ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC vs.
Revision 1.365 by root, Mon Jan 31 00:07:21 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
…		…
856	more often than 100 times per second:	975	more often than 100 times per second:
857		976
858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	977	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	978	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		979
		980	=item ev_invoke_pending (loop)
		981
		982	This call will simply invoke all pending watchers while resetting their
		983	pending state. Normally, C<ev_run> does this automatically when required,
		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.
		994
		995	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		996
		997	This overrides the invoke pending functionality of the loop: Instead of
		998	invoking all pending watchers when there are any, C<ev_run> will call
		999	this callback instead. This is useful, for example, when you want to
		1000	invoke the actual watchers inside another context (another thread etc.).
		1001
		1002	If you want to reset the callback, use C<ev_invoke_pending> as new
		1003	callback.
		1004
		1005	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1006
		1007	Sometimes you want to share the same loop between multiple threads. This
		1008	can be done relatively simply by putting mutex_lock/unlock calls around
		1009	each call to a libev function.
		1010
		1011	However, C<ev_run> can run an indefinite time, so it is not feasible
		1012	to wait for it to return. One way around this is to wake up the event
		1013	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1014	I<release> and I<acquire> callbacks on the loop.
		1015
		1016	When set, then C<release> will be called just before the thread is
		1017	suspended waiting for new events, and C<acquire> is called just
		1018	afterwards.
		1019
		1020	Ideally, C<release> will just call your mutex_unlock function, and
		1021	C<acquire> will just call the mutex_lock function again.
		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
		1036	=item ev_set_userdata (loop, void *data)
		1037
		1038	=item void *ev_userdata (loop)
		1039
		1040	Set and retrieve a single C<void *> associated with a loop. When
		1041	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1042	C<0>.
		1043
		1044	These two functions can be used to associate arbitrary data with a loop,
		1045	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1046	C<acquire> callbacks described above, but of course can be (ab-)used for
		1047	any other purpose as well.
		1048
861	=item ev_loop_verify (loop)	1049	=item ev_verify (loop)
862		1050
863	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
864	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
865	through all internal structures and checks them for validity. If anything	1053	through all internal structures and checks them for validity. If anything
866	is found to be inconsistent, it will print an error message to standard	1054	is found to be inconsistent, it will print an error message to standard
…		…
877		1065
878	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
879	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
880	watchers and C<ev_io_start> for I/O watchers.	1068	watchers and C<ev_io_start> for I/O watchers.
881		1069
882	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
883	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
884	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:
885		1074
886	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)
887	{	1076	{
888	ev_io_stop (w);	1077	ev_io_stop (w);
889	ev_unloop (loop, EVUNLOOP_ALL);	1078	ev_break (loop, EVBREAK_ALL);
890	}	1079	}
891		1080
892	struct ev_loop *loop = ev_default_loop (0);	1081	struct ev_loop *loop = ev_default_loop (0);
893		1082
894	ev_io stdin_watcher;	1083	ev_io stdin_watcher;
895		1084
896	ev_init (&stdin_watcher, my_cb);	1085	ev_init (&stdin_watcher, my_cb);
897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1086	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
898	ev_io_start (loop, &stdin_watcher);	1087	ev_io_start (loop, &stdin_watcher);
899		1088
900	ev_loop (loop, 0);	1089	ev_run (loop, 0);
901		1090
902	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
903	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
904	stack).	1093	stack).
905		1094
906	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>
907	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).
908		1097
909	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
910	(watcher *, callback)>, which expects a callback to be provided. This	1099	*, callback)>, which expects a callback to be provided. This callback is
911	callback gets invoked each time the event occurs (or, in the case of I/O	1100	invoked each time the event occurs (or, in the case of I/O watchers, each
912	watchers, each time the event loop detects that the file descriptor given	1101	time the event loop detects that the file descriptor given is readable
913	is readable and/or writable).	1102	and/or writable).
914		1103
915	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 *, ...) >>
916	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
917	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<<
918	ev_TYPE_init (watcher *, callback, ...) >>.	1107	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
941	=item C<EV_WRITE>	1130	=item C<EV_WRITE>
942		1131
943	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
944	writable.	1133	writable.
945		1134
946	=item C<EV_TIMEOUT>	1135	=item C<EV_TIMER>
947		1136
948	The C<ev_timer> watcher has timed out.	1137	The C<ev_timer> watcher has timed out.
949		1138
950	=item C<EV_PERIODIC>	1139	=item C<EV_PERIODIC>
951		1140
…		…
969		1158
970	=item C<EV_PREPARE>	1159	=item C<EV_PREPARE>
971		1160
972	=item C<EV_CHECK>	1161	=item C<EV_CHECK>
973		1162
974	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
975	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
976	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
977	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
978	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
979	(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
980	C<ev_loop> from blocking).	1169	C<ev_run> from blocking).
981		1170
982	=item C<EV_EMBED>	1171	=item C<EV_EMBED>
983		1172
984	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.
985		1174
986	=item C<EV_FORK>	1175	=item C<EV_FORK>
987		1176
988	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
989	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>).
990		1183
991	=item C<EV_ASYNC>	1184	=item C<EV_ASYNC>
992		1185
993	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>).
994		1187
…		…
1041		1234
1042	ev_io w;	1235	ev_io w;
1043	ev_init (&w, my_cb);	1236	ev_init (&w, my_cb);
1044	ev_io_set (&w, STDIN_FILENO, EV_READ);	1237	ev_io_set (&w, STDIN_FILENO, EV_READ);
1045		1238
1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1239	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1047		1240
1048	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
1049	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
1050	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
1051	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
…		…
1064		1257
1065	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.
1066		1259
1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1260	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1068		1261
1069	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1262	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1070		1263
1071	Starts (activates) the given watcher. Only active watchers will receive	1264	Starts (activates) the given watcher. Only active watchers will receive
1072	events. If the watcher is already active nothing will happen.	1265	events. If the watcher is already active nothing will happen.
1073		1266
1074	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
1075	whole section.	1268	whole section.
1076		1269
1077	ev_io_start (EV_DEFAULT_UC, &w);	1270	ev_io_start (EV_DEFAULT_UC, &w);
1078		1271
1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1272	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1080		1273
1081	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
1082	the watcher was active or not).	1275	the watcher was active or not).
1083		1276
1084	It is possible that stopped watchers are pending - for example,	1277	It is possible that stopped watchers are pending - for example,
…		…
1109	=item ev_cb_set (ev_TYPE *watcher, callback)	1302	=item ev_cb_set (ev_TYPE *watcher, callback)
1110		1303
1111	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
1112	(modulo threads).	1305	(modulo threads).
1113		1306
1114	=item ev_set_priority (ev_TYPE *watcher, priority)	1307	=item ev_set_priority (ev_TYPE *watcher, int priority)
1115		1308
1116	=item int ev_priority (ev_TYPE *watcher)	1309	=item int ev_priority (ev_TYPE *watcher)
1117		1310
1118	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
1119	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>
…		…
1151	watcher isn't pending it does nothing and returns C<0>.	1344	watcher isn't pending it does nothing and returns C<0>.
1152		1345
1153	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
1154	callback to be invoked, which can be accomplished with this function.	1347	callback to be invoked, which can be accomplished with this function.
1155		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
1156	=back	1363	=back
1157		1364
		1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1366	OWN COMPOSITE WATCHERS> idioms.
1158		1367
1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1368	=head2 WATCHER STATES
1160		1369
1161	Each watcher has, by default, a member C<void *data> that you can change	1370	There are various watcher states mentioned throughout this manual -
1162	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
1163	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
1164	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".
1165	member, you can also "subclass" the watcher type and provide your own
1166	data:
1167		1374
1168	struct my_io	1375	=over 4
1169	{
1170	ev_io io;
1171	int otherfd;
1172	void *somedata;
1173	struct whatever *mostinteresting;
1174	};
1175		1376
1176	...	1377	=item initialiased
1177	struct my_io w;
1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
1179		1378
1180	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
1181	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.
1182		1382
1183	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
1184	{	1384	use in an event loop. It can be moved around, freed, reused etc. at
1185	struct my_io *w = (struct my_io *)w_;	1385	will - as long as you either keep the memory contents intact, or call
1186	...	1386	C<ev_TYPE_init> again.
1187	}
1188		1387
1189	More interesting and less C-conformant ways of casting your callback type	1388	=item started/running/active
1190	instead have been omitted.
1191		1389
1192	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
1193	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.
1194		1395
1195	struct my_biggy	1396	=item pending
1196	{
1197	int some_data;
1198	ev_timer t1;
1199	ev_timer t2;
1200	}
1201		1397
1202	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
1203	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
1204	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
1205	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
1206	programmers):	1402	callback.
1207		1403
1208	#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.
1209		1410
1210	static void	1411	It is also possible to feed an event on a watcher that is not active (e.g.
1211	t1_cb (EV_P_ ev_timer *w, int revents)	1412	via C<ev_feed_event>), in which case it becomes pending without being
1212	{	1413	active.
1213	struct my_biggy big = (struct my_biggy *)
1214	(((char *)w) - offsetof (struct my_biggy, t1));
1215	}
1216		1414
1217	static void	1415	=item stopped
1218	t2_cb (EV_P_ ev_timer *w, int revents)	1416
1219	{	1417	A watcher can be stopped implicitly by libev (in which case it might still
1220	struct my_biggy big = (struct my_biggy *)	1418	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1221	(((char *)w) - offsetof (struct my_biggy, t2));	1419	latter will clear any pending state the watcher might be in, regardless
1222	}	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
1223		1429
1224	=head2 WATCHER PRIORITY MODELS	1430	=head2 WATCHER PRIORITY MODELS
1225		1431
1226	Many event loops support I<watcher priorities>, which are usually small	1432	Many event loops support I<watcher priorities>, which are usually small
1227	integers that influence the ordering of event callback invocation	1433	integers that influence the ordering of event callback invocation
…		…
1270		1476
1271	For example, to emulate how many other event libraries handle priorities,	1477	For example, to emulate how many other event libraries handle priorities,
1272	you can associate an C<ev_idle> watcher to each such watcher, and in	1478	you can associate an C<ev_idle> watcher to each such watcher, and in
1273	the normal watcher callback, you just start the idle watcher. The real	1479	the normal watcher callback, you just start the idle watcher. The real
1274	processing is done in the idle watcher callback. This causes libev to	1480	processing is done in the idle watcher callback. This causes libev to
1275	continously poll and process kernel event data for the watcher, but when	1481	continuously poll and process kernel event data for the watcher, but when
1276	the lock-out case is known to be rare (which in turn is rare :), this is	1482	the lock-out case is known to be rare (which in turn is rare :), this is
1277	workable.	1483	workable.
1278		1484
1279	Usually, however, the lock-out model implemented that way will perform	1485	Usually, however, the lock-out model implemented that way will perform
1280	miserably under the type of load it was designed to handle. In that case,	1486	miserably under the type of load it was designed to handle. In that case,
…		…
1294	{	1500	{
1295	// stop the I/O watcher, we received the event, but	1501	// stop the I/O watcher, we received the event, but
1296	// are not yet ready to handle it.	1502	// are not yet ready to handle it.
1297	ev_io_stop (EV_A_ w);	1503	ev_io_stop (EV_A_ w);
1298		1504
1299	// start the idle watcher to ahndle the actual event.	1505	// start the idle watcher to handle the actual event.
1300	// it will not be executed as long as other watchers	1506	// it will not be executed as long as other watchers
1301	// with the default priority are receiving events.	1507	// with the default priority are receiving events.
1302	ev_idle_start (EV_A_ &idle);	1508	ev_idle_start (EV_A_ &idle);
1303	}	1509	}
1304		1510
…		…
1354	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
1355	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
1356	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
1357	required if you know what you are doing).	1563	required if you know what you are doing).
1358		1564
1359	If you cannot use non-blocking mode, then force the use of a
1360	known-to-be-good backend (at the time of this writing, this includes only
1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1362	descriptors for which non-blocking operation makes no sense (such as
1363	files) - libev doesn't guarentee any specific behaviour in that case.
1364
1365	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
1366	receive "spurious" readiness notifications, that is your callback might	1566	receive "spurious" readiness notifications, that is, your callback might
1367	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1567	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1368	because there is no data. Not only are some backends known to create a	1568	because there is no data. It is very easy to get into this situation even
1369	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
1370	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
1371	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1372	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1571	preferable to a program hanging until some data arrives.
1373		1572
1374	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
1375	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
1376	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
1377	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
1378	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
1379	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
1380	indefinitely.	1579	indefinitely.
1381		1580
1382	But really, best use non-blocking mode.	1581	But really, best use non-blocking mode.
1383		1582
…		…
1411		1610
1412	There is no workaround possible except not registering events	1611	There is no workaround possible except not registering events
1413	for potentially C<dup ()>'ed file descriptors, or to resort to	1612	for potentially C<dup ()>'ed file descriptors, or to resort to
1414	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1613	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1415		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
1416	=head3 The special problem of fork	1648	=head3 The special problem of fork
1417		1649
1418	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
1419	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
1420	it in the child.	1652	it in the child if you want to continue to use it in the child.
1421		1653
1422	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
1423	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
1424	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1656	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1425	C<EVBACKEND_POLL>.
1426		1657
1427	=head3 The special problem of SIGPIPE	1658	=head3 The special problem of SIGPIPE
1428		1659
1429	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>:
1430	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
…		…
1433		1664
1434	So when you encounter spurious, unexplained daemon exits, make sure you	1665	So when you encounter spurious, unexplained daemon exits, make sure you
1435	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1666	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1436	somewhere, as that would have given you a big clue).	1667	somewhere, as that would have given you a big clue).
1437		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.
1438		1707
1439	=head3 Watcher-Specific Functions	1708	=head3 Watcher-Specific Functions
1440		1709
1441	=over 4	1710	=over 4
1442		1711
…		…
1474	...	1743	...
1475	struct ev_loop *loop = ev_default_init (0);	1744	struct ev_loop *loop = ev_default_init (0);
1476	ev_io stdin_readable;	1745	ev_io stdin_readable;
1477	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);
1478	ev_io_start (loop, &stdin_readable);	1747	ev_io_start (loop, &stdin_readable);
1479	ev_loop (loop, 0);	1748	ev_run (loop, 0);
1480		1749
1481		1750
1482	=head2 C<ev_timer> - relative and optionally repeating timeouts	1751	=head2 C<ev_timer> - relative and optionally repeating timeouts
1483		1752
1484	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
…		…
1493	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
1494	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
1495	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
1496	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
1497	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
1498	no longer true when a callback calls C<ev_loop> recursively).	1767	no longer true when a callback calls C<ev_run> recursively).
1499		1768
1500	=head3 Be smart about timeouts	1769	=head3 Be smart about timeouts
1501		1770
1502	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
1503	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,
…		…
1589	ev_tstamp timeout = last_activity + 60.;	1858	ev_tstamp timeout = last_activity + 60.;
1590		1859
1591	// 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
1592	if (timeout < now)	1861	if (timeout < now)
1593	{	1862	{
1594	// timeout occured, take action	1863	// timeout occurred, take action
1595	}	1864	}
1596	else	1865	else
1597	{	1866	{
1598	// callback was invoked, but there was some activity, re-arm	1867	// callback was invoked, but there was some activity, re-arm
1599	// the watcher to fire in last_activity + 60, which is	1868	// the watcher to fire in last_activity + 60, which is
…		…
1621	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
1622	callback, which will "do the right thing" and start the timer:	1891	callback, which will "do the right thing" and start the timer:
1623		1892
1624	ev_init (timer, callback);	1893	ev_init (timer, callback);
1625	last_activity = ev_now (loop);	1894	last_activity = ev_now (loop);
1626	callback (loop, timer, EV_TIMEOUT);	1895	callback (loop, timer, EV_TIMER);
1627		1896
1628	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
1629	C<last_activity>, no libev calls at all:	1898	C<last_activity>, no libev calls at all:
1630		1899
1631	last_actiivty = ev_now (loop);	1900	last_activity = ev_now (loop);
1632		1901
1633	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
1634	time-out is unlikely to be triggered, much more efficient.	1903	time-out is unlikely to be triggered, much more efficient.
1635		1904
1636	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
…		…
1674		1943
1675	=head3 The special problem of time updates	1944	=head3 The special problem of time updates
1676		1945
1677	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
1678	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
1679	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
1680	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
1681	lots of events in one iteration.	1950	lots of events in one iteration.
1682		1951
1683	The relative timeouts are calculated relative to the C<ev_now ()>	1952	The relative timeouts are calculated relative to the C<ev_now ()>
1684	time. This is usually the right thing as this timestamp refers to the time	1953	time. This is usually the right thing as this timestamp refers to the time
…		…
1690		1959
1691	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
1692	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
1693	()>.	1962	()>.
1694		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
1695	=head3 Watcher-Specific Functions and Data Members	1994	=head3 Watcher-Specific Functions and Data Members
1696		1995
1697	=over 4	1996	=over 4
1698		1997
1699	=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)
…		…
1725	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.
1726		2025
1727	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
1728	usage example.	2027	usage example.
1729		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
1730	=item ev_tstamp repeat [read-write]	2041	=item ev_tstamp repeat [read-write]
1731		2042
1732	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
1733	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),
1734	which is also when any modifications are taken into account.	2045	which is also when any modifications are taken into account.
…		…
1759	}	2070	}
1760		2071
1761	ev_timer mytimer;	2072	ev_timer mytimer;
1762	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 */
1763	ev_timer_again (&mytimer); /* start timer */	2074	ev_timer_again (&mytimer); /* start timer */
1764	ev_loop (loop, 0);	2075	ev_run (loop, 0);
1765		2076
1766	// 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":
1767	// reset the timeout to start ticking again at 10 seconds	2078	// reset the timeout to start ticking again at 10 seconds
1768	ev_timer_again (&mytimer);	2079	ev_timer_again (&mytimer);
1769		2080
…		…
1795		2106
1796	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
1797	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
1798	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
1799	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
1800	(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).
1801		2112
1802	=head3 Watcher-Specific Functions and Data Members	2113	=head3 Watcher-Specific Functions and Data Members
1803		2114
1804	=over 4	2115	=over 4
1805		2116
…		…
1933	Example: Call a callback every hour, or, more precisely, whenever the	2244	Example: Call a callback every hour, or, more precisely, whenever the
1934	system time is divisible by 3600. The callback invocation times have	2245	system time is divisible by 3600. The callback invocation times have
1935	potentially a lot of jitter, but good long-term stability.	2246	potentially a lot of jitter, but good long-term stability.
1936		2247
1937	static void	2248	static void
1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2249	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1939	{	2250	{
1940	... 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)
1941	}	2252	}
1942		2253
1943	ev_periodic hourly_tick;	2254	ev_periodic hourly_tick;
…		…
1966		2277
1967	=head2 C<ev_signal> - signal me when a signal gets signalled!	2278	=head2 C<ev_signal> - signal me when a signal gets signalled!
1968		2279
1969	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
1970	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
1971	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
1972	normal event processing, like any other event.	2283	normal event processing, like any other event.
1973		2284
1974	If you want signals asynchronously, just use C<sigaction> as you would	2285	If you want signals to be delivered truly asynchronously, just use
1975	do without libev and forget about sharing the signal. You can even use	2286	C<sigaction> as you would do without libev and forget about sharing
1976	C<ev_async> from a signal handler to synchronously wake up an event loop.	2287	the signal. You can even use C<ev_async> from a signal handler to
		2288	synchronously wake up an event loop.
1977		2289
1978	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
1979	first watcher gets started will libev actually register a signal handler	2296	When the first watcher gets started will libev actually register something
1980	with the kernel (thus it coexists with your own signal handlers as long as	2297	with the kernel (thus it coexists with your own signal handlers as long as
1981	you don't register any with libev for the same signal). Similarly, when	2298	you don't register any with libev for the same signal).
1982	the last signal watcher for a signal is stopped, libev will reset the
1983	signal handler to SIG_DFL (regardless of what it was set to before).
1984		2299
1985	If possible and supported, libev will install its handlers with	2300	If possible and supported, libev will install its handlers with
1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2301	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1987	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
1988	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
1989	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>.
1990		2349
1991	=head3 Watcher-Specific Functions and Data Members	2350	=head3 Watcher-Specific Functions and Data Members
1992		2351
1993	=over 4	2352	=over 4
1994		2353
…		…
2010	Example: Try to exit cleanly on SIGINT.	2369	Example: Try to exit cleanly on SIGINT.
2011		2370
2012	static void	2371	static void
2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2372	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2014	{	2373	{
2015	ev_unloop (loop, EVUNLOOP_ALL);	2374	ev_break (loop, EVBREAK_ALL);
2016	}	2375	}
2017		2376
2018	ev_signal signal_watcher;	2377	ev_signal signal_watcher;
2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2378	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2020	ev_signal_start (loop, &signal_watcher);	2379	ev_signal_start (loop, &signal_watcher);
…		…
2033		2392
2034	Only the default event loop is capable of handling signals, and therefore	2393	Only the default event loop is capable of handling signals, and therefore
2035	you can only register child watchers in the default event loop.	2394	you can only register child watchers in the default event loop.
2036		2395
2037	Due to some design glitches inside libev, child watchers will always be	2396	Due to some design glitches inside libev, child watchers will always be
2038	handled at maximum priority (their priority is set to EV_MAXPRI by libev)	2397	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2398	libev)
2039		2399
2040	=head3 Process Interaction	2400	=head3 Process Interaction
2041		2401
2042	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
2043	initialised. This is necessary to guarantee proper behaviour even if	2403	initialised. This is necessary to guarantee proper behaviour even if the
2044	the first child watcher is started after the child exits. The occurrence	2404	first child watcher is started after the child exits. The occurrence
2045	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2405	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2046	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
2047	children, even ones not watched.	2407	children, even ones not watched.
2048		2408
2049	=head3 Overriding the Built-In Processing	2409	=head3 Overriding the Built-In Processing
…		…
2059	=head3 Stopping the Child Watcher	2419	=head3 Stopping the Child Watcher
2060		2420
2061	Currently, the child watcher never gets stopped, even when the	2421	Currently, the child watcher never gets stopped, even when the
2062	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
2063	callback. Future versions of libev might stop the watcher automatically	2423	callback. Future versions of libev might stop the watcher automatically
2064	when a child exit is detected.	2424	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2425	problem).
2065		2426
2066	=head3 Watcher-Specific Functions and Data Members	2427	=head3 Watcher-Specific Functions and Data Members
2067		2428
2068	=over 4	2429	=over 4
2069		2430
…		…
2404		2765
2405	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:
2406	prepare watchers get invoked before the process blocks and check watchers	2767	prepare watchers get invoked before the process blocks and check watchers
2407	afterwards.	2768	afterwards.
2408		2769
2409	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
2410	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>
2411	watchers. Other loops than the current one are fine, however. The	2772	watchers. Other loops than the current one are fine, however. The
2412	rationale behind this is that you do not need to check for recursion in	2773	rationale behind this is that you do not need to check for recursion in
2413	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2774	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2414	C<ev_check> so if you have one watcher of each kind they will always be	2775	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2582		2943
2583	if (timeout >= 0)	2944	if (timeout >= 0)
2584	// create/start timer	2945	// create/start timer
2585		2946
2586	// poll	2947	// poll
2587	ev_loop (EV_A_ 0);	2948	ev_run (EV_A_ 0);
2588		2949
2589	// stop timer again	2950	// stop timer again
2590	if (timeout >= 0)	2951	if (timeout >= 0)
2591	ev_timer_stop (EV_A_ &to);	2952	ev_timer_stop (EV_A_ &to);
2592		2953
…		…
2670	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).
2671		3032
2672	=item ev_embed_sweep (loop, ev_embed *)	3033	=item ev_embed_sweep (loop, ev_embed *)
2673		3034
2674	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
2675	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
2676	appropriate way for embedded loops.	3037	appropriate way for embedded loops.
2677		3038
2678	=item struct ev_loop *other [read-only]	3039	=item struct ev_loop *other [read-only]
2679		3040
2680	The embedded event loop.	3041	The embedded event loop.
…		…
2740	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
2741	handlers will be invoked, too, of course.	3102	handlers will be invoked, too, of course.
2742		3103
2743	=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?
2744		3105
2745	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
2746	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
2747	sequence should be handled by libev without any problems.	3108	sequence should be handled by libev without any problems.
2748		3109
2749	This changes when the application actually wants to do event handling	3110	This changes when the application actually wants to do event handling
2750	in the child, or both parent in child, in effect "continuing" after the	3111	in the child, or both parent in child, in effect "continuing" after the
…		…
2766	disadvantage of having to use multiple event loops (which do not support	3127	disadvantage of having to use multiple event loops (which do not support
2767	signal watchers).	3128	signal watchers).
2768		3129
2769	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
2770	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
2771	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3132	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2772	the default loop will "orphan" (not stop) all registered watchers, so you	3133	Destroying the default loop will "orphan" (not stop) all registered
2773	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
2774	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.
2775		3137
2776	=head3 Watcher-Specific Functions and Data Members	3138	=head3 Watcher-Specific Functions and Data Members
2777		3139
2778	=over 4	3140	=over 4
2779		3141
2780	=item ev_fork_init (ev_signal *, callback)	3142	=item ev_fork_init (ev_fork *, callback)
2781		3143
2782	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
2783	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,
2784	believe me.	3146	really.
2785		3147
2786	=back	3148	=back
2787		3149
2788		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
2789	=head2 C<ev_async> - how to wake up another event loop	3191	=head2 C<ev_async> - how to wake up an event loop
2790		3192
2791	In general, you cannot use an C<ev_loop> from multiple threads or other	3193	In general, you cannot use an C<ev_loop> from multiple threads or other
2792	asynchronous sources such as signal handlers (as opposed to multiple event	3194	asynchronous sources such as signal handlers (as opposed to multiple event
2793	loops - those are of course safe to use in different threads).	3195	loops - those are of course safe to use in different threads).
2794		3196
2795	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,
2796	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>
2797	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
2798	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.
2799	safe.
2800		3201
2801	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,
2802	too, are asynchronous in nature, and signals, too, will be compressed	3203	too, are asynchronous in nature, and signals, too, will be compressed
2803	(i.e. the number of callback invocations may be less than the number of	3204	(i.e. the number of callback invocations may be less than the number of
2804	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.
2805		3209
2806	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
2807	just the default loop.	3211	just the default loop.
2808		3212
2809	=head3 Queueing	3213	=head3 Queueing
2810		3214
2811	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
2812	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
2813	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
2814	need elaborate support such as pthreads.	3218	need elaborate support such as pthreads or unportable memory access
		3219	semantics.
2815		3220
2816	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
2817	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
2818	queue:	3223	queue:
2819		3224
…		…
2903	trust me.	3308	trust me.
2904		3309
2905	=item ev_async_send (loop, ev_async *)	3310	=item ev_async_send (loop, ev_async *)
2906		3311
2907	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3312	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2908	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3313	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3314	returns.
		3315
2909	C<ev_feed_event>, this call is safe to do from other threads, signal or	3316	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2910	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3317	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2911	section below on what exactly this means).	3318	embedding section below on what exactly this means).
2912		3319
2913	Note that, as with other watchers in libev, multiple events might get	3320	Note that, as with other watchers in libev, multiple events might get
2914	compressed into a single callback invocation (another way to look at this	3321	compressed into a single callback invocation (another way to look at this
2915	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3322	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
2916	reset when the event loop detects that).	3323	reset when the event loop detects that).
…		…
2958		3365
2959	If C<timeout> is less than 0, then no timeout watcher will be	3366	If C<timeout> is less than 0, then no timeout watcher will be
2960	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3367	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2961	repeat = 0) will be started. C<0> is a valid timeout.	3368	repeat = 0) will be started. C<0> is a valid timeout.
2962		3369
2963	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3370	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2964	passed an C<revents> set like normal event callbacks (a combination of	3371	passed an C<revents> set like normal event callbacks (a combination of
2965	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3372	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2966	value passed to C<ev_once>. Note that it is possible to receive I<both>	3373	value passed to C<ev_once>. Note that it is possible to receive I<both>
2967	a timeout and an io event at the same time - you probably should give io	3374	a timeout and an io event at the same time - you probably should give io
2968	events precedence.	3375	events precedence.
2969		3376
2970	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3377	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2971		3378
2972	static void stdin_ready (int revents, void *arg)	3379	static void stdin_ready (int revents, void *arg)
2973	{	3380	{
2974	if (revents & EV_READ)	3381	if (revents & EV_READ)
2975	/* stdin might have data for us, joy! */;	3382	/* stdin might have data for us, joy! */;
2976	else if (revents & EV_TIMEOUT)	3383	else if (revents & EV_TIMER)
2977	/* doh, nothing entered */;	3384	/* doh, nothing entered */;
2978	}	3385	}
2979		3386
2980	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3387	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2981		3388
2982	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2983
2984	Feeds the given event set into the event loop, as if the specified event
2985	had happened for the specified watcher (which must be a pointer to an
2986	initialised but not necessarily started event watcher).
2987
2988	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3389	=item ev_feed_fd_event (loop, int fd, int revents)
2989		3390
2990	Feed an event on the given fd, as if a file descriptor backend detected	3391	Feed an event on the given fd, as if a file descriptor backend detected
2991	the given events it.	3392	the given events it.
2992		3393
2993	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3394	=item ev_feed_signal_event (loop, int signum)
2994		3395
2995	Feed an event as if the given signal occurred (C<loop> must be the default	3396	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2996	loop!).	3397	which is async-safe.
2997		3398
2998	=back	3399	=back
		3400
		3401
		3402	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3403
		3404	This section explains some common idioms that are not immediately
		3405	obvious. Note that examples are sprinkled over the whole manual, and this
		3406	section only contains stuff that wouldn't fit anywhere else.
		3407
		3408	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3409
		3410	Each watcher has, by default, a C<void *data> member that you can read
		3411	or modify at any time: libev will completely ignore it. This can be used
		3412	to associate arbitrary data with your watcher. If you need more data and
		3413	don't want to allocate memory separately and store a pointer to it in that
		3414	data member, you can also "subclass" the watcher type and provide your own
		3415	data:
		3416
		3417	struct my_io
		3418	{
		3419	ev_io io;
		3420	int otherfd;
		3421	void *somedata;
		3422	struct whatever *mostinteresting;
		3423	};
		3424
		3425	...
		3426	struct my_io w;
		3427	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3428
		3429	And since your callback will be called with a pointer to the watcher, you
		3430	can cast it back to your own type:
		3431
		3432	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3433	{
		3434	struct my_io *w = (struct my_io *)w_;
		3435	...
		3436	}
		3437
		3438	More interesting and less C-conformant ways of casting your callback
		3439	function type instead have been omitted.
		3440
		3441	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3442
		3443	Another common scenario is to use some data structure with multiple
		3444	embedded watchers, in effect creating your own watcher that combines
		3445	multiple libev event sources into one "super-watcher":
		3446
		3447	struct my_biggy
		3448	{
		3449	int some_data;
		3450	ev_timer t1;
		3451	ev_timer t2;
		3452	}
		3453
		3454	In this case getting the pointer to C<my_biggy> is a bit more
		3455	complicated: Either you store the address of your C<my_biggy> struct in
		3456	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3457	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3458	real programmers):
		3459
		3460	#include <stddef.h>
		3461
		3462	static void
		3463	t1_cb (EV_P_ ev_timer *w, int revents)
		3464	{
		3465	struct my_biggy big = (struct my_biggy *)
		3466	(((char *)w) - offsetof (struct my_biggy, t1));
		3467	}
		3468
		3469	static void
		3470	t2_cb (EV_P_ ev_timer *w, int revents)
		3471	{
		3472	struct my_biggy big = (struct my_biggy *)
		3473	(((char *)w) - offsetof (struct my_biggy, t2));
		3474	}
		3475
		3476	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3477
		3478	Often (especially in GUI toolkits) there are places where you have
		3479	I<modal> interaction, which is most easily implemented by recursively
		3480	invoking C<ev_run>.
		3481
		3482	This brings the problem of exiting - a callback might want to finish the
		3483	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3484	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3485	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3486	other combination: In these cases, C<ev_break> will not work alone.
		3487
		3488	The solution is to maintain "break this loop" variable for each C<ev_run>
		3489	invocation, and use a loop around C<ev_run> until the condition is
		3490	triggered, using C<EVRUN_ONCE>:
		3491
		3492	// main loop
		3493	int exit_main_loop = 0;
		3494
		3495	while (!exit_main_loop)
		3496	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3497
		3498	// in a model watcher
		3499	int exit_nested_loop = 0;
		3500
		3501	while (!exit_nested_loop)
		3502	ev_run (EV_A_ EVRUN_ONCE);
		3503
		3504	To exit from any of these loops, just set the corresponding exit variable:
		3505
		3506	// exit modal loop
		3507	exit_nested_loop = 1;
		3508
		3509	// exit main program, after modal loop is finished
		3510	exit_main_loop = 1;
		3511
		3512	// exit both
		3513	exit_main_loop = exit_nested_loop = 1;
		3514
		3515	=head2 THREAD LOCKING EXAMPLE
		3516
		3517	Here is a fictitious example of how to run an event loop in a different
		3518	thread from where callbacks are being invoked and watchers are
		3519	created/added/removed.
		3520
		3521	For a real-world example, see the C<EV::Loop::Async> perl module,
		3522	which uses exactly this technique (which is suited for many high-level
		3523	languages).
		3524
		3525	The example uses a pthread mutex to protect the loop data, a condition
		3526	variable to wait for callback invocations, an async watcher to notify the
		3527	event loop thread and an unspecified mechanism to wake up the main thread.
		3528
		3529	First, you need to associate some data with the event loop:
		3530
		3531	typedef struct {
		3532	mutex_t lock; /* global loop lock */
		3533	ev_async async_w;
		3534	thread_t tid;
		3535	cond_t invoke_cv;
		3536	} userdata;
		3537
		3538	void prepare_loop (EV_P)
		3539	{
		3540	// for simplicity, we use a static userdata struct.
		3541	static userdata u;
		3542
		3543	ev_async_init (&u->async_w, async_cb);
		3544	ev_async_start (EV_A_ &u->async_w);
		3545
		3546	pthread_mutex_init (&u->lock, 0);
		3547	pthread_cond_init (&u->invoke_cv, 0);
		3548
		3549	// now associate this with the loop
		3550	ev_set_userdata (EV_A_ u);
		3551	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3552	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3553
		3554	// then create the thread running ev_run
		3555	pthread_create (&u->tid, 0, l_run, EV_A);
		3556	}
		3557
		3558	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3559	solely to wake up the event loop so it takes notice of any new watchers
		3560	that might have been added:
		3561
		3562	static void
		3563	async_cb (EV_P_ ev_async *w, int revents)
		3564	{
		3565	// just used for the side effects
		3566	}
		3567
		3568	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3569	protecting the loop data, respectively.
		3570
		3571	static void
		3572	l_release (EV_P)
		3573	{
		3574	userdata *u = ev_userdata (EV_A);
		3575	pthread_mutex_unlock (&u->lock);
		3576	}
		3577
		3578	static void
		3579	l_acquire (EV_P)
		3580	{
		3581	userdata *u = ev_userdata (EV_A);
		3582	pthread_mutex_lock (&u->lock);
		3583	}
		3584
		3585	The event loop thread first acquires the mutex, and then jumps straight
		3586	into C<ev_run>:
		3587
		3588	void *
		3589	l_run (void *thr_arg)
		3590	{
		3591	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3592
		3593	l_acquire (EV_A);
		3594	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3595	ev_run (EV_A_ 0);
		3596	l_release (EV_A);
		3597
		3598	return 0;
		3599	}
		3600
		3601	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3602	signal the main thread via some unspecified mechanism (signals? pipe
		3603	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3604	have been called (in a while loop because a) spurious wakeups are possible
		3605	and b) skipping inter-thread-communication when there are no pending
		3606	watchers is very beneficial):
		3607
		3608	static void
		3609	l_invoke (EV_P)
		3610	{
		3611	userdata *u = ev_userdata (EV_A);
		3612
		3613	while (ev_pending_count (EV_A))
		3614	{
		3615	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3616	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3617	}
		3618	}
		3619
		3620	Now, whenever the main thread gets told to invoke pending watchers, it
		3621	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3622	thread to continue:
		3623
		3624	static void
		3625	real_invoke_pending (EV_P)
		3626	{
		3627	userdata *u = ev_userdata (EV_A);
		3628
		3629	pthread_mutex_lock (&u->lock);
		3630	ev_invoke_pending (EV_A);
		3631	pthread_cond_signal (&u->invoke_cv);
		3632	pthread_mutex_unlock (&u->lock);
		3633	}
		3634
		3635	Whenever you want to start/stop a watcher or do other modifications to an
		3636	event loop, you will now have to lock:
		3637
		3638	ev_timer timeout_watcher;
		3639	userdata *u = ev_userdata (EV_A);
		3640
		3641	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3642
		3643	pthread_mutex_lock (&u->lock);
		3644	ev_timer_start (EV_A_ &timeout_watcher);
		3645	ev_async_send (EV_A_ &u->async_w);
		3646	pthread_mutex_unlock (&u->lock);
		3647
		3648	Note that sending the C<ev_async> watcher is required because otherwise
		3649	an event loop currently blocking in the kernel will have no knowledge
		3650	about the newly added timer. By waking up the loop it will pick up any new
		3651	watchers in the next event loop iteration.
		3652
		3653	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3654
		3655	While the overhead of a callback that e.g. schedules a thread is small, it
		3656	is still an overhead. If you embed libev, and your main usage is with some
		3657	kind of threads or coroutines, you might want to customise libev so that
		3658	doesn't need callbacks anymore.
		3659
		3660	Imagine you have coroutines that you can switch to using a function
		3661	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3662	and that due to some magic, the currently active coroutine is stored in a
		3663	global called C<current_coro>. Then you can build your own "wait for libev
		3664	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3665	the differing C<;> conventions):
		3666
		3667	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3668	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3669
		3670	That means instead of having a C callback function, you store the
		3671	coroutine to switch to in each watcher, and instead of having libev call
		3672	your callback, you instead have it switch to that coroutine.
		3673
		3674	A coroutine might now wait for an event with a function called
		3675	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3676	matter when, or whether the watcher is active or not when this function is
		3677	called):
		3678
		3679	void
		3680	wait_for_event (ev_watcher *w)
		3681	{
		3682	ev_cb_set (w) = current_coro;
		3683	switch_to (libev_coro);
		3684	}
		3685
		3686	That basically suspends the coroutine inside C<wait_for_event> and
		3687	continues the libev coroutine, which, when appropriate, switches back to
		3688	this or any other coroutine. I am sure if you sue this your own :)
		3689
		3690	You can do similar tricks if you have, say, threads with an event queue -
		3691	instead of storing a coroutine, you store the queue object and instead of
		3692	switching to a coroutine, you push the watcher onto the queue and notify
		3693	any waiters.
		3694
		3695	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3696	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3697
		3698	// my_ev.h
		3699	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3700	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3701	#include "../libev/ev.h"
		3702
		3703	// my_ev.c
		3704	#define EV_H "my_ev.h"
		3705	#include "../libev/ev.c"
		3706
		3707	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3708	F<my_ev.c> into your project. When properly specifying include paths, you
		3709	can even use F<ev.h> as header file name directly.
2999		3710
3000		3711
3001	=head1 LIBEVENT EMULATION	3712	=head1 LIBEVENT EMULATION
3002		3713
3003	Libev offers a compatibility emulation layer for libevent. It cannot	3714	Libev offers a compatibility emulation layer for libevent. It cannot
3004	emulate the internals of libevent, so here are some usage hints:	3715	emulate the internals of libevent, so here are some usage hints:
3005		3716
3006	=over 4	3717	=over 4
		3718
		3719	=item * Only the libevent-1.4.1-beta API is being emulated.
		3720
		3721	This was the newest libevent version available when libev was implemented,
		3722	and is still mostly unchanged in 2010.
3007		3723
3008	=item * Use it by including <event.h>, as usual.	3724	=item * Use it by including <event.h>, as usual.
3009		3725
3010	=item * The following members are fully supported: ev_base, ev_callback,	3726	=item * The following members are fully supported: ev_base, ev_callback,
3011	ev_arg, ev_fd, ev_res, ev_events.	3727	ev_arg, ev_fd, ev_res, ev_events.
…		…
3017	=item * Priorities are not currently supported. Initialising priorities	3733	=item * Priorities are not currently supported. Initialising priorities
3018	will fail and all watchers will have the same priority, even though there	3734	will fail and all watchers will have the same priority, even though there
3019	is an ev_pri field.	3735	is an ev_pri field.
3020		3736
3021	=item * In libevent, the last base created gets the signals, in libev, the	3737	=item * In libevent, the last base created gets the signals, in libev, the
3022	first base created (== the default loop) gets the signals.	3738	base that registered the signal gets the signals.
3023		3739
3024	=item * Other members are not supported.	3740	=item * Other members are not supported.
3025		3741
3026	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3742	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3027	to use the libev header file and library.	3743	to use the libev header file and library.
…		…
3046	Care has been taken to keep the overhead low. The only data member the C++	3762	Care has been taken to keep the overhead low. The only data member the C++
3047	classes add (compared to plain C-style watchers) is the event loop pointer	3763	classes add (compared to plain C-style watchers) is the event loop pointer
3048	that the watcher is associated with (or no additional members at all if	3764	that the watcher is associated with (or no additional members at all if
3049	you disable C<EV_MULTIPLICITY> when embedding libev).	3765	you disable C<EV_MULTIPLICITY> when embedding libev).
3050		3766
3051	Currently, functions, and static and non-static member functions can be	3767	Currently, functions, static and non-static member functions and classes
3052	used as callbacks. Other types should be easy to add as long as they only	3768	with C<operator ()> can be used as callbacks. Other types should be easy
3053	need one additional pointer for context. If you need support for other	3769	to add as long as they only need one additional pointer for context. If
3054	types of functors please contact the author (preferably after implementing	3770	you need support for other types of functors please contact the author
3055	it).	3771	(preferably after implementing it).
3056		3772
3057	Here is a list of things available in the C<ev> namespace:	3773	Here is a list of things available in the C<ev> namespace:
3058		3774
3059	=over 4	3775	=over 4
3060		3776
…		…
3078		3794
3079	=over 4	3795	=over 4
3080		3796
3081	=item ev::TYPE::TYPE ()	3797	=item ev::TYPE::TYPE ()
3082		3798
3083	=item ev::TYPE::TYPE (struct ev_loop *)	3799	=item ev::TYPE::TYPE (loop)
3084		3800
3085	=item ev::TYPE::~TYPE	3801	=item ev::TYPE::~TYPE
3086		3802
3087	The constructor (optionally) takes an event loop to associate the watcher	3803	The constructor (optionally) takes an event loop to associate the watcher
3088	with. If it is omitted, it will use C<EV_DEFAULT>.	3804	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3121	myclass obj;	3837	myclass obj;
3122	ev::io iow;	3838	ev::io iow;
3123	iow.set <myclass, &myclass::io_cb> (&obj);	3839	iow.set <myclass, &myclass::io_cb> (&obj);
3124		3840
3125	=item w->set (object *)	3841	=item w->set (object *)
3126
3127	This is an B<experimental> feature that might go away in a future version.
3128		3842
3129	This is a variation of a method callback - leaving out the method to call	3843	This is a variation of a method callback - leaving out the method to call
3130	will default the method to C<operator ()>, which makes it possible to use	3844	will default the method to C<operator ()>, which makes it possible to use
3131	functor objects without having to manually specify the C<operator ()> all	3845	functor objects without having to manually specify the C<operator ()> all
3132	the time. Incidentally, you can then also leave out the template argument	3846	the time. Incidentally, you can then also leave out the template argument
…		…
3165	Example: Use a plain function as callback.	3879	Example: Use a plain function as callback.
3166		3880
3167	static void io_cb (ev::io &w, int revents) { }	3881	static void io_cb (ev::io &w, int revents) { }
3168	iow.set <io_cb> ();	3882	iow.set <io_cb> ();
3169		3883
3170	=item w->set (struct ev_loop *)	3884	=item w->set (loop)
3171		3885
3172	Associates a different C<struct ev_loop> with this watcher. You can only	3886	Associates a different C<struct ev_loop> with this watcher. You can only
3173	do this when the watcher is inactive (and not pending either).	3887	do this when the watcher is inactive (and not pending either).
3174		3888
3175	=item w->set ([arguments])	3889	=item w->set ([arguments])
3176		3890
3177	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3891	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3178	called at least once. Unlike the C counterpart, an active watcher gets	3892	method or a suitable start method must be called at least once. Unlike the
3179	automatically stopped and restarted when reconfiguring it with this	3893	C counterpart, an active watcher gets automatically stopped and restarted
3180	method.	3894	when reconfiguring it with this method.
3181		3895
3182	=item w->start ()	3896	=item w->start ()
3183		3897
3184	Starts the watcher. Note that there is no C<loop> argument, as the	3898	Starts the watcher. Note that there is no C<loop> argument, as the
3185	constructor already stores the event loop.	3899	constructor already stores the event loop.
3186		3900
		3901	=item w->start ([arguments])
		3902
		3903	Instead of calling C<set> and C<start> methods separately, it is often
		3904	convenient to wrap them in one call. Uses the same type of arguments as
		3905	the configure C<set> method of the watcher.
		3906
3187	=item w->stop ()	3907	=item w->stop ()
3188		3908
3189	Stops the watcher if it is active. Again, no C<loop> argument.	3909	Stops the watcher if it is active. Again, no C<loop> argument.
3190		3910
3191	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3911	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3203		3923
3204	=back	3924	=back
3205		3925
3206	=back	3926	=back
3207		3927
3208	Example: Define a class with an IO and idle watcher, start one of them in	3928	Example: Define a class with two I/O and idle watchers, start the I/O
3209	the constructor.	3929	watchers in the constructor.
3210		3930
3211	class myclass	3931	class myclass
3212	{	3932	{
3213	ev::io io ; void io_cb (ev::io &w, int revents);	3933	ev::io io ; void io_cb (ev::io &w, int revents);
		3934	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3214	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3935	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3215		3936
3216	myclass (int fd)	3937	myclass (int fd)
3217	{	3938	{
3218	io .set <myclass, &myclass::io_cb > (this);	3939	io .set <myclass, &myclass::io_cb > (this);
		3940	io2 .set <myclass, &myclass::io2_cb > (this);
3219	idle.set <myclass, &myclass::idle_cb> (this);	3941	idle.set <myclass, &myclass::idle_cb> (this);
3220		3942
3221	io.start (fd, ev::READ);	3943	io.set (fd, ev::WRITE); // configure the watcher
		3944	io.start (); // start it whenever convenient
		3945
		3946	io2.start (fd, ev::READ); // set + start in one call
3222	}	3947	}
3223	};	3948	};
3224		3949
3225		3950
3226	=head1 OTHER LANGUAGE BINDINGS	3951	=head1 OTHER LANGUAGE BINDINGS
…		…
3272	=item Ocaml	3997	=item Ocaml
3273		3998
3274	Erkki Seppala has written Ocaml bindings for libev, to be found at	3999	Erkki Seppala has written Ocaml bindings for libev, to be found at
3275	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4000	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3276		4001
		4002	=item Lua
		4003
		4004	Brian Maher has written a partial interface to libev for lua (at the
		4005	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4006	L<http://github.com/brimworks/lua-ev>.
		4007
3277	=back	4008	=back
3278		4009
3279		4010
3280	=head1 MACRO MAGIC	4011	=head1 MACRO MAGIC
3281		4012
…		…
3294	loop argument"). The C<EV_A> form is used when this is the sole argument,	4025	loop argument"). The C<EV_A> form is used when this is the sole argument,
3295	C<EV_A_> is used when other arguments are following. Example:	4026	C<EV_A_> is used when other arguments are following. Example:
3296		4027
3297	ev_unref (EV_A);	4028	ev_unref (EV_A);
3298	ev_timer_add (EV_A_ watcher);	4029	ev_timer_add (EV_A_ watcher);
3299	ev_loop (EV_A_ 0);	4030	ev_run (EV_A_ 0);
3300		4031
3301	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4032	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3302	which is often provided by the following macro.	4033	which is often provided by the following macro.
3303		4034
3304	=item C<EV_P>, C<EV_P_>	4035	=item C<EV_P>, C<EV_P_>
…		…
3344	}	4075	}
3345		4076
3346	ev_check check;	4077	ev_check check;
3347	ev_check_init (&check, check_cb);	4078	ev_check_init (&check, check_cb);
3348	ev_check_start (EV_DEFAULT_ &check);	4079	ev_check_start (EV_DEFAULT_ &check);
3349	ev_loop (EV_DEFAULT_ 0);	4080	ev_run (EV_DEFAULT_ 0);
3350		4081
3351	=head1 EMBEDDING	4082	=head1 EMBEDDING
3352		4083
3353	Libev can (and often is) directly embedded into host	4084	Libev can (and often is) directly embedded into host
3354	applications. Examples of applications that embed it include the Deliantra	4085	applications. Examples of applications that embed it include the Deliantra
…		…
3434	libev.m4	4165	libev.m4
3435		4166
3436	=head2 PREPROCESSOR SYMBOLS/MACROS	4167	=head2 PREPROCESSOR SYMBOLS/MACROS
3437		4168
3438	Libev can be configured via a variety of preprocessor symbols you have to	4169	Libev can be configured via a variety of preprocessor symbols you have to
3439	define before including any of its files. The default in the absence of	4170	define before including (or compiling) any of its files. The default in
3440	autoconf is documented for every option.	4171	the absence of autoconf is documented for every option.
		4172
		4173	Symbols marked with "(h)" do not change the ABI, and can have different
		4174	values when compiling libev vs. including F<ev.h>, so it is permissible
		4175	to redefine them before including F<ev.h> without breaking compatibility
		4176	to a compiled library. All other symbols change the ABI, which means all
		4177	users of libev and the libev code itself must be compiled with compatible
		4178	settings.
3441		4179
3442	=over 4	4180	=over 4
3443		4181
		4182	=item EV_COMPAT3 (h)
		4183
		4184	Backwards compatibility is a major concern for libev. This is why this
		4185	release of libev comes with wrappers for the functions and symbols that
		4186	have been renamed between libev version 3 and 4.
		4187
		4188	You can disable these wrappers (to test compatibility with future
		4189	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4190	sources. This has the additional advantage that you can drop the C<struct>
		4191	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4192	typedef in that case.
		4193
		4194	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4195	and in some even more future version the compatibility code will be
		4196	removed completely.
		4197
3444	=item EV_STANDALONE	4198	=item EV_STANDALONE (h)
3445		4199
3446	Must always be C<1> if you do not use autoconf configuration, which	4200	Must always be C<1> if you do not use autoconf configuration, which
3447	keeps libev from including F<config.h>, and it also defines dummy	4201	keeps libev from including F<config.h>, and it also defines dummy
3448	implementations for some libevent functions (such as logging, which is not	4202	implementations for some libevent functions (such as logging, which is not
3449	supported). It will also not define any of the structs usually found in	4203	supported). It will also not define any of the structs usually found in
3450	F<event.h> that are not directly supported by the libev core alone.	4204	F<event.h> that are not directly supported by the libev core alone.
3451		4205
3452	In stanbdalone mode, libev will still try to automatically deduce the	4206	In standalone mode, libev will still try to automatically deduce the
3453	configuration, but has to be more conservative.	4207	configuration, but has to be more conservative.
3454		4208
3455	=item EV_USE_MONOTONIC	4209	=item EV_USE_MONOTONIC
3456		4210
3457	If defined to be C<1>, libev will try to detect the availability of the	4211	If defined to be C<1>, libev will try to detect the availability of the
…		…
3522	be used is the winsock select). This means that it will call	4276	be used is the winsock select). This means that it will call
3523	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4277	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3524	it is assumed that all these functions actually work on fds, even	4278	it is assumed that all these functions actually work on fds, even
3525	on win32. Should not be defined on non-win32 platforms.	4279	on win32. Should not be defined on non-win32 platforms.
3526		4280
3527	=item EV_FD_TO_WIN32_HANDLE	4281	=item EV_FD_TO_WIN32_HANDLE(fd)
3528		4282
3529	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4283	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3530	file descriptors to socket handles. When not defining this symbol (the	4284	file descriptors to socket handles. When not defining this symbol (the
3531	default), then libev will call C<_get_osfhandle>, which is usually	4285	default), then libev will call C<_get_osfhandle>, which is usually
3532	correct. In some cases, programs use their own file descriptor management,	4286	correct. In some cases, programs use their own file descriptor management,
3533	in which case they can provide this function to map fds to socket handles.	4287	in which case they can provide this function to map fds to socket handles.
		4288
		4289	=item EV_WIN32_HANDLE_TO_FD(handle)
		4290
		4291	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4292	using the standard C<_open_osfhandle> function. For programs implementing
		4293	their own fd to handle mapping, overwriting this function makes it easier
		4294	to do so. This can be done by defining this macro to an appropriate value.
		4295
		4296	=item EV_WIN32_CLOSE_FD(fd)
		4297
		4298	If programs implement their own fd to handle mapping on win32, then this
		4299	macro can be used to override the C<close> function, useful to unregister
		4300	file descriptors again. Note that the replacement function has to close
		4301	the underlying OS handle.
3534		4302
3535	=item EV_USE_POLL	4303	=item EV_USE_POLL
3536		4304
3537	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4305	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3538	backend. Otherwise it will be enabled on non-win32 platforms. It	4306	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3585	as well as for signal and thread safety in C<ev_async> watchers.	4353	as well as for signal and thread safety in C<ev_async> watchers.
3586		4354
3587	In the absence of this define, libev will use C<sig_atomic_t volatile>	4355	In the absence of this define, libev will use C<sig_atomic_t volatile>
3588	(from F<signal.h>), which is usually good enough on most platforms.	4356	(from F<signal.h>), which is usually good enough on most platforms.
3589		4357
3590	=item EV_H	4358	=item EV_H (h)
3591		4359
3592	The name of the F<ev.h> header file used to include it. The default if	4360	The name of the F<ev.h> header file used to include it. The default if
3593	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4361	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3594	used to virtually rename the F<ev.h> header file in case of conflicts.	4362	used to virtually rename the F<ev.h> header file in case of conflicts.
3595		4363
3596	=item EV_CONFIG_H	4364	=item EV_CONFIG_H (h)
3597		4365
3598	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4366	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3599	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4367	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3600	C<EV_H>, above.	4368	C<EV_H>, above.
3601		4369
3602	=item EV_EVENT_H	4370	=item EV_EVENT_H (h)
3603		4371
3604	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4372	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3605	of how the F<event.h> header can be found, the default is C<"event.h">.	4373	of how the F<event.h> header can be found, the default is C<"event.h">.
3606		4374
3607	=item EV_PROTOTYPES	4375	=item EV_PROTOTYPES (h)
3608		4376
3609	If defined to be C<0>, then F<ev.h> will not define any function	4377	If defined to be C<0>, then F<ev.h> will not define any function
3610	prototypes, but still define all the structs and other symbols. This is	4378	prototypes, but still define all the structs and other symbols. This is
3611	occasionally useful if you want to provide your own wrapper functions	4379	occasionally useful if you want to provide your own wrapper functions
3612	around libev functions.	4380	around libev functions.
…		…
3634	fine.	4402	fine.
3635		4403
3636	If your embedding application does not need any priorities, defining these	4404	If your embedding application does not need any priorities, defining these
3637	both to C<0> will save some memory and CPU.	4405	both to C<0> will save some memory and CPU.
3638		4406
3639	=item EV_PERIODIC_ENABLE	4407	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4408	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4409	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3640		4410
3641	If undefined or defined to be C<1>, then periodic timers are supported. If	4411	If undefined or defined to be C<1> (and the platform supports it), then
3642	defined to be C<0>, then they are not. Disabling them saves a few kB of	4412	the respective watcher type is supported. If defined to be C<0>, then it
3643	code.	4413	is not. Disabling watcher types mainly saves code size.
3644		4414
3645	=item EV_IDLE_ENABLE	4415	=item EV_FEATURES
3646
3647	If undefined or defined to be C<1>, then idle watchers are supported. If
3648	defined to be C<0>, then they are not. Disabling them saves a few kB of
3649	code.
3650
3651	=item EV_EMBED_ENABLE
3652
3653	If undefined or defined to be C<1>, then embed watchers are supported. If
3654	defined to be C<0>, then they are not. Embed watchers rely on most other
3655	watcher types, which therefore must not be disabled.
3656
3657	=item EV_STAT_ENABLE
3658
3659	If undefined or defined to be C<1>, then stat watchers are supported. If
3660	defined to be C<0>, then they are not.
3661
3662	=item EV_FORK_ENABLE
3663
3664	If undefined or defined to be C<1>, then fork watchers are supported. If
3665	defined to be C<0>, then they are not.
3666
3667	=item EV_ASYNC_ENABLE
3668
3669	If undefined or defined to be C<1>, then async watchers are supported. If
3670	defined to be C<0>, then they are not.
3671
3672	=item EV_MINIMAL
3673		4416
3674	If you need to shave off some kilobytes of code at the expense of some	4417	If you need to shave off some kilobytes of code at the expense of some
3675	speed, define this symbol to C<1>. Currently this is used to override some	4418	speed (but with the full API), you can define this symbol to request
3676	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4419	certain subsets of functionality. The default is to enable all features
3677	much smaller 2-heap for timer management over the default 4-heap.	4420	that can be enabled on the platform.
		4421
		4422	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4423	with some broad features you want) and then selectively re-enable
		4424	additional parts you want, for example if you want everything minimal,
		4425	but multiple event loop support, async and child watchers and the poll
		4426	backend, use this:
		4427
		4428	#define EV_FEATURES 0
		4429	#define EV_MULTIPLICITY 1
		4430	#define EV_USE_POLL 1
		4431	#define EV_CHILD_ENABLE 1
		4432	#define EV_ASYNC_ENABLE 1
		4433
		4434	The actual value is a bitset, it can be a combination of the following
		4435	values:
		4436
		4437	=over 4
		4438
		4439	=item C<1> - faster/larger code
		4440
		4441	Use larger code to speed up some operations.
		4442
		4443	Currently this is used to override some inlining decisions (enlarging the
		4444	code size by roughly 30% on amd64).
		4445
		4446	When optimising for size, use of compiler flags such as C<-Os> with
		4447	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4448	assertions.
		4449
		4450	=item C<2> - faster/larger data structures
		4451
		4452	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4453	hash table sizes and so on. This will usually further increase code size
		4454	and can additionally have an effect on the size of data structures at
		4455	runtime.
		4456
		4457	=item C<4> - full API configuration
		4458
		4459	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4460	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4461
		4462	=item C<8> - full API
		4463
		4464	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4465	details on which parts of the API are still available without this
		4466	feature, and do not complain if this subset changes over time.
		4467
		4468	=item C<16> - enable all optional watcher types
		4469
		4470	Enables all optional watcher types. If you want to selectively enable
		4471	only some watcher types other than I/O and timers (e.g. prepare,
		4472	embed, async, child...) you can enable them manually by defining
		4473	C<EV_watchertype_ENABLE> to C<1> instead.
		4474
		4475	=item C<32> - enable all backends
		4476
		4477	This enables all backends - without this feature, you need to enable at
		4478	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4479
		4480	=item C<64> - enable OS-specific "helper" APIs
		4481
		4482	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4483	default.
		4484
		4485	=back
		4486
		4487	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4488	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4489	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4490	watchers, timers and monotonic clock support.
		4491
		4492	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4493	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4494	your program might be left out as well - a binary starting a timer and an
		4495	I/O watcher then might come out at only 5Kb.
		4496
		4497	=item EV_AVOID_STDIO
		4498
		4499	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4500	functions (printf, scanf, perror etc.). This will increase the code size
		4501	somewhat, but if your program doesn't otherwise depend on stdio and your
		4502	libc allows it, this avoids linking in the stdio library which is quite
		4503	big.
		4504
		4505	Note that error messages might become less precise when this option is
		4506	enabled.
		4507
		4508	=item EV_NSIG
		4509
		4510	The highest supported signal number, +1 (or, the number of
		4511	signals): Normally, libev tries to deduce the maximum number of signals
		4512	automatically, but sometimes this fails, in which case it can be
		4513	specified. Also, using a lower number than detected (C<32> should be
		4514	good for about any system in existence) can save some memory, as libev
		4515	statically allocates some 12-24 bytes per signal number.
3678		4516
3679	=item EV_PID_HASHSIZE	4517	=item EV_PID_HASHSIZE
3680		4518
3681	C<ev_child> watchers use a small hash table to distribute workload by	4519	C<ev_child> watchers use a small hash table to distribute workload by
3682	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4520	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3683	than enough. If you need to manage thousands of children you might want to	4521	usually more than enough. If you need to manage thousands of children you
3684	increase this value (I<must> be a power of two).	4522	might want to increase this value (I<must> be a power of two).
3685		4523
3686	=item EV_INOTIFY_HASHSIZE	4524	=item EV_INOTIFY_HASHSIZE
3687		4525
3688	C<ev_stat> watchers use a small hash table to distribute workload by	4526	C<ev_stat> watchers use a small hash table to distribute workload by
3689	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4527	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3690	usually more than enough. If you need to manage thousands of C<ev_stat>	4528	disabled), usually more than enough. If you need to manage thousands of
3691	watchers you might want to increase this value (I<must> be a power of	4529	C<ev_stat> watchers you might want to increase this value (I<must> be a
3692	two).	4530	power of two).
3693		4531
3694	=item EV_USE_4HEAP	4532	=item EV_USE_4HEAP
3695		4533
3696	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4534	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3697	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4535	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3698	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4536	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3699	faster performance with many (thousands) of watchers.	4537	faster performance with many (thousands) of watchers.
3700		4538
3701	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4539	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3702	(disabled).	4540	will be C<0>.
3703		4541
3704	=item EV_HEAP_CACHE_AT	4542	=item EV_HEAP_CACHE_AT
3705		4543
3706	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4544	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3707	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4545	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3708	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4546	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3709	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4547	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3710	but avoids random read accesses on heap changes. This improves performance	4548	but avoids random read accesses on heap changes. This improves performance
3711	noticeably with many (hundreds) of watchers.	4549	noticeably with many (hundreds) of watchers.
3712		4550
3713	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4551	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3714	(disabled).	4552	will be C<0>.
3715		4553
3716	=item EV_VERIFY	4554	=item EV_VERIFY
3717		4555
3718	Controls how much internal verification (see C<ev_loop_verify ()>) will	4556	Controls how much internal verification (see C<ev_verify ()>) will
3719	be done: If set to C<0>, no internal verification code will be compiled	4557	be done: If set to C<0>, no internal verification code will be compiled
3720	in. If set to C<1>, then verification code will be compiled in, but not	4558	in. If set to C<1>, then verification code will be compiled in, but not
3721	called. If set to C<2>, then the internal verification code will be	4559	called. If set to C<2>, then the internal verification code will be
3722	called once per loop, which can slow down libev. If set to C<3>, then the	4560	called once per loop, which can slow down libev. If set to C<3>, then the
3723	verification code will be called very frequently, which will slow down	4561	verification code will be called very frequently, which will slow down
3724	libev considerably.	4562	libev considerably.
3725		4563
3726	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4564	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3727	C<0>.	4565	will be C<0>.
3728		4566
3729	=item EV_COMMON	4567	=item EV_COMMON
3730		4568
3731	By default, all watchers have a C<void *data> member. By redefining	4569	By default, all watchers have a C<void *data> member. By redefining
3732	this macro to a something else you can include more and other types of	4570	this macro to something else you can include more and other types of
3733	members. You have to define it each time you include one of the files,	4571	members. You have to define it each time you include one of the files,
3734	though, and it must be identical each time.	4572	though, and it must be identical each time.
3735		4573
3736	For example, the perl EV module uses something like this:	4574	For example, the perl EV module uses something like this:
3737		4575
…		…
3790	file.	4628	file.
3791		4629
3792	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4630	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3793	that everybody includes and which overrides some configure choices:	4631	that everybody includes and which overrides some configure choices:
3794		4632
3795	#define EV_MINIMAL 1	4633	#define EV_FEATURES 8
3796	#define EV_USE_POLL 0	4634	#define EV_USE_SELECT 1
3797	#define EV_MULTIPLICITY 0
3798	#define EV_PERIODIC_ENABLE 0	4635	#define EV_PREPARE_ENABLE 1
		4636	#define EV_IDLE_ENABLE 1
3799	#define EV_STAT_ENABLE 0	4637	#define EV_SIGNAL_ENABLE 1
3800	#define EV_FORK_ENABLE 0	4638	#define EV_CHILD_ENABLE 1
		4639	#define EV_USE_STDEXCEPT 0
3801	#define EV_CONFIG_H <config.h>	4640	#define EV_CONFIG_H <config.h>
3802	#define EV_MINPRI 0
3803	#define EV_MAXPRI 0
3804		4641
3805	#include "ev++.h"	4642	#include "ev++.h"
3806		4643
3807	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4644	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3808		4645
3809	#include "ev_cpp.h"	4646	#include "ev_cpp.h"
3810	#include "ev.c"	4647	#include "ev.c"
3811		4648
3812	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4649	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3813		4650
3814	=head2 THREADS AND COROUTINES	4651	=head2 THREADS AND COROUTINES
3815		4652
3816	=head3 THREADS	4653	=head3 THREADS
3817		4654
…		…
3868	default loop and triggering an C<ev_async> watcher from the default loop	4705	default loop and triggering an C<ev_async> watcher from the default loop
3869	watcher callback into the event loop interested in the signal.	4706	watcher callback into the event loop interested in the signal.
3870		4707
3871	=back	4708	=back
3872		4709
		4710	See also L<THREAD LOCKING EXAMPLE>.
		4711
3873	=head3 COROUTINES	4712	=head3 COROUTINES
3874		4713
3875	Libev is very accommodating to coroutines ("cooperative threads"):	4714	Libev is very accommodating to coroutines ("cooperative threads"):
3876	libev fully supports nesting calls to its functions from different	4715	libev fully supports nesting calls to its functions from different
3877	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4716	coroutines (e.g. you can call C<ev_run> on the same loop from two
3878	different coroutines, and switch freely between both coroutines running the	4717	different coroutines, and switch freely between both coroutines running
3879	loop, as long as you don't confuse yourself). The only exception is that	4718	the loop, as long as you don't confuse yourself). The only exception is
3880	you must not do this from C<ev_periodic> reschedule callbacks.	4719	that you must not do this from C<ev_periodic> reschedule callbacks.
3881		4720
3882	Care has been taken to ensure that libev does not keep local state inside	4721	Care has been taken to ensure that libev does not keep local state inside
3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4722	C<ev_run>, and other calls do not usually allow for coroutine switches as
3884	they do not call any callbacks.	4723	they do not call any callbacks.
3885		4724
3886	=head2 COMPILER WARNINGS	4725	=head2 COMPILER WARNINGS
3887		4726
3888	Depending on your compiler and compiler settings, you might get no or a	4727	Depending on your compiler and compiler settings, you might get no or a
…		…
3899	maintainable.	4738	maintainable.
3900		4739
3901	And of course, some compiler warnings are just plain stupid, or simply	4740	And of course, some compiler warnings are just plain stupid, or simply
3902	wrong (because they don't actually warn about the condition their message	4741	wrong (because they don't actually warn about the condition their message
3903	seems to warn about). For example, certain older gcc versions had some	4742	seems to warn about). For example, certain older gcc versions had some
3904	warnings that resulted an extreme number of false positives. These have	4743	warnings that resulted in an extreme number of false positives. These have
3905	been fixed, but some people still insist on making code warn-free with	4744	been fixed, but some people still insist on making code warn-free with
3906	such buggy versions.	4745	such buggy versions.
3907		4746
3908	While libev is written to generate as few warnings as possible,	4747	While libev is written to generate as few warnings as possible,
3909	"warn-free" code is not a goal, and it is recommended not to build libev	4748	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3945	I suggest using suppression lists.	4784	I suggest using suppression lists.
3946		4785
3947		4786
3948	=head1 PORTABILITY NOTES	4787	=head1 PORTABILITY NOTES
3949		4788
		4789	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4790
		4791	GNU/Linux is the only common platform that supports 64 bit file/large file
		4792	interfaces but I<disables> them by default.
		4793
		4794	That means that libev compiled in the default environment doesn't support
		4795	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4796
		4797	Unfortunately, many programs try to work around this GNU/Linux issue
		4798	by enabling the large file API, which makes them incompatible with the
		4799	standard libev compiled for their system.
		4800
		4801	Likewise, libev cannot enable the large file API itself as this would
		4802	suddenly make it incompatible to the default compile time environment,
		4803	i.e. all programs not using special compile switches.
		4804
		4805	=head2 OS/X AND DARWIN BUGS
		4806
		4807	The whole thing is a bug if you ask me - basically any system interface
		4808	you touch is broken, whether it is locales, poll, kqueue or even the
		4809	OpenGL drivers.
		4810
		4811	=head3 C<kqueue> is buggy
		4812
		4813	The kqueue syscall is broken in all known versions - most versions support
		4814	only sockets, many support pipes.
		4815
		4816	Libev tries to work around this by not using C<kqueue> by default on this
		4817	rotten platform, but of course you can still ask for it when creating a
		4818	loop - embedding a socket-only kqueue loop into a select-based one is
		4819	probably going to work well.
		4820
		4821	=head3 C<poll> is buggy
		4822
		4823	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4824	implementation by something calling C<kqueue> internally around the 10.5.6
		4825	release, so now C<kqueue> I<and> C<poll> are broken.
		4826
		4827	Libev tries to work around this by not using C<poll> by default on
		4828	this rotten platform, but of course you can still ask for it when creating
		4829	a loop.
		4830
		4831	=head3 C<select> is buggy
		4832
		4833	All that's left is C<select>, and of course Apple found a way to fuck this
		4834	one up as well: On OS/X, C<select> actively limits the number of file
		4835	descriptors you can pass in to 1024 - your program suddenly crashes when
		4836	you use more.
		4837
		4838	There is an undocumented "workaround" for this - defining
		4839	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4840	work on OS/X.
		4841
		4842	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4843
		4844	=head3 C<errno> reentrancy
		4845
		4846	The default compile environment on Solaris is unfortunately so
		4847	thread-unsafe that you can't even use components/libraries compiled
		4848	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4849	defined by default. A valid, if stupid, implementation choice.
		4850
		4851	If you want to use libev in threaded environments you have to make sure
		4852	it's compiled with C<_REENTRANT> defined.
		4853
		4854	=head3 Event port backend
		4855
		4856	The scalable event interface for Solaris is called "event
		4857	ports". Unfortunately, this mechanism is very buggy in all major
		4858	releases. If you run into high CPU usage, your program freezes or you get
		4859	a large number of spurious wakeups, make sure you have all the relevant
		4860	and latest kernel patches applied. No, I don't know which ones, but there
		4861	are multiple ones to apply, and afterwards, event ports actually work
		4862	great.
		4863
		4864	If you can't get it to work, you can try running the program by setting
		4865	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4866	C<select> backends.
		4867
		4868	=head2 AIX POLL BUG
		4869
		4870	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4871	this by trying to avoid the poll backend altogether (i.e. it's not even
		4872	compiled in), which normally isn't a big problem as C<select> works fine
		4873	with large bitsets on AIX, and AIX is dead anyway.
		4874
3950	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4875	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4876
		4877	=head3 General issues
3951		4878
3952	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4879	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3953	requires, and its I/O model is fundamentally incompatible with the POSIX	4880	requires, and its I/O model is fundamentally incompatible with the POSIX
3954	model. Libev still offers limited functionality on this platform in	4881	model. Libev still offers limited functionality on this platform in
3955	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4882	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3956	descriptors. This only applies when using Win32 natively, not when using	4883	descriptors. This only applies when using Win32 natively, not when using
3957	e.g. cygwin.	4884	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4885	as every compielr comes with a slightly differently broken/incompatible
		4886	environment.
3958		4887
3959	Lifting these limitations would basically require the full	4888	Lifting these limitations would basically require the full
3960	re-implementation of the I/O system. If you are into these kinds of	4889	re-implementation of the I/O system. If you are into this kind of thing,
3961	things, then note that glib does exactly that for you in a very portable	4890	then note that glib does exactly that for you in a very portable way (note
3962	way (note also that glib is the slowest event library known to man).	4891	also that glib is the slowest event library known to man).
3963		4892
3964	There is no supported compilation method available on windows except	4893	There is no supported compilation method available on windows except
3965	embedding it into other applications.	4894	embedding it into other applications.
3966		4895
3967	Sensible signal handling is officially unsupported by Microsoft - libev	4896	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
3995	you do I<not> compile the F<ev.c> or any other embedded source files!):	4924	you do I<not> compile the F<ev.c> or any other embedded source files!):
3996		4925
3997	#include "evwrap.h"	4926	#include "evwrap.h"
3998	#include "ev.c"	4927	#include "ev.c"
3999		4928
4000	=over 4
4001
4002	=item The winsocket select function	4929	=head3 The winsocket C<select> function
4003		4930
4004	The winsocket C<select> function doesn't follow POSIX in that it	4931	The winsocket C<select> function doesn't follow POSIX in that it
4005	requires socket I<handles> and not socket I<file descriptors> (it is	4932	requires socket I<handles> and not socket I<file descriptors> (it is
4006	also extremely buggy). This makes select very inefficient, and also	4933	also extremely buggy). This makes select very inefficient, and also
4007	requires a mapping from file descriptors to socket handles (the Microsoft	4934	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4016	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4943	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4017		4944
4018	Note that winsockets handling of fd sets is O(n), so you can easily get a	4945	Note that winsockets handling of fd sets is O(n), so you can easily get a
4019	complexity in the O(n²) range when using win32.	4946	complexity in the O(n²) range when using win32.
4020		4947
4021	=item Limited number of file descriptors	4948	=head3 Limited number of file descriptors
4022		4949
4023	Windows has numerous arbitrary (and low) limits on things.	4950	Windows has numerous arbitrary (and low) limits on things.
4024		4951
4025	Early versions of winsocket's select only supported waiting for a maximum	4952	Early versions of winsocket's select only supported waiting for a maximum
4026	of C<64> handles (probably owning to the fact that all windows kernels	4953	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4041	runtime libraries. This might get you to about C<512> or C<2048> sockets	4968	runtime libraries. This might get you to about C<512> or C<2048> sockets
4042	(depending on windows version and/or the phase of the moon). To get more,	4969	(depending on windows version and/or the phase of the moon). To get more,
4043	you need to wrap all I/O functions and provide your own fd management, but	4970	you need to wrap all I/O functions and provide your own fd management, but
4044	the cost of calling select (O(n²)) will likely make this unworkable.	4971	the cost of calling select (O(n²)) will likely make this unworkable.
4045		4972
4046	=back
4047
4048	=head2 PORTABILITY REQUIREMENTS	4973	=head2 PORTABILITY REQUIREMENTS
4049		4974
4050	In addition to a working ISO-C implementation and of course the	4975	In addition to a working ISO-C implementation and of course the
4051	backend-specific APIs, libev relies on a few additional extensions:	4976	backend-specific APIs, libev relies on a few additional extensions:
4052		4977
…		…
4058	Libev assumes not only that all watcher pointers have the same internal	4983	Libev assumes not only that all watcher pointers have the same internal
4059	structure (guaranteed by POSIX but not by ISO C for example), but it also	4984	structure (guaranteed by POSIX but not by ISO C for example), but it also
4060	assumes that the same (machine) code can be used to call any watcher	4985	assumes that the same (machine) code can be used to call any watcher
4061	callback: The watcher callbacks have different type signatures, but libev	4986	callback: The watcher callbacks have different type signatures, but libev
4062	calls them using an C<ev_watcher *> internally.	4987	calls them using an C<ev_watcher *> internally.
		4988
		4989	=item pointer accesses must be thread-atomic
		4990
		4991	Accessing a pointer value must be atomic, it must both be readable and
		4992	writable in one piece - this is the case on all current architectures.
4063		4993
4064	=item C<sig_atomic_t volatile> must be thread-atomic as well	4994	=item C<sig_atomic_t volatile> must be thread-atomic as well
4065		4995
4066	The type C<sig_atomic_t volatile> (or whatever is defined as	4996	The type C<sig_atomic_t volatile> (or whatever is defined as
4067	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4997	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4090	watchers.	5020	watchers.
4091		5021
4092	=item C<double> must hold a time value in seconds with enough accuracy	5022	=item C<double> must hold a time value in seconds with enough accuracy
4093		5023
4094	The type C<double> is used to represent timestamps. It is required to	5024	The type C<double> is used to represent timestamps. It is required to
4095	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5025	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4096	enough for at least into the year 4000. This requirement is fulfilled by	5026	good enough for at least into the year 4000 with millisecond accuracy
		5027	(the design goal for libev). This requirement is overfulfilled by
4097	implementations implementing IEEE 754, which is basically all existing	5028	implementations using IEEE 754, which is basically all existing ones. With
4098	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5029	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4099	2200.
4100		5030
4101	=back	5031	=back
4102		5032
4103	If you know of other additional requirements drop me a note.	5033	If you know of other additional requirements drop me a note.
4104		5034
…		…
4172	involves iterating over all running async watchers or all signal numbers.	5102	involves iterating over all running async watchers or all signal numbers.
4173		5103
4174	=back	5104	=back
4175		5105
4176		5106
		5107	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5108
		5109	The major version 4 introduced some incompatible changes to the API.
		5110
		5111	At the moment, the C<ev.h> header file provides compatibility definitions
		5112	for all changes, so most programs should still compile. The compatibility
		5113	layer might be removed in later versions of libev, so better update to the
		5114	new API early than late.
		5115
		5116	=over 4
		5117
		5118	=item C<EV_COMPAT3> backwards compatibility mechanism
		5119
		5120	The backward compatibility mechanism can be controlled by
		5121	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5122	section.
		5123
		5124	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5125
		5126	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5127
		5128	ev_loop_destroy (EV_DEFAULT_UC);
		5129	ev_loop_fork (EV_DEFAULT);
		5130
		5131	=item function/symbol renames
		5132
		5133	A number of functions and symbols have been renamed:
		5134
		5135	ev_loop => ev_run
		5136	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5137	EVLOOP_ONESHOT => EVRUN_ONCE
		5138
		5139	ev_unloop => ev_break
		5140	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5141	EVUNLOOP_ONE => EVBREAK_ONE
		5142	EVUNLOOP_ALL => EVBREAK_ALL
		5143
		5144	EV_TIMEOUT => EV_TIMER
		5145
		5146	ev_loop_count => ev_iteration
		5147	ev_loop_depth => ev_depth
		5148	ev_loop_verify => ev_verify
		5149
		5150	Most functions working on C<struct ev_loop> objects don't have an
		5151	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5152	associated constants have been renamed to not collide with the C<struct
		5153	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5154	as all other watcher types. Note that C<ev_loop_fork> is still called
		5155	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5156	typedef.
		5157
		5158	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5159
		5160	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5161	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5162	and work, but the library code will of course be larger.
		5163
		5164	=back
		5165
		5166
4177	=head1 GLOSSARY	5167	=head1 GLOSSARY
4178		5168
4179	=over 4	5169	=over 4
4180		5170
4181	=item active	5171	=item active
4182		5172
4183	A watcher is active as long as it has been started (has been attached to	5173	A watcher is active as long as it has been started and not yet stopped.
4184	an event loop) but not yet stopped (disassociated from the event loop).	5174	See L<WATCHER STATES> for details.
4185		5175
4186	=item application	5176	=item application
4187		5177
4188	In this document, an application is whatever is using libev.	5178	In this document, an application is whatever is using libev.
		5179
		5180	=item backend
		5181
		5182	The part of the code dealing with the operating system interfaces.
4189		5183
4190	=item callback	5184	=item callback
4191		5185
4192	The address of a function that is called when some event has been	5186	The address of a function that is called when some event has been
4193	detected. Callbacks are being passed the event loop, the watcher that	5187	detected. Callbacks are being passed the event loop, the watcher that
4194	received the event, and the actual event bitset.	5188	received the event, and the actual event bitset.
4195		5189
4196	=item callback invocation	5190	=item callback/watcher invocation
4197		5191
4198	The act of calling the callback associated with a watcher.	5192	The act of calling the callback associated with a watcher.
4199		5193
4200	=item event	5194	=item event
4201		5195
4202	A change of state of some external event, such as data now being available	5196	A change of state of some external event, such as data now being available
4203	for reading on a file descriptor, time having passed or simply not having	5197	for reading on a file descriptor, time having passed or simply not having
4204	any other events happening anymore.	5198	any other events happening anymore.
4205		5199
4206	In libev, events are represented as single bits (such as C<EV_READ> or	5200	In libev, events are represented as single bits (such as C<EV_READ> or
4207	C<EV_TIMEOUT>).	5201	C<EV_TIMER>).
4208		5202
4209	=item event library	5203	=item event library
4210		5204
4211	A software package implementing an event model and loop.	5205	A software package implementing an event model and loop.
4212		5206
…		…
4220	The model used to describe how an event loop handles and processes	5214	The model used to describe how an event loop handles and processes
4221	watchers and events.	5215	watchers and events.
4222		5216
4223	=item pending	5217	=item pending
4224		5218
4225	A watcher is pending as soon as the corresponding event has been detected,	5219	A watcher is pending as soon as the corresponding event has been
4226	and stops being pending as soon as the watcher will be invoked or its	5220	detected. See L<WATCHER STATES> for details.
4227	pending status is explicitly cleared by the application.
4228
4229	A watcher can be pending, but not active. Stopping a watcher also clears
4230	its pending status.
4231		5221
4232	=item real time	5222	=item real time
4233		5223
4234	The physical time that is observed. It is apparently strictly monotonic :)	5224	The physical time that is observed. It is apparently strictly monotonic :)
4235		5225
…		…
4242	=item watcher	5232	=item watcher
4243		5233
4244	A data structure that describes interest in certain events. Watchers need	5234	A data structure that describes interest in certain events. Watchers need
4245	to be started (attached to an event loop) before they can receive events.	5235	to be started (attached to an event loop) before they can receive events.
4246		5236
4247	=item watcher invocation
4248
4249	The act of calling the callback associated with a watcher.
4250
4251	=back	5237	=back
4252		5238
4253	=head1 AUTHOR	5239	=head1 AUTHOR
4254		5240
4255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5241	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5242	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4256		5243

Diff Legend

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