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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// unloop was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
68		70
69	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
70	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		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
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		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>.
		90
		91	=head1 ABOUT LIBEV
72		92
73	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
74	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
75	these event sources and provide your program with events.	95	these event sources and provide your program with events.
76		96
…		…
86	=head2 FEATURES	106	=head2 FEATURES
87		107
88	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
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
90	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
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	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
96	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
97	(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>).
98		119
99	It also is quite fast (see this	120	It also is quite fast (see this
100	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
101	for example).	122	for example).
102		123
…		…
105	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)
106	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
108	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
109	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
110	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
111	this argument.	132	this argument.
112		133
113	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
114		135
115	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
118	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
119	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
120	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
121	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
122	throughout libev.	144	time differences (e.g. delays) throughout libev.
123		145
124	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
125		147
126	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	149	and internal errors (bugs).
…		…
151		173
152	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
153		175
154	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
155	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
156	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>.
157		180
158	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
159		182
160	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
161	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
…		…
178	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
179	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
180	not a problem.	203	not a problem.
181		204
182	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
183	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
184		208
185	assert (("libev version mismatch",	209	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
188		212
…		…
199	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
201		225
202	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
203		227
204	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
205	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
206	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
207	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
208	(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
209	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
210		235
211	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
212		237
213	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
214	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
215	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
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
218		243
219	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
220		245
221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
222		247
223	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
224	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
225	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
226	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
…		…
252	}	277	}
253		278
254	...	279	...
255	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
256		281
257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
258		283
259	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
260	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
261	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
262	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
…		…
274	}	299	}
275		300
276	...	301	...
277	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
278		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
279	=back	317	=back
280		318
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		320
283	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
284	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
285	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
286		324
287	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
288	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
289	not.	327	do not.
290		328
291	=over 4	329	=over 4
292		330
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		332
295	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
296	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
297	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
298	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".
299		343
300	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
301	function.	345	function (or via the C<EV_DEFAULT> macro).
302		346
303	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
304	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
305	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).
306		351
307	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,
308	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
309	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
310	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
311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	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.
313		376
314	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
315	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>).
316		379
317	The following flags are supported:	380	The following flags are supported:
…		…
332	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
333	around bugs.	396	around bugs.
334		397
335	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
336		399
337	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
338	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.
339	enabling this flag.
340		402
341	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,
342	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
343	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
344	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
…		…
350	flag.	412	flag.
351		413
352	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>
353	environment variable.	415	environment variable.
354		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	This flag's behaviour will become the default in future versions of libev.
		448
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		450
357	This is your standard select(2) backend. Not I<completely> standard, as	451	This is your standard select(2) backend. Not I<completely> standard, as
358	libev tries to roll its own fd_set with no limits on the number of fds,	452	libev tries to roll its own fd_set with no limits on the number of fds,
359	but if that fails, expect a fairly low limit on the number of fds when	453	but if that fails, expect a fairly low limit on the number of fds when
…		…
383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		479
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
387		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
		484
388	For few fds, this backend is a bit little slower than poll and select,	485	For few fds, this backend is a bit little slower than poll and select,
389	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
390	like O(total_fds) where n is the total number of fds (or the highest fd),	487	like O(total_fds) where n is the total number of fds (or the highest fd),
391	epoll scales either O(1) or O(active_fds).	488	epoll scales either O(1) or O(active_fds).
392		489
393	The epoll mechanism deserves honorable mention as the most misdesigned	490	The epoll mechanism deserves honorable mention as the most misdesigned
394	of the more advanced event mechanisms: mere annoyances include silently	491	of the more advanced event mechanisms: mere annoyances include silently
395	dropping file descriptors, requiring a system call per change per file	492	dropping file descriptors, requiring a system call per change per file
396	descriptor (and unnecessary guessing of parameters), problems with dup and	493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
397	so on. The biggest issue is fork races, however - if a program forks then	496	0.1ms) and so on. The biggest issue is fork races, however - if a program
398	I<both> parent and child process have to recreate the epoll set, which can	497	forks then I<both> parent and child process have to recreate the epoll
399	take considerable time (one syscall per file descriptor) and is of course	498	set, which can take considerable time (one syscall per file descriptor)
400	hard to detect.	499	and is of course hard to detect.
401		500
402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
403	of course I<doesn't>, and epoll just loves to report events for totally	502	of course I<doesn't>, and epoll just loves to report events for totally
404	I<different> file descriptors (even already closed ones, so one cannot	503	I<different> file descriptors (even already closed ones, so one cannot
405	even remove them from the set) than registered in the set (especially	504	even remove them from the set) than registered in the set (especially
406	on SMP systems). Libev tries to counter these spurious notifications by	505	on SMP systems). Libev tries to counter these spurious notifications by
407	employing an additional generation counter and comparing that against the	506	employing an additional generation counter and comparing that against the
408	events to filter out spurious ones, recreating the set when required.	507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms.
409		512
410	While stopping, setting and starting an I/O watcher in the same iteration	513	While stopping, setting and starting an I/O watcher in the same iteration
411	will result in some caching, there is still a system call per such	514	will result in some caching, there is still a system call per such
412	incident (because the same I<file descriptor> could point to a different	515	incident (because the same I<file descriptor> could point to a different
413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	516	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	582	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
480		583
481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	584	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
482	it's really slow, but it still scales very well (O(active_fds)).	585	it's really slow, but it still scales very well (O(active_fds)).
483		586
484	Please note that Solaris event ports can deliver a lot of spurious
485	notifications, so you need to use non-blocking I/O or other means to avoid
486	blocking when no data (or space) is available.
487
488	While this backend scales well, it requires one system call per active	587	While this backend scales well, it requires one system call per active
489	file descriptor per loop iteration. For small and medium numbers of file	588	file descriptor per loop iteration. For small and medium numbers of file
490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	589	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
491	might perform better.	590	might perform better.
492		591
493	On the positive side, with the exception of the spurious readiness	592	On the positive side, this backend actually performed fully to
494	notifications, this backend actually performed fully to specification
495	in all tests and is fully embeddable, which is a rare feat among the	593	specification in all tests and is fully embeddable, which is a rare feat
496	OS-specific backends (I vastly prefer correctness over speed hacks).	594	among the OS-specific backends (I vastly prefer correctness over speed
		595	hacks).
		596
		597	On the negative side, the interface is I<bizarre>, with the event polling
		598	function sometimes returning events to the caller even though an error
		599	occured, but with no indication whether it has done so or not (yes, it's
		600	even documented that way) - deadly for edge-triggered interfaces, but
		601	fortunately libev seems to be able to work around it.
497		602
498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	603	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
499	C<EVBACKEND_POLL>.	604	C<EVBACKEND_POLL>.
500		605
501	=item C<EVBACKEND_ALL>	606	=item C<EVBACKEND_ALL>
502		607
503	Try all backends (even potentially broken ones that wouldn't be tried	608	Try all backends (even potentially broken ones that wouldn't be tried
504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	609	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	610	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		611
507	It is definitely not recommended to use this flag.	612	It is definitely not recommended to use this flag, use whatever
		613	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		614	at all.
		615
		616	=item C<EVBACKEND_MASK>
		617
		618	Not a backend at all, but a mask to select all backend bits from a
		619	C<flags> value, in case you want to mask out any backends from a flags
		620	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		621
509	=back	622	=back
510		623
511	If one or more of these are or'ed into the flags value, then only these	624	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	625	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	626	here). If none are specified, all backends in C<ev_recommended_backends
514		627	()> will be tried.
515	Example: This is the most typical usage.
516
517	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519
520	Example: Restrict libev to the select and poll backends, and do not allow
521	environment settings to be taken into account:
522
523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
524
525	Example: Use whatever libev has to offer, but make sure that kqueue is
526	used if available (warning, breaks stuff, best use only with your own
527	private event loop and only if you know the OS supports your types of
528	fds):
529
530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
531
532	=item struct ev_loop *ev_loop_new (unsigned int flags)
533
534	Similar to C<ev_default_loop>, but always creates a new event loop that is
535	always distinct from the default loop. Unlike the default loop, it cannot
536	handle signal and child watchers, and attempts to do so will be greeted by
537	undefined behaviour (or a failed assertion if assertions are enabled).
538
539	Note that this function I<is> thread-safe, and the recommended way to use
540	libev with threads is indeed to create one loop per thread, and using the
541	default loop in the "main" or "initial" thread.
542		628
543	Example: Try to create a event loop that uses epoll and nothing else.	629	Example: Try to create a event loop that uses epoll and nothing else.
544		630
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	631	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	632	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	633	fatal ("no epoll found here, maybe it hides under your chair");
548		634
		635	Example: Use whatever libev has to offer, but make sure that kqueue is
		636	used if available.
		637
		638	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		639
549	=item ev_default_destroy ()	640	=item ev_loop_destroy (loop)
550		641
551	Destroys the default loop again (frees all memory and kernel state	642	Destroys an event loop object (frees all memory and kernel state
552	etc.). None of the active event watchers will be stopped in the normal	643	etc.). None of the active event watchers will be stopped in the normal
553	sense, so e.g. C<ev_is_active> might still return true. It is your	644	sense, so e.g. C<ev_is_active> might still return true. It is your
554	responsibility to either stop all watchers cleanly yourself I<before>	645	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	646	calling this function, or cope with the fact afterwards (which is usually
556	the easiest thing, you can just ignore the watchers and/or C<free ()> them	647	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		649
559	Note that certain global state, such as signal state (and installed signal	650	Note that certain global state, such as signal state (and installed signal
560	handlers), will not be freed by this function, and related watchers (such	651	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	652	as signal and child watchers) would need to be stopped manually.
562		653
563	In general it is not advisable to call this function except in the	654	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	655	C<ev_loop_new>, but it can also be used on the default loop returned by
		656	C<ev_default_loop>, in which case it is not thread-safe.
		657
		658	Note that it is not advisable to call this function on the default loop
		659	except in the rare occasion where you really need to free its resources.
565	pipe fds. If you need dynamically allocated loops it is better to use	660	If you need dynamically allocated loops it is better to use C<ev_loop_new>
566	C<ev_loop_new> and C<ev_loop_destroy>).	661	and C<ev_loop_destroy>.
567		662
568	=item ev_loop_destroy (loop)	663	=item ev_loop_fork (loop)
569		664
570	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.
572
573	=item ev_default_fork ()
574
575	This function sets a flag that causes subsequent C<ev_loop> iterations	665	This function sets a flag that causes subsequent C<ev_run> iterations to
576	to reinitialise the kernel state for backends that have one. Despite the	666	reinitialise the kernel state for backends that have one. Despite the
577	name, you can call it anytime, but it makes most sense after forking, in	667	name, you can call it anytime, but it makes most sense after forking, in
578	the child process (or both child and parent, but that again makes little	668	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
579	sense). You I<must> call it in the child before using any of the libev	669	child before resuming or calling C<ev_run>.
580	functions, and it will only take effect at the next C<ev_loop> iteration.	670
		671	Again, you I<have> to call it on I<any> loop that you want to re-use after
		672	a fork, I<even if you do not plan to use the loop in the parent>. This is
		673	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		674	during fork.
581		675
582	On the other hand, you only need to call this function in the child	676	On the other hand, you only need to call this function in the child
583	process if and only if you want to use the event library in the child. If	677	process if and only if you want to use the event loop in the child. If
584	you just fork+exec, you don't have to call it at all.	678	you just fork+exec or create a new loop in the child, you don't have to
		679	call it at all (in fact, C<epoll> is so badly broken that it makes a
		680	difference, but libev will usually detect this case on its own and do a
		681	costly reset of the backend).
585		682
586	The function itself is quite fast and it's usually not a problem to call	683	The function itself is quite fast and it's usually not a problem to call
587	it just in case after a fork. To make this easy, the function will fit in	684	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		685
		686	Example: Automate calling C<ev_loop_fork> on the default loop when
		687	using pthreads.
		688
		689	static void
		690	post_fork_child (void)
		691	{
		692	ev_loop_fork (EV_DEFAULT);
		693	}
		694
		695	...
590	pthread_atfork (0, 0, ev_default_fork);	696	pthread_atfork (0, 0, post_fork_child);
591
592	=item ev_loop_fork (loop)
593
594	Like C<ev_default_fork>, but acts on an event loop created by
595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
596	after fork that you want to re-use in the child, and how you do this is
597	entirely your own problem.
598		697
599	=item int ev_is_default_loop (loop)	698	=item int ev_is_default_loop (loop)
600		699
601	Returns true when the given loop is, in fact, the default loop, and false	700	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	701	otherwise.
603		702
604	=item unsigned int ev_loop_count (loop)	703	=item unsigned int ev_iteration (loop)
605		704
606	Returns the count of loop iterations for the loop, which is identical to	705	Returns the current iteration count for the event loop, which is identical
607	the number of times libev did poll for new events. It starts at C<0> and	706	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	707	and happily wraps around with enough iterations.
609		708
610	This value can sometimes be useful as a generation counter of sorts (it	709	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	710	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	711	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		712	prepare and check phases.
		713
		714	=item unsigned int ev_depth (loop)
		715
		716	Returns the number of times C<ev_run> was entered minus the number of
		717	times C<ev_run> was exited normally, in other words, the recursion depth.
		718
		719	Outside C<ev_run>, this number is zero. In a callback, this number is
		720	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		721	in which case it is higher.
		722
		723	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		724	throwing an exception etc.), doesn't count as "exit" - consider this
		725	as a hint to avoid such ungentleman-like behaviour unless it's really
		726	convenient, in which case it is fully supported.
613		727
614	=item unsigned int ev_backend (loop)	728	=item unsigned int ev_backend (loop)
615		729
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	730	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	731	use.
…		…
626		740
627	=item ev_now_update (loop)	741	=item ev_now_update (loop)
628		742
629	Establishes the current time by querying the kernel, updating the time	743	Establishes the current time by querying the kernel, updating the time
630	returned by C<ev_now ()> in the progress. This is a costly operation and	744	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	745	is usually done automatically within C<ev_run ()>.
632		746
633	This function is rarely useful, but when some event callback runs for a	747	This function is rarely useful, but when some event callback runs for a
634	very long time without entering the event loop, updating libev's idea of	748	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	749	the current time is a good idea.
636		750
637	See also "The special problem of time updates" in the C<ev_timer> section.	751	See also L<The special problem of time updates> in the C<ev_timer> section.
638		752
		753	=item ev_suspend (loop)
		754
		755	=item ev_resume (loop)
		756
		757	These two functions suspend and resume an event loop, for use when the
		758	loop is not used for a while and timeouts should not be processed.
		759
		760	A typical use case would be an interactive program such as a game: When
		761	the user presses C<^Z> to suspend the game and resumes it an hour later it
		762	would be best to handle timeouts as if no time had actually passed while
		763	the program was suspended. This can be achieved by calling C<ev_suspend>
		764	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		765	C<ev_resume> directly afterwards to resume timer processing.
		766
		767	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		768	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		769	will be rescheduled (that is, they will lose any events that would have
		770	occurred while suspended).
		771
		772	After calling C<ev_suspend> you B<must not> call I<any> function on the
		773	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		774	without a previous call to C<ev_suspend>.
		775
		776	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		777	event loop time (see C<ev_now_update>).
		778
639	=item ev_loop (loop, int flags)	779	=item ev_run (loop, int flags)
640		780
641	Finally, this is it, the event handler. This function usually is called	781	Finally, this is it, the event handler. This function usually is called
642	after you initialised all your watchers and you want to start handling	782	after you have initialised all your watchers and you want to start
643	events.	783	handling events. It will ask the operating system for any new events, call
		784	the watcher callbacks, an then repeat the whole process indefinitely: This
		785	is why event loops are called I<loops>.
644		786
645	If the flags argument is specified as C<0>, it will not return until	787	If the flags argument is specified as C<0>, it will keep handling events
646	either no event watchers are active anymore or C<ev_unloop> was called.	788	until either no event watchers are active anymore or C<ev_break> was
		789	called.
647		790
648	Please note that an explicit C<ev_unloop> is usually better than	791	Please note that an explicit C<ev_break> is usually better than
649	relying on all watchers to be stopped when deciding when a program has	792	relying on all watchers to be stopped when deciding when a program has
650	finished (especially in interactive programs), but having a program	793	finished (especially in interactive programs), but having a program
651	that automatically loops as long as it has to and no longer by virtue	794	that automatically loops as long as it has to and no longer by virtue
652	of relying on its watchers stopping correctly, that is truly a thing of	795	of relying on its watchers stopping correctly, that is truly a thing of
653	beauty.	796	beauty.
654		797
		798	This function is also I<mostly> exception-safe - you can break out of
		799	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		800	exception and so on. This does not decrement the C<ev_depth> value, nor
		801	will it clear any outstanding C<EVBREAK_ONE> breaks.
		802
655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	803	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
656	those events and any already outstanding ones, but will not block your	804	those events and any already outstanding ones, but will not wait and
657	process in case there are no events and will return after one iteration of	805	block your process in case there are no events and will return after one
658	the loop.	806	iteration of the loop. This is sometimes useful to poll and handle new
		807	events while doing lengthy calculations, to keep the program responsive.
659		808
660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	809	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
661	necessary) and will handle those and any already outstanding ones. It	810	necessary) and will handle those and any already outstanding ones. It
662	will block your process until at least one new event arrives (which could	811	will block your process until at least one new event arrives (which could
663	be an event internal to libev itself, so there is no guarantee that a	812	be an event internal to libev itself, so there is no guarantee that a
664	user-registered callback will be called), and will return after one	813	user-registered callback will be called), and will return after one
665	iteration of the loop.	814	iteration of the loop.
666		815
667	This is useful if you are waiting for some external event in conjunction	816	This is useful if you are waiting for some external event in conjunction
668	with something not expressible using other libev watchers (i.e. "roll your	817	with something not expressible using other libev watchers (i.e. "roll your
669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	818	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
670	usually a better approach for this kind of thing.	819	usually a better approach for this kind of thing.
671		820
672	Here are the gory details of what C<ev_loop> does:	821	Here are the gory details of what C<ev_run> does:
673		822
		823	- Increment loop depth.
		824	- Reset the ev_break status.
674	- Before the first iteration, call any pending watchers.	825	- Before the first iteration, call any pending watchers.
		826	LOOP:
675	* If EVFLAG_FORKCHECK was used, check for a fork.	827	- If EVFLAG_FORKCHECK was used, check for a fork.
676	- If a fork was detected (by any means), queue and call all fork watchers.	828	- If a fork was detected (by any means), queue and call all fork watchers.
677	- Queue and call all prepare watchers.	829	- Queue and call all prepare watchers.
		830	- If ev_break was called, goto FINISH.
678	- If we have been forked, detach and recreate the kernel state	831	- If we have been forked, detach and recreate the kernel state
679	as to not disturb the other process.	832	as to not disturb the other process.
680	- Update the kernel state with all outstanding changes.	833	- Update the kernel state with all outstanding changes.
681	- Update the "event loop time" (ev_now ()).	834	- Update the "event loop time" (ev_now ()).
682	- Calculate for how long to sleep or block, if at all	835	- Calculate for how long to sleep or block, if at all
683	(active idle watchers, EVLOOP_NONBLOCK or not having	836	(active idle watchers, EVRUN_NOWAIT or not having
684	any active watchers at all will result in not sleeping).	837	any active watchers at all will result in not sleeping).
685	- Sleep if the I/O and timer collect interval say so.	838	- Sleep if the I/O and timer collect interval say so.
		839	- Increment loop iteration counter.
686	- Block the process, waiting for any events.	840	- Block the process, waiting for any events.
687	- Queue all outstanding I/O (fd) events.	841	- Queue all outstanding I/O (fd) events.
688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	842	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
689	- Queue all expired timers.	843	- Queue all expired timers.
690	- Queue all expired periodics.	844	- Queue all expired periodics.
691	- Unless any events are pending now, queue all idle watchers.	845	- Queue all idle watchers with priority higher than that of pending events.
692	- Queue all check watchers.	846	- Queue all check watchers.
693	- Call all queued watchers in reverse order (i.e. check watchers first).	847	- Call all queued watchers in reverse order (i.e. check watchers first).
694	Signals and child watchers are implemented as I/O watchers, and will	848	Signals and child watchers are implemented as I/O watchers, and will
695	be handled here by queueing them when their watcher gets executed.	849	be handled here by queueing them when their watcher gets executed.
696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	850	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
697	were used, or there are no active watchers, return, otherwise	851	were used, or there are no active watchers, goto FINISH, otherwise
698	continue with step *.	852	continue with step LOOP.
		853	FINISH:
		854	- Reset the ev_break status iff it was EVBREAK_ONE.
		855	- Decrement the loop depth.
		856	- Return.
699		857
700	Example: Queue some jobs and then loop until no events are outstanding	858	Example: Queue some jobs and then loop until no events are outstanding
701	anymore.	859	anymore.
702		860
703	... queue jobs here, make sure they register event watchers as long	861	... queue jobs here, make sure they register event watchers as long
704	... as they still have work to do (even an idle watcher will do..)	862	... as they still have work to do (even an idle watcher will do..)
705	ev_loop (my_loop, 0);	863	ev_run (my_loop, 0);
706	... jobs done or somebody called unloop. yeah!	864	... jobs done or somebody called unloop. yeah!
707		865
708	=item ev_unloop (loop, how)	866	=item ev_break (loop, how)
709		867
710	Can be used to make a call to C<ev_loop> return early (but only after it	868	Can be used to make a call to C<ev_run> return early (but only after it
711	has processed all outstanding events). The C<how> argument must be either	869	has processed all outstanding events). The C<how> argument must be either
712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	870	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	871	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
714		872
715	This "unloop state" will be cleared when entering C<ev_loop> again.	873	This "break state" will be cleared on the next call to C<ev_run>.
716		874
717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	875	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		876	which case it will have no effect.
718		877
719	=item ev_ref (loop)	878	=item ev_ref (loop)
720		879
721	=item ev_unref (loop)	880	=item ev_unref (loop)
722		881
723	Ref/unref can be used to add or remove a reference count on the event	882	Ref/unref can be used to add or remove a reference count on the event
724	loop: Every watcher keeps one reference, and as long as the reference	883	loop: Every watcher keeps one reference, and as long as the reference
725	count is nonzero, C<ev_loop> will not return on its own.	884	count is nonzero, C<ev_run> will not return on its own.
726		885
727	If you have a watcher you never unregister that should not keep C<ev_loop>	886	This is useful when you have a watcher that you never intend to
728	from returning, call ev_unref() after starting, and ev_ref() before	887	unregister, but that nevertheless should not keep C<ev_run> from
		888	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
729	stopping it.	889	before stopping it.
730		890
731	As an example, libev itself uses this for its internal signal pipe: It is	891	As an example, libev itself uses this for its internal signal pipe: It
732	not visible to the libev user and should not keep C<ev_loop> from exiting	892	is not visible to the libev user and should not keep C<ev_run> from
733	if no event watchers registered by it are active. It is also an excellent	893	exiting if no event watchers registered by it are active. It is also an
734	way to do this for generic recurring timers or from within third-party	894	excellent way to do this for generic recurring timers or from within
735	libraries. Just remember to I<unref after start> and I<ref before stop>	895	third-party libraries. Just remember to I<unref after start> and I<ref
736	(but only if the watcher wasn't active before, or was active before,	896	before stop> (but only if the watcher wasn't active before, or was active
737	respectively).	897	before, respectively. Note also that libev might stop watchers itself
		898	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		899	in the callback).
738		900
739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	901	Example: Create a signal watcher, but keep it from keeping C<ev_run>
740	running when nothing else is active.	902	running when nothing else is active.
741		903
742	ev_signal exitsig;	904	ev_signal exitsig;
743	ev_signal_init (&exitsig, sig_cb, SIGINT);	905	ev_signal_init (&exitsig, sig_cb, SIGINT);
744	ev_signal_start (loop, &exitsig);	906	ev_signal_start (loop, &exitsig);
745	evf_unref (loop);	907	ev_unref (loop);
746		908
747	Example: For some weird reason, unregister the above signal handler again.	909	Example: For some weird reason, unregister the above signal handler again.
748		910
749	ev_ref (loop);	911	ev_ref (loop);
750	ev_signal_stop (loop, &exitsig);	912	ev_signal_stop (loop, &exitsig);
…		…
771		933
772	By setting a higher I<io collect interval> you allow libev to spend more	934	By setting a higher I<io collect interval> you allow libev to spend more
773	time collecting I/O events, so you can handle more events per iteration,	935	time collecting I/O events, so you can handle more events per iteration,
774	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	936	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
775	C<ev_timer>) will be not affected. Setting this to a non-null value will	937	C<ev_timer>) will be not affected. Setting this to a non-null value will
776	introduce an additional C<ev_sleep ()> call into most loop iterations.	938	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		939	sleep time ensures that libev will not poll for I/O events more often then
		940	once per this interval, on average.
777		941
778	Likewise, by setting a higher I<timeout collect interval> you allow libev	942	Likewise, by setting a higher I<timeout collect interval> you allow libev
779	to spend more time collecting timeouts, at the expense of increased	943	to spend more time collecting timeouts, at the expense of increased
780	latency/jitter/inexactness (the watcher callback will be called	944	latency/jitter/inexactness (the watcher callback will be called
781	later). C<ev_io> watchers will not be affected. Setting this to a non-null	945	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
783		947
784	Many (busy) programs can usually benefit by setting the I/O collect	948	Many (busy) programs can usually benefit by setting the I/O collect
785	interval to a value near C<0.1> or so, which is often enough for	949	interval to a value near C<0.1> or so, which is often enough for
786	interactive servers (of course not for games), likewise for timeouts. It	950	interactive servers (of course not for games), likewise for timeouts. It
787	usually doesn't make much sense to set it to a lower value than C<0.01>,	951	usually doesn't make much sense to set it to a lower value than C<0.01>,
788	as this approaches the timing granularity of most systems.	952	as this approaches the timing granularity of most systems. Note that if
		953	you do transactions with the outside world and you can't increase the
		954	parallelity, then this setting will limit your transaction rate (if you
		955	need to poll once per transaction and the I/O collect interval is 0.01,
		956	then you can't do more than 100 transactions per second).
789		957
790	Setting the I<timeout collect interval> can improve the opportunity for	958	Setting the I<timeout collect interval> can improve the opportunity for
791	saving power, as the program will "bundle" timer callback invocations that	959	saving power, as the program will "bundle" timer callback invocations that
792	are "near" in time together, by delaying some, thus reducing the number of	960	are "near" in time together, by delaying some, thus reducing the number of
793	times the process sleeps and wakes up again. Another useful technique to	961	times the process sleeps and wakes up again. Another useful technique to
794	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	962	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
795	they fire on, say, one-second boundaries only.	963	they fire on, say, one-second boundaries only.
796		964
		965	Example: we only need 0.1s timeout granularity, and we wish not to poll
		966	more often than 100 times per second:
		967
		968	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		969	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		970
		971	=item ev_invoke_pending (loop)
		972
		973	This call will simply invoke all pending watchers while resetting their
		974	pending state. Normally, C<ev_run> does this automatically when required,
		975	but when overriding the invoke callback this call comes handy. This
		976	function can be invoked from a watcher - this can be useful for example
		977	when you want to do some lengthy calculation and want to pass further
		978	event handling to another thread (you still have to make sure only one
		979	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		980
		981	=item int ev_pending_count (loop)
		982
		983	Returns the number of pending watchers - zero indicates that no watchers
		984	are pending.
		985
		986	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		987
		988	This overrides the invoke pending functionality of the loop: Instead of
		989	invoking all pending watchers when there are any, C<ev_run> will call
		990	this callback instead. This is useful, for example, when you want to
		991	invoke the actual watchers inside another context (another thread etc.).
		992
		993	If you want to reset the callback, use C<ev_invoke_pending> as new
		994	callback.
		995
		996	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		997
		998	Sometimes you want to share the same loop between multiple threads. This
		999	can be done relatively simply by putting mutex_lock/unlock calls around
		1000	each call to a libev function.
		1001
		1002	However, C<ev_run> can run an indefinite time, so it is not feasible
		1003	to wait for it to return. One way around this is to wake up the event
		1004	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1005	I<release> and I<acquire> callbacks on the loop.
		1006
		1007	When set, then C<release> will be called just before the thread is
		1008	suspended waiting for new events, and C<acquire> is called just
		1009	afterwards.
		1010
		1011	Ideally, C<release> will just call your mutex_unlock function, and
		1012	C<acquire> will just call the mutex_lock function again.
		1013
		1014	While event loop modifications are allowed between invocations of
		1015	C<release> and C<acquire> (that's their only purpose after all), no
		1016	modifications done will affect the event loop, i.e. adding watchers will
		1017	have no effect on the set of file descriptors being watched, or the time
		1018	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1019	to take note of any changes you made.
		1020
		1021	In theory, threads executing C<ev_run> will be async-cancel safe between
		1022	invocations of C<release> and C<acquire>.
		1023
		1024	See also the locking example in the C<THREADS> section later in this
		1025	document.
		1026
		1027	=item ev_set_userdata (loop, void *data)
		1028
		1029	=item void *ev_userdata (loop)
		1030
		1031	Set and retrieve a single C<void *> associated with a loop. When
		1032	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1033	C<0>.
		1034
		1035	These two functions can be used to associate arbitrary data with a loop,
		1036	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1037	C<acquire> callbacks described above, but of course can be (ab-)used for
		1038	any other purpose as well.
		1039
797	=item ev_loop_verify (loop)	1040	=item ev_verify (loop)
798		1041
799	This function only does something when C<EV_VERIFY> support has been	1042	This function only does something when C<EV_VERIFY> support has been
800	compiled in, which is the default for non-minimal builds. It tries to go	1043	compiled in, which is the default for non-minimal builds. It tries to go
801	through all internal structures and checks them for validity. If anything	1044	through all internal structures and checks them for validity. If anything
802	is found to be inconsistent, it will print an error message to standard	1045	is found to be inconsistent, it will print an error message to standard
…		…
813		1056
814	In the following description, uppercase C<TYPE> in names stands for the	1057	In the following description, uppercase C<TYPE> in names stands for the
815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1058	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
816	watchers and C<ev_io_start> for I/O watchers.	1059	watchers and C<ev_io_start> for I/O watchers.
817		1060
818	A watcher is a structure that you create and register to record your	1061	A watcher is an opaque structure that you allocate and register to record
819	interest in some event. For instance, if you want to wait for STDIN to	1062	your interest in some event. To make a concrete example, imagine you want
820	become readable, you would create an C<ev_io> watcher for that:	1063	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1064	for that:
821		1065
822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1066	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
823	{	1067	{
824	ev_io_stop (w);	1068	ev_io_stop (w);
825	ev_unloop (loop, EVUNLOOP_ALL);	1069	ev_break (loop, EVBREAK_ALL);
826	}	1070	}
827		1071
828	struct ev_loop *loop = ev_default_loop (0);	1072	struct ev_loop *loop = ev_default_loop (0);
829		1073
830	ev_io stdin_watcher;	1074	ev_io stdin_watcher;
831		1075
832	ev_init (&stdin_watcher, my_cb);	1076	ev_init (&stdin_watcher, my_cb);
833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1077	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
834	ev_io_start (loop, &stdin_watcher);	1078	ev_io_start (loop, &stdin_watcher);
835		1079
836	ev_loop (loop, 0);	1080	ev_run (loop, 0);
837		1081
838	As you can see, you are responsible for allocating the memory for your	1082	As you can see, you are responsible for allocating the memory for your
839	watcher structures (and it is I<usually> a bad idea to do this on the	1083	watcher structures (and it is I<usually> a bad idea to do this on the
840	stack).	1084	stack).
841		1085
842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1086	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1087	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
844		1088
845	Each watcher structure must be initialised by a call to C<ev_init	1089	Each watcher structure must be initialised by a call to C<ev_init (watcher
846	(watcher *, callback)>, which expects a callback to be provided. This	1090	*, callback)>, which expects a callback to be provided. This callback is
847	callback gets invoked each time the event occurs (or, in the case of I/O	1091	invoked each time the event occurs (or, in the case of I/O watchers, each
848	watchers, each time the event loop detects that the file descriptor given	1092	time the event loop detects that the file descriptor given is readable
849	is readable and/or writable).	1093	and/or writable).
850		1094
851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1095	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
852	macro to configure it, with arguments specific to the watcher type. There	1096	macro to configure it, with arguments specific to the watcher type. There
853	is also a macro to combine initialisation and setting in one call: C<<	1097	is also a macro to combine initialisation and setting in one call: C<<
854	ev_TYPE_init (watcher *, callback, ...) >>.	1098	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
877	=item C<EV_WRITE>	1121	=item C<EV_WRITE>
878		1122
879	The file descriptor in the C<ev_io> watcher has become readable and/or	1123	The file descriptor in the C<ev_io> watcher has become readable and/or
880	writable.	1124	writable.
881		1125
882	=item C<EV_TIMEOUT>	1126	=item C<EV_TIMER>
883		1127
884	The C<ev_timer> watcher has timed out.	1128	The C<ev_timer> watcher has timed out.
885		1129
886	=item C<EV_PERIODIC>	1130	=item C<EV_PERIODIC>
887		1131
…		…
905		1149
906	=item C<EV_PREPARE>	1150	=item C<EV_PREPARE>
907		1151
908	=item C<EV_CHECK>	1152	=item C<EV_CHECK>
909		1153
910	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1154	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
911	to gather new events, and all C<ev_check> watchers are invoked just after	1155	to gather new events, and all C<ev_check> watchers are invoked just after
912	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1156	C<ev_run> has gathered them, but before it invokes any callbacks for any
913	received events. Callbacks of both watcher types can start and stop as	1157	received events. Callbacks of both watcher types can start and stop as
914	many watchers as they want, and all of them will be taken into account	1158	many watchers as they want, and all of them will be taken into account
915	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1159	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
916	C<ev_loop> from blocking).	1160	C<ev_run> from blocking).
917		1161
918	=item C<EV_EMBED>	1162	=item C<EV_EMBED>
919		1163
920	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1164	The embedded event loop specified in the C<ev_embed> watcher needs attention.
921		1165
922	=item C<EV_FORK>	1166	=item C<EV_FORK>
923		1167
924	The event loop has been resumed in the child process after fork (see	1168	The event loop has been resumed in the child process after fork (see
925	C<ev_fork>).	1169	C<ev_fork>).
926		1170
		1171	=item C<EV_CLEANUP>
		1172
		1173	The event loop is about to be destroyed (see C<ev_cleanup>).
		1174
927	=item C<EV_ASYNC>	1175	=item C<EV_ASYNC>
928		1176
929	The given async watcher has been asynchronously notified (see C<ev_async>).	1177	The given async watcher has been asynchronously notified (see C<ev_async>).
		1178
		1179	=item C<EV_CUSTOM>
		1180
		1181	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1182	by libev users to signal watchers (e.g. via C<ev_feed_event>).
930		1183
931	=item C<EV_ERROR>	1184	=item C<EV_ERROR>
932		1185
933	An unspecified error has occurred, the watcher has been stopped. This might	1186	An unspecified error has occurred, the watcher has been stopped. This might
934	happen because the watcher could not be properly started because libev	1187	happen because the watcher could not be properly started because libev
…		…
972		1225
973	ev_io w;	1226	ev_io w;
974	ev_init (&w, my_cb);	1227	ev_init (&w, my_cb);
975	ev_io_set (&w, STDIN_FILENO, EV_READ);	1228	ev_io_set (&w, STDIN_FILENO, EV_READ);
976		1229
977	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1230	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
978		1231
979	This macro initialises the type-specific parts of a watcher. You need to	1232	This macro initialises the type-specific parts of a watcher. You need to
980	call C<ev_init> at least once before you call this macro, but you can	1233	call C<ev_init> at least once before you call this macro, but you can
981	call C<ev_TYPE_set> any number of times. You must not, however, call this	1234	call C<ev_TYPE_set> any number of times. You must not, however, call this
982	macro on a watcher that is active (it can be pending, however, which is a	1235	macro on a watcher that is active (it can be pending, however, which is a
…		…
995		1248
996	Example: Initialise and set an C<ev_io> watcher in one step.	1249	Example: Initialise and set an C<ev_io> watcher in one step.
997		1250
998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1251	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
999		1252
1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1253	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1001		1254
1002	Starts (activates) the given watcher. Only active watchers will receive	1255	Starts (activates) the given watcher. Only active watchers will receive
1003	events. If the watcher is already active nothing will happen.	1256	events. If the watcher is already active nothing will happen.
1004		1257
1005	Example: Start the C<ev_io> watcher that is being abused as example in this	1258	Example: Start the C<ev_io> watcher that is being abused as example in this
1006	whole section.	1259	whole section.
1007		1260
1008	ev_io_start (EV_DEFAULT_UC, &w);	1261	ev_io_start (EV_DEFAULT_UC, &w);
1009		1262
1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1263	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1011		1264
1012	Stops the given watcher if active, and clears the pending status (whether	1265	Stops the given watcher if active, and clears the pending status (whether
1013	the watcher was active or not).	1266	the watcher was active or not).
1014		1267
1015	It is possible that stopped watchers are pending - for example,	1268	It is possible that stopped watchers are pending - for example,
…		…
1040	=item ev_cb_set (ev_TYPE *watcher, callback)	1293	=item ev_cb_set (ev_TYPE *watcher, callback)
1041		1294
1042	Change the callback. You can change the callback at virtually any time	1295	Change the callback. You can change the callback at virtually any time
1043	(modulo threads).	1296	(modulo threads).
1044		1297
1045	=item ev_set_priority (ev_TYPE *watcher, priority)	1298	=item ev_set_priority (ev_TYPE *watcher, int priority)
1046		1299
1047	=item int ev_priority (ev_TYPE *watcher)	1300	=item int ev_priority (ev_TYPE *watcher)
1048		1301
1049	Set and query the priority of the watcher. The priority is a small	1302	Set and query the priority of the watcher. The priority is a small
1050	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1303	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1051	(default: C<-2>). Pending watchers with higher priority will be invoked	1304	(default: C<-2>). Pending watchers with higher priority will be invoked
1052	before watchers with lower priority, but priority will not keep watchers	1305	before watchers with lower priority, but priority will not keep watchers
1053	from being executed (except for C<ev_idle> watchers).	1306	from being executed (except for C<ev_idle> watchers).
1054		1307
1055	This means that priorities are I<only> used for ordering callback
1056	invocation after new events have been received. This is useful, for
1057	example, to reduce latency after idling, or more often, to bind two
1058	watchers on the same event and make sure one is called first.
1059
1060	If you need to suppress invocation when higher priority events are pending	1308	If you need to suppress invocation when higher priority events are pending
1061	you need to look at C<ev_idle> watchers, which provide this functionality.	1309	you need to look at C<ev_idle> watchers, which provide this functionality.
1062		1310
1063	You I<must not> change the priority of a watcher as long as it is active or	1311	You I<must not> change the priority of a watcher as long as it is active or
1064	pending.	1312	pending.
1065
1066	The default priority used by watchers when no priority has been set is
1067	always C<0>, which is supposed to not be too high and not be too low :).
1068		1313
1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1314	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1070	fine, as long as you do not mind that the priority value you query might	1315	fine, as long as you do not mind that the priority value you query might
1071	or might not have been clamped to the valid range.	1316	or might not have been clamped to the valid range.
		1317
		1318	The default priority used by watchers when no priority has been set is
		1319	always C<0>, which is supposed to not be too high and not be too low :).
		1320
		1321	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1322	priorities.
1072		1323
1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1324	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1074		1325
1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1326	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1076	C<loop> nor C<revents> need to be valid as long as the watcher callback	1327	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1084	watcher isn't pending it does nothing and returns C<0>.	1335	watcher isn't pending it does nothing and returns C<0>.
1085		1336
1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1337	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1087	callback to be invoked, which can be accomplished with this function.	1338	callback to be invoked, which can be accomplished with this function.
1088		1339
		1340	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1341
		1342	Feeds the given event set into the event loop, as if the specified event
		1343	had happened for the specified watcher (which must be a pointer to an
		1344	initialised but not necessarily started event watcher). Obviously you must
		1345	not free the watcher as long as it has pending events.
		1346
		1347	Stopping the watcher, letting libev invoke it, or calling
		1348	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1349	not started in the first place.
		1350
		1351	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1352	functions that do not need a watcher.
		1353
1089	=back	1354	=back
1090
1091		1355
1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1356	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1093		1357
1094	Each watcher has, by default, a member C<void *data> that you can change	1358	Each watcher has, by default, a member C<void *data> that you can change
1095	and read at any time: libev will completely ignore it. This can be used	1359	and read at any time: libev will completely ignore it. This can be used
…		…
1141	#include <stddef.h>	1405	#include <stddef.h>
1142		1406
1143	static void	1407	static void
1144	t1_cb (EV_P_ ev_timer *w, int revents)	1408	t1_cb (EV_P_ ev_timer *w, int revents)
1145	{	1409	{
1146	struct my_biggy big = (struct my_biggy *	1410	struct my_biggy big = (struct my_biggy *)
1147	(((char *)w) - offsetof (struct my_biggy, t1));	1411	(((char *)w) - offsetof (struct my_biggy, t1));
1148	}	1412	}
1149		1413
1150	static void	1414	static void
1151	t2_cb (EV_P_ ev_timer *w, int revents)	1415	t2_cb (EV_P_ ev_timer *w, int revents)
1152	{	1416	{
1153	struct my_biggy big = (struct my_biggy *	1417	struct my_biggy big = (struct my_biggy *)
1154	(((char *)w) - offsetof (struct my_biggy, t2));	1418	(((char *)w) - offsetof (struct my_biggy, t2));
1155	}	1419	}
		1420
		1421	=head2 WATCHER STATES
		1422
		1423	There are various watcher states mentioned throughout this manual -
		1424	active, pending and so on. In this section these states and the rules to
		1425	transition between them will be described in more detail - and while these
		1426	rules might look complicated, they usually do "the right thing".
		1427
		1428	=over 4
		1429
		1430	=item initialiased
		1431
		1432	Before a watcher can be registered with the event looop it has to be
		1433	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1434	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1435
		1436	In this state it is simply some block of memory that is suitable for use
		1437	in an event loop. It can be moved around, freed, reused etc. at will.
		1438
		1439	=item started/running/active
		1440
		1441	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1442	property of the event loop, and is actively waiting for events. While in
		1443	this state it cannot be accessed (except in a few documented ways), moved,
		1444	freed or anything else - the only legal thing is to keep a pointer to it,
		1445	and call libev functions on it that are documented to work on active watchers.
		1446
		1447	=item pending
		1448
		1449	If a watcher is active and libev determines that an event it is interested
		1450	in has occurred (such as a timer expiring), it will become pending. It will
		1451	stay in this pending state until either it is stopped or its callback is
		1452	about to be invoked, so it is not normally pending inside the watcher
		1453	callback.
		1454
		1455	The watcher might or might not be active while it is pending (for example,
		1456	an expired non-repeating timer can be pending but no longer active). If it
		1457	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1458	but it is still property of the event loop at this time, so cannot be
		1459	moved, freed or reused. And if it is active the rules described in the
		1460	previous item still apply.
		1461
		1462	It is also possible to feed an event on a watcher that is not active (e.g.
		1463	via C<ev_feed_event>), in which case it becomes pending without being
		1464	active.
		1465
		1466	=item stopped
		1467
		1468	A watcher can be stopped implicitly by libev (in which case it might still
		1469	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1470	latter will clear any pending state the watcher might be in, regardless
		1471	of whether it was active or not, so stopping a watcher explicitly before
		1472	freeing it is often a good idea.
		1473
		1474	While stopped (and not pending) the watcher is essentially in the
		1475	initialised state, that is it can be reused, moved, modified in any way
		1476	you wish.
		1477
		1478	=back
		1479
		1480	=head2 WATCHER PRIORITY MODELS
		1481
		1482	Many event loops support I<watcher priorities>, which are usually small
		1483	integers that influence the ordering of event callback invocation
		1484	between watchers in some way, all else being equal.
		1485
		1486	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1487	description for the more technical details such as the actual priority
		1488	range.
		1489
		1490	There are two common ways how these these priorities are being interpreted
		1491	by event loops:
		1492
		1493	In the more common lock-out model, higher priorities "lock out" invocation
		1494	of lower priority watchers, which means as long as higher priority
		1495	watchers receive events, lower priority watchers are not being invoked.
		1496
		1497	The less common only-for-ordering model uses priorities solely to order
		1498	callback invocation within a single event loop iteration: Higher priority
		1499	watchers are invoked before lower priority ones, but they all get invoked
		1500	before polling for new events.
		1501
		1502	Libev uses the second (only-for-ordering) model for all its watchers
		1503	except for idle watchers (which use the lock-out model).
		1504
		1505	The rationale behind this is that implementing the lock-out model for
		1506	watchers is not well supported by most kernel interfaces, and most event
		1507	libraries will just poll for the same events again and again as long as
		1508	their callbacks have not been executed, which is very inefficient in the
		1509	common case of one high-priority watcher locking out a mass of lower
		1510	priority ones.
		1511
		1512	Static (ordering) priorities are most useful when you have two or more
		1513	watchers handling the same resource: a typical usage example is having an
		1514	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1515	timeouts. Under load, data might be received while the program handles
		1516	other jobs, but since timers normally get invoked first, the timeout
		1517	handler will be executed before checking for data. In that case, giving
		1518	the timer a lower priority than the I/O watcher ensures that I/O will be
		1519	handled first even under adverse conditions (which is usually, but not
		1520	always, what you want).
		1521
		1522	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1523	will only be executed when no same or higher priority watchers have
		1524	received events, they can be used to implement the "lock-out" model when
		1525	required.
		1526
		1527	For example, to emulate how many other event libraries handle priorities,
		1528	you can associate an C<ev_idle> watcher to each such watcher, and in
		1529	the normal watcher callback, you just start the idle watcher. The real
		1530	processing is done in the idle watcher callback. This causes libev to
		1531	continuously poll and process kernel event data for the watcher, but when
		1532	the lock-out case is known to be rare (which in turn is rare :), this is
		1533	workable.
		1534
		1535	Usually, however, the lock-out model implemented that way will perform
		1536	miserably under the type of load it was designed to handle. In that case,
		1537	it might be preferable to stop the real watcher before starting the
		1538	idle watcher, so the kernel will not have to process the event in case
		1539	the actual processing will be delayed for considerable time.
		1540
		1541	Here is an example of an I/O watcher that should run at a strictly lower
		1542	priority than the default, and which should only process data when no
		1543	other events are pending:
		1544
		1545	ev_idle idle; // actual processing watcher
		1546	ev_io io; // actual event watcher
		1547
		1548	static void
		1549	io_cb (EV_P_ ev_io *w, int revents)
		1550	{
		1551	// stop the I/O watcher, we received the event, but
		1552	// are not yet ready to handle it.
		1553	ev_io_stop (EV_A_ w);
		1554
		1555	// start the idle watcher to handle the actual event.
		1556	// it will not be executed as long as other watchers
		1557	// with the default priority are receiving events.
		1558	ev_idle_start (EV_A_ &idle);
		1559	}
		1560
		1561	static void
		1562	idle_cb (EV_P_ ev_idle *w, int revents)
		1563	{
		1564	// actual processing
		1565	read (STDIN_FILENO, ...);
		1566
		1567	// have to start the I/O watcher again, as
		1568	// we have handled the event
		1569	ev_io_start (EV_P_ &io);
		1570	}
		1571
		1572	// initialisation
		1573	ev_idle_init (&idle, idle_cb);
		1574	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1575	ev_io_start (EV_DEFAULT_ &io);
		1576
		1577	In the "real" world, it might also be beneficial to start a timer, so that
		1578	low-priority connections can not be locked out forever under load. This
		1579	enables your program to keep a lower latency for important connections
		1580	during short periods of high load, while not completely locking out less
		1581	important ones.
1156		1582
1157		1583
1158	=head1 WATCHER TYPES	1584	=head1 WATCHER TYPES
1159		1585
1160	This section describes each watcher in detail, but will not repeat	1586	This section describes each watcher in detail, but will not repeat
…		…
1186	descriptors to non-blocking mode is also usually a good idea (but not	1612	descriptors to non-blocking mode is also usually a good idea (but not
1187	required if you know what you are doing).	1613	required if you know what you are doing).
1188		1614
1189	If you cannot use non-blocking mode, then force the use of a	1615	If you cannot use non-blocking mode, then force the use of a
1190	known-to-be-good backend (at the time of this writing, this includes only	1616	known-to-be-good backend (at the time of this writing, this includes only
1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1617	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1618	descriptors for which non-blocking operation makes no sense (such as
		1619	files) - libev doesn't guarantee any specific behaviour in that case.
1192		1620
1193	Another thing you have to watch out for is that it is quite easy to	1621	Another thing you have to watch out for is that it is quite easy to
1194	receive "spurious" readiness notifications, that is your callback might	1622	receive "spurious" readiness notifications, that is your callback might
1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1623	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1196	because there is no data. Not only are some backends known to create a	1624	because there is no data. Not only are some backends known to create a
…		…
1261		1689
1262	So when you encounter spurious, unexplained daemon exits, make sure you	1690	So when you encounter spurious, unexplained daemon exits, make sure you
1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1691	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1264	somewhere, as that would have given you a big clue).	1692	somewhere, as that would have given you a big clue).
1265		1693
		1694	=head3 The special problem of accept()ing when you can't
		1695
		1696	Many implementations of the POSIX C<accept> function (for example,
		1697	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1698	connection from the pending queue in all error cases.
		1699
		1700	For example, larger servers often run out of file descriptors (because
		1701	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1702	rejecting the connection, leading to libev signalling readiness on
		1703	the next iteration again (the connection still exists after all), and
		1704	typically causing the program to loop at 100% CPU usage.
		1705
		1706	Unfortunately, the set of errors that cause this issue differs between
		1707	operating systems, there is usually little the app can do to remedy the
		1708	situation, and no known thread-safe method of removing the connection to
		1709	cope with overload is known (to me).
		1710
		1711	One of the easiest ways to handle this situation is to just ignore it
		1712	- when the program encounters an overload, it will just loop until the
		1713	situation is over. While this is a form of busy waiting, no OS offers an
		1714	event-based way to handle this situation, so it's the best one can do.
		1715
		1716	A better way to handle the situation is to log any errors other than
		1717	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1718	messages, and continue as usual, which at least gives the user an idea of
		1719	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1720	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1721	usage.
		1722
		1723	If your program is single-threaded, then you could also keep a dummy file
		1724	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1725	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1726	close that fd, and create a new dummy fd. This will gracefully refuse
		1727	clients under typical overload conditions.
		1728
		1729	The last way to handle it is to simply log the error and C<exit>, as
		1730	is often done with C<malloc> failures, but this results in an easy
		1731	opportunity for a DoS attack.
1266		1732
1267	=head3 Watcher-Specific Functions	1733	=head3 Watcher-Specific Functions
1268		1734
1269	=over 4	1735	=over 4
1270		1736
…		…
1302	...	1768	...
1303	struct ev_loop *loop = ev_default_init (0);	1769	struct ev_loop *loop = ev_default_init (0);
1304	ev_io stdin_readable;	1770	ev_io stdin_readable;
1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1771	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1306	ev_io_start (loop, &stdin_readable);	1772	ev_io_start (loop, &stdin_readable);
1307	ev_loop (loop, 0);	1773	ev_run (loop, 0);
1308		1774
1309		1775
1310	=head2 C<ev_timer> - relative and optionally repeating timeouts	1776	=head2 C<ev_timer> - relative and optionally repeating timeouts
1311		1777
1312	Timer watchers are simple relative timers that generate an event after a	1778	Timer watchers are simple relative timers that generate an event after a
…		…
1317	year, it will still time out after (roughly) one hour. "Roughly" because	1783	year, it will still time out after (roughly) one hour. "Roughly" because
1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1784	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1319	monotonic clock option helps a lot here).	1785	monotonic clock option helps a lot here).
1320		1786
1321	The callback is guaranteed to be invoked only I<after> its timeout has	1787	The callback is guaranteed to be invoked only I<after> its timeout has
1322	passed, but if multiple timers become ready during the same loop iteration	1788	passed (not I<at>, so on systems with very low-resolution clocks this
1323	then order of execution is undefined.	1789	might introduce a small delay). If multiple timers become ready during the
		1790	same loop iteration then the ones with earlier time-out values are invoked
		1791	before ones of the same priority with later time-out values (but this is
		1792	no longer true when a callback calls C<ev_run> recursively).
1324		1793
1325	=head3 Be smart about timeouts	1794	=head3 Be smart about timeouts
1326		1795
1327	Many real-world problems involve some kind of timeout, usually for error	1796	Many real-world problems involve some kind of timeout, usually for error
1328	recovery. A typical example is an HTTP request - if the other side hangs,	1797	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1841	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1373	member and C<ev_timer_again>.	1842	member and C<ev_timer_again>.
1374		1843
1375	At start:	1844	At start:
1376		1845
1377	ev_timer_init (timer, callback);	1846	ev_init (timer, callback);
1378	timer->repeat = 60.;	1847	timer->repeat = 60.;
1379	ev_timer_again (loop, timer);	1848	ev_timer_again (loop, timer);
1380		1849
1381	Each time there is some activity:	1850	Each time there is some activity:
1382		1851
…		…
1414	ev_tstamp timeout = last_activity + 60.;	1883	ev_tstamp timeout = last_activity + 60.;
1415		1884
1416	// if last_activity + 60. is older than now, we did time out	1885	// if last_activity + 60. is older than now, we did time out
1417	if (timeout < now)	1886	if (timeout < now)
1418	{	1887	{
1419	// timeout occured, take action	1888	// timeout occurred, take action
1420	}	1889	}
1421	else	1890	else
1422	{	1891	{
1423	// callback was invoked, but there was some activity, re-arm	1892	// callback was invoked, but there was some activity, re-arm
1424	// the watcher to fire in last_activity + 60, which is	1893	// the watcher to fire in last_activity + 60, which is
…		…
1444		1913
1445	To start the timer, simply initialise the watcher and set C<last_activity>	1914	To start the timer, simply initialise the watcher and set C<last_activity>
1446	to the current time (meaning we just have some activity :), then call the	1915	to the current time (meaning we just have some activity :), then call the
1447	callback, which will "do the right thing" and start the timer:	1916	callback, which will "do the right thing" and start the timer:
1448		1917
1449	ev_timer_init (timer, callback);	1918	ev_init (timer, callback);
1450	last_activity = ev_now (loop);	1919	last_activity = ev_now (loop);
1451	callback (loop, timer, EV_TIMEOUT);	1920	callback (loop, timer, EV_TIMER);
1452		1921
1453	And when there is some activity, simply store the current time in	1922	And when there is some activity, simply store the current time in
1454	C<last_activity>, no libev calls at all:	1923	C<last_activity>, no libev calls at all:
1455		1924
1456	last_actiivty = ev_now (loop);	1925	last_activity = ev_now (loop);
1457		1926
1458	This technique is slightly more complex, but in most cases where the	1927	This technique is slightly more complex, but in most cases where the
1459	time-out is unlikely to be triggered, much more efficient.	1928	time-out is unlikely to be triggered, much more efficient.
1460		1929
1461	Changing the timeout is trivial as well (if it isn't hard-coded in the	1930	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1499		1968
1500	=head3 The special problem of time updates	1969	=head3 The special problem of time updates
1501		1970
1502	Establishing the current time is a costly operation (it usually takes at	1971	Establishing the current time is a costly operation (it usually takes at
1503	least two system calls): EV therefore updates its idea of the current	1972	least two system calls): EV therefore updates its idea of the current
1504	time only before and after C<ev_loop> collects new events, which causes a	1973	time only before and after C<ev_run> collects new events, which causes a
1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1974	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1506	lots of events in one iteration.	1975	lots of events in one iteration.
1507		1976
1508	The relative timeouts are calculated relative to the C<ev_now ()>	1977	The relative timeouts are calculated relative to the C<ev_now ()>
1509	time. This is usually the right thing as this timestamp refers to the time	1978	time. This is usually the right thing as this timestamp refers to the time
…		…
1515		1984
1516	If the event loop is suspended for a long time, you can also force an	1985	If the event loop is suspended for a long time, you can also force an
1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1986	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1518	()>.	1987	()>.
1519		1988
		1989	=head3 The special problems of suspended animation
		1990
		1991	When you leave the server world it is quite customary to hit machines that
		1992	can suspend/hibernate - what happens to the clocks during such a suspend?
		1993
		1994	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1995	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1996	to run until the system is suspended, but they will not advance while the
		1997	system is suspended. That means, on resume, it will be as if the program
		1998	was frozen for a few seconds, but the suspend time will not be counted
		1999	towards C<ev_timer> when a monotonic clock source is used. The real time
		2000	clock advanced as expected, but if it is used as sole clocksource, then a
		2001	long suspend would be detected as a time jump by libev, and timers would
		2002	be adjusted accordingly.
		2003
		2004	I would not be surprised to see different behaviour in different between
		2005	operating systems, OS versions or even different hardware.
		2006
		2007	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2008	time jump in the monotonic clocks and the realtime clock. If the program
		2009	is suspended for a very long time, and monotonic clock sources are in use,
		2010	then you can expect C<ev_timer>s to expire as the full suspension time
		2011	will be counted towards the timers. When no monotonic clock source is in
		2012	use, then libev will again assume a timejump and adjust accordingly.
		2013
		2014	It might be beneficial for this latter case to call C<ev_suspend>
		2015	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2016	deterministic behaviour in this case (you can do nothing against
		2017	C<SIGSTOP>).
		2018
1520	=head3 Watcher-Specific Functions and Data Members	2019	=head3 Watcher-Specific Functions and Data Members
1521		2020
1522	=over 4	2021	=over 4
1523		2022
1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2023	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1547	If the timer is started but non-repeating, stop it (as if it timed out).	2046	If the timer is started but non-repeating, stop it (as if it timed out).
1548		2047
1549	If the timer is repeating, either start it if necessary (with the	2048	If the timer is repeating, either start it if necessary (with the
1550	C<repeat> value), or reset the running timer to the C<repeat> value.	2049	C<repeat> value), or reset the running timer to the C<repeat> value.
1551		2050
1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2051	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1553	usage example.	2052	usage example.
		2053
		2054	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2055
		2056	Returns the remaining time until a timer fires. If the timer is active,
		2057	then this time is relative to the current event loop time, otherwise it's
		2058	the timeout value currently configured.
		2059
		2060	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2061	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2062	will return C<4>. When the timer expires and is restarted, it will return
		2063	roughly C<7> (likely slightly less as callback invocation takes some time,
		2064	too), and so on.
1554		2065
1555	=item ev_tstamp repeat [read-write]	2066	=item ev_tstamp repeat [read-write]
1556		2067
1557	The current C<repeat> value. Will be used each time the watcher times out	2068	The current C<repeat> value. Will be used each time the watcher times out
1558	or C<ev_timer_again> is called, and determines the next timeout (if any),	2069	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1584	}	2095	}
1585		2096
1586	ev_timer mytimer;	2097	ev_timer mytimer;
1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2098	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1588	ev_timer_again (&mytimer); /* start timer */	2099	ev_timer_again (&mytimer); /* start timer */
1589	ev_loop (loop, 0);	2100	ev_run (loop, 0);
1590		2101
1591	// and in some piece of code that gets executed on any "activity":	2102	// and in some piece of code that gets executed on any "activity":
1592	// reset the timeout to start ticking again at 10 seconds	2103	// reset the timeout to start ticking again at 10 seconds
1593	ev_timer_again (&mytimer);	2104	ev_timer_again (&mytimer);
1594		2105
…		…
1596	=head2 C<ev_periodic> - to cron or not to cron?	2107	=head2 C<ev_periodic> - to cron or not to cron?
1597		2108
1598	Periodic watchers are also timers of a kind, but they are very versatile	2109	Periodic watchers are also timers of a kind, but they are very versatile
1599	(and unfortunately a bit complex).	2110	(and unfortunately a bit complex).
1600		2111
1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2112	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1602	but on wall clock time (absolute time). You can tell a periodic watcher	2113	relative time, the physical time that passes) but on wall clock time
1603	to trigger after some specific point in time. For example, if you tell a	2114	(absolute time, the thing you can read on your calender or clock). The
1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2115	difference is that wall clock time can run faster or slower than real
1605	+ 10.>, that is, an absolute time not a delay) and then reset your system	2116	time, and time jumps are not uncommon (e.g. when you adjust your
1606	clock to January of the previous year, then it will take more than year	2117	wrist-watch).
1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1608	roughly 10 seconds later as it uses a relative timeout).
1609		2118
		2119	You can tell a periodic watcher to trigger after some specific point
		2120	in time: for example, if you tell a periodic watcher to trigger "in 10
		2121	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2122	not a delay) and then reset your system clock to January of the previous
		2123	year, then it will take a year or more to trigger the event (unlike an
		2124	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2125	it, as it uses a relative timeout).
		2126
1610	C<ev_periodic>s can also be used to implement vastly more complex timers,	2127	C<ev_periodic> watchers can also be used to implement vastly more complex
1611	such as triggering an event on each "midnight, local time", or other	2128	timers, such as triggering an event on each "midnight, local time", or
1612	complicated rules.	2129	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2130	those cannot react to time jumps.
1613		2131
1614	As with timers, the callback is guaranteed to be invoked only when the	2132	As with timers, the callback is guaranteed to be invoked only when the
1615	time (C<at>) has passed, but if multiple periodic timers become ready	2133	point in time where it is supposed to trigger has passed. If multiple
1616	during the same loop iteration, then order of execution is undefined.	2134	timers become ready during the same loop iteration then the ones with
		2135	earlier time-out values are invoked before ones with later time-out values
		2136	(but this is no longer true when a callback calls C<ev_run> recursively).
1617		2137
1618	=head3 Watcher-Specific Functions and Data Members	2138	=head3 Watcher-Specific Functions and Data Members
1619		2139
1620	=over 4	2140	=over 4
1621		2141
1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2142	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2143
1624	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2144	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1625		2145
1626	Lots of arguments, lets sort it out... There are basically three modes of	2146	Lots of arguments, let's sort it out... There are basically three modes of
1627	operation, and we will explain them from simplest to most complex:	2147	operation, and we will explain them from simplest to most complex:
1628		2148
1629	=over 4	2149	=over 4
1630		2150
1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2151	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1632		2152
1633	In this configuration the watcher triggers an event after the wall clock	2153	In this configuration the watcher triggers an event after the wall clock
1634	time C<at> has passed. It will not repeat and will not adjust when a time	2154	time C<offset> has passed. It will not repeat and will not adjust when a
1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2155	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1636	only run when the system clock reaches or surpasses this time.	2156	will be stopped and invoked when the system clock reaches or surpasses
		2157	this point in time.
1637		2158
1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2159	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1639		2160
1640	In this mode the watcher will always be scheduled to time out at the next	2161	In this mode the watcher will always be scheduled to time out at the next
1641	C<at + N * interval> time (for some integer N, which can also be negative)	2162	C<offset + N * interval> time (for some integer N, which can also be
1642	and then repeat, regardless of any time jumps.	2163	negative) and then repeat, regardless of any time jumps. The C<offset>
		2164	argument is merely an offset into the C<interval> periods.
1643		2165
1644	This can be used to create timers that do not drift with respect to the	2166	This can be used to create timers that do not drift with respect to the
1645	system clock, for example, here is a C<ev_periodic> that triggers each	2167	system clock, for example, here is an C<ev_periodic> that triggers each
1646	hour, on the hour:	2168	hour, on the hour (with respect to UTC):
1647		2169
1648	ev_periodic_set (&periodic, 0., 3600., 0);	2170	ev_periodic_set (&periodic, 0., 3600., 0);
1649		2171
1650	This doesn't mean there will always be 3600 seconds in between triggers,	2172	This doesn't mean there will always be 3600 seconds in between triggers,
1651	but only that the callback will be called when the system time shows a	2173	but only that the callback will be called when the system time shows a
1652	full hour (UTC), or more correctly, when the system time is evenly divisible	2174	full hour (UTC), or more correctly, when the system time is evenly divisible
1653	by 3600.	2175	by 3600.
1654		2176
1655	Another way to think about it (for the mathematically inclined) is that	2177	Another way to think about it (for the mathematically inclined) is that
1656	C<ev_periodic> will try to run the callback in this mode at the next possible	2178	C<ev_periodic> will try to run the callback in this mode at the next possible
1657	time where C<time = at (mod interval)>, regardless of any time jumps.	2179	time where C<time = offset (mod interval)>, regardless of any time jumps.
1658		2180
1659	For numerical stability it is preferable that the C<at> value is near	2181	For numerical stability it is preferable that the C<offset> value is near
1660	C<ev_now ()> (the current time), but there is no range requirement for	2182	C<ev_now ()> (the current time), but there is no range requirement for
1661	this value, and in fact is often specified as zero.	2183	this value, and in fact is often specified as zero.
1662		2184
1663	Note also that there is an upper limit to how often a timer can fire (CPU	2185	Note also that there is an upper limit to how often a timer can fire (CPU
1664	speed for example), so if C<interval> is very small then timing stability	2186	speed for example), so if C<interval> is very small then timing stability
1665	will of course deteriorate. Libev itself tries to be exact to be about one	2187	will of course deteriorate. Libev itself tries to be exact to be about one
1666	millisecond (if the OS supports it and the machine is fast enough).	2188	millisecond (if the OS supports it and the machine is fast enough).
1667		2189
1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2190	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1669		2191
1670	In this mode the values for C<interval> and C<at> are both being	2192	In this mode the values for C<interval> and C<offset> are both being
1671	ignored. Instead, each time the periodic watcher gets scheduled, the	2193	ignored. Instead, each time the periodic watcher gets scheduled, the
1672	reschedule callback will be called with the watcher as first, and the	2194	reschedule callback will be called with the watcher as first, and the
1673	current time as second argument.	2195	current time as second argument.
1674		2196
1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2197	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1676	ever, or make ANY event loop modifications whatsoever>.	2198	or make ANY other event loop modifications whatsoever, unless explicitly
		2199	allowed by documentation here>.
1677		2200
1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2201	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2202	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1680	only event loop modification you are allowed to do).	2203	only event loop modification you are allowed to do).
1681		2204
…		…
1711	a different time than the last time it was called (e.g. in a crond like	2234	a different time than the last time it was called (e.g. in a crond like
1712	program when the crontabs have changed).	2235	program when the crontabs have changed).
1713		2236
1714	=item ev_tstamp ev_periodic_at (ev_periodic *)	2237	=item ev_tstamp ev_periodic_at (ev_periodic *)
1715		2238
1716	When active, returns the absolute time that the watcher is supposed to	2239	When active, returns the absolute time that the watcher is supposed
1717	trigger next.	2240	to trigger next. This is not the same as the C<offset> argument to
		2241	C<ev_periodic_set>, but indeed works even in interval and manual
		2242	rescheduling modes.
1718		2243
1719	=item ev_tstamp offset [read-write]	2244	=item ev_tstamp offset [read-write]
1720		2245
1721	When repeating, this contains the offset value, otherwise this is the	2246	When repeating, this contains the offset value, otherwise this is the
1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2247	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2248	although libev might modify this value for better numerical stability).
1723		2249
1724	Can be modified any time, but changes only take effect when the periodic	2250	Can be modified any time, but changes only take effect when the periodic
1725	timer fires or C<ev_periodic_again> is being called.	2251	timer fires or C<ev_periodic_again> is being called.
1726		2252
1727	=item ev_tstamp interval [read-write]	2253	=item ev_tstamp interval [read-write]
…		…
1743	Example: Call a callback every hour, or, more precisely, whenever the	2269	Example: Call a callback every hour, or, more precisely, whenever the
1744	system time is divisible by 3600. The callback invocation times have	2270	system time is divisible by 3600. The callback invocation times have
1745	potentially a lot of jitter, but good long-term stability.	2271	potentially a lot of jitter, but good long-term stability.
1746		2272
1747	static void	2273	static void
1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2274	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1749	{	2275	{
1750	... its now a full hour (UTC, or TAI or whatever your clock follows)	2276	... its now a full hour (UTC, or TAI or whatever your clock follows)
1751	}	2277	}
1752		2278
1753	ev_periodic hourly_tick;	2279	ev_periodic hourly_tick;
…		…
1776		2302
1777	=head2 C<ev_signal> - signal me when a signal gets signalled!	2303	=head2 C<ev_signal> - signal me when a signal gets signalled!
1778		2304
1779	Signal watchers will trigger an event when the process receives a specific	2305	Signal watchers will trigger an event when the process receives a specific
1780	signal one or more times. Even though signals are very asynchronous, libev	2306	signal one or more times. Even though signals are very asynchronous, libev
1781	will try it's best to deliver signals synchronously, i.e. as part of the	2307	will try its best to deliver signals synchronously, i.e. as part of the
1782	normal event processing, like any other event.	2308	normal event processing, like any other event.
1783		2309
1784	If you want signals asynchronously, just use C<sigaction> as you would	2310	If you want signals to be delivered truly asynchronously, just use
1785	do without libev and forget about sharing the signal. You can even use	2311	C<sigaction> as you would do without libev and forget about sharing
1786	C<ev_async> from a signal handler to synchronously wake up an event loop.	2312	the signal. You can even use C<ev_async> from a signal handler to
		2313	synchronously wake up an event loop.
1787		2314
1788	You can configure as many watchers as you like per signal. Only when the	2315	You can configure as many watchers as you like for the same signal, but
		2316	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2317	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2318	C<SIGINT> in both the default loop and another loop at the same time. At
		2319	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2320
1789	first watcher gets started will libev actually register a signal handler	2321	When the first watcher gets started will libev actually register something
1790	with the kernel (thus it coexists with your own signal handlers as long as	2322	with the kernel (thus it coexists with your own signal handlers as long as
1791	you don't register any with libev for the same signal). Similarly, when	2323	you don't register any with libev for the same signal).
1792	the last signal watcher for a signal is stopped, libev will reset the
1793	signal handler to SIG_DFL (regardless of what it was set to before).
1794		2324
1795	If possible and supported, libev will install its handlers with	2325	If possible and supported, libev will install its handlers with
1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2326	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1797	interrupted. If you have a problem with system calls getting interrupted by	2327	not be unduly interrupted. If you have a problem with system calls getting
1798	signals you can block all signals in an C<ev_check> watcher and unblock	2328	interrupted by signals you can block all signals in an C<ev_check> watcher
1799	them in an C<ev_prepare> watcher.	2329	and unblock them in an C<ev_prepare> watcher.
		2330
		2331	=head3 The special problem of inheritance over fork/execve/pthread_create
		2332
		2333	Both the signal mask (C<sigprocmask>) and the signal disposition
		2334	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2335	stopping it again), that is, libev might or might not block the signal,
		2336	and might or might not set or restore the installed signal handler.
		2337
		2338	While this does not matter for the signal disposition (libev never
		2339	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2340	C<execve>), this matters for the signal mask: many programs do not expect
		2341	certain signals to be blocked.
		2342
		2343	This means that before calling C<exec> (from the child) you should reset
		2344	the signal mask to whatever "default" you expect (all clear is a good
		2345	choice usually).
		2346
		2347	The simplest way to ensure that the signal mask is reset in the child is
		2348	to install a fork handler with C<pthread_atfork> that resets it. That will
		2349	catch fork calls done by libraries (such as the libc) as well.
		2350
		2351	In current versions of libev, the signal will not be blocked indefinitely
		2352	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2353	the window of opportunity for problems, it will not go away, as libev
		2354	I<has> to modify the signal mask, at least temporarily.
		2355
		2356	So I can't stress this enough: I<If you do not reset your signal mask when
		2357	you expect it to be empty, you have a race condition in your code>. This
		2358	is not a libev-specific thing, this is true for most event libraries.
		2359
		2360	=head3 The special problem of threads signal handling
		2361
		2362	POSIX threads has problematic signal handling semantics, specifically,
		2363	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2364	threads in a process block signals, which is hard to achieve.
		2365
		2366	When you want to use sigwait (or mix libev signal handling with your own
		2367	for the same signals), you can tackle this problem by globally blocking
		2368	all signals before creating any threads (or creating them with a fully set
		2369	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2370	loops. Then designate one thread as "signal receiver thread" which handles
		2371	these signals. You can pass on any signals that libev might be interested
		2372	in by calling C<ev_feed_signal>.
1800		2373
1801	=head3 Watcher-Specific Functions and Data Members	2374	=head3 Watcher-Specific Functions and Data Members
1802		2375
1803	=over 4	2376	=over 4
1804		2377
…		…
1820	Example: Try to exit cleanly on SIGINT.	2393	Example: Try to exit cleanly on SIGINT.
1821		2394
1822	static void	2395	static void
1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2396	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1824	{	2397	{
1825	ev_unloop (loop, EVUNLOOP_ALL);	2398	ev_break (loop, EVBREAK_ALL);
1826	}	2399	}
1827		2400
1828	ev_signal signal_watcher;	2401	ev_signal signal_watcher;
1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2402	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1830	ev_signal_start (loop, &signal_watcher);	2403	ev_signal_start (loop, &signal_watcher);
…		…
1836	some child status changes (most typically when a child of yours dies or	2409	some child status changes (most typically when a child of yours dies or
1837	exits). It is permissible to install a child watcher I<after> the child	2410	exits). It is permissible to install a child watcher I<after> the child
1838	has been forked (which implies it might have already exited), as long	2411	has been forked (which implies it might have already exited), as long
1839	as the event loop isn't entered (or is continued from a watcher), i.e.,	2412	as the event loop isn't entered (or is continued from a watcher), i.e.,
1840	forking and then immediately registering a watcher for the child is fine,	2413	forking and then immediately registering a watcher for the child is fine,
1841	but forking and registering a watcher a few event loop iterations later is	2414	but forking and registering a watcher a few event loop iterations later or
1842	not.	2415	in the next callback invocation is not.
1843		2416
1844	Only the default event loop is capable of handling signals, and therefore	2417	Only the default event loop is capable of handling signals, and therefore
1845	you can only register child watchers in the default event loop.	2418	you can only register child watchers in the default event loop.
1846		2419
		2420	Due to some design glitches inside libev, child watchers will always be
		2421	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2422	libev)
		2423
1847	=head3 Process Interaction	2424	=head3 Process Interaction
1848		2425
1849	Libev grabs C<SIGCHLD> as soon as the default event loop is	2426	Libev grabs C<SIGCHLD> as soon as the default event loop is
1850	initialised. This is necessary to guarantee proper behaviour even if	2427	initialised. This is necessary to guarantee proper behaviour even if the
1851	the first child watcher is started after the child exits. The occurrence	2428	first child watcher is started after the child exits. The occurrence
1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2429	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1853	synchronously as part of the event loop processing. Libev always reaps all	2430	synchronously as part of the event loop processing. Libev always reaps all
1854	children, even ones not watched.	2431	children, even ones not watched.
1855		2432
1856	=head3 Overriding the Built-In Processing	2433	=head3 Overriding the Built-In Processing
…		…
1866	=head3 Stopping the Child Watcher	2443	=head3 Stopping the Child Watcher
1867		2444
1868	Currently, the child watcher never gets stopped, even when the	2445	Currently, the child watcher never gets stopped, even when the
1869	child terminates, so normally one needs to stop the watcher in the	2446	child terminates, so normally one needs to stop the watcher in the
1870	callback. Future versions of libev might stop the watcher automatically	2447	callback. Future versions of libev might stop the watcher automatically
1871	when a child exit is detected.	2448	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2449	problem).
1872		2450
1873	=head3 Watcher-Specific Functions and Data Members	2451	=head3 Watcher-Specific Functions and Data Members
1874		2452
1875	=over 4	2453	=over 4
1876		2454
…		…
2179		2757
2180	=head3 Watcher-Specific Functions and Data Members	2758	=head3 Watcher-Specific Functions and Data Members
2181		2759
2182	=over 4	2760	=over 4
2183		2761
2184	=item ev_idle_init (ev_signal *, callback)	2762	=item ev_idle_init (ev_idle *, callback)
2185		2763
2186	Initialises and configures the idle watcher - it has no parameters of any	2764	Initialises and configures the idle watcher - it has no parameters of any
2187	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2765	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2188	believe me.	2766	believe me.
2189		2767
…		…
2202	// no longer anything immediate to do.	2780	// no longer anything immediate to do.
2203	}	2781	}
2204		2782
2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2783	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2206	ev_idle_init (idle_watcher, idle_cb);	2784	ev_idle_init (idle_watcher, idle_cb);
2207	ev_idle_start (loop, idle_cb);	2785	ev_idle_start (loop, idle_watcher);
2208		2786
2209		2787
2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2788	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2211		2789
2212	Prepare and check watchers are usually (but not always) used in pairs:	2790	Prepare and check watchers are usually (but not always) used in pairs:
2213	prepare watchers get invoked before the process blocks and check watchers	2791	prepare watchers get invoked before the process blocks and check watchers
2214	afterwards.	2792	afterwards.
2215		2793
2216	You I<must not> call C<ev_loop> or similar functions that enter	2794	You I<must not> call C<ev_run> or similar functions that enter
2217	the current event loop from either C<ev_prepare> or C<ev_check>	2795	the current event loop from either C<ev_prepare> or C<ev_check>
2218	watchers. Other loops than the current one are fine, however. The	2796	watchers. Other loops than the current one are fine, however. The
2219	rationale behind this is that you do not need to check for recursion in	2797	rationale behind this is that you do not need to check for recursion in
2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2798	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2221	C<ev_check> so if you have one watcher of each kind they will always be	2799	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2305	struct pollfd fds [nfd];	2883	struct pollfd fds [nfd];
2306	// actual code will need to loop here and realloc etc.	2884	// actual code will need to loop here and realloc etc.
2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2885	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2308		2886
2309	/* the callback is illegal, but won't be called as we stop during check */	2887	/* the callback is illegal, but won't be called as we stop during check */
2310	ev_timer_init (&tw, 0, timeout * 1e-3);	2888	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2311	ev_timer_start (loop, &tw);	2889	ev_timer_start (loop, &tw);
2312		2890
2313	// create one ev_io per pollfd	2891	// create one ev_io per pollfd
2314	for (int i = 0; i < nfd; ++i)	2892	for (int i = 0; i < nfd; ++i)
2315	{	2893	{
…		…
2389		2967
2390	if (timeout >= 0)	2968	if (timeout >= 0)
2391	// create/start timer	2969	// create/start timer
2392		2970
2393	// poll	2971	// poll
2394	ev_loop (EV_A_ 0);	2972	ev_run (EV_A_ 0);
2395		2973
2396	// stop timer again	2974	// stop timer again
2397	if (timeout >= 0)	2975	if (timeout >= 0)
2398	ev_timer_stop (EV_A_ &to);	2976	ev_timer_stop (EV_A_ &to);
2399		2977
…		…
2477	if you do not want that, you need to temporarily stop the embed watcher).	3055	if you do not want that, you need to temporarily stop the embed watcher).
2478		3056
2479	=item ev_embed_sweep (loop, ev_embed *)	3057	=item ev_embed_sweep (loop, ev_embed *)
2480		3058
2481	Make a single, non-blocking sweep over the embedded loop. This works	3059	Make a single, non-blocking sweep over the embedded loop. This works
2482	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3060	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2483	appropriate way for embedded loops.	3061	appropriate way for embedded loops.
2484		3062
2485	=item struct ev_loop *other [read-only]	3063	=item struct ev_loop *other [read-only]
2486		3064
2487	The embedded event loop.	3065	The embedded event loop.
…		…
2545	event loop blocks next and before C<ev_check> watchers are being called,	3123	event loop blocks next and before C<ev_check> watchers are being called,
2546	and only in the child after the fork. If whoever good citizen calling	3124	and only in the child after the fork. If whoever good citizen calling
2547	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3125	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2548	handlers will be invoked, too, of course.	3126	handlers will be invoked, too, of course.
2549		3127
		3128	=head3 The special problem of life after fork - how is it possible?
		3129
		3130	Most uses of C<fork()> consist of forking, then some simple calls to set
		3131	up/change the process environment, followed by a call to C<exec()>. This
		3132	sequence should be handled by libev without any problems.
		3133
		3134	This changes when the application actually wants to do event handling
		3135	in the child, or both parent in child, in effect "continuing" after the
		3136	fork.
		3137
		3138	The default mode of operation (for libev, with application help to detect
		3139	forks) is to duplicate all the state in the child, as would be expected
		3140	when I<either> the parent I<or> the child process continues.
		3141
		3142	When both processes want to continue using libev, then this is usually the
		3143	wrong result. In that case, usually one process (typically the parent) is
		3144	supposed to continue with all watchers in place as before, while the other
		3145	process typically wants to start fresh, i.e. without any active watchers.
		3146
		3147	The cleanest and most efficient way to achieve that with libev is to
		3148	simply create a new event loop, which of course will be "empty", and
		3149	use that for new watchers. This has the advantage of not touching more
		3150	memory than necessary, and thus avoiding the copy-on-write, and the
		3151	disadvantage of having to use multiple event loops (which do not support
		3152	signal watchers).
		3153
		3154	When this is not possible, or you want to use the default loop for
		3155	other reasons, then in the process that wants to start "fresh", call
		3156	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3157	Destroying the default loop will "orphan" (not stop) all registered
		3158	watchers, so you have to be careful not to execute code that modifies
		3159	those watchers. Note also that in that case, you have to re-register any
		3160	signal watchers.
		3161
2550	=head3 Watcher-Specific Functions and Data Members	3162	=head3 Watcher-Specific Functions and Data Members
2551		3163
2552	=over 4	3164	=over 4
2553		3165
2554	=item ev_fork_init (ev_signal *, callback)	3166	=item ev_fork_init (ev_fork *, callback)
2555		3167
2556	Initialises and configures the fork watcher - it has no parameters of any	3168	Initialises and configures the fork watcher - it has no parameters of any
2557	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3169	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2558	believe me.	3170	really.
2559		3171
2560	=back	3172	=back
2561		3173
2562		3174
		3175	=head2 C<ev_cleanup> - even the best things end
		3176
		3177	Cleanup watchers are called just before the event loop is being destroyed
		3178	by a call to C<ev_loop_destroy>.
		3179
		3180	While there is no guarantee that the event loop gets destroyed, cleanup
		3181	watchers provide a convenient method to install cleanup hooks for your
		3182	program, worker threads and so on - you just to make sure to destroy the
		3183	loop when you want them to be invoked.
		3184
		3185	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3186	all other watchers, they do not keep a reference to the event loop (which
		3187	makes a lot of sense if you think about it). Like all other watchers, you
		3188	can call libev functions in the callback, except C<ev_cleanup_start>.
		3189
		3190	=head3 Watcher-Specific Functions and Data Members
		3191
		3192	=over 4
		3193
		3194	=item ev_cleanup_init (ev_cleanup *, callback)
		3195
		3196	Initialises and configures the cleanup watcher - it has no parameters of
		3197	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3198	pointless, I assure you.
		3199
		3200	=back
		3201
		3202	Example: Register an atexit handler to destroy the default loop, so any
		3203	cleanup functions are called.
		3204
		3205	static void
		3206	program_exits (void)
		3207	{
		3208	ev_loop_destroy (EV_DEFAULT_UC);
		3209	}
		3210
		3211	...
		3212	atexit (program_exits);
		3213
		3214
2563	=head2 C<ev_async> - how to wake up another event loop	3215	=head2 C<ev_async> - how to wake up an event loop
2564		3216
2565	In general, you cannot use an C<ev_loop> from multiple threads or other	3217	In general, you cannot use an C<ev_run> from multiple threads or other
2566	asynchronous sources such as signal handlers (as opposed to multiple event	3218	asynchronous sources such as signal handlers (as opposed to multiple event
2567	loops - those are of course safe to use in different threads).	3219	loops - those are of course safe to use in different threads).
2568		3220
2569	Sometimes, however, you need to wake up another event loop you do not	3221	Sometimes, however, you need to wake up an event loop you do not control,
2570	control, for example because it belongs to another thread. This is what	3222	for example because it belongs to another thread. This is what C<ev_async>
2571	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3223	watchers do: as long as the C<ev_async> watcher is active, you can signal
2572	can signal it by calling C<ev_async_send>, which is thread- and signal	3224	it by calling C<ev_async_send>, which is thread- and signal safe.
2573	safe.
2574		3225
2575	This functionality is very similar to C<ev_signal> watchers, as signals,	3226	This functionality is very similar to C<ev_signal> watchers, as signals,
2576	too, are asynchronous in nature, and signals, too, will be compressed	3227	too, are asynchronous in nature, and signals, too, will be compressed
2577	(i.e. the number of callback invocations may be less than the number of	3228	(i.e. the number of callback invocations may be less than the number of
2578	C<ev_async_sent> calls).	3229	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3230	of "global async watchers" by using a watcher on an otherwise unused
		3231	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3232	even without knowing which loop owns the signal.
2579		3233
2580	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3234	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2581	just the default loop.	3235	just the default loop.
2582		3236
2583	=head3 Queueing	3237	=head3 Queueing
2584		3238
2585	C<ev_async> does not support queueing of data in any way. The reason	3239	C<ev_async> does not support queueing of data in any way. The reason
2586	is that the author does not know of a simple (or any) algorithm for a	3240	is that the author does not know of a simple (or any) algorithm for a
2587	multiple-writer-single-reader queue that works in all cases and doesn't	3241	multiple-writer-single-reader queue that works in all cases and doesn't
2588	need elaborate support such as pthreads.	3242	need elaborate support such as pthreads or unportable memory access
		3243	semantics.
2589		3244
2590	That means that if you want to queue data, you have to provide your own	3245	That means that if you want to queue data, you have to provide your own
2591	queue. But at least I can tell you how to implement locking around your	3246	queue. But at least I can tell you how to implement locking around your
2592	queue:	3247	queue:
2593		3248
…		…
2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3337	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2683	C<ev_feed_event>, this call is safe to do from other threads, signal or	3338	C<ev_feed_event>, this call is safe to do from other threads, signal or
2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3339	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2685	section below on what exactly this means).	3340	section below on what exactly this means).
2686		3341
		3342	Note that, as with other watchers in libev, multiple events might get
		3343	compressed into a single callback invocation (another way to look at this
		3344	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3345	reset when the event loop detects that).
		3346
2687	This call incurs the overhead of a system call only once per loop iteration,	3347	This call incurs the overhead of a system call only once per event loop
2688	so while the overhead might be noticeable, it doesn't apply to repeated	3348	iteration, so while the overhead might be noticeable, it doesn't apply to
2689	calls to C<ev_async_send>.	3349	repeated calls to C<ev_async_send> for the same event loop.
2690		3350
2691	=item bool = ev_async_pending (ev_async *)	3351	=item bool = ev_async_pending (ev_async *)
2692		3352
2693	Returns a non-zero value when C<ev_async_send> has been called on the	3353	Returns a non-zero value when C<ev_async_send> has been called on the
2694	watcher but the event has not yet been processed (or even noted) by the	3354	watcher but the event has not yet been processed (or even noted) by the
…		…
2697	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3357	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2698	the loop iterates next and checks for the watcher to have become active,	3358	the loop iterates next and checks for the watcher to have become active,
2699	it will reset the flag again. C<ev_async_pending> can be used to very	3359	it will reset the flag again. C<ev_async_pending> can be used to very
2700	quickly check whether invoking the loop might be a good idea.	3360	quickly check whether invoking the loop might be a good idea.
2701		3361
2702	Not that this does I<not> check whether the watcher itself is pending, only	3362	Not that this does I<not> check whether the watcher itself is pending,
2703	whether it has been requested to make this watcher pending.	3363	only whether it has been requested to make this watcher pending: there
		3364	is a time window between the event loop checking and resetting the async
		3365	notification, and the callback being invoked.
2704		3366
2705	=back	3367	=back
2706		3368
2707		3369
2708	=head1 OTHER FUNCTIONS	3370	=head1 OTHER FUNCTIONS
…		…
2725		3387
2726	If C<timeout> is less than 0, then no timeout watcher will be	3388	If C<timeout> is less than 0, then no timeout watcher will be
2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3389	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2728	repeat = 0) will be started. C<0> is a valid timeout.	3390	repeat = 0) will be started. C<0> is a valid timeout.
2729		3391
2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3392	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2731	passed an C<revents> set like normal event callbacks (a combination of	3393	passed an C<revents> set like normal event callbacks (a combination of
2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3394	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2733	value passed to C<ev_once>. Note that it is possible to receive I<both>	3395	value passed to C<ev_once>. Note that it is possible to receive I<both>
2734	a timeout and an io event at the same time - you probably should give io	3396	a timeout and an io event at the same time - you probably should give io
2735	events precedence.	3397	events precedence.
2736		3398
2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3399	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2738		3400
2739	static void stdin_ready (int revents, void *arg)	3401	static void stdin_ready (int revents, void *arg)
2740	{	3402	{
2741	if (revents & EV_READ)	3403	if (revents & EV_READ)
2742	/* stdin might have data for us, joy! */;	3404	/* stdin might have data for us, joy! */;
2743	else if (revents & EV_TIMEOUT)	3405	else if (revents & EV_TIMER)
2744	/* doh, nothing entered */;	3406	/* doh, nothing entered */;
2745	}	3407	}
2746		3408
2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3409	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2748		3410
2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2750
2751	Feeds the given event set into the event loop, as if the specified event
2752	had happened for the specified watcher (which must be a pointer to an
2753	initialised but not necessarily started event watcher).
2754
2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3411	=item ev_feed_fd_event (loop, int fd, int revents)
2756		3412
2757	Feed an event on the given fd, as if a file descriptor backend detected	3413	Feed an event on the given fd, as if a file descriptor backend detected
2758	the given events it.	3414	the given events it.
2759		3415
2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3416	=item ev_feed_signal_event (loop, int signum)
2761		3417
2762	Feed an event as if the given signal occurred (C<loop> must be the default	3418	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2763	loop!).	3419	which is async-safe.
		3420
		3421	=back
		3422
		3423
		3424	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3425
		3426	This section explains some common idioms that are not immediately
		3427	obvious. Note that examples are sprinkled over the whole manual, and this
		3428	section only contains stuff that wouldn't fit anywhere else.
		3429
		3430	=over 4
		3431
		3432	=item Model/nested event loop invocations and exit conditions.
		3433
		3434	Often (especially in GUI toolkits) there are places where you have
		3435	I<modal> interaction, which is most easily implemented by recursively
		3436	invoking C<ev_run>.
		3437
		3438	This brings the problem of exiting - a callback might want to finish the
		3439	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3440	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3441	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3442	other combination: In these cases, C<ev_break> will not work alone.
		3443
		3444	The solution is to maintain "break this loop" variable for each C<ev_run>
		3445	invocation, and use a loop around C<ev_run> until the condition is
		3446	triggered, using C<EVRUN_ONCE>:
		3447
		3448	// main loop
		3449	int exit_main_loop = 0;
		3450
		3451	while (!exit_main_loop)
		3452	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3453
		3454	// in a model watcher
		3455	int exit_nested_loop = 0;
		3456
		3457	while (!exit_nested_loop)
		3458	ev_run (EV_A_ EVRUN_ONCE);
		3459
		3460	To exit from any of these loops, just set the corresponding exit variable:
		3461
		3462	// exit modal loop
		3463	exit_nested_loop = 1;
		3464
		3465	// exit main program, after modal loop is finished
		3466	exit_main_loop = 1;
		3467
		3468	// exit both
		3469	exit_main_loop = exit_nested_loop = 1;
2764		3470
2765	=back	3471	=back
2766		3472
2767		3473
2768	=head1 LIBEVENT EMULATION	3474	=head1 LIBEVENT EMULATION
2769		3475
2770	Libev offers a compatibility emulation layer for libevent. It cannot	3476	Libev offers a compatibility emulation layer for libevent. It cannot
2771	emulate the internals of libevent, so here are some usage hints:	3477	emulate the internals of libevent, so here are some usage hints:
2772		3478
2773	=over 4	3479	=over 4
		3480
		3481	=item * Only the libevent-1.4.1-beta API is being emulated.
		3482
		3483	This was the newest libevent version available when libev was implemented,
		3484	and is still mostly unchanged in 2010.
2774		3485
2775	=item * Use it by including <event.h>, as usual.	3486	=item * Use it by including <event.h>, as usual.
2776		3487
2777	=item * The following members are fully supported: ev_base, ev_callback,	3488	=item * The following members are fully supported: ev_base, ev_callback,
2778	ev_arg, ev_fd, ev_res, ev_events.	3489	ev_arg, ev_fd, ev_res, ev_events.
…		…
2784	=item * Priorities are not currently supported. Initialising priorities	3495	=item * Priorities are not currently supported. Initialising priorities
2785	will fail and all watchers will have the same priority, even though there	3496	will fail and all watchers will have the same priority, even though there
2786	is an ev_pri field.	3497	is an ev_pri field.
2787		3498
2788	=item * In libevent, the last base created gets the signals, in libev, the	3499	=item * In libevent, the last base created gets the signals, in libev, the
2789	first base created (== the default loop) gets the signals.	3500	base that registered the signal gets the signals.
2790		3501
2791	=item * Other members are not supported.	3502	=item * Other members are not supported.
2792		3503
2793	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3504	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2794	to use the libev header file and library.	3505	to use the libev header file and library.
…		…
2813	Care has been taken to keep the overhead low. The only data member the C++	3524	Care has been taken to keep the overhead low. The only data member the C++
2814	classes add (compared to plain C-style watchers) is the event loop pointer	3525	classes add (compared to plain C-style watchers) is the event loop pointer
2815	that the watcher is associated with (or no additional members at all if	3526	that the watcher is associated with (or no additional members at all if
2816	you disable C<EV_MULTIPLICITY> when embedding libev).	3527	you disable C<EV_MULTIPLICITY> when embedding libev).
2817		3528
2818	Currently, functions, and static and non-static member functions can be	3529	Currently, functions, static and non-static member functions and classes
2819	used as callbacks. Other types should be easy to add as long as they only	3530	with C<operator ()> can be used as callbacks. Other types should be easy
2820	need one additional pointer for context. If you need support for other	3531	to add as long as they only need one additional pointer for context. If
2821	types of functors please contact the author (preferably after implementing	3532	you need support for other types of functors please contact the author
2822	it).	3533	(preferably after implementing it).
2823		3534
2824	Here is a list of things available in the C<ev> namespace:	3535	Here is a list of things available in the C<ev> namespace:
2825		3536
2826	=over 4	3537	=over 4
2827		3538
…		…
2845		3556
2846	=over 4	3557	=over 4
2847		3558
2848	=item ev::TYPE::TYPE ()	3559	=item ev::TYPE::TYPE ()
2849		3560
2850	=item ev::TYPE::TYPE (struct ev_loop *)	3561	=item ev::TYPE::TYPE (loop)
2851		3562
2852	=item ev::TYPE::~TYPE	3563	=item ev::TYPE::~TYPE
2853		3564
2854	The constructor (optionally) takes an event loop to associate the watcher	3565	The constructor (optionally) takes an event loop to associate the watcher
2855	with. If it is omitted, it will use C<EV_DEFAULT>.	3566	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2888	myclass obj;	3599	myclass obj;
2889	ev::io iow;	3600	ev::io iow;
2890	iow.set <myclass, &myclass::io_cb> (&obj);	3601	iow.set <myclass, &myclass::io_cb> (&obj);
2891		3602
2892	=item w->set (object *)	3603	=item w->set (object *)
2893
2894	This is an B<experimental> feature that might go away in a future version.
2895		3604
2896	This is a variation of a method callback - leaving out the method to call	3605	This is a variation of a method callback - leaving out the method to call
2897	will default the method to C<operator ()>, which makes it possible to use	3606	will default the method to C<operator ()>, which makes it possible to use
2898	functor objects without having to manually specify the C<operator ()> all	3607	functor objects without having to manually specify the C<operator ()> all
2899	the time. Incidentally, you can then also leave out the template argument	3608	the time. Incidentally, you can then also leave out the template argument
…		…
2932	Example: Use a plain function as callback.	3641	Example: Use a plain function as callback.
2933		3642
2934	static void io_cb (ev::io &w, int revents) { }	3643	static void io_cb (ev::io &w, int revents) { }
2935	iow.set <io_cb> ();	3644	iow.set <io_cb> ();
2936		3645
2937	=item w->set (struct ev_loop *)	3646	=item w->set (loop)
2938		3647
2939	Associates a different C<struct ev_loop> with this watcher. You can only	3648	Associates a different C<struct ev_loop> with this watcher. You can only
2940	do this when the watcher is inactive (and not pending either).	3649	do this when the watcher is inactive (and not pending either).
2941		3650
2942	=item w->set ([arguments])	3651	=item w->set ([arguments])
2943		3652
2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3653	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2945	called at least once. Unlike the C counterpart, an active watcher gets	3654	method or a suitable start method must be called at least once. Unlike the
2946	automatically stopped and restarted when reconfiguring it with this	3655	C counterpart, an active watcher gets automatically stopped and restarted
2947	method.	3656	when reconfiguring it with this method.
2948		3657
2949	=item w->start ()	3658	=item w->start ()
2950		3659
2951	Starts the watcher. Note that there is no C<loop> argument, as the	3660	Starts the watcher. Note that there is no C<loop> argument, as the
2952	constructor already stores the event loop.	3661	constructor already stores the event loop.
2953		3662
		3663	=item w->start ([arguments])
		3664
		3665	Instead of calling C<set> and C<start> methods separately, it is often
		3666	convenient to wrap them in one call. Uses the same type of arguments as
		3667	the configure C<set> method of the watcher.
		3668
2954	=item w->stop ()	3669	=item w->stop ()
2955		3670
2956	Stops the watcher if it is active. Again, no C<loop> argument.	3671	Stops the watcher if it is active. Again, no C<loop> argument.
2957		3672
2958	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3673	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2970		3685
2971	=back	3686	=back
2972		3687
2973	=back	3688	=back
2974		3689
2975	Example: Define a class with an IO and idle watcher, start one of them in	3690	Example: Define a class with two I/O and idle watchers, start the I/O
2976	the constructor.	3691	watchers in the constructor.
2977		3692
2978	class myclass	3693	class myclass
2979	{	3694	{
2980	ev::io io ; void io_cb (ev::io &w, int revents);	3695	ev::io io ; void io_cb (ev::io &w, int revents);
		3696	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3697	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2982		3698
2983	myclass (int fd)	3699	myclass (int fd)
2984	{	3700	{
2985	io .set <myclass, &myclass::io_cb > (this);	3701	io .set <myclass, &myclass::io_cb > (this);
		3702	io2 .set <myclass, &myclass::io2_cb > (this);
2986	idle.set <myclass, &myclass::idle_cb> (this);	3703	idle.set <myclass, &myclass::idle_cb> (this);
2987		3704
2988	io.start (fd, ev::READ);	3705	io.set (fd, ev::WRITE); // configure the watcher
		3706	io.start (); // start it whenever convenient
		3707
		3708	io2.start (fd, ev::READ); // set + start in one call
2989	}	3709	}
2990	};	3710	};
2991		3711
2992		3712
2993	=head1 OTHER LANGUAGE BINDINGS	3713	=head1 OTHER LANGUAGE BINDINGS
…		…
3012	L<http://software.schmorp.de/pkg/EV>.	3732	L<http://software.schmorp.de/pkg/EV>.
3013		3733
3014	=item Python	3734	=item Python
3015		3735
3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3736	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
3017	seems to be quite complete and well-documented. Note, however, that the	3737	seems to be quite complete and well-documented.
3018	patch they require for libev is outright dangerous as it breaks the ABI
3019	for everybody else, and therefore, should never be applied in an installed
3020	libev (if python requires an incompatible ABI then it needs to embed
3021	libev).
3022		3738
3023	=item Ruby	3739	=item Ruby
3024		3740
3025	Tony Arcieri has written a ruby extension that offers access to a subset	3741	Tony Arcieri has written a ruby extension that offers access to a subset
3026	of the libev API and adds file handle abstractions, asynchronous DNS and	3742	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
3028	L<http://rev.rubyforge.org/>.	3744	L<http://rev.rubyforge.org/>.
3029		3745
3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>	3746	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
3031	makes rev work even on mingw.	3747	makes rev work even on mingw.
3032		3748
		3749	=item Haskell
		3750
		3751	A haskell binding to libev is available at
		3752	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3753
3033	=item D	3754	=item D
3034		3755
3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3756	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3757	be found at L<http://proj.llucax.com.ar/wiki/evd>.
3037		3758
3038	=item Ocaml	3759	=item Ocaml
3039		3760
3040	Erkki Seppala has written Ocaml bindings for libev, to be found at	3761	Erkki Seppala has written Ocaml bindings for libev, to be found at
3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3762	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3763
		3764	=item Lua
		3765
		3766	Brian Maher has written a partial interface to libev for lua (at the
		3767	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3768	L<http://github.com/brimworks/lua-ev>.
3042		3769
3043	=back	3770	=back
3044		3771
3045		3772
3046	=head1 MACRO MAGIC	3773	=head1 MACRO MAGIC
…		…
3060	loop argument"). The C<EV_A> form is used when this is the sole argument,	3787	loop argument"). The C<EV_A> form is used when this is the sole argument,
3061	C<EV_A_> is used when other arguments are following. Example:	3788	C<EV_A_> is used when other arguments are following. Example:
3062		3789
3063	ev_unref (EV_A);	3790	ev_unref (EV_A);
3064	ev_timer_add (EV_A_ watcher);	3791	ev_timer_add (EV_A_ watcher);
3065	ev_loop (EV_A_ 0);	3792	ev_run (EV_A_ 0);
3066		3793
3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3794	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3068	which is often provided by the following macro.	3795	which is often provided by the following macro.
3069		3796
3070	=item C<EV_P>, C<EV_P_>	3797	=item C<EV_P>, C<EV_P_>
…		…
3110	}	3837	}
3111		3838
3112	ev_check check;	3839	ev_check check;
3113	ev_check_init (&check, check_cb);	3840	ev_check_init (&check, check_cb);
3114	ev_check_start (EV_DEFAULT_ &check);	3841	ev_check_start (EV_DEFAULT_ &check);
3115	ev_loop (EV_DEFAULT_ 0);	3842	ev_run (EV_DEFAULT_ 0);
3116		3843
3117	=head1 EMBEDDING	3844	=head1 EMBEDDING
3118		3845
3119	Libev can (and often is) directly embedded into host	3846	Libev can (and often is) directly embedded into host
3120	applications. Examples of applications that embed it include the Deliantra	3847	applications. Examples of applications that embed it include the Deliantra
…		…
3200	libev.m4	3927	libev.m4
3201		3928
3202	=head2 PREPROCESSOR SYMBOLS/MACROS	3929	=head2 PREPROCESSOR SYMBOLS/MACROS
3203		3930
3204	Libev can be configured via a variety of preprocessor symbols you have to	3931	Libev can be configured via a variety of preprocessor symbols you have to
3205	define before including any of its files. The default in the absence of	3932	define before including (or compiling) any of its files. The default in
3206	autoconf is documented for every option.	3933	the absence of autoconf is documented for every option.
		3934
		3935	Symbols marked with "(h)" do not change the ABI, and can have different
		3936	values when compiling libev vs. including F<ev.h>, so it is permissible
		3937	to redefine them before including F<ev.h> without breaking compatibility
		3938	to a compiled library. All other symbols change the ABI, which means all
		3939	users of libev and the libev code itself must be compiled with compatible
		3940	settings.
3207		3941
3208	=over 4	3942	=over 4
3209		3943
		3944	=item EV_COMPAT3 (h)
		3945
		3946	Backwards compatibility is a major concern for libev. This is why this
		3947	release of libev comes with wrappers for the functions and symbols that
		3948	have been renamed between libev version 3 and 4.
		3949
		3950	You can disable these wrappers (to test compatibility with future
		3951	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3952	sources. This has the additional advantage that you can drop the C<struct>
		3953	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3954	typedef in that case.
		3955
		3956	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3957	and in some even more future version the compatibility code will be
		3958	removed completely.
		3959
3210	=item EV_STANDALONE	3960	=item EV_STANDALONE (h)
3211		3961
3212	Must always be C<1> if you do not use autoconf configuration, which	3962	Must always be C<1> if you do not use autoconf configuration, which
3213	keeps libev from including F<config.h>, and it also defines dummy	3963	keeps libev from including F<config.h>, and it also defines dummy
3214	implementations for some libevent functions (such as logging, which is not	3964	implementations for some libevent functions (such as logging, which is not
3215	supported). It will also not define any of the structs usually found in	3965	supported). It will also not define any of the structs usually found in
3216	F<event.h> that are not directly supported by the libev core alone.	3966	F<event.h> that are not directly supported by the libev core alone.
3217		3967
3218	In stanbdalone mode, libev will still try to automatically deduce the	3968	In standalone mode, libev will still try to automatically deduce the
3219	configuration, but has to be more conservative.	3969	configuration, but has to be more conservative.
3220		3970
3221	=item EV_USE_MONOTONIC	3971	=item EV_USE_MONOTONIC
3222		3972
3223	If defined to be C<1>, libev will try to detect the availability of the	3973	If defined to be C<1>, libev will try to detect the availability of the
…		…
3288	be used is the winsock select). This means that it will call	4038	be used is the winsock select). This means that it will call
3289	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4039	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3290	it is assumed that all these functions actually work on fds, even	4040	it is assumed that all these functions actually work on fds, even
3291	on win32. Should not be defined on non-win32 platforms.	4041	on win32. Should not be defined on non-win32 platforms.
3292		4042
3293	=item EV_FD_TO_WIN32_HANDLE	4043	=item EV_FD_TO_WIN32_HANDLE(fd)
3294		4044
3295	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4045	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3296	file descriptors to socket handles. When not defining this symbol (the	4046	file descriptors to socket handles. When not defining this symbol (the
3297	default), then libev will call C<_get_osfhandle>, which is usually	4047	default), then libev will call C<_get_osfhandle>, which is usually
3298	correct. In some cases, programs use their own file descriptor management,	4048	correct. In some cases, programs use their own file descriptor management,
3299	in which case they can provide this function to map fds to socket handles.	4049	in which case they can provide this function to map fds to socket handles.
		4050
		4051	=item EV_WIN32_HANDLE_TO_FD(handle)
		4052
		4053	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4054	using the standard C<_open_osfhandle> function. For programs implementing
		4055	their own fd to handle mapping, overwriting this function makes it easier
		4056	to do so. This can be done by defining this macro to an appropriate value.
		4057
		4058	=item EV_WIN32_CLOSE_FD(fd)
		4059
		4060	If programs implement their own fd to handle mapping on win32, then this
		4061	macro can be used to override the C<close> function, useful to unregister
		4062	file descriptors again. Note that the replacement function has to close
		4063	the underlying OS handle.
3300		4064
3301	=item EV_USE_POLL	4065	=item EV_USE_POLL
3302		4066
3303	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4067	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3304	backend. Otherwise it will be enabled on non-win32 platforms. It	4068	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3351	as well as for signal and thread safety in C<ev_async> watchers.	4115	as well as for signal and thread safety in C<ev_async> watchers.
3352		4116
3353	In the absence of this define, libev will use C<sig_atomic_t volatile>	4117	In the absence of this define, libev will use C<sig_atomic_t volatile>
3354	(from F<signal.h>), which is usually good enough on most platforms.	4118	(from F<signal.h>), which is usually good enough on most platforms.
3355		4119
3356	=item EV_H	4120	=item EV_H (h)
3357		4121
3358	The name of the F<ev.h> header file used to include it. The default if	4122	The name of the F<ev.h> header file used to include it. The default if
3359	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4123	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3360	used to virtually rename the F<ev.h> header file in case of conflicts.	4124	used to virtually rename the F<ev.h> header file in case of conflicts.
3361		4125
3362	=item EV_CONFIG_H	4126	=item EV_CONFIG_H (h)
3363		4127
3364	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4128	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3365	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4129	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3366	C<EV_H>, above.	4130	C<EV_H>, above.
3367		4131
3368	=item EV_EVENT_H	4132	=item EV_EVENT_H (h)
3369		4133
3370	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4134	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3371	of how the F<event.h> header can be found, the default is C<"event.h">.	4135	of how the F<event.h> header can be found, the default is C<"event.h">.
3372		4136
3373	=item EV_PROTOTYPES	4137	=item EV_PROTOTYPES (h)
3374		4138
3375	If defined to be C<0>, then F<ev.h> will not define any function	4139	If defined to be C<0>, then F<ev.h> will not define any function
3376	prototypes, but still define all the structs and other symbols. This is	4140	prototypes, but still define all the structs and other symbols. This is
3377	occasionally useful if you want to provide your own wrapper functions	4141	occasionally useful if you want to provide your own wrapper functions
3378	around libev functions.	4142	around libev functions.
…		…
3400	fine.	4164	fine.
3401		4165
3402	If your embedding application does not need any priorities, defining these	4166	If your embedding application does not need any priorities, defining these
3403	both to C<0> will save some memory and CPU.	4167	both to C<0> will save some memory and CPU.
3404		4168
3405	=item EV_PERIODIC_ENABLE	4169	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4170	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4171	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3406		4172
3407	If undefined or defined to be C<1>, then periodic timers are supported. If	4173	If undefined or defined to be C<1> (and the platform supports it), then
3408	defined to be C<0>, then they are not. Disabling them saves a few kB of	4174	the respective watcher type is supported. If defined to be C<0>, then it
3409	code.	4175	is not. Disabling watcher types mainly saves code size.
3410		4176
3411	=item EV_IDLE_ENABLE	4177	=item EV_FEATURES
3412
3413	If undefined or defined to be C<1>, then idle watchers are supported. If
3414	defined to be C<0>, then they are not. Disabling them saves a few kB of
3415	code.
3416
3417	=item EV_EMBED_ENABLE
3418
3419	If undefined or defined to be C<1>, then embed watchers are supported. If
3420	defined to be C<0>, then they are not. Embed watchers rely on most other
3421	watcher types, which therefore must not be disabled.
3422
3423	=item EV_STAT_ENABLE
3424
3425	If undefined or defined to be C<1>, then stat watchers are supported. If
3426	defined to be C<0>, then they are not.
3427
3428	=item EV_FORK_ENABLE
3429
3430	If undefined or defined to be C<1>, then fork watchers are supported. If
3431	defined to be C<0>, then they are not.
3432
3433	=item EV_ASYNC_ENABLE
3434
3435	If undefined or defined to be C<1>, then async watchers are supported. If
3436	defined to be C<0>, then they are not.
3437
3438	=item EV_MINIMAL
3439		4178
3440	If you need to shave off some kilobytes of code at the expense of some	4179	If you need to shave off some kilobytes of code at the expense of some
3441	speed, define this symbol to C<1>. Currently this is used to override some	4180	speed (but with the full API), you can define this symbol to request
3442	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4181	certain subsets of functionality. The default is to enable all features
3443	much smaller 2-heap for timer management over the default 4-heap.	4182	that can be enabled on the platform.
		4183
		4184	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4185	with some broad features you want) and then selectively re-enable
		4186	additional parts you want, for example if you want everything minimal,
		4187	but multiple event loop support, async and child watchers and the poll
		4188	backend, use this:
		4189
		4190	#define EV_FEATURES 0
		4191	#define EV_MULTIPLICITY 1
		4192	#define EV_USE_POLL 1
		4193	#define EV_CHILD_ENABLE 1
		4194	#define EV_ASYNC_ENABLE 1
		4195
		4196	The actual value is a bitset, it can be a combination of the following
		4197	values:
		4198
		4199	=over 4
		4200
		4201	=item C<1> - faster/larger code
		4202
		4203	Use larger code to speed up some operations.
		4204
		4205	Currently this is used to override some inlining decisions (enlarging the
		4206	code size by roughly 30% on amd64).
		4207
		4208	When optimising for size, use of compiler flags such as C<-Os> with
		4209	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4210	assertions.
		4211
		4212	=item C<2> - faster/larger data structures
		4213
		4214	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4215	hash table sizes and so on. This will usually further increase code size
		4216	and can additionally have an effect on the size of data structures at
		4217	runtime.
		4218
		4219	=item C<4> - full API configuration
		4220
		4221	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4222	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4223
		4224	=item C<8> - full API
		4225
		4226	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4227	details on which parts of the API are still available without this
		4228	feature, and do not complain if this subset changes over time.
		4229
		4230	=item C<16> - enable all optional watcher types
		4231
		4232	Enables all optional watcher types. If you want to selectively enable
		4233	only some watcher types other than I/O and timers (e.g. prepare,
		4234	embed, async, child...) you can enable them manually by defining
		4235	C<EV_watchertype_ENABLE> to C<1> instead.
		4236
		4237	=item C<32> - enable all backends
		4238
		4239	This enables all backends - without this feature, you need to enable at
		4240	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4241
		4242	=item C<64> - enable OS-specific "helper" APIs
		4243
		4244	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4245	default.
		4246
		4247	=back
		4248
		4249	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4250	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4251	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4252	watchers, timers and monotonic clock support.
		4253
		4254	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4255	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4256	your program might be left out as well - a binary starting a timer and an
		4257	I/O watcher then might come out at only 5Kb.
		4258
		4259	=item EV_AVOID_STDIO
		4260
		4261	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4262	functions (printf, scanf, perror etc.). This will increase the code size
		4263	somewhat, but if your program doesn't otherwise depend on stdio and your
		4264	libc allows it, this avoids linking in the stdio library which is quite
		4265	big.
		4266
		4267	Note that error messages might become less precise when this option is
		4268	enabled.
		4269
		4270	=item EV_NSIG
		4271
		4272	The highest supported signal number, +1 (or, the number of
		4273	signals): Normally, libev tries to deduce the maximum number of signals
		4274	automatically, but sometimes this fails, in which case it can be
		4275	specified. Also, using a lower number than detected (C<32> should be
		4276	good for about any system in existence) can save some memory, as libev
		4277	statically allocates some 12-24 bytes per signal number.
3444		4278
3445	=item EV_PID_HASHSIZE	4279	=item EV_PID_HASHSIZE
3446		4280
3447	C<ev_child> watchers use a small hash table to distribute workload by	4281	C<ev_child> watchers use a small hash table to distribute workload by
3448	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4282	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3449	than enough. If you need to manage thousands of children you might want to	4283	usually more than enough. If you need to manage thousands of children you
3450	increase this value (I<must> be a power of two).	4284	might want to increase this value (I<must> be a power of two).
3451		4285
3452	=item EV_INOTIFY_HASHSIZE	4286	=item EV_INOTIFY_HASHSIZE
3453		4287
3454	C<ev_stat> watchers use a small hash table to distribute workload by	4288	C<ev_stat> watchers use a small hash table to distribute workload by
3455	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4289	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3456	usually more than enough. If you need to manage thousands of C<ev_stat>	4290	disabled), usually more than enough. If you need to manage thousands of
3457	watchers you might want to increase this value (I<must> be a power of	4291	C<ev_stat> watchers you might want to increase this value (I<must> be a
3458	two).	4292	power of two).
3459		4293
3460	=item EV_USE_4HEAP	4294	=item EV_USE_4HEAP
3461		4295
3462	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4296	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3463	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4297	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3464	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4298	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3465	faster performance with many (thousands) of watchers.	4299	faster performance with many (thousands) of watchers.
3466		4300
3467	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4301	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3468	(disabled).	4302	will be C<0>.
3469		4303
3470	=item EV_HEAP_CACHE_AT	4304	=item EV_HEAP_CACHE_AT
3471		4305
3472	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4306	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3473	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4307	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3474	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4308	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3475	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4309	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3476	but avoids random read accesses on heap changes. This improves performance	4310	but avoids random read accesses on heap changes. This improves performance
3477	noticeably with many (hundreds) of watchers.	4311	noticeably with many (hundreds) of watchers.
3478		4312
3479	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4313	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3480	(disabled).	4314	will be C<0>.
3481		4315
3482	=item EV_VERIFY	4316	=item EV_VERIFY
3483		4317
3484	Controls how much internal verification (see C<ev_loop_verify ()>) will	4318	Controls how much internal verification (see C<ev_verify ()>) will
3485	be done: If set to C<0>, no internal verification code will be compiled	4319	be done: If set to C<0>, no internal verification code will be compiled
3486	in. If set to C<1>, then verification code will be compiled in, but not	4320	in. If set to C<1>, then verification code will be compiled in, but not
3487	called. If set to C<2>, then the internal verification code will be	4321	called. If set to C<2>, then the internal verification code will be
3488	called once per loop, which can slow down libev. If set to C<3>, then the	4322	called once per loop, which can slow down libev. If set to C<3>, then the
3489	verification code will be called very frequently, which will slow down	4323	verification code will be called very frequently, which will slow down
3490	libev considerably.	4324	libev considerably.
3491		4325
3492	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4326	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3493	C<0>.	4327	will be C<0>.
3494		4328
3495	=item EV_COMMON	4329	=item EV_COMMON
3496		4330
3497	By default, all watchers have a C<void *data> member. By redefining	4331	By default, all watchers have a C<void *data> member. By redefining
3498	this macro to a something else you can include more and other types of	4332	this macro to something else you can include more and other types of
3499	members. You have to define it each time you include one of the files,	4333	members. You have to define it each time you include one of the files,
3500	though, and it must be identical each time.	4334	though, and it must be identical each time.
3501		4335
3502	For example, the perl EV module uses something like this:	4336	For example, the perl EV module uses something like this:
3503		4337
…		…
3556	file.	4390	file.
3557		4391
3558	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4392	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3559	that everybody includes and which overrides some configure choices:	4393	that everybody includes and which overrides some configure choices:
3560		4394
3561	#define EV_MINIMAL 1	4395	#define EV_FEATURES 8
3562	#define EV_USE_POLL 0	4396	#define EV_USE_SELECT 1
3563	#define EV_MULTIPLICITY 0
3564	#define EV_PERIODIC_ENABLE 0	4397	#define EV_PREPARE_ENABLE 1
		4398	#define EV_IDLE_ENABLE 1
3565	#define EV_STAT_ENABLE 0	4399	#define EV_SIGNAL_ENABLE 1
3566	#define EV_FORK_ENABLE 0	4400	#define EV_CHILD_ENABLE 1
		4401	#define EV_USE_STDEXCEPT 0
3567	#define EV_CONFIG_H <config.h>	4402	#define EV_CONFIG_H <config.h>
3568	#define EV_MINPRI 0
3569	#define EV_MAXPRI 0
3570		4403
3571	#include "ev++.h"	4404	#include "ev++.h"
3572		4405
3573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4406	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3574		4407
…		…
3634	default loop and triggering an C<ev_async> watcher from the default loop	4467	default loop and triggering an C<ev_async> watcher from the default loop
3635	watcher callback into the event loop interested in the signal.	4468	watcher callback into the event loop interested in the signal.
3636		4469
3637	=back	4470	=back
3638		4471
		4472	=head4 THREAD LOCKING EXAMPLE
		4473
		4474	Here is a fictitious example of how to run an event loop in a different
		4475	thread than where callbacks are being invoked and watchers are
		4476	created/added/removed.
		4477
		4478	For a real-world example, see the C<EV::Loop::Async> perl module,
		4479	which uses exactly this technique (which is suited for many high-level
		4480	languages).
		4481
		4482	The example uses a pthread mutex to protect the loop data, a condition
		4483	variable to wait for callback invocations, an async watcher to notify the
		4484	event loop thread and an unspecified mechanism to wake up the main thread.
		4485
		4486	First, you need to associate some data with the event loop:
		4487
		4488	typedef struct {
		4489	mutex_t lock; /* global loop lock */
		4490	ev_async async_w;
		4491	thread_t tid;
		4492	cond_t invoke_cv;
		4493	} userdata;
		4494
		4495	void prepare_loop (EV_P)
		4496	{
		4497	// for simplicity, we use a static userdata struct.
		4498	static userdata u;
		4499
		4500	ev_async_init (&u->async_w, async_cb);
		4501	ev_async_start (EV_A_ &u->async_w);
		4502
		4503	pthread_mutex_init (&u->lock, 0);
		4504	pthread_cond_init (&u->invoke_cv, 0);
		4505
		4506	// now associate this with the loop
		4507	ev_set_userdata (EV_A_ u);
		4508	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4509	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4510
		4511	// then create the thread running ev_loop
		4512	pthread_create (&u->tid, 0, l_run, EV_A);
		4513	}
		4514
		4515	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4516	solely to wake up the event loop so it takes notice of any new watchers
		4517	that might have been added:
		4518
		4519	static void
		4520	async_cb (EV_P_ ev_async *w, int revents)
		4521	{
		4522	// just used for the side effects
		4523	}
		4524
		4525	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4526	protecting the loop data, respectively.
		4527
		4528	static void
		4529	l_release (EV_P)
		4530	{
		4531	userdata *u = ev_userdata (EV_A);
		4532	pthread_mutex_unlock (&u->lock);
		4533	}
		4534
		4535	static void
		4536	l_acquire (EV_P)
		4537	{
		4538	userdata *u = ev_userdata (EV_A);
		4539	pthread_mutex_lock (&u->lock);
		4540	}
		4541
		4542	The event loop thread first acquires the mutex, and then jumps straight
		4543	into C<ev_run>:
		4544
		4545	void *
		4546	l_run (void *thr_arg)
		4547	{
		4548	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4549
		4550	l_acquire (EV_A);
		4551	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4552	ev_run (EV_A_ 0);
		4553	l_release (EV_A);
		4554
		4555	return 0;
		4556	}
		4557
		4558	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4559	signal the main thread via some unspecified mechanism (signals? pipe
		4560	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4561	have been called (in a while loop because a) spurious wakeups are possible
		4562	and b) skipping inter-thread-communication when there are no pending
		4563	watchers is very beneficial):
		4564
		4565	static void
		4566	l_invoke (EV_P)
		4567	{
		4568	userdata *u = ev_userdata (EV_A);
		4569
		4570	while (ev_pending_count (EV_A))
		4571	{
		4572	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4573	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4574	}
		4575	}
		4576
		4577	Now, whenever the main thread gets told to invoke pending watchers, it
		4578	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4579	thread to continue:
		4580
		4581	static void
		4582	real_invoke_pending (EV_P)
		4583	{
		4584	userdata *u = ev_userdata (EV_A);
		4585
		4586	pthread_mutex_lock (&u->lock);
		4587	ev_invoke_pending (EV_A);
		4588	pthread_cond_signal (&u->invoke_cv);
		4589	pthread_mutex_unlock (&u->lock);
		4590	}
		4591
		4592	Whenever you want to start/stop a watcher or do other modifications to an
		4593	event loop, you will now have to lock:
		4594
		4595	ev_timer timeout_watcher;
		4596	userdata *u = ev_userdata (EV_A);
		4597
		4598	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4599
		4600	pthread_mutex_lock (&u->lock);
		4601	ev_timer_start (EV_A_ &timeout_watcher);
		4602	ev_async_send (EV_A_ &u->async_w);
		4603	pthread_mutex_unlock (&u->lock);
		4604
		4605	Note that sending the C<ev_async> watcher is required because otherwise
		4606	an event loop currently blocking in the kernel will have no knowledge
		4607	about the newly added timer. By waking up the loop it will pick up any new
		4608	watchers in the next event loop iteration.
		4609
3639	=head3 COROUTINES	4610	=head3 COROUTINES
3640		4611
3641	Libev is very accommodating to coroutines ("cooperative threads"):	4612	Libev is very accommodating to coroutines ("cooperative threads"):
3642	libev fully supports nesting calls to its functions from different	4613	libev fully supports nesting calls to its functions from different
3643	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4614	coroutines (e.g. you can call C<ev_run> on the same loop from two
3644	different coroutines, and switch freely between both coroutines running the	4615	different coroutines, and switch freely between both coroutines running
3645	loop, as long as you don't confuse yourself). The only exception is that	4616	the loop, as long as you don't confuse yourself). The only exception is
3646	you must not do this from C<ev_periodic> reschedule callbacks.	4617	that you must not do this from C<ev_periodic> reschedule callbacks.
3647		4618
3648	Care has been taken to ensure that libev does not keep local state inside	4619	Care has been taken to ensure that libev does not keep local state inside
3649	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4620	C<ev_run>, and other calls do not usually allow for coroutine switches as
3650	they do not call any callbacks.	4621	they do not call any callbacks.
3651		4622
3652	=head2 COMPILER WARNINGS	4623	=head2 COMPILER WARNINGS
3653		4624
3654	Depending on your compiler and compiler settings, you might get no or a	4625	Depending on your compiler and compiler settings, you might get no or a
…		…
3665	maintainable.	4636	maintainable.
3666		4637
3667	And of course, some compiler warnings are just plain stupid, or simply	4638	And of course, some compiler warnings are just plain stupid, or simply
3668	wrong (because they don't actually warn about the condition their message	4639	wrong (because they don't actually warn about the condition their message
3669	seems to warn about). For example, certain older gcc versions had some	4640	seems to warn about). For example, certain older gcc versions had some
3670	warnings that resulted an extreme number of false positives. These have	4641	warnings that resulted in an extreme number of false positives. These have
3671	been fixed, but some people still insist on making code warn-free with	4642	been fixed, but some people still insist on making code warn-free with
3672	such buggy versions.	4643	such buggy versions.
3673		4644
3674	While libev is written to generate as few warnings as possible,	4645	While libev is written to generate as few warnings as possible,
3675	"warn-free" code is not a goal, and it is recommended not to build libev	4646	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3711	I suggest using suppression lists.	4682	I suggest using suppression lists.
3712		4683
3713		4684
3714	=head1 PORTABILITY NOTES	4685	=head1 PORTABILITY NOTES
3715		4686
		4687	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4688
		4689	GNU/Linux is the only common platform that supports 64 bit file/large file
		4690	interfaces but I<disables> them by default.
		4691
		4692	That means that libev compiled in the default environment doesn't support
		4693	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4694
		4695	Unfortunately, many programs try to work around this GNU/Linux issue
		4696	by enabling the large file API, which makes them incompatible with the
		4697	standard libev compiled for their system.
		4698
		4699	Likewise, libev cannot enable the large file API itself as this would
		4700	suddenly make it incompatible to the default compile time environment,
		4701	i.e. all programs not using special compile switches.
		4702
		4703	=head2 OS/X AND DARWIN BUGS
		4704
		4705	The whole thing is a bug if you ask me - basically any system interface
		4706	you touch is broken, whether it is locales, poll, kqueue or even the
		4707	OpenGL drivers.
		4708
		4709	=head3 C<kqueue> is buggy
		4710
		4711	The kqueue syscall is broken in all known versions - most versions support
		4712	only sockets, many support pipes.
		4713
		4714	Libev tries to work around this by not using C<kqueue> by default on this
		4715	rotten platform, but of course you can still ask for it when creating a
		4716	loop - embedding a socket-only kqueue loop into a select-based one is
		4717	probably going to work well.
		4718
		4719	=head3 C<poll> is buggy
		4720
		4721	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4722	implementation by something calling C<kqueue> internally around the 10.5.6
		4723	release, so now C<kqueue> I<and> C<poll> are broken.
		4724
		4725	Libev tries to work around this by not using C<poll> by default on
		4726	this rotten platform, but of course you can still ask for it when creating
		4727	a loop.
		4728
		4729	=head3 C<select> is buggy
		4730
		4731	All that's left is C<select>, and of course Apple found a way to fuck this
		4732	one up as well: On OS/X, C<select> actively limits the number of file
		4733	descriptors you can pass in to 1024 - your program suddenly crashes when
		4734	you use more.
		4735
		4736	There is an undocumented "workaround" for this - defining
		4737	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4738	work on OS/X.
		4739
		4740	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4741
		4742	=head3 C<errno> reentrancy
		4743
		4744	The default compile environment on Solaris is unfortunately so
		4745	thread-unsafe that you can't even use components/libraries compiled
		4746	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4747	defined by default. A valid, if stupid, implementation choice.
		4748
		4749	If you want to use libev in threaded environments you have to make sure
		4750	it's compiled with C<_REENTRANT> defined.
		4751
		4752	=head3 Event port backend
		4753
		4754	The scalable event interface for Solaris is called "event
		4755	ports". Unfortunately, this mechanism is very buggy in all major
		4756	releases. If you run into high CPU usage, your program freezes or you get
		4757	a large number of spurious wakeups, make sure you have all the relevant
		4758	and latest kernel patches applied. No, I don't know which ones, but there
		4759	are multiple ones to apply, and afterwards, event ports actually work
		4760	great.
		4761
		4762	If you can't get it to work, you can try running the program by setting
		4763	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4764	C<select> backends.
		4765
		4766	=head2 AIX POLL BUG
		4767
		4768	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4769	this by trying to avoid the poll backend altogether (i.e. it's not even
		4770	compiled in), which normally isn't a big problem as C<select> works fine
		4771	with large bitsets on AIX, and AIX is dead anyway.
		4772
3716	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4773	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4774
		4775	=head3 General issues
3717		4776
3718	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4777	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3719	requires, and its I/O model is fundamentally incompatible with the POSIX	4778	requires, and its I/O model is fundamentally incompatible with the POSIX
3720	model. Libev still offers limited functionality on this platform in	4779	model. Libev still offers limited functionality on this platform in
3721	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4780	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3722	descriptors. This only applies when using Win32 natively, not when using	4781	descriptors. This only applies when using Win32 natively, not when using
3723	e.g. cygwin.	4782	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4783	as every compielr comes with a slightly differently broken/incompatible
		4784	environment.
3724		4785
3725	Lifting these limitations would basically require the full	4786	Lifting these limitations would basically require the full
3726	re-implementation of the I/O system. If you are into these kinds of	4787	re-implementation of the I/O system. If you are into this kind of thing,
3727	things, then note that glib does exactly that for you in a very portable	4788	then note that glib does exactly that for you in a very portable way (note
3728	way (note also that glib is the slowest event library known to man).	4789	also that glib is the slowest event library known to man).
3729		4790
3730	There is no supported compilation method available on windows except	4791	There is no supported compilation method available on windows except
3731	embedding it into other applications.	4792	embedding it into other applications.
		4793
		4794	Sensible signal handling is officially unsupported by Microsoft - libev
		4795	tries its best, but under most conditions, signals will simply not work.
3732		4796
3733	Not a libev limitation but worth mentioning: windows apparently doesn't	4797	Not a libev limitation but worth mentioning: windows apparently doesn't
3734	accept large writes: instead of resulting in a partial write, windows will	4798	accept large writes: instead of resulting in a partial write, windows will
3735	either accept everything or return C<ENOBUFS> if the buffer is too large,	4799	either accept everything or return C<ENOBUFS> if the buffer is too large,
3736	so make sure you only write small amounts into your sockets (less than a	4800	so make sure you only write small amounts into your sockets (less than a
…		…
3741	the abysmal performance of winsockets, using a large number of sockets	4805	the abysmal performance of winsockets, using a large number of sockets
3742	is not recommended (and not reasonable). If your program needs to use	4806	is not recommended (and not reasonable). If your program needs to use
3743	more than a hundred or so sockets, then likely it needs to use a totally	4807	more than a hundred or so sockets, then likely it needs to use a totally
3744	different implementation for windows, as libev offers the POSIX readiness	4808	different implementation for windows, as libev offers the POSIX readiness
3745	notification model, which cannot be implemented efficiently on windows	4809	notification model, which cannot be implemented efficiently on windows
3746	(Microsoft monopoly games).	4810	(due to Microsoft monopoly games).
3747		4811
3748	A typical way to use libev under windows is to embed it (see the embedding	4812	A typical way to use libev under windows is to embed it (see the embedding
3749	section for details) and use the following F<evwrap.h> header file instead	4813	section for details) and use the following F<evwrap.h> header file instead
3750	of F<ev.h>:	4814	of F<ev.h>:
3751		4815
…		…
3758	you do I<not> compile the F<ev.c> or any other embedded source files!):	4822	you do I<not> compile the F<ev.c> or any other embedded source files!):
3759		4823
3760	#include "evwrap.h"	4824	#include "evwrap.h"
3761	#include "ev.c"	4825	#include "ev.c"
3762		4826
3763	=over 4
3764
3765	=item The winsocket select function	4827	=head3 The winsocket C<select> function
3766		4828
3767	The winsocket C<select> function doesn't follow POSIX in that it	4829	The winsocket C<select> function doesn't follow POSIX in that it
3768	requires socket I<handles> and not socket I<file descriptors> (it is	4830	requires socket I<handles> and not socket I<file descriptors> (it is
3769	also extremely buggy). This makes select very inefficient, and also	4831	also extremely buggy). This makes select very inefficient, and also
3770	requires a mapping from file descriptors to socket handles (the Microsoft	4832	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3779	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4841	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3780		4842
3781	Note that winsockets handling of fd sets is O(n), so you can easily get a	4843	Note that winsockets handling of fd sets is O(n), so you can easily get a
3782	complexity in the O(n²) range when using win32.	4844	complexity in the O(n²) range when using win32.
3783		4845
3784	=item Limited number of file descriptors	4846	=head3 Limited number of file descriptors
3785		4847
3786	Windows has numerous arbitrary (and low) limits on things.	4848	Windows has numerous arbitrary (and low) limits on things.
3787		4849
3788	Early versions of winsocket's select only supported waiting for a maximum	4850	Early versions of winsocket's select only supported waiting for a maximum
3789	of C<64> handles (probably owning to the fact that all windows kernels	4851	of C<64> handles (probably owning to the fact that all windows kernels
3790	can only wait for C<64> things at the same time internally; Microsoft	4852	can only wait for C<64> things at the same time internally; Microsoft
3791	recommends spawning a chain of threads and wait for 63 handles and the	4853	recommends spawning a chain of threads and wait for 63 handles and the
3792	previous thread in each. Great).	4854	previous thread in each. Sounds great!).
3793		4855
3794	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4856	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3795	to some high number (e.g. C<2048>) before compiling the winsocket select	4857	to some high number (e.g. C<2048>) before compiling the winsocket select
3796	call (which might be in libev or elsewhere, for example, perl does its own	4858	call (which might be in libev or elsewhere, for example, perl and many
3797	select emulation on windows).	4859	other interpreters do their own select emulation on windows).
3798		4860
3799	Another limit is the number of file descriptors in the Microsoft runtime	4861	Another limit is the number of file descriptors in the Microsoft runtime
3800	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4862	libraries, which by default is C<64> (there must be a hidden I<64>
3801	or something like this inside Microsoft). You can increase this by calling	4863	fetish or something like this inside Microsoft). You can increase this
3802	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4864	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3803	arbitrary limit), but is broken in many versions of the Microsoft runtime	4865	(another arbitrary limit), but is broken in many versions of the Microsoft
3804	libraries.
3805
3806	This might get you to about C<512> or C<2048> sockets (depending on	4866	runtime libraries. This might get you to about C<512> or C<2048> sockets
3807	windows version and/or the phase of the moon). To get more, you need to	4867	(depending on windows version and/or the phase of the moon). To get more,
3808	wrap all I/O functions and provide your own fd management, but the cost of	4868	you need to wrap all I/O functions and provide your own fd management, but
3809	calling select (O(n²)) will likely make this unworkable.	4869	the cost of calling select (O(n²)) will likely make this unworkable.
3810
3811	=back
3812		4870
3813	=head2 PORTABILITY REQUIREMENTS	4871	=head2 PORTABILITY REQUIREMENTS
3814		4872
3815	In addition to a working ISO-C implementation and of course the	4873	In addition to a working ISO-C implementation and of course the
3816	backend-specific APIs, libev relies on a few additional extensions:	4874	backend-specific APIs, libev relies on a few additional extensions:
…		…
3823	Libev assumes not only that all watcher pointers have the same internal	4881	Libev assumes not only that all watcher pointers have the same internal
3824	structure (guaranteed by POSIX but not by ISO C for example), but it also	4882	structure (guaranteed by POSIX but not by ISO C for example), but it also
3825	assumes that the same (machine) code can be used to call any watcher	4883	assumes that the same (machine) code can be used to call any watcher
3826	callback: The watcher callbacks have different type signatures, but libev	4884	callback: The watcher callbacks have different type signatures, but libev
3827	calls them using an C<ev_watcher *> internally.	4885	calls them using an C<ev_watcher *> internally.
		4886
		4887	=item pointer accesses must be thread-atomic
		4888
		4889	Accessing a pointer value must be atomic, it must both be readable and
		4890	writable in one piece - this is the case on all current architectures.
3828		4891
3829	=item C<sig_atomic_t volatile> must be thread-atomic as well	4892	=item C<sig_atomic_t volatile> must be thread-atomic as well
3830		4893
3831	The type C<sig_atomic_t volatile> (or whatever is defined as	4894	The type C<sig_atomic_t volatile> (or whatever is defined as
3832	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4895	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3855	watchers.	4918	watchers.
3856		4919
3857	=item C<double> must hold a time value in seconds with enough accuracy	4920	=item C<double> must hold a time value in seconds with enough accuracy
3858		4921
3859	The type C<double> is used to represent timestamps. It is required to	4922	The type C<double> is used to represent timestamps. It is required to
3860	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4923	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3861	enough for at least into the year 4000. This requirement is fulfilled by	4924	good enough for at least into the year 4000 with millisecond accuracy
		4925	(the design goal for libev). This requirement is overfulfilled by
3862	implementations implementing IEEE 754 (basically all existing ones).	4926	implementations using IEEE 754, which is basically all existing ones. With
		4927	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3863		4928
3864	=back	4929	=back
3865		4930
3866	If you know of other additional requirements drop me a note.	4931	If you know of other additional requirements drop me a note.
3867		4932
…		…
3935	involves iterating over all running async watchers or all signal numbers.	5000	involves iterating over all running async watchers or all signal numbers.
3936		5001
3937	=back	5002	=back
3938		5003
3939		5004
		5005	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5006
		5007	The major version 4 introduced some incompatible changes to the API.
		5008
		5009	At the moment, the C<ev.h> header file provides compatibility definitions
		5010	for all changes, so most programs should still compile. The compatibility
		5011	layer might be removed in later versions of libev, so better update to the
		5012	new API early than late.
		5013
		5014	=over 4
		5015
		5016	=item C<EV_COMPAT3> backwards compatibility mechanism
		5017
		5018	The backward compatibility mechanism can be controlled by
		5019	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5020	section.
		5021
		5022	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5023
		5024	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5025
		5026	ev_loop_destroy (EV_DEFAULT_UC);
		5027	ev_loop_fork (EV_DEFAULT);
		5028
		5029	=item function/symbol renames
		5030
		5031	A number of functions and symbols have been renamed:
		5032
		5033	ev_loop => ev_run
		5034	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5035	EVLOOP_ONESHOT => EVRUN_ONCE
		5036
		5037	ev_unloop => ev_break
		5038	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5039	EVUNLOOP_ONE => EVBREAK_ONE
		5040	EVUNLOOP_ALL => EVBREAK_ALL
		5041
		5042	EV_TIMEOUT => EV_TIMER
		5043
		5044	ev_loop_count => ev_iteration
		5045	ev_loop_depth => ev_depth
		5046	ev_loop_verify => ev_verify
		5047
		5048	Most functions working on C<struct ev_loop> objects don't have an
		5049	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5050	associated constants have been renamed to not collide with the C<struct
		5051	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5052	as all other watcher types. Note that C<ev_loop_fork> is still called
		5053	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5054	typedef.
		5055
		5056	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5057
		5058	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5059	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5060	and work, but the library code will of course be larger.
		5061
		5062	=back
		5063
		5064
		5065	=head1 GLOSSARY
		5066
		5067	=over 4
		5068
		5069	=item active
		5070
		5071	A watcher is active as long as it has been started and not yet stopped.
		5072	See L<WATCHER STATES> for details.
		5073
		5074	=item application
		5075
		5076	In this document, an application is whatever is using libev.
		5077
		5078	=item backend
		5079
		5080	The part of the code dealing with the operating system interfaces.
		5081
		5082	=item callback
		5083
		5084	The address of a function that is called when some event has been
		5085	detected. Callbacks are being passed the event loop, the watcher that
		5086	received the event, and the actual event bitset.
		5087
		5088	=item callback/watcher invocation
		5089
		5090	The act of calling the callback associated with a watcher.
		5091
		5092	=item event
		5093
		5094	A change of state of some external event, such as data now being available
		5095	for reading on a file descriptor, time having passed or simply not having
		5096	any other events happening anymore.
		5097
		5098	In libev, events are represented as single bits (such as C<EV_READ> or
		5099	C<EV_TIMER>).
		5100
		5101	=item event library
		5102
		5103	A software package implementing an event model and loop.
		5104
		5105	=item event loop
		5106
		5107	An entity that handles and processes external events and converts them
		5108	into callback invocations.
		5109
		5110	=item event model
		5111
		5112	The model used to describe how an event loop handles and processes
		5113	watchers and events.
		5114
		5115	=item pending
		5116
		5117	A watcher is pending as soon as the corresponding event has been
		5118	detected. See L<WATCHER STATES> for details.
		5119
		5120	=item real time
		5121
		5122	The physical time that is observed. It is apparently strictly monotonic :)
		5123
		5124	=item wall-clock time
		5125
		5126	The time and date as shown on clocks. Unlike real time, it can actually
		5127	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5128	clock.
		5129
		5130	=item watcher
		5131
		5132	A data structure that describes interest in certain events. Watchers need
		5133	to be started (attached to an event loop) before they can receive events.
		5134
		5135	=back
		5136
3940	=head1 AUTHOR	5137	=head1 AUTHOR
3941		5138
3942	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5139	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5140	Magnusson and Emanuele Giaquinta.
3943		5141

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