedded watchers, in effect creating your own watcher that combines
		3443	multiple libev event sources into one "super-watcher":
		3444
		3445	struct my_biggy
		3446	{
		3447	int some_data;
		3448	ev_timer t1;
		3449	ev_timer t2;
		3450	}
		3451
		3452	In this case getting the pointer to C<my_biggy> is a bit more
		3453	complicated: Either you store the address of your C<my_biggy> struct in
		3454	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3455	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3456	real programmers):
		3457
		3458	#include <stddef.h>
		3459
		3460	static void
		3461	t1_cb (EV_P_ ev_timer *w, int revents)
		3462	{
		3463	struct my_biggy big = (struct my_biggy *)
		3464	(((char *)w) - offsetof (struct my_biggy, t1));
		3465	}
		3466
		3467	static void
		3468	t2_cb (EV_P_ ev_timer *w, int revents)
		3469	{
		3470	struct my_biggy big = (struct my_biggy *)
		3471	(((char *)w) - offsetof (struct my_biggy, t2));
		3472	}
		3473
		3474	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3475
		3476	Often (especially in GUI toolkits) there are places where you have
		3477	I<modal> interaction, which is most easily implemented by recursively
		3478	invoking C<ev_run>.
		3479
		3480	This brings the problem of exiting - a callback might want to finish the
		3481	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3482	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3483	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3484	other combination: In these cases, C<ev_break> will not work alone.
		3485
		3486	The solution is to maintain "break this loop" variable for each C<ev_run>
		3487	invocation, and use a loop around C<ev_run> until the condition is
		3488	triggered, using C<EVRUN_ONCE>:
		3489
		3490	// main loop
		3491	int exit_main_loop = 0;
		3492
		3493	while (!exit_main_loop)
		3494	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3495
		3496	// in a model watcher
		3497	int exit_nested_loop = 0;
		3498
		3499	while (!exit_nested_loop)
		3500	ev_run (EV_A_ EVRUN_ONCE);
		3501
		3502	To exit from any of these loops, just set the corresponding exit variable:
		3503
		3504	// exit modal loop
		3505	exit_nested_loop = 1;
		3506
		3507	// exit main program, after modal loop is finished
		3508	exit_main_loop = 1;
		3509
		3510	// exit both
		3511	exit_main_loop = exit_nested_loop = 1;
		3512
		3513	=head2 THREAD LOCKING EXAMPLE
		3514
		3515	Here is a fictitious example of how to run an event loop in a different
		3516	thread from where callbacks are being invoked and watchers are
		3517	created/added/removed.
		3518
		3519	For a real-world example, see the C<EV::Loop::Async> perl module,
		3520	which uses exactly this technique (which is suited for many high-level
		3521	languages).
		3522
		3523	The example uses a pthread mutex to protect the loop data, a condition
		3524	variable to wait for callback invocations, an async watcher to notify the
		3525	event loop thread and an unspecified mechanism to wake up the main thread.
		3526
		3527	First, you need to associate some data with the event loop:
		3528
		3529	typedef struct {
		3530	mutex_t lock; /* global loop lock */
		3531	ev_async async_w;
		3532	thread_t tid;
		3533	cond_t invoke_cv;
		3534	} userdata;
		3535
		3536	void prepare_loop (EV_P)
		3537	{
		3538	// for simplicity, we use a static userdata struct.
		3539	static userdata u;
		3540
		3541	ev_async_init (&u->async_w, async_cb);
		3542	ev_async_start (EV_A_ &u->async_w);
		3543
		3544	pthread_mutex_init (&u->lock, 0);
		3545	pthread_cond_init (&u->invoke_cv, 0);
		3546
		3547	// now associate this with the loop
		3548	ev_set_userdata (EV_A_ u);
		3549	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3550	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3551
		3552	// then create the thread running ev_run
		3553	pthread_create (&u->tid, 0, l_run, EV_A);
		3554	}
		3555
		3556	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3557	solely to wake up the event loop so it takes notice of any new watchers
		3558	that might have been added:
		3559
		3560	static void
		3561	async_cb (EV_P_ ev_async *w, int revents)
		3562	{
		3563	// just used for the side effects
		3564	}
		3565
		3566	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3567	protecting the loop data, respectively.
		3568
		3569	static void
		3570	l_release (EV_P)
		3571	{
		3572	userdata *u = ev_userdata (EV_A);
		3573	pthread_mutex_unlock (&u->lock);
		3574	}
		3575
		3576	static void
		3577	l_acquire (EV_P)
		3578	{
		3579	userdata *u = ev_userdata (EV_A);
		3580	pthread_mutex_lock (&u->lock);
		3581	}
		3582
		3583	The event loop thread first acquires the mutex, and then jumps straight
		3584	into C<ev_run>:
		3585
		3586	void *
		3587	l_run (void *thr_arg)
		3588	{
		3589	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3590
		3591	l_acquire (EV_A);
		3592	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3593	ev_run (EV_A_ 0);
		3594	l_release (EV_A);
		3595
		3596	return 0;
		3597	}
		3598
		3599	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3600	signal the main thread via some unspecified mechanism (signals? pipe
		3601	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3602	have been called (in a while loop because a) spurious wakeups are possible
		3603	and b) skipping inter-thread-communication when there are no pending
		3604	watchers is very beneficial):
		3605
		3606	static void
		3607	l_invoke (EV_P)
		3608	{
		3609	userdata *u = ev_userdata (EV_A);
		3610
		3611	while (ev_pending_count (EV_A))
		3612	{
		3613	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3614	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3615	}
		3616	}
		3617
		3618	Now, whenever the main thread gets told to invoke pending watchers, it
		3619	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3620	thread to continue:
		3621
		3622	static void
		3623	real_invoke_pending (EV_P)
		3624	{
		3625	userdata *u = ev_userdata (EV_A);
		3626
		3627	pthread_mutex_lock (&u->lock);
		3628	ev_invoke_pending (EV_A);
		3629	pthread_cond_signal (&u->invoke_cv);
		3630	pthread_mutex_unlock (&u->lock);
		3631	}
		3632
		3633	Whenever you want to start/stop a watcher or do other modifications to an
		3634	event loop, you will now have to lock:
		3635
		3636	ev_timer timeout_watcher;
		3637	userdata *u = ev_userdata (EV_A);
		3638
		3639	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3640
		3641	pthread_mutex_lock (&u->lock);
		3642	ev_timer_start (EV_A_ &timeout_watcher);
		3643	ev_async_send (EV_A_ &u->async_w);
		3644	pthread_mutex_unlock (&u->lock);
		3645
		3646	Note that sending the C<ev_async> watcher is required because otherwise
		3647	an event loop currently blocking in the kernel will have no knowledge
		3648	about the newly added timer. By waking up the loop it will pick up any new
		3649	watchers in the next event loop iteration.
		3650
		3651	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3652
		3653	While the overhead of a callback that e.g. schedules a thread is small, it
		3654	is still an overhead. If you embed libev, and your main usage is with some
		3655	kind of threads or coroutines, you might want to customise libev so that
		3656	doesn't need callbacks anymore.
		3657
		3658	Imagine you have coroutines that you can switch to using a function
		3659	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3660	and that due to some magic, the currently active coroutine is stored in a
		3661	global called C<current_coro>. Then you can build your own "wait for libev
		3662	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3663	the differing C<;> conventions):
		3664
		3665	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3666	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3667
		3668	That means instead of having a C callback function, you store the
		3669	coroutine to switch to in each watcher, and instead of having libev call
		3670	your callback, you instead have it switch to that coroutine.
		3671
		3672	A coroutine might now wait for an event with a function called
		3673	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3674	matter when, or whether the watcher is active or not when this function is
		3675	called):
		3676
		3677	void
		3678	wait_for_event (ev_watcher *w)
		3679	{
		3680	ev_cb_set (w) = current_coro;
		3681	switch_to (libev_coro);
		3682	}
		3683
		3684	That basically suspends the coroutine inside C<wait_for_event> and
		3685	continues the libev coroutine, which, when appropriate, switches back to
		3686	this or any other coroutine. I am sure if you sue this your own :)
		3687
		3688	You can do similar tricks if you have, say, threads with an event queue -
		3689	instead of storing a coroutine, you store the queue object and instead of
		3690	switching to a coroutine, you push the watcher onto the queue and notify
		3691	any waiters.
		3692
		3693	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3694	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3695
		3696	// my_ev.h
		3697	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3698	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3699	#include "../libev/ev.h"
		3700
		3701	// my_ev.c
		3702	#define EV_H "my_ev.h"
		3703	#include "../libev/ev.c"
		3704
		3705	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3706	F<my_ev.c> into your project. When properly specifying include paths, you
		3707	can even use F<ev.h> as header file name directly.
3047		3708
3048		3709
3049	=head1 LIBEVENT EMULATION	3710	=head1 LIBEVENT EMULATION
3050		3711
3051	Libev offers a compatibility emulation layer for libevent. It cannot	3712	Libev offers a compatibility emulation layer for libevent. It cannot
3052	emulate the internals of libevent, so here are some usage hints:	3713	emulate the internals of libevent, so here are some usage hints:
3053		3714
3054	=over 4	3715	=over 4
		3716
		3717	=item * Only the libevent-1.4.1-beta API is being emulated.
		3718
		3719	This was the newest libevent version available when libev was implemented,
		3720	and is still mostly unchanged in 2010.
3055		3721
3056	=item * Use it by including <event.h>, as usual.	3722	=item * Use it by including <event.h>, as usual.
3057		3723
3058	=item * The following members are fully supported: ev_base, ev_callback,	3724	=item * The following members are fully supported: ev_base, ev_callback,
3059	ev_arg, ev_fd, ev_res, ev_events.	3725	ev_arg, ev_fd, ev_res, ev_events.
…		…
3065	=item * Priorities are not currently supported. Initialising priorities	3731	=item * Priorities are not currently supported. Initialising priorities
3066	will fail and all watchers will have the same priority, even though there	3732	will fail and all watchers will have the same priority, even though there
3067	is an ev_pri field.	3733	is an ev_pri field.
3068		3734
3069	=item * In libevent, the last base created gets the signals, in libev, the	3735	=item * In libevent, the last base created gets the signals, in libev, the
3070	first base created (== the default loop) gets the signals.	3736	base that registered the signal gets the signals.
3071		3737
3072	=item * Other members are not supported.	3738	=item * Other members are not supported.
3073		3739
3074	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3740	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3075	to use the libev header file and library.	3741	to use the libev header file and library.
…		…
3094	Care has been taken to keep the overhead low. The only data member the C++	3760	Care has been taken to keep the overhead low. The only data member the C++
3095	classes add (compared to plain C-style watchers) is the event loop pointer	3761	classes add (compared to plain C-style watchers) is the event loop pointer
3096	that the watcher is associated with (or no additional members at all if	3762	that the watcher is associated with (or no additional members at all if
3097	you disable C<EV_MULTIPLICITY> when embedding libev).	3763	you disable C<EV_MULTIPLICITY> when embedding libev).
3098		3764
3099	Currently, functions, and static and non-static member functions can be	3765	Currently, functions, static and non-static member functions and classes
3100	used as callbacks. Other types should be easy to add as long as they only	3766	with C<operator ()> can be used as callbacks. Other types should be easy
3101	need one additional pointer for context. If you need support for other	3767	to add as long as they only need one additional pointer for context. If
3102	types of functors please contact the author (preferably after implementing	3768	you need support for other types of functors please contact the author
3103	it).	3769	(preferably after implementing it).
3104		3770
3105	Here is a list of things available in the C<ev> namespace:	3771	Here is a list of things available in the C<ev> namespace:
3106		3772
3107	=over 4	3773	=over 4
3108		3774
…		…
3126		3792
3127	=over 4	3793	=over 4
3128		3794
3129	=item ev::TYPE::TYPE ()	3795	=item ev::TYPE::TYPE ()
3130		3796
3131	=item ev::TYPE::TYPE (struct ev_loop *)	3797	=item ev::TYPE::TYPE (loop)
3132		3798
3133	=item ev::TYPE::~TYPE	3799	=item ev::TYPE::~TYPE
3134		3800
3135	The constructor (optionally) takes an event loop to associate the watcher	3801	The constructor (optionally) takes an event loop to associate the watcher
3136	with. If it is omitted, it will use C<EV_DEFAULT>.	3802	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3169	myclass obj;	3835	myclass obj;
3170	ev::io iow;	3836	ev::io iow;
3171	iow.set <myclass, &myclass::io_cb> (&obj);	3837	iow.set <myclass, &myclass::io_cb> (&obj);
3172		3838
3173	=item w->set (object *)	3839	=item w->set (object *)
3174
3175	This is an B<experimental> feature that might go away in a future version.
3176		3840
3177	This is a variation of a method callback - leaving out the method to call	3841	This is a variation of a method callback - leaving out the method to call
3178	will default the method to C<operator ()>, which makes it possible to use	3842	will default the method to C<operator ()>, which makes it possible to use
3179	functor objects without having to manually specify the C<operator ()> all	3843	functor objects without having to manually specify the C<operator ()> all
3180	the time. Incidentally, you can then also leave out the template argument	3844	the time. Incidentally, you can then also leave out the template argument
…		…
3213	Example: Use a plain function as callback.	3877	Example: Use a plain function as callback.
3214		3878
3215	static void io_cb (ev::io &w, int revents) { }	3879	static void io_cb (ev::io &w, int revents) { }
3216	iow.set <io_cb> ();	3880	iow.set <io_cb> ();
3217		3881
3218	=item w->set (struct ev_loop *)	3882	=item w->set (loop)
3219		3883
3220	Associates a different C<struct ev_loop> with this watcher. You can only	3884	Associates a different C<struct ev_loop> with this watcher. You can only
3221	do this when the watcher is inactive (and not pending either).	3885	do this when the watcher is inactive (and not pending either).
3222		3886
3223	=item w->set ([arguments])	3887	=item w->set ([arguments])
3224		3888
3225	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3889	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3226	called at least once. Unlike the C counterpart, an active watcher gets	3890	method or a suitable start method must be called at least once. Unlike the
3227	automatically stopped and restarted when reconfiguring it with this	3891	C counterpart, an active watcher gets automatically stopped and restarted
3228	method.	3892	when reconfiguring it with this method.
3229		3893
3230	=item w->start ()	3894	=item w->start ()
3231		3895
3232	Starts the watcher. Note that there is no C<loop> argument, as the	3896	Starts the watcher. Note that there is no C<loop> argument, as the
3233	constructor already stores the event loop.	3897	constructor already stores the event loop.
3234		3898
		3899	=item w->start ([arguments])
		3900
		3901	Instead of calling C<set> and C<start> methods separately, it is often
		3902	convenient to wrap them in one call. Uses the same type of arguments as
		3903	the configure C<set> method of the watcher.
		3904
3235	=item w->stop ()	3905	=item w->stop ()
3236		3906
3237	Stops the watcher if it is active. Again, no C<loop> argument.	3907	Stops the watcher if it is active. Again, no C<loop> argument.
3238		3908
3239	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3909	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3251		3921
3252	=back	3922	=back
3253		3923
3254	=back	3924	=back
3255		3925
3256	Example: Define a class with an IO and idle watcher, start one of them in	3926	Example: Define a class with two I/O and idle watchers, start the I/O
3257	the constructor.	3927	watchers in the constructor.
3258		3928
3259	class myclass	3929	class myclass
3260	{	3930	{
3261	ev::io io ; void io_cb (ev::io &w, int revents);	3931	ev::io io ; void io_cb (ev::io &w, int revents);
		3932	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3262	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3933	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3263		3934
3264	myclass (int fd)	3935	myclass (int fd)
3265	{	3936	{
3266	io .set <myclass, &myclass::io_cb > (this);	3937	io .set <myclass, &myclass::io_cb > (this);
		3938	io2 .set <myclass, &myclass::io2_cb > (this);
3267	idle.set <myclass, &myclass::idle_cb> (this);	3939	idle.set <myclass, &myclass::idle_cb> (this);
3268		3940
3269	io.start (fd, ev::READ);	3941	io.set (fd, ev::WRITE); // configure the watcher
		3942	io.start (); // start it whenever convenient
		3943
		3944	io2.start (fd, ev::READ); // set + start in one call
3270	}	3945	}
3271	};	3946	};
3272		3947
3273		3948
3274	=head1 OTHER LANGUAGE BINDINGS	3949	=head1 OTHER LANGUAGE BINDINGS
…		…
3320	=item Ocaml	3995	=item Ocaml
3321		3996
3322	Erkki Seppala has written Ocaml bindings for libev, to be found at	3997	Erkki Seppala has written Ocaml bindings for libev, to be found at
3323	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3998	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3324		3999
		4000	=item Lua
		4001
		4002	Brian Maher has written a partial interface to libev for lua (at the
		4003	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4004	L<http://github.com/brimworks/lua-ev>.
		4005
3325	=back	4006	=back
3326		4007
3327		4008
3328	=head1 MACRO MAGIC	4009	=head1 MACRO MAGIC
3329		4010
…		…
3342	loop argument"). The C<EV_A> form is used when this is the sole argument,	4023	loop argument"). The C<EV_A> form is used when this is the sole argument,
3343	C<EV_A_> is used when other arguments are following. Example:	4024	C<EV_A_> is used when other arguments are following. Example:
3344		4025
3345	ev_unref (EV_A);	4026	ev_unref (EV_A);
3346	ev_timer_add (EV_A_ watcher);	4027	ev_timer_add (EV_A_ watcher);
3347	ev_loop (EV_A_ 0);	4028	ev_run (EV_A_ 0);
3348		4029
3349	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4030	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3350	which is often provided by the following macro.	4031	which is often provided by the following macro.
3351		4032
3352	=item C<EV_P>, C<EV_P_>	4033	=item C<EV_P>, C<EV_P_>
…		…
3392	}	4073	}
3393		4074
3394	ev_check check;	4075	ev_check check;
3395	ev_check_init (&check, check_cb);	4076	ev_check_init (&check, check_cb);
3396	ev_check_start (EV_DEFAULT_ &check);	4077	ev_check_start (EV_DEFAULT_ &check);
3397	ev_loop (EV_DEFAULT_ 0);	4078	ev_run (EV_DEFAULT_ 0);
3398		4079
3399	=head1 EMBEDDING	4080	=head1 EMBEDDING
3400		4081
3401	Libev can (and often is) directly embedded into host	4082	Libev can (and often is) directly embedded into host
3402	applications. Examples of applications that embed it include the Deliantra	4083	applications. Examples of applications that embed it include the Deliantra
…		…
3482	libev.m4	4163	libev.m4
3483		4164
3484	=head2 PREPROCESSOR SYMBOLS/MACROS	4165	=head2 PREPROCESSOR SYMBOLS/MACROS
3485		4166
3486	Libev can be configured via a variety of preprocessor symbols you have to	4167	Libev can be configured via a variety of preprocessor symbols you have to
3487	define before including any of its files. The default in the absence of	4168	define before including (or compiling) any of its files. The default in
3488	autoconf is documented for every option.	4169	the absence of autoconf is documented for every option.
		4170
		4171	Symbols marked with "(h)" do not change the ABI, and can have different
		4172	values when compiling libev vs. including F<ev.h>, so it is permissible
		4173	to redefine them before including F<ev.h> without breaking compatibility
		4174	to a compiled library. All other symbols change the ABI, which means all
		4175	users of libev and the libev code itself must be compiled with compatible
		4176	settings.
3489		4177
3490	=over 4	4178	=over 4
3491		4179
		4180	=item EV_COMPAT3 (h)
		4181
		4182	Backwards compatibility is a major concern for libev. This is why this
		4183	release of libev comes with wrappers for the functions and symbols that
		4184	have been renamed between libev version 3 and 4.
		4185
		4186	You can disable these wrappers (to test compatibility with future
		4187	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4188	sources. This has the additional advantage that you can drop the C<struct>
		4189	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4190	typedef in that case.
		4191
		4192	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4193	and in some even more future version the compatibility code will be
		4194	removed completely.
		4195
3492	=item EV_STANDALONE	4196	=item EV_STANDALONE (h)
3493		4197
3494	Must always be C<1> if you do not use autoconf configuration, which	4198	Must always be C<1> if you do not use autoconf configuration, which
3495	keeps libev from including F<config.h>, and it also defines dummy	4199	keeps libev from including F<config.h>, and it also defines dummy
3496	implementations for some libevent functions (such as logging, which is not	4200	implementations for some libevent functions (such as logging, which is not
3497	supported). It will also not define any of the structs usually found in	4201	supported). It will also not define any of the structs usually found in
3498	F<event.h> that are not directly supported by the libev core alone.	4202	F<event.h> that are not directly supported by the libev core alone.
3499		4203
3500	In stanbdalone mode, libev will still try to automatically deduce the	4204	In standalone mode, libev will still try to automatically deduce the
3501	configuration, but has to be more conservative.	4205	configuration, but has to be more conservative.
3502		4206
3503	=item EV_USE_MONOTONIC	4207	=item EV_USE_MONOTONIC
3504		4208
3505	If defined to be C<1>, libev will try to detect the availability of the	4209	If defined to be C<1>, libev will try to detect the availability of the
…		…
3570	be used is the winsock select). This means that it will call	4274	be used is the winsock select). This means that it will call
3571	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4275	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3572	it is assumed that all these functions actually work on fds, even	4276	it is assumed that all these functions actually work on fds, even
3573	on win32. Should not be defined on non-win32 platforms.	4277	on win32. Should not be defined on non-win32 platforms.
3574		4278
3575	=item EV_FD_TO_WIN32_HANDLE	4279	=item EV_FD_TO_WIN32_HANDLE(fd)
3576		4280
3577	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4281	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3578	file descriptors to socket handles. When not defining this symbol (the	4282	file descriptors to socket handles. When not defining this symbol (the
3579	default), then libev will call C<_get_osfhandle>, which is usually	4283	default), then libev will call C<_get_osfhandle>, which is usually
3580	correct. In some cases, programs use their own file descriptor management,	4284	correct. In some cases, programs use their own file descriptor management,
3581	in which case they can provide this function to map fds to socket handles.	4285	in which case they can provide this function to map fds to socket handles.
		4286
		4287	=item EV_WIN32_HANDLE_TO_FD(handle)
		4288
		4289	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4290	using the standard C<_open_osfhandle> function. For programs implementing
		4291	their own fd to handle mapping, overwriting this function makes it easier
		4292	to do so. This can be done by defining this macro to an appropriate value.
		4293
		4294	=item EV_WIN32_CLOSE_FD(fd)
		4295
		4296	If programs implement their own fd to handle mapping on win32, then this
		4297	macro can be used to override the C<close> function, useful to unregister
		4298	file descriptors again. Note that the replacement function has to close
		4299	the underlying OS handle.
3582		4300
3583	=item EV_USE_POLL	4301	=item EV_USE_POLL
3584		4302
3585	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4303	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3586	backend. Otherwise it will be enabled on non-win32 platforms. It	4304	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3633	as well as for signal and thread safety in C<ev_async> watchers.	4351	as well as for signal and thread safety in C<ev_async> watchers.
3634		4352
3635	In the absence of this define, libev will use C<sig_atomic_t volatile>	4353	In the absence of this define, libev will use C<sig_atomic_t volatile>
3636	(from F<signal.h>), which is usually good enough on most platforms.	4354	(from F<signal.h>), which is usually good enough on most platforms.
3637		4355
3638	=item EV_H	4356	=item EV_H (h)
3639		4357
3640	The name of the F<ev.h> header file used to include it. The default if	4358	The name of the F<ev.h> header file used to include it. The default if
3641	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4359	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3642	used to virtually rename the F<ev.h> header file in case of conflicts.	4360	used to virtually rename the F<ev.h> header file in case of conflicts.
3643		4361
3644	=item EV_CONFIG_H	4362	=item EV_CONFIG_H (h)
3645		4363
3646	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4364	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3647	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4365	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3648	C<EV_H>, above.	4366	C<EV_H>, above.
3649		4367
3650	=item EV_EVENT_H	4368	=item EV_EVENT_H (h)
3651		4369
3652	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4370	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3653	of how the F<event.h> header can be found, the default is C<"event.h">.	4371	of how the F<event.h> header can be found, the default is C<"event.h">.
3654		4372
3655	=item EV_PROTOTYPES	4373	=item EV_PROTOTYPES (h)
3656		4374
3657	If defined to be C<0>, then F<ev.h> will not define any function	4375	If defined to be C<0>, then F<ev.h> will not define any function
3658	prototypes, but still define all the structs and other symbols. This is	4376	prototypes, but still define all the structs and other symbols. This is
3659	occasionally useful if you want to provide your own wrapper functions	4377	occasionally useful if you want to provide your own wrapper functions
3660	around libev functions.	4378	around libev functions.
…		…
3682	fine.	4400	fine.
3683		4401
3684	If your embedding application does not need any priorities, defining these	4402	If your embedding application does not need any priorities, defining these
3685	both to C<0> will save some memory and CPU.	4403	both to C<0> will save some memory and CPU.
3686		4404
3687	=item EV_PERIODIC_ENABLE	4405	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4406	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4407	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3688		4408
3689	If undefined or defined to be C<1>, then periodic timers are supported. If	4409	If undefined or defined to be C<1> (and the platform supports it), then
3690	defined to be C<0>, then they are not. Disabling them saves a few kB of	4410	the respective watcher type is supported. If defined to be C<0>, then it
3691	code.	4411	is not. Disabling watcher types mainly saves code size.
3692		4412
3693	=item EV_IDLE_ENABLE	4413	=item EV_FEATURES
3694
3695	If undefined or defined to be C<1>, then idle watchers are supported. If
3696	defined to be C<0>, then they are not. Disabling them saves a few kB of
3697	code.
3698
3699	=item EV_EMBED_ENABLE
3700
3701	If undefined or defined to be C<1>, then embed watchers are supported. If
3702	defined to be C<0>, then they are not. Embed watchers rely on most other
3703	watcher types, which therefore must not be disabled.
3704
3705	=item EV_STAT_ENABLE
3706
3707	If undefined or defined to be C<1>, then stat watchers are supported. If
3708	defined to be C<0>, then they are not.
3709
3710	=item EV_FORK_ENABLE
3711
3712	If undefined or defined to be C<1>, then fork watchers are supported. If
3713	defined to be C<0>, then they are not.
3714
3715	=item EV_ASYNC_ENABLE
3716
3717	If undefined or defined to be C<1>, then async watchers are supported. If
3718	defined to be C<0>, then they are not.
3719
3720	=item EV_MINIMAL
3721		4414
3722	If you need to shave off some kilobytes of code at the expense of some	4415	If you need to shave off some kilobytes of code at the expense of some
3723	speed (but with the full API), define this symbol to C<1>. Currently this	4416	speed (but with the full API), you can define this symbol to request
3724	is used to override some inlining decisions, saves roughly 30% code size	4417	certain subsets of functionality. The default is to enable all features
3725	on amd64. It also selects a much smaller 2-heap for timer management over	4418	that can be enabled on the platform.
3726	the default 4-heap.
3727		4419
3728	You can save even more by disabling watcher types you do not need	4420	A typical way to use this symbol is to define it to C<0> (or to a bitset
3729	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4421	with some broad features you want) and then selectively re-enable
3730	(C<-DNDEBUG>) will usually reduce code size a lot.	4422	additional parts you want, for example if you want everything minimal,
		4423	but multiple event loop support, async and child watchers and the poll
		4424	backend, use this:
3731		4425
3732	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4426	#define EV_FEATURES 0
3733	provide a bare-bones event library. See C<ev.h> for details on what parts	4427	#define EV_MULTIPLICITY 1
3734	of the API are still available, and do not complain if this subset changes	4428	#define EV_USE_POLL 1
3735	over time.	4429	#define EV_CHILD_ENABLE 1
		4430	#define EV_ASYNC_ENABLE 1
		4431
		4432	The actual value is a bitset, it can be a combination of the following
		4433	values:
		4434
		4435	=over 4
		4436
		4437	=item C<1> - faster/larger code
		4438
		4439	Use larger code to speed up some operations.
		4440
		4441	Currently this is used to override some inlining decisions (enlarging the
		4442	code size by roughly 30% on amd64).
		4443
		4444	When optimising for size, use of compiler flags such as C<-Os> with
		4445	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4446	assertions.
		4447
		4448	=item C<2> - faster/larger data structures
		4449
		4450	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4451	hash table sizes and so on. This will usually further increase code size
		4452	and can additionally have an effect on the size of data structures at
		4453	runtime.
		4454
		4455	=item C<4> - full API configuration
		4456
		4457	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4458	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4459
		4460	=item C<8> - full API
		4461
		4462	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4463	details on which parts of the API are still available without this
		4464	feature, and do not complain if this subset changes over time.
		4465
		4466	=item C<16> - enable all optional watcher types
		4467
		4468	Enables all optional watcher types. If you want to selectively enable
		4469	only some watcher types other than I/O and timers (e.g. prepare,
		4470	embed, async, child...) you can enable them manually by defining
		4471	C<EV_watchertype_ENABLE> to C<1> instead.
		4472
		4473	=item C<32> - enable all backends
		4474
		4475	This enables all backends - without this feature, you need to enable at
		4476	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4477
		4478	=item C<64> - enable OS-specific "helper" APIs
		4479
		4480	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4481	default.
		4482
		4483	=back
		4484
		4485	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4486	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4487	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4488	watchers, timers and monotonic clock support.
		4489
		4490	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4491	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4492	your program might be left out as well - a binary starting a timer and an
		4493	I/O watcher then might come out at only 5Kb.
		4494
		4495	=item EV_AVOID_STDIO
		4496
		4497	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4498	functions (printf, scanf, perror etc.). This will increase the code size
		4499	somewhat, but if your program doesn't otherwise depend on stdio and your
		4500	libc allows it, this avoids linking in the stdio library which is quite
		4501	big.
		4502
		4503	Note that error messages might become less precise when this option is
		4504	enabled.
		4505
		4506	=item EV_NSIG
		4507
		4508	The highest supported signal number, +1 (or, the number of
		4509	signals): Normally, libev tries to deduce the maximum number of signals
		4510	automatically, but sometimes this fails, in which case it can be
		4511	specified. Also, using a lower number than detected (C<32> should be
		4512	good for about any system in existence) can save some memory, as libev
		4513	statically allocates some 12-24 bytes per signal number.
3736		4514
3737	=item EV_PID_HASHSIZE	4515	=item EV_PID_HASHSIZE
3738		4516
3739	C<ev_child> watchers use a small hash table to distribute workload by	4517	C<ev_child> watchers use a small hash table to distribute workload by
3740	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4518	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3741	than enough. If you need to manage thousands of children you might want to	4519	usually more than enough. If you need to manage thousands of children you
3742	increase this value (I<must> be a power of two).	4520	might want to increase this value (I<must> be a power of two).
3743		4521
3744	=item EV_INOTIFY_HASHSIZE	4522	=item EV_INOTIFY_HASHSIZE
3745		4523
3746	C<ev_stat> watchers use a small hash table to distribute workload by	4524	C<ev_stat> watchers use a small hash table to distribute workload by
3747	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4525	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3748	usually more than enough. If you need to manage thousands of C<ev_stat>	4526	disabled), usually more than enough. If you need to manage thousands of
3749	watchers you might want to increase this value (I<must> be a power of	4527	C<ev_stat> watchers you might want to increase this value (I<must> be a
3750	two).	4528	power of two).
3751		4529
3752	=item EV_USE_4HEAP	4530	=item EV_USE_4HEAP
3753		4531
3754	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4532	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3755	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4533	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3756	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4534	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3757	faster performance with many (thousands) of watchers.	4535	faster performance with many (thousands) of watchers.
3758		4536
3759	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4537	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3760	(disabled).	4538	will be C<0>.
3761		4539
3762	=item EV_HEAP_CACHE_AT	4540	=item EV_HEAP_CACHE_AT
3763		4541
3764	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4542	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3765	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4543	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3766	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4544	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3767	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4545	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3768	but avoids random read accesses on heap changes. This improves performance	4546	but avoids random read accesses on heap changes. This improves performance
3769	noticeably with many (hundreds) of watchers.	4547	noticeably with many (hundreds) of watchers.
3770		4548
3771	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4549	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3772	(disabled).	4550	will be C<0>.
3773		4551
3774	=item EV_VERIFY	4552	=item EV_VERIFY
3775		4553
3776	Controls how much internal verification (see C<ev_loop_verify ()>) will	4554	Controls how much internal verification (see C<ev_verify ()>) will
3777	be done: If set to C<0>, no internal verification code will be compiled	4555	be done: If set to C<0>, no internal verification code will be compiled
3778	in. If set to C<1>, then verification code will be compiled in, but not	4556	in. If set to C<1>, then verification code will be compiled in, but not
3779	called. If set to C<2>, then the internal verification code will be	4557	called. If set to C<2>, then the internal verification code will be
3780	called once per loop, which can slow down libev. If set to C<3>, then the	4558	called once per loop, which can slow down libev. If set to C<3>, then the
3781	verification code will be called very frequently, which will slow down	4559	verification code will be called very frequently, which will slow down
3782	libev considerably.	4560	libev considerably.
3783		4561
3784	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4562	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3785	C<0>.	4563	will be C<0>.
3786		4564
3787	=item EV_COMMON	4565	=item EV_COMMON
3788		4566
3789	By default, all watchers have a C<void *data> member. By redefining	4567	By default, all watchers have a C<void *data> member. By redefining
3790	this macro to a something else you can include more and other types of	4568	this macro to something else you can include more and other types of
3791	members. You have to define it each time you include one of the files,	4569	members. You have to define it each time you include one of the files,
3792	though, and it must be identical each time.	4570	though, and it must be identical each time.
3793		4571
3794	For example, the perl EV module uses something like this:	4572	For example, the perl EV module uses something like this:
3795		4573
…		…
3848	file.	4626	file.
3849		4627
3850	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4628	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3851	that everybody includes and which overrides some configure choices:	4629	that everybody includes and which overrides some configure choices:
3852		4630
3853	#define EV_MINIMAL 1	4631	#define EV_FEATURES 8
3854	#define EV_USE_POLL 0	4632	#define EV_USE_SELECT 1
3855	#define EV_MULTIPLICITY 0
3856	#define EV_PERIODIC_ENABLE 0	4633	#define EV_PREPARE_ENABLE 1
		4634	#define EV_IDLE_ENABLE 1
3857	#define EV_STAT_ENABLE 0	4635	#define EV_SIGNAL_ENABLE 1
3858	#define EV_FORK_ENABLE 0	4636	#define EV_CHILD_ENABLE 1
		4637	#define EV_USE_STDEXCEPT 0
3859	#define EV_CONFIG_H <config.h>	4638	#define EV_CONFIG_H <config.h>
3860	#define EV_MINPRI 0
3861	#define EV_MAXPRI 0
3862		4639
3863	#include "ev++.h"	4640	#include "ev++.h"
3864		4641
3865	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4642	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3866		4643
3867	#include "ev_cpp.h"	4644	#include "ev_cpp.h"
3868	#include "ev.c"	4645	#include "ev.c"
3869		4646
3870	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4647	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3871		4648
3872	=head2 THREADS AND COROUTINES	4649	=head2 THREADS AND COROUTINES
3873		4650
3874	=head3 THREADS	4651	=head3 THREADS
3875		4652
…		…
3926	default loop and triggering an C<ev_async> watcher from the default loop	4703	default loop and triggering an C<ev_async> watcher from the default loop
3927	watcher callback into the event loop interested in the signal.	4704	watcher callback into the event loop interested in the signal.
3928		4705
3929	=back	4706	=back
3930		4707
3931	=head4 THREAD LOCKING EXAMPLE	4708	See also L<THREAD LOCKING EXAMPLE>.
3932		4709
3933	=head3 COROUTINES	4710	=head3 COROUTINES
3934		4711
3935	Libev is very accommodating to coroutines ("cooperative threads"):	4712	Libev is very accommodating to coroutines ("cooperative threads"):
3936	libev fully supports nesting calls to its functions from different	4713	libev fully supports nesting calls to its functions from different
3937	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4714	coroutines (e.g. you can call C<ev_run> on the same loop from two
3938	different coroutines, and switch freely between both coroutines running the	4715	different coroutines, and switch freely between both coroutines running
3939	loop, as long as you don't confuse yourself). The only exception is that	4716	the loop, as long as you don't confuse yourself). The only exception is
3940	you must not do this from C<ev_periodic> reschedule callbacks.	4717	that you must not do this from C<ev_periodic> reschedule callbacks.
3941		4718
3942	Care has been taken to ensure that libev does not keep local state inside	4719	Care has been taken to ensure that libev does not keep local state inside
3943	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4720	C<ev_run>, and other calls do not usually allow for coroutine switches as
3944	they do not call any callbacks.	4721	they do not call any callbacks.
3945		4722
3946	=head2 COMPILER WARNINGS	4723	=head2 COMPILER WARNINGS
3947		4724
3948	Depending on your compiler and compiler settings, you might get no or a	4725	Depending on your compiler and compiler settings, you might get no or a
…		…
3959	maintainable.	4736	maintainable.
3960		4737
3961	And of course, some compiler warnings are just plain stupid, or simply	4738	And of course, some compiler warnings are just plain stupid, or simply
3962	wrong (because they don't actually warn about the condition their message	4739	wrong (because they don't actually warn about the condition their message
3963	seems to warn about). For example, certain older gcc versions had some	4740	seems to warn about). For example, certain older gcc versions had some
3964	warnings that resulted an extreme number of false positives. These have	4741	warnings that resulted in an extreme number of false positives. These have
3965	been fixed, but some people still insist on making code warn-free with	4742	been fixed, but some people still insist on making code warn-free with
3966	such buggy versions.	4743	such buggy versions.
3967		4744
3968	While libev is written to generate as few warnings as possible,	4745	While libev is written to generate as few warnings as possible,
3969	"warn-free" code is not a goal, and it is recommended not to build libev	4746	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4005	I suggest using suppression lists.	4782	I suggest using suppression lists.
4006		4783
4007		4784
4008	=head1 PORTABILITY NOTES	4785	=head1 PORTABILITY NOTES
4009		4786
		4787	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4788
		4789	GNU/Linux is the only common platform that supports 64 bit file/large file
		4790	interfaces but I<disables> them by default.
		4791
		4792	That means that libev compiled in the default environment doesn't support
		4793	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4794
		4795	Unfortunately, many programs try to work around this GNU/Linux issue
		4796	by enabling the large file API, which makes them incompatible with the
		4797	standard libev compiled for their system.
		4798
		4799	Likewise, libev cannot enable the large file API itself as this would
		4800	suddenly make it incompatible to the default compile time environment,
		4801	i.e. all programs not using special compile switches.
		4802
		4803	=head2 OS/X AND DARWIN BUGS
		4804
		4805	The whole thing is a bug if you ask me - basically any system interface
		4806	you touch is broken, whether it is locales, poll, kqueue or even the
		4807	OpenGL drivers.
		4808
		4809	=head3 C<kqueue> is buggy
		4810
		4811	The kqueue syscall is broken in all known versions - most versions support
		4812	only sockets, many support pipes.
		4813
		4814	Libev tries to work around this by not using C<kqueue> by default on this
		4815	rotten platform, but of course you can still ask for it when creating a
		4816	loop - embedding a socket-only kqueue loop into a select-based one is
		4817	probably going to work well.
		4818
		4819	=head3 C<poll> is buggy
		4820
		4821	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4822	implementation by something calling C<kqueue> internally around the 10.5.6
		4823	release, so now C<kqueue> I<and> C<poll> are broken.
		4824
		4825	Libev tries to work around this by not using C<poll> by default on
		4826	this rotten platform, but of course you can still ask for it when creating
		4827	a loop.
		4828
		4829	=head3 C<select> is buggy
		4830
		4831	All that's left is C<select>, and of course Apple found a way to fuck this
		4832	one up as well: On OS/X, C<select> actively limits the number of file
		4833	descriptors you can pass in to 1024 - your program suddenly crashes when
		4834	you use more.
		4835
		4836	There is an undocumented "workaround" for this - defining
		4837	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4838	work on OS/X.
		4839
		4840	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4841
		4842	=head3 C<errno> reentrancy
		4843
		4844	The default compile environment on Solaris is unfortunately so
		4845	thread-unsafe that you can't even use components/libraries compiled
		4846	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4847	defined by default. A valid, if stupid, implementation choice.
		4848
		4849	If you want to use libev in threaded environments you have to make sure
		4850	it's compiled with C<_REENTRANT> defined.
		4851
		4852	=head3 Event port backend
		4853
		4854	The scalable event interface for Solaris is called "event
		4855	ports". Unfortunately, this mechanism is very buggy in all major
		4856	releases. If you run into high CPU usage, your program freezes or you get
		4857	a large number of spurious wakeups, make sure you have all the relevant
		4858	and latest kernel patches applied. No, I don't know which ones, but there
		4859	are multiple ones to apply, and afterwards, event ports actually work
		4860	great.
		4861
		4862	If you can't get it to work, you can try running the program by setting
		4863	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4864	C<select> backends.
		4865
		4866	=head2 AIX POLL BUG
		4867
		4868	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4869	this by trying to avoid the poll backend altogether (i.e. it's not even
		4870	compiled in), which normally isn't a big problem as C<select> works fine
		4871	with large bitsets on AIX, and AIX is dead anyway.
		4872
4010	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4873	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4874
		4875	=head3 General issues
4011		4876
4012	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4877	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4013	requires, and its I/O model is fundamentally incompatible with the POSIX	4878	requires, and its I/O model is fundamentally incompatible with the POSIX
4014	model. Libev still offers limited functionality on this platform in	4879	model. Libev still offers limited functionality on this platform in
4015	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4880	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4016	descriptors. This only applies when using Win32 natively, not when using	4881	descriptors. This only applies when using Win32 natively, not when using
4017	e.g. cygwin.	4882	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4883	as every compielr comes with a slightly differently broken/incompatible
		4884	environment.
4018		4885
4019	Lifting these limitations would basically require the full	4886	Lifting these limitations would basically require the full
4020	re-implementation of the I/O system. If you are into these kinds of	4887	re-implementation of the I/O system. If you are into this kind of thing,
4021	things, then note that glib does exactly that for you in a very portable	4888	then note that glib does exactly that for you in a very portable way (note
4022	way (note also that glib is the slowest event library known to man).	4889	also that glib is the slowest event library known to man).
4023		4890
4024	There is no supported compilation method available on windows except	4891	There is no supported compilation method available on windows except
4025	embedding it into other applications.	4892	embedding it into other applications.
4026		4893
4027	Sensible signal handling is officially unsupported by Microsoft - libev	4894	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4055	you do I<not> compile the F<ev.c> or any other embedded source files!):	4922	you do I<not> compile the F<ev.c> or any other embedded source files!):
4056		4923
4057	#include "evwrap.h"	4924	#include "evwrap.h"
4058	#include "ev.c"	4925	#include "ev.c"
4059		4926
4060	=over 4
4061
4062	=item The winsocket select function	4927	=head3 The winsocket C<select> function
4063		4928
4064	The winsocket C<select> function doesn't follow POSIX in that it	4929	The winsocket C<select> function doesn't follow POSIX in that it
4065	requires socket I<handles> and not socket I<file descriptors> (it is	4930	requires socket I<handles> and not socket I<file descriptors> (it is
4066	also extremely buggy). This makes select very inefficient, and also	4931	also extremely buggy). This makes select very inefficient, and also
4067	requires a mapping from file descriptors to socket handles (the Microsoft	4932	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4076	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4941	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4077		4942
4078	Note that winsockets handling of fd sets is O(n), so you can easily get a	4943	Note that winsockets handling of fd sets is O(n), so you can easily get a
4079	complexity in the O(n²) range when using win32.	4944	complexity in the O(n²) range when using win32.
4080		4945
4081	=item Limited number of file descriptors	4946	=head3 Limited number of file descriptors
4082		4947
4083	Windows has numerous arbitrary (and low) limits on things.	4948	Windows has numerous arbitrary (and low) limits on things.
4084		4949
4085	Early versions of winsocket's select only supported waiting for a maximum	4950	Early versions of winsocket's select only supported waiting for a maximum
4086	of C<64> handles (probably owning to the fact that all windows kernels	4951	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4101	runtime libraries. This might get you to about C<512> or C<2048> sockets	4966	runtime libraries. This might get you to about C<512> or C<2048> sockets
4102	(depending on windows version and/or the phase of the moon). To get more,	4967	(depending on windows version and/or the phase of the moon). To get more,
4103	you need to wrap all I/O functions and provide your own fd management, but	4968	you need to wrap all I/O functions and provide your own fd management, but
4104	the cost of calling select (O(n²)) will likely make this unworkable.	4969	the cost of calling select (O(n²)) will likely make this unworkable.
4105		4970
4106	=back
4107
4108	=head2 PORTABILITY REQUIREMENTS	4971	=head2 PORTABILITY REQUIREMENTS
4109		4972
4110	In addition to a working ISO-C implementation and of course the	4973	In addition to a working ISO-C implementation and of course the
4111	backend-specific APIs, libev relies on a few additional extensions:	4974	backend-specific APIs, libev relies on a few additional extensions:
4112		4975
…		…
4118	Libev assumes not only that all watcher pointers have the same internal	4981	Libev assumes not only that all watcher pointers have the same internal
4119	structure (guaranteed by POSIX but not by ISO C for example), but it also	4982	structure (guaranteed by POSIX but not by ISO C for example), but it also
4120	assumes that the same (machine) code can be used to call any watcher	4983	assumes that the same (machine) code can be used to call any watcher
4121	callback: The watcher callbacks have different type signatures, but libev	4984	callback: The watcher callbacks have different type signatures, but libev
4122	calls them using an C<ev_watcher *> internally.	4985	calls them using an C<ev_watcher *> internally.
		4986
		4987	=item pointer accesses must be thread-atomic
		4988
		4989	Accessing a pointer value must be atomic, it must both be readable and
		4990	writable in one piece - this is the case on all current architectures.
4123		4991
4124	=item C<sig_atomic_t volatile> must be thread-atomic as well	4992	=item C<sig_atomic_t volatile> must be thread-atomic as well
4125		4993
4126	The type C<sig_atomic_t volatile> (or whatever is defined as	4994	The type C<sig_atomic_t volatile> (or whatever is defined as
4127	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4995	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4150	watchers.	5018	watchers.
4151		5019
4152	=item C<double> must hold a time value in seconds with enough accuracy	5020	=item C<double> must hold a time value in seconds with enough accuracy
4153		5021
4154	The type C<double> is used to represent timestamps. It is required to	5022	The type C<double> is used to represent timestamps. It is required to
4155	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5023	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4156	enough for at least into the year 4000. This requirement is fulfilled by	5024	good enough for at least into the year 4000 with millisecond accuracy
		5025	(the design goal for libev). This requirement is overfulfilled by
4157	implementations implementing IEEE 754, which is basically all existing	5026	implementations using IEEE 754, which is basically all existing ones. With
4158	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5027	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4159	2200.
4160		5028
4161	=back	5029	=back
4162		5030
4163	If you know of other additional requirements drop me a note.	5031	If you know of other additional requirements drop me a note.
4164		5032
…		…
4232	involves iterating over all running async watchers or all signal numbers.	5100	involves iterating over all running async watchers or all signal numbers.
4233		5101
4234	=back	5102	=back
4235		5103
4236		5104
		5105	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5106
		5107	The major version 4 introduced some incompatible changes to the API.
		5108
		5109	At the moment, the C<ev.h> header file provides compatibility definitions
		5110	for all changes, so most programs should still compile. The compatibility
		5111	layer might be removed in later versions of libev, so better update to the
		5112	new API early than late.
		5113
		5114	=over 4
		5115
		5116	=item C<EV_COMPAT3> backwards compatibility mechanism
		5117
		5118	The backward compatibility mechanism can be controlled by
		5119	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5120	section.
		5121
		5122	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5123
		5124	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5125
		5126	ev_loop_destroy (EV_DEFAULT_UC);
		5127	ev_loop_fork (EV_DEFAULT);
		5128
		5129	=item function/symbol renames
		5130
		5131	A number of functions and symbols have been renamed:
		5132
		5133	ev_loop => ev_run
		5134	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5135	EVLOOP_ONESHOT => EVRUN_ONCE
		5136
		5137	ev_unloop => ev_break
		5138	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5139	EVUNLOOP_ONE => EVBREAK_ONE
		5140	EVUNLOOP_ALL => EVBREAK_ALL
		5141
		5142	EV_TIMEOUT => EV_TIMER
		5143
		5144	ev_loop_count => ev_iteration
		5145	ev_loop_depth => ev_depth
		5146	ev_loop_verify => ev_verify
		5147
		5148	Most functions working on C<struct ev_loop> objects don't have an
		5149	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5150	associated constants have been renamed to not collide with the C<struct
		5151	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5152	as all other watcher types. Note that C<ev_loop_fork> is still called
		5153	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5154	typedef.
		5155
		5156	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5157
		5158	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5159	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5160	and work, but the library code will of course be larger.
		5161
		5162	=back
		5163
		5164
4237	=head1 GLOSSARY	5165	=head1 GLOSSARY
4238		5166
4239	=over 4	5167	=over 4
4240		5168
4241	=item active	5169	=item active
4242		5170
4243	A watcher is active as long as it has been started (has been attached to	5171	A watcher is active as long as it has been started and not yet stopped.
4244	an event loop) but not yet stopped (disassociated from the event loop).	5172	See L<WATCHER STATES> for details.
4245		5173
4246	=item application	5174	=item application
4247		5175
4248	In this document, an application is whatever is using libev.	5176	In this document, an application is whatever is using libev.
		5177
		5178	=item backend
		5179
		5180	The part of the code dealing with the operating system interfaces.
4249		5181
4250	=item callback	5182	=item callback
4251		5183
4252	The address of a function that is called when some event has been	5184	The address of a function that is called when some event has been
4253	detected. Callbacks are being passed the event loop, the watcher that	5185	detected. Callbacks are being passed the event loop, the watcher that
4254	received the event, and the actual event bitset.	5186	received the event, and the actual event bitset.
4255		5187
4256	=item callback invocation	5188	=item callback/watcher invocation
4257		5189
4258	The act of calling the callback associated with a watcher.	5190	The act of calling the callback associated with a watcher.
4259		5191
4260	=item event	5192	=item event
4261		5193
4262	A change of state of some external event, such as data now being available	5194	A change of state of some external event, such as data now being available
4263	for reading on a file descriptor, time having passed or simply not having	5195	for reading on a file descriptor, time having passed or simply not having
4264	any other events happening anymore.	5196	any other events happening anymore.
4265		5197
4266	In libev, events are represented as single bits (such as C<EV_READ> or	5198	In libev, events are represented as single bits (such as C<EV_READ> or
4267	C<EV_TIMEOUT>).	5199	C<EV_TIMER>).
4268		5200
4269	=item event library	5201	=item event library
4270		5202
4271	A software package implementing an event model and loop.	5203	A software package implementing an event model and loop.
4272		5204
…		…
4280	The model used to describe how an event loop handles and processes	5212	The model used to describe how an event loop handles and processes
4281	watchers and events.	5213	watchers and events.
4282		5214
4283	=item pending	5215	=item pending
4284		5216
4285	A watcher is pending as soon as the corresponding event has been detected,	5217	A watcher is pending as soon as the corresponding event has been
4286	and stops being pending as soon as the watcher will be invoked or its	5218	detected. See L<WATCHER STATES> for details.
4287	pending status is explicitly cleared by the application.
4288
4289	A watcher can be pending, but not active. Stopping a watcher also clears
4290	its pending status.
4291		5219
4292	=item real time	5220	=item real time
4293		5221
4294	The physical time that is observed. It is apparently strictly monotonic :)	5222	The physical time that is observed. It is apparently strictly monotonic :)
4295		5223
…		…
4302	=item watcher	5230	=item watcher
4303		5231
4304	A data structure that describes interest in certain events. Watchers need	5232	A data structure that describes interest in certain events. Watchers need
4305	to be started (attached to an event loop) before they can receive events.	5233	to be started (attached to an event loop) before they can receive events.
4306		5234
4307	=item watcher invocation
4308
4309	The act of calling the callback associated with a watcher.
4310
4311	=back	5235	=back
4312		5236
4313	=head1 AUTHOR	5237	=head1 AUTHOR
4314		5238
4315	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5239	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5240	Magnusson and Emanuele Giaquinta.
4316		5241

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines