ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.215 by root, Wed Nov 5 21:44:21 2008 UTC vs.
Revision 1.337 by root, Sun Oct 31 20:20:20 2010 UTC

…		…
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
		13
		14	#include <stdio.h> // for puts
13		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	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);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	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
68	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
69	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
70		92
71	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
72	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
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	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
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	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
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	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
94	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
95	(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>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	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
99	for example).	122	for example).
100		123
…		…
103	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)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	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
107	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
108	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
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	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
116	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
117	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
118	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
119	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
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	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
153	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
154	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>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	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
159	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
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	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
178	not a problem.	203	not a problem.
179		204
180	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
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	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
203	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
204	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
205	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
206	(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
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	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
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	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
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		247
…		…
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
277	=back	304	=back
278		305
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		307
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	310	libev 3 had an C<ev_loop> function colliding with the struct name).
284		311
285	The library knows two types of such loops, the I<default> loop, which	312	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	313	supports child process events, and dynamically created event loops which
287	not.	314	do not.
288		315
289	=over 4	316	=over 4
290		317
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		319
293	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
297		330
298	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
299	function.	332	function (or via the C<EV_DEFAULT> macro).
300		333
301	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot be shared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
304		338
305	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	341	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	Note that this function I<is> thread-safe, and one common way to use
		361	libev with threads is indeed to create one loop per thread, and using the
		362	default loop in the "main" or "initial" thread.
311		363
312	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		366
315	The following flags are supported:	367	The following flags are supported:
…		…
330	useful to try out specific backends to test their performance, or to work	382	useful to try out specific backends to test their performance, or to work
331	around bugs.	383	around bugs.
332		384
333	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
334		386
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	388	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		389
339	This works by calling C<getpid ()> on every iteration of the loop,	390	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	391	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	392	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	399	flag.
349		400
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	402	environment variable.
352		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
		423
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		425
355	This is your standard select(2) backend. Not I<completely> standard, as	426	This is your standard select(2) backend. Not I<completely> standard, as
356	libev tries to roll its own fd_set with no limits on the number of fds,	427	libev tries to roll its own fd_set with no limits on the number of fds,
357	but if that fails, expect a fairly low limit on the number of fds when	428	but if that fails, expect a fairly low limit on the number of fds when
…		…
381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		454
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
		459
386	For few fds, this backend is a bit little slower than poll and select,	460	For few fds, this backend is a bit little slower than poll and select,
387	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
388	like O(total_fds) where n is the total number of fds (or the highest fd),	462	like O(total_fds) where n is the total number of fds (or the highest fd),
389	epoll scales either O(1) or O(active_fds).	463	epoll scales either O(1) or O(active_fds).
390		464
391	The epoll mechanism deserves honorable mention as the most misdesigned	465	The epoll mechanism deserves honorable mention as the most misdesigned
392	of the more advanced event mechanisms: mere annoyances include silently	466	of the more advanced event mechanisms: mere annoyances include silently
393	dropping file descriptors, requiring a system call per change per file	467	dropping file descriptors, requiring a system call per change per file
394	descriptor (and unnecessary guessing of parameters), problems with dup and	468	descriptor (and unnecessary guessing of parameters), problems with dup,
		469	returning before the timeout value requiring additional iterations and so
395	so on. The biggest issue is fork races, however - if a program forks then	470	on. The biggest issue is fork races, however - if a program forks then
396	I<both> parent and child process have to recreate the epoll set, which can	471	I<both> parent and child process have to recreate the epoll set, which can
397	take considerable time (one syscall per file descriptor) and is of course	472	take considerable time (one syscall per file descriptor) and is of course
398	hard to detect.	473	hard to detect.
399		474
400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	475	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
401	of course I<doesn't>, and epoll just loves to report events for totally	476	of course I<doesn't>, and epoll just loves to report events for totally
402	I<different> file descriptors (even already closed ones, so one cannot	477	I<different> file descriptors (even already closed ones, so one cannot
403	even remove them from the set) than registered in the set (especially	478	even remove them from the set) than registered in the set (especially
404	on SMP systems). Libev tries to counter these spurious notifications by	479	on SMP systems). Libev tries to counter these spurious notifications by
405	employing an additional generation counter and comparing that against the	480	employing an additional generation counter and comparing that against the
406	events to filter out spurious ones, recreating the set when required.	481	events to filter out spurious ones, recreating the set when required. Last
		482	not least, it also refuses to work with some file descriptors which work
		483	perfectly fine with C<select> (files, many character devices...).
407		484
408	While stopping, setting and starting an I/O watcher in the same iteration	485	While stopping, setting and starting an I/O watcher in the same iteration
409	will result in some caching, there is still a system call per such	486	will result in some caching, there is still a system call per such
410	incident (because the same I<file descriptor> could point to a different	487	incident (because the same I<file descriptor> could point to a different
411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	488	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
458		535
459	While nominally embeddable in other event loops, this doesn't work	536	While nominally embeddable in other event loops, this doesn't work
460	everywhere, so you might need to test for this. And since it is broken	537	everywhere, so you might need to test for this. And since it is broken
461	almost everywhere, you should only use it when you have a lot of sockets	538	almost everywhere, you should only use it when you have a lot of sockets
462	(for which it usually works), by embedding it into another event loop	539	(for which it usually works), by embedding it into another event loop
463	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	540	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
464	using it only for sockets.	541	also broken on OS X)) and, did I mention it, using it only for sockets.
465		542
466	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	543	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
467	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	544	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
468	C<NOTE_EOF>.	545	C<NOTE_EOF>.
469		546
…		…
504		581
505	It is definitely not recommended to use this flag.	582	It is definitely not recommended to use this flag.
506		583
507	=back	584	=back
508		585
509	If one or more of these are or'ed into the flags value, then only these	586	If one or more of the backend flags are or'ed into the flags value,
510	backends will be tried (in the reverse order as listed here). If none are	587	then only these backends will be tried (in the reverse order as listed
511	specified, all backends in C<ev_recommended_backends ()> will be tried.	588	here). If none are specified, all backends in C<ev_recommended_backends
512		589	()> will be tried.
513	Example: This is the most typical usage.
514
515	if (!ev_default_loop (0))
516	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
517
518	Example: Restrict libev to the select and poll backends, and do not allow
519	environment settings to be taken into account:
520
521	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
522
523	Example: Use whatever libev has to offer, but make sure that kqueue is
524	used if available (warning, breaks stuff, best use only with your own
525	private event loop and only if you know the OS supports your types of
526	fds):
527
528	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
529
530	=item struct ev_loop *ev_loop_new (unsigned int flags)
531
532	Similar to C<ev_default_loop>, but always creates a new event loop that is
533	always distinct from the default loop. Unlike the default loop, it cannot
534	handle signal and child watchers, and attempts to do so will be greeted by
535	undefined behaviour (or a failed assertion if assertions are enabled).
536
537	Note that this function I<is> thread-safe, and the recommended way to use
538	libev with threads is indeed to create one loop per thread, and using the
539	default loop in the "main" or "initial" thread.
540		590
541	Example: Try to create a event loop that uses epoll and nothing else.	591	Example: Try to create a event loop that uses epoll and nothing else.
542		592
543	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	593	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
544	if (!epoller)	594	if (!epoller)
545	fatal ("no epoll found here, maybe it hides under your chair");	595	fatal ("no epoll found here, maybe it hides under your chair");
546		596
		597	Example: Use whatever libev has to offer, but make sure that kqueue is
		598	used if available.
		599
		600	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		601
547	=item ev_default_destroy ()	602	=item ev_loop_destroy (loop)
548		603
549	Destroys the default loop again (frees all memory and kernel state	604	Destroys an event loop object (frees all memory and kernel state
550	etc.). None of the active event watchers will be stopped in the normal	605	etc.). None of the active event watchers will be stopped in the normal
551	sense, so e.g. C<ev_is_active> might still return true. It is your	606	sense, so e.g. C<ev_is_active> might still return true. It is your
552	responsibility to either stop all watchers cleanly yourself I<before>	607	responsibility to either stop all watchers cleanly yourself I<before>
553	calling this function, or cope with the fact afterwards (which is usually	608	calling this function, or cope with the fact afterwards (which is usually
554	the easiest thing, you can just ignore the watchers and/or C<free ()> them	609	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
556		611
557	Note that certain global state, such as signal state (and installed signal	612	Note that certain global state, such as signal state (and installed signal
558	handlers), will not be freed by this function, and related watchers (such	613	handlers), will not be freed by this function, and related watchers (such
559	as signal and child watchers) would need to be stopped manually.	614	as signal and child watchers) would need to be stopped manually.
560		615
561	In general it is not advisable to call this function except in the	616	This function is normally used on loop objects allocated by
562	rare occasion where you really need to free e.g. the signal handling	617	C<ev_loop_new>, but it can also be used on the default loop returned by
		618	C<ev_default_loop>, in which case it is not thread-safe.
		619
		620	Note that it is not advisable to call this function on the default loop
		621	except in the rare occasion where you really need to free it's resources.
563	pipe fds. If you need dynamically allocated loops it is better to use	622	If you need dynamically allocated loops it is better to use C<ev_loop_new>
564	C<ev_loop_new> and C<ev_loop_destroy>).	623	and C<ev_loop_destroy>.
565		624
566	=item ev_loop_destroy (loop)	625	=item ev_loop_fork (loop)
567		626
568	Like C<ev_default_destroy>, but destroys an event loop created by an
569	earlier call to C<ev_loop_new>.
570
571	=item ev_default_fork ()
572
573	This function sets a flag that causes subsequent C<ev_loop> iterations	627	This function sets a flag that causes subsequent C<ev_run> iterations to
574	to reinitialise the kernel state for backends that have one. Despite the	628	reinitialise the kernel state for backends that have one. Despite the
575	name, you can call it anytime, but it makes most sense after forking, in	629	name, you can call it anytime, but it makes most sense after forking, in
576	the child process (or both child and parent, but that again makes little	630	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
577	sense). You I<must> call it in the child before using any of the libev	631	child before resuming or calling C<ev_run>.
578	functions, and it will only take effect at the next C<ev_loop> iteration.	632
		633	Again, you I<have> to call it on I<any> loop that you want to re-use after
		634	a fork, I<even if you do not plan to use the loop in the parent>. This is
		635	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		636	during fork.
579		637
580	On the other hand, you only need to call this function in the child	638	On the other hand, you only need to call this function in the child
581	process if and only if you want to use the event library in the child. If	639	process if and only if you want to use the event loop in the child. If
582	you just fork+exec, you don't have to call it at all.	640	you just fork+exec or create a new loop in the child, you don't have to
		641	call it at all (in fact, C<epoll> is so badly broken that it makes a
		642	difference, but libev will usually detect this case on its own and do a
		643	costly reset of the backend).
583		644
584	The function itself is quite fast and it's usually not a problem to call	645	The function itself is quite fast and it's usually not a problem to call
585	it just in case after a fork. To make this easy, the function will fit in	646	it just in case after a fork.
586	quite nicely into a call to C<pthread_atfork>:
587		647
		648	Example: Automate calling C<ev_loop_fork> on the default loop when
		649	using pthreads.
		650
		651	static void
		652	post_fork_child (void)
		653	{
		654	ev_loop_fork (EV_DEFAULT);
		655	}
		656
		657	...
588	pthread_atfork (0, 0, ev_default_fork);	658	pthread_atfork (0, 0, post_fork_child);
589
590	=item ev_loop_fork (loop)
591
592	Like C<ev_default_fork>, but acts on an event loop created by
593	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
594	after fork that you want to re-use in the child, and how you do this is
595	entirely your own problem.
596		659
597	=item int ev_is_default_loop (loop)	660	=item int ev_is_default_loop (loop)
598		661
599	Returns true when the given loop is, in fact, the default loop, and false	662	Returns true when the given loop is, in fact, the default loop, and false
600	otherwise.	663	otherwise.
601		664
602	=item unsigned int ev_loop_count (loop)	665	=item unsigned int ev_iteration (loop)
603		666
604	Returns the count of loop iterations for the loop, which is identical to	667	Returns the current iteration count for the event loop, which is identical
605	the number of times libev did poll for new events. It starts at C<0> and	668	to the number of times libev did poll for new events. It starts at C<0>
606	happily wraps around with enough iterations.	669	and happily wraps around with enough iterations.
607		670
608	This value can sometimes be useful as a generation counter of sorts (it	671	This value can sometimes be useful as a generation counter of sorts (it
609	"ticks" the number of loop iterations), as it roughly corresponds with	672	"ticks" the number of loop iterations), as it roughly corresponds with
610	C<ev_prepare> and C<ev_check> calls.	673	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		674	prepare and check phases.
		675
		676	=item unsigned int ev_depth (loop)
		677
		678	Returns the number of times C<ev_run> was entered minus the number of
		679	times C<ev_run> was exited, in other words, the recursion depth.
		680
		681	Outside C<ev_run>, this number is zero. In a callback, this number is
		682	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		683	in which case it is higher.
		684
		685	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		686	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		687	ungentleman-like behaviour unless it's really convenient.
611		688
612	=item unsigned int ev_backend (loop)	689	=item unsigned int ev_backend (loop)
613		690
614	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	691	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
615	use.	692	use.
…		…
624		701
625	=item ev_now_update (loop)	702	=item ev_now_update (loop)
626		703
627	Establishes the current time by querying the kernel, updating the time	704	Establishes the current time by querying the kernel, updating the time
628	returned by C<ev_now ()> in the progress. This is a costly operation and	705	returned by C<ev_now ()> in the progress. This is a costly operation and
629	is usually done automatically within C<ev_loop ()>.	706	is usually done automatically within C<ev_run ()>.
630		707
631	This function is rarely useful, but when some event callback runs for a	708	This function is rarely useful, but when some event callback runs for a
632	very long time without entering the event loop, updating libev's idea of	709	very long time without entering the event loop, updating libev's idea of
633	the current time is a good idea.	710	the current time is a good idea.
634		711
635	See also "The special problem of time updates" in the C<ev_timer> section.	712	See also L<The special problem of time updates> in the C<ev_timer> section.
636		713
		714	=item ev_suspend (loop)
		715
		716	=item ev_resume (loop)
		717
		718	These two functions suspend and resume an event loop, for use when the
		719	loop is not used for a while and timeouts should not be processed.
		720
		721	A typical use case would be an interactive program such as a game: When
		722	the user presses C<^Z> to suspend the game and resumes it an hour later it
		723	would be best to handle timeouts as if no time had actually passed while
		724	the program was suspended. This can be achieved by calling C<ev_suspend>
		725	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		726	C<ev_resume> directly afterwards to resume timer processing.
		727
		728	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		729	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		730	will be rescheduled (that is, they will lose any events that would have
		731	occurred while suspended).
		732
		733	After calling C<ev_suspend> you B<must not> call I<any> function on the
		734	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		735	without a previous call to C<ev_suspend>.
		736
		737	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		738	event loop time (see C<ev_now_update>).
		739
637	=item ev_loop (loop, int flags)	740	=item ev_run (loop, int flags)
638		741
639	Finally, this is it, the event handler. This function usually is called	742	Finally, this is it, the event handler. This function usually is called
640	after you initialised all your watchers and you want to start handling	743	after you have initialised all your watchers and you want to start
641	events.	744	handling events. It will ask the operating system for any new events, call
		745	the watcher callbacks, an then repeat the whole process indefinitely: This
		746	is why event loops are called I<loops>.
642		747
643	If the flags argument is specified as C<0>, it will not return until	748	If the flags argument is specified as C<0>, it will keep handling events
644	either no event watchers are active anymore or C<ev_unloop> was called.	749	until either no event watchers are active anymore or C<ev_break> was
		750	called.
645		751
646	Please note that an explicit C<ev_unloop> is usually better than	752	Please note that an explicit C<ev_break> is usually better than
647	relying on all watchers to be stopped when deciding when a program has	753	relying on all watchers to be stopped when deciding when a program has
648	finished (especially in interactive programs), but having a program	754	finished (especially in interactive programs), but having a program
649	that automatically loops as long as it has to and no longer by virtue	755	that automatically loops as long as it has to and no longer by virtue
650	of relying on its watchers stopping correctly, that is truly a thing of	756	of relying on its watchers stopping correctly, that is truly a thing of
651	beauty.	757	beauty.
652		758
653	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	759	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
654	those events and any already outstanding ones, but will not block your	760	those events and any already outstanding ones, but will not wait and
655	process in case there are no events and will return after one iteration of	761	block your process in case there are no events and will return after one
656	the loop.	762	iteration of the loop. This is sometimes useful to poll and handle new
		763	events while doing lengthy calculations, to keep the program responsive.
657		764
658	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	765	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
659	necessary) and will handle those and any already outstanding ones. It	766	necessary) and will handle those and any already outstanding ones. It
660	will block your process until at least one new event arrives (which could	767	will block your process until at least one new event arrives (which could
661	be an event internal to libev itself, so there is no guarantee that a	768	be an event internal to libev itself, so there is no guarantee that a
662	user-registered callback will be called), and will return after one	769	user-registered callback will be called), and will return after one
663	iteration of the loop.	770	iteration of the loop.
664		771
665	This is useful if you are waiting for some external event in conjunction	772	This is useful if you are waiting for some external event in conjunction
666	with something not expressible using other libev watchers (i.e. "roll your	773	with something not expressible using other libev watchers (i.e. "roll your
667	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	774	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
668	usually a better approach for this kind of thing.	775	usually a better approach for this kind of thing.
669		776
670	Here are the gory details of what C<ev_loop> does:	777	Here are the gory details of what C<ev_run> does:
671		778
		779	- Increment loop depth.
		780	- Reset the ev_break status.
672	- Before the first iteration, call any pending watchers.	781	- Before the first iteration, call any pending watchers.
		782	LOOP:
673	* If EVFLAG_FORKCHECK was used, check for a fork.	783	- If EVFLAG_FORKCHECK was used, check for a fork.
674	- If a fork was detected (by any means), queue and call all fork watchers.	784	- If a fork was detected (by any means), queue and call all fork watchers.
675	- Queue and call all prepare watchers.	785	- Queue and call all prepare watchers.
		786	- If ev_break was called, goto FINISH.
676	- If we have been forked, detach and recreate the kernel state	787	- If we have been forked, detach and recreate the kernel state
677	as to not disturb the other process.	788	as to not disturb the other process.
678	- Update the kernel state with all outstanding changes.	789	- Update the kernel state with all outstanding changes.
679	- Update the "event loop time" (ev_now ()).	790	- Update the "event loop time" (ev_now ()).
680	- Calculate for how long to sleep or block, if at all	791	- Calculate for how long to sleep or block, if at all
681	(active idle watchers, EVLOOP_NONBLOCK or not having	792	(active idle watchers, EVRUN_NOWAIT or not having
682	any active watchers at all will result in not sleeping).	793	any active watchers at all will result in not sleeping).
683	- Sleep if the I/O and timer collect interval say so.	794	- Sleep if the I/O and timer collect interval say so.
		795	- Increment loop iteration counter.
684	- Block the process, waiting for any events.	796	- Block the process, waiting for any events.
685	- Queue all outstanding I/O (fd) events.	797	- Queue all outstanding I/O (fd) events.
686	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	798	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
687	- Queue all expired timers.	799	- Queue all expired timers.
688	- Queue all expired periodics.	800	- Queue all expired periodics.
689	- Unless any events are pending now, queue all idle watchers.	801	- Queue all idle watchers with priority higher than that of pending events.
690	- Queue all check watchers.	802	- Queue all check watchers.
691	- Call all queued watchers in reverse order (i.e. check watchers first).	803	- Call all queued watchers in reverse order (i.e. check watchers first).
692	Signals and child watchers are implemented as I/O watchers, and will	804	Signals and child watchers are implemented as I/O watchers, and will
693	be handled here by queueing them when their watcher gets executed.	805	be handled here by queueing them when their watcher gets executed.
694	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	806	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
695	were used, or there are no active watchers, return, otherwise	807	were used, or there are no active watchers, goto FINISH, otherwise
696	continue with step *.	808	continue with step LOOP.
		809	FINISH:
		810	- Reset the ev_break status iff it was EVBREAK_ONE.
		811	- Decrement the loop depth.
		812	- Return.
697		813
698	Example: Queue some jobs and then loop until no events are outstanding	814	Example: Queue some jobs and then loop until no events are outstanding
699	anymore.	815	anymore.
700		816
701	... queue jobs here, make sure they register event watchers as long	817	... queue jobs here, make sure they register event watchers as long
702	... as they still have work to do (even an idle watcher will do..)	818	... as they still have work to do (even an idle watcher will do..)
703	ev_loop (my_loop, 0);	819	ev_run (my_loop, 0);
704	... jobs done or somebody called unloop. yeah!	820	... jobs done or somebody called unloop. yeah!
705		821
706	=item ev_unloop (loop, how)	822	=item ev_break (loop, how)
707		823
708	Can be used to make a call to C<ev_loop> return early (but only after it	824	Can be used to make a call to C<ev_run> return early (but only after it
709	has processed all outstanding events). The C<how> argument must be either	825	has processed all outstanding events). The C<how> argument must be either
710	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	826	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
711	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	827	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
712		828
713	This "unloop state" will be cleared when entering C<ev_loop> again.	829	This "break state" will be cleared when entering C<ev_run> again.
714		830
715	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	831	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.
716		832
717	=item ev_ref (loop)	833	=item ev_ref (loop)
718		834
719	=item ev_unref (loop)	835	=item ev_unref (loop)
720		836
721	Ref/unref can be used to add or remove a reference count on the event	837	Ref/unref can be used to add or remove a reference count on the event
722	loop: Every watcher keeps one reference, and as long as the reference	838	loop: Every watcher keeps one reference, and as long as the reference
723	count is nonzero, C<ev_loop> will not return on its own.	839	count is nonzero, C<ev_run> will not return on its own.
724		840
725	If you have a watcher you never unregister that should not keep C<ev_loop>	841	This is useful when you have a watcher that you never intend to
726	from returning, call ev_unref() after starting, and ev_ref() before	842	unregister, but that nevertheless should not keep C<ev_run> from
		843	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
727	stopping it.	844	before stopping it.
728		845
729	As an example, libev itself uses this for its internal signal pipe: It is	846	As an example, libev itself uses this for its internal signal pipe: It
730	not visible to the libev user and should not keep C<ev_loop> from exiting	847	is not visible to the libev user and should not keep C<ev_run> from
731	if no event watchers registered by it are active. It is also an excellent	848	exiting if no event watchers registered by it are active. It is also an
732	way to do this for generic recurring timers or from within third-party	849	excellent way to do this for generic recurring timers or from within
733	libraries. Just remember to I<unref after start> and I<ref before stop>	850	third-party libraries. Just remember to I<unref after start> and I<ref
734	(but only if the watcher wasn't active before, or was active before,	851	before stop> (but only if the watcher wasn't active before, or was active
735	respectively).	852	before, respectively. Note also that libev might stop watchers itself
		853	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		854	in the callback).
736		855
737	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	856	Example: Create a signal watcher, but keep it from keeping C<ev_run>
738	running when nothing else is active.	857	running when nothing else is active.
739		858
740	ev_signal exitsig;	859	ev_signal exitsig;
741	ev_signal_init (&exitsig, sig_cb, SIGINT);	860	ev_signal_init (&exitsig, sig_cb, SIGINT);
742	ev_signal_start (loop, &exitsig);	861	ev_signal_start (loop, &exitsig);
…		…
769		888
770	By setting a higher I<io collect interval> you allow libev to spend more	889	By setting a higher I<io collect interval> you allow libev to spend more
771	time collecting I/O events, so you can handle more events per iteration,	890	time collecting I/O events, so you can handle more events per iteration,
772	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	891	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
773	C<ev_timer>) will be not affected. Setting this to a non-null value will	892	C<ev_timer>) will be not affected. Setting this to a non-null value will
774	introduce an additional C<ev_sleep ()> call into most loop iterations.	893	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		894	sleep time ensures that libev will not poll for I/O events more often then
		895	once per this interval, on average.
775		896
776	Likewise, by setting a higher I<timeout collect interval> you allow libev	897	Likewise, by setting a higher I<timeout collect interval> you allow libev
777	to spend more time collecting timeouts, at the expense of increased	898	to spend more time collecting timeouts, at the expense of increased
778	latency/jitter/inexactness (the watcher callback will be called	899	latency/jitter/inexactness (the watcher callback will be called
779	later). C<ev_io> watchers will not be affected. Setting this to a non-null	900	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
781		902
782	Many (busy) programs can usually benefit by setting the I/O collect	903	Many (busy) programs can usually benefit by setting the I/O collect
783	interval to a value near C<0.1> or so, which is often enough for	904	interval to a value near C<0.1> or so, which is often enough for
784	interactive servers (of course not for games), likewise for timeouts. It	905	interactive servers (of course not for games), likewise for timeouts. It
785	usually doesn't make much sense to set it to a lower value than C<0.01>,	906	usually doesn't make much sense to set it to a lower value than C<0.01>,
786	as this approaches the timing granularity of most systems.	907	as this approaches the timing granularity of most systems. Note that if
		908	you do transactions with the outside world and you can't increase the
		909	parallelity, then this setting will limit your transaction rate (if you
		910	need to poll once per transaction and the I/O collect interval is 0.01,
		911	then you can't do more than 100 transactions per second).
787		912
788	Setting the I<timeout collect interval> can improve the opportunity for	913	Setting the I<timeout collect interval> can improve the opportunity for
789	saving power, as the program will "bundle" timer callback invocations that	914	saving power, as the program will "bundle" timer callback invocations that
790	are "near" in time together, by delaying some, thus reducing the number of	915	are "near" in time together, by delaying some, thus reducing the number of
791	times the process sleeps and wakes up again. Another useful technique to	916	times the process sleeps and wakes up again. Another useful technique to
792	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	917	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
793	they fire on, say, one-second boundaries only.	918	they fire on, say, one-second boundaries only.
794		919
		920	Example: we only need 0.1s timeout granularity, and we wish not to poll
		921	more often than 100 times per second:
		922
		923	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		924	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		925
		926	=item ev_invoke_pending (loop)
		927
		928	This call will simply invoke all pending watchers while resetting their
		929	pending state. Normally, C<ev_run> does this automatically when required,
		930	but when overriding the invoke callback this call comes handy. This
		931	function can be invoked from a watcher - this can be useful for example
		932	when you want to do some lengthy calculation and want to pass further
		933	event handling to another thread (you still have to make sure only one
		934	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		935
		936	=item int ev_pending_count (loop)
		937
		938	Returns the number of pending watchers - zero indicates that no watchers
		939	are pending.
		940
		941	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		942
		943	This overrides the invoke pending functionality of the loop: Instead of
		944	invoking all pending watchers when there are any, C<ev_run> will call
		945	this callback instead. This is useful, for example, when you want to
		946	invoke the actual watchers inside another context (another thread etc.).
		947
		948	If you want to reset the callback, use C<ev_invoke_pending> as new
		949	callback.
		950
		951	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		952
		953	Sometimes you want to share the same loop between multiple threads. This
		954	can be done relatively simply by putting mutex_lock/unlock calls around
		955	each call to a libev function.
		956
		957	However, C<ev_run> can run an indefinite time, so it is not feasible
		958	to wait for it to return. One way around this is to wake up the event
		959	loop via C<ev_break> and C<av_async_send>, another way is to set these
		960	I<release> and I<acquire> callbacks on the loop.
		961
		962	When set, then C<release> will be called just before the thread is
		963	suspended waiting for new events, and C<acquire> is called just
		964	afterwards.
		965
		966	Ideally, C<release> will just call your mutex_unlock function, and
		967	C<acquire> will just call the mutex_lock function again.
		968
		969	While event loop modifications are allowed between invocations of
		970	C<release> and C<acquire> (that's their only purpose after all), no
		971	modifications done will affect the event loop, i.e. adding watchers will
		972	have no effect on the set of file descriptors being watched, or the time
		973	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		974	to take note of any changes you made.
		975
		976	In theory, threads executing C<ev_run> will be async-cancel safe between
		977	invocations of C<release> and C<acquire>.
		978
		979	See also the locking example in the C<THREADS> section later in this
		980	document.
		981
		982	=item ev_set_userdata (loop, void *data)
		983
		984	=item ev_userdata (loop)
		985
		986	Set and retrieve a single C<void *> associated with a loop. When
		987	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		988	C<0.>
		989
		990	These two functions can be used to associate arbitrary data with a loop,
		991	and are intended solely for the C<invoke_pending_cb>, C<release> and
		992	C<acquire> callbacks described above, but of course can be (ab-)used for
		993	any other purpose as well.
		994
795	=item ev_loop_verify (loop)	995	=item ev_verify (loop)
796		996
797	This function only does something when C<EV_VERIFY> support has been	997	This function only does something when C<EV_VERIFY> support has been
798	compiled in, which is the default for non-minimal builds. It tries to go	998	compiled in, which is the default for non-minimal builds. It tries to go
799	through all internal structures and checks them for validity. If anything	999	through all internal structures and checks them for validity. If anything
800	is found to be inconsistent, it will print an error message to standard	1000	is found to be inconsistent, it will print an error message to standard
…		…
811		1011
812	In the following description, uppercase C<TYPE> in names stands for the	1012	In the following description, uppercase C<TYPE> in names stands for the
813	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1013	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
814	watchers and C<ev_io_start> for I/O watchers.	1014	watchers and C<ev_io_start> for I/O watchers.
815		1015
816	A watcher is a structure that you create and register to record your	1016	A watcher is an opaque structure that you allocate and register to record
817	interest in some event. For instance, if you want to wait for STDIN to	1017	your interest in some event. To make a concrete example, imagine you want
818	become readable, you would create an C<ev_io> watcher for that:	1018	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1019	for that:
819		1020
820	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1021	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
821	{	1022	{
822	ev_io_stop (w);	1023	ev_io_stop (w);
823	ev_unloop (loop, EVUNLOOP_ALL);	1024	ev_break (loop, EVBREAK_ALL);
824	}	1025	}
825		1026
826	struct ev_loop *loop = ev_default_loop (0);	1027	struct ev_loop *loop = ev_default_loop (0);
827		1028
828	ev_io stdin_watcher;	1029	ev_io stdin_watcher;
829		1030
830	ev_init (&stdin_watcher, my_cb);	1031	ev_init (&stdin_watcher, my_cb);
831	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1032	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
832	ev_io_start (loop, &stdin_watcher);	1033	ev_io_start (loop, &stdin_watcher);
833		1034
834	ev_loop (loop, 0);	1035	ev_run (loop, 0);
835		1036
836	As you can see, you are responsible for allocating the memory for your	1037	As you can see, you are responsible for allocating the memory for your
837	watcher structures (and it is I<usually> a bad idea to do this on the	1038	watcher structures (and it is I<usually> a bad idea to do this on the
838	stack).	1039	stack).
839		1040
840	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1041	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
841	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1042	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
842		1043
843	Each watcher structure must be initialised by a call to C<ev_init	1044	Each watcher structure must be initialised by a call to C<ev_init (watcher
844	(watcher *, callback)>, which expects a callback to be provided. This	1045	*, callback)>, which expects a callback to be provided. This callback is
845	callback gets invoked each time the event occurs (or, in the case of I/O	1046	invoked each time the event occurs (or, in the case of I/O watchers, each
846	watchers, each time the event loop detects that the file descriptor given	1047	time the event loop detects that the file descriptor given is readable
847	is readable and/or writable).	1048	and/or writable).
848		1049
849	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1050	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
850	macro to configure it, with arguments specific to the watcher type. There	1051	macro to configure it, with arguments specific to the watcher type. There
851	is also a macro to combine initialisation and setting in one call: C<<	1052	is also a macro to combine initialisation and setting in one call: C<<
852	ev_TYPE_init (watcher *, callback, ...) >>.	1053	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
875	=item C<EV_WRITE>	1076	=item C<EV_WRITE>
876		1077
877	The file descriptor in the C<ev_io> watcher has become readable and/or	1078	The file descriptor in the C<ev_io> watcher has become readable and/or
878	writable.	1079	writable.
879		1080
880	=item C<EV_TIMEOUT>	1081	=item C<EV_TIMER>
881		1082
882	The C<ev_timer> watcher has timed out.	1083	The C<ev_timer> watcher has timed out.
883		1084
884	=item C<EV_PERIODIC>	1085	=item C<EV_PERIODIC>
885		1086
…		…
903		1104
904	=item C<EV_PREPARE>	1105	=item C<EV_PREPARE>
905		1106
906	=item C<EV_CHECK>	1107	=item C<EV_CHECK>
907		1108
908	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1109	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
909	to gather new events, and all C<ev_check> watchers are invoked just after	1110	to gather new events, and all C<ev_check> watchers are invoked just after
910	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1111	C<ev_run> has gathered them, but before it invokes any callbacks for any
911	received events. Callbacks of both watcher types can start and stop as	1112	received events. Callbacks of both watcher types can start and stop as
912	many watchers as they want, and all of them will be taken into account	1113	many watchers as they want, and all of them will be taken into account
913	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1114	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
914	C<ev_loop> from blocking).	1115	C<ev_run> from blocking).
915		1116
916	=item C<EV_EMBED>	1117	=item C<EV_EMBED>
917		1118
918	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1119	The embedded event loop specified in the C<ev_embed> watcher needs attention.
919		1120
920	=item C<EV_FORK>	1121	=item C<EV_FORK>
921		1122
922	The event loop has been resumed in the child process after fork (see	1123	The event loop has been resumed in the child process after fork (see
923	C<ev_fork>).	1124	C<ev_fork>).
924		1125
		1126	=item C<EV_CLEANUP>
		1127
		1128	The event loop is about to be destroyed (see C<ev_cleanup>).
		1129
925	=item C<EV_ASYNC>	1130	=item C<EV_ASYNC>
926		1131
927	The given async watcher has been asynchronously notified (see C<ev_async>).	1132	The given async watcher has been asynchronously notified (see C<ev_async>).
		1133
		1134	=item C<EV_CUSTOM>
		1135
		1136	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1137	by libev users to signal watchers (e.g. via C<ev_feed_event>).
928		1138
929	=item C<EV_ERROR>	1139	=item C<EV_ERROR>
930		1140
931	An unspecified error has occurred, the watcher has been stopped. This might	1141	An unspecified error has occurred, the watcher has been stopped. This might
932	happen because the watcher could not be properly started because libev	1142	happen because the watcher could not be properly started because libev
…		…
970		1180
971	ev_io w;	1181	ev_io w;
972	ev_init (&w, my_cb);	1182	ev_init (&w, my_cb);
973	ev_io_set (&w, STDIN_FILENO, EV_READ);	1183	ev_io_set (&w, STDIN_FILENO, EV_READ);
974		1184
975	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1185	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
976		1186
977	This macro initialises the type-specific parts of a watcher. You need to	1187	This macro initialises the type-specific parts of a watcher. You need to
978	call C<ev_init> at least once before you call this macro, but you can	1188	call C<ev_init> at least once before you call this macro, but you can
979	call C<ev_TYPE_set> any number of times. You must not, however, call this	1189	call C<ev_TYPE_set> any number of times. You must not, however, call this
980	macro on a watcher that is active (it can be pending, however, which is a	1190	macro on a watcher that is active (it can be pending, however, which is a
…		…
993		1203
994	Example: Initialise and set an C<ev_io> watcher in one step.	1204	Example: Initialise and set an C<ev_io> watcher in one step.
995		1205
996	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1206	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
997		1207
998	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1208	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
999		1209
1000	Starts (activates) the given watcher. Only active watchers will receive	1210	Starts (activates) the given watcher. Only active watchers will receive
1001	events. If the watcher is already active nothing will happen.	1211	events. If the watcher is already active nothing will happen.
1002		1212
1003	Example: Start the C<ev_io> watcher that is being abused as example in this	1213	Example: Start the C<ev_io> watcher that is being abused as example in this
1004	whole section.	1214	whole section.
1005		1215
1006	ev_io_start (EV_DEFAULT_UC, &w);	1216	ev_io_start (EV_DEFAULT_UC, &w);
1007		1217
1008	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1218	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1009		1219
1010	Stops the given watcher if active, and clears the pending status (whether	1220	Stops the given watcher if active, and clears the pending status (whether
1011	the watcher was active or not).	1221	the watcher was active or not).
1012		1222
1013	It is possible that stopped watchers are pending - for example,	1223	It is possible that stopped watchers are pending - for example,
…		…
1038	=item ev_cb_set (ev_TYPE *watcher, callback)	1248	=item ev_cb_set (ev_TYPE *watcher, callback)
1039		1249
1040	Change the callback. You can change the callback at virtually any time	1250	Change the callback. You can change the callback at virtually any time
1041	(modulo threads).	1251	(modulo threads).
1042		1252
1043	=item ev_set_priority (ev_TYPE *watcher, priority)	1253	=item ev_set_priority (ev_TYPE *watcher, int priority)
1044		1254
1045	=item int ev_priority (ev_TYPE *watcher)	1255	=item int ev_priority (ev_TYPE *watcher)
1046		1256
1047	Set and query the priority of the watcher. The priority is a small	1257	Set and query the priority of the watcher. The priority is a small
1048	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1258	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1049	(default: C<-2>). Pending watchers with higher priority will be invoked	1259	(default: C<-2>). Pending watchers with higher priority will be invoked
1050	before watchers with lower priority, but priority will not keep watchers	1260	before watchers with lower priority, but priority will not keep watchers
1051	from being executed (except for C<ev_idle> watchers).	1261	from being executed (except for C<ev_idle> watchers).
1052		1262
1053	This means that priorities are I<only> used for ordering callback
1054	invocation after new events have been received. This is useful, for
1055	example, to reduce latency after idling, or more often, to bind two
1056	watchers on the same event and make sure one is called first.
1057
1058	If you need to suppress invocation when higher priority events are pending	1263	If you need to suppress invocation when higher priority events are pending
1059	you need to look at C<ev_idle> watchers, which provide this functionality.	1264	you need to look at C<ev_idle> watchers, which provide this functionality.
1060		1265
1061	You I<must not> change the priority of a watcher as long as it is active or	1266	You I<must not> change the priority of a watcher as long as it is active or
1062	pending.	1267	pending.
1063
1064	The default priority used by watchers when no priority has been set is
1065	always C<0>, which is supposed to not be too high and not be too low :).
1066		1268
1067	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1269	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1068	fine, as long as you do not mind that the priority value you query might	1270	fine, as long as you do not mind that the priority value you query might
1069	or might not have been clamped to the valid range.	1271	or might not have been clamped to the valid range.
		1272
		1273	The default priority used by watchers when no priority has been set is
		1274	always C<0>, which is supposed to not be too high and not be too low :).
		1275
		1276	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1277	priorities.
1070		1278
1071	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1279	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1072		1280
1073	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1281	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1074	C<loop> nor C<revents> need to be valid as long as the watcher callback	1282	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1082	watcher isn't pending it does nothing and returns C<0>.	1290	watcher isn't pending it does nothing and returns C<0>.
1083		1291
1084	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1292	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1085	callback to be invoked, which can be accomplished with this function.	1293	callback to be invoked, which can be accomplished with this function.
1086		1294
		1295	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1296
		1297	Feeds the given event set into the event loop, as if the specified event
		1298	had happened for the specified watcher (which must be a pointer to an
		1299	initialised but not necessarily started event watcher). Obviously you must
		1300	not free the watcher as long as it has pending events.
		1301
		1302	Stopping the watcher, letting libev invoke it, or calling
		1303	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1304	not started in the first place.
		1305
		1306	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1307	functions that do not need a watcher.
		1308
1087	=back	1309	=back
1088
1089		1310
1090	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1311	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1091		1312
1092	Each watcher has, by default, a member C<void *data> that you can change	1313	Each watcher has, by default, a member C<void *data> that you can change
1093	and read at any time: libev will completely ignore it. This can be used	1314	and read at any time: libev will completely ignore it. This can be used
…		…
1139	#include <stddef.h>	1360	#include <stddef.h>
1140		1361
1141	static void	1362	static void
1142	t1_cb (EV_P_ ev_timer *w, int revents)	1363	t1_cb (EV_P_ ev_timer *w, int revents)
1143	{	1364	{
1144	struct my_biggy big = (struct my_biggy *	1365	struct my_biggy big = (struct my_biggy *)
1145	(((char *)w) - offsetof (struct my_biggy, t1));	1366	(((char *)w) - offsetof (struct my_biggy, t1));
1146	}	1367	}
1147		1368
1148	static void	1369	static void
1149	t2_cb (EV_P_ ev_timer *w, int revents)	1370	t2_cb (EV_P_ ev_timer *w, int revents)
1150	{	1371	{
1151	struct my_biggy big = (struct my_biggy *	1372	struct my_biggy big = (struct my_biggy *)
1152	(((char *)w) - offsetof (struct my_biggy, t2));	1373	(((char *)w) - offsetof (struct my_biggy, t2));
1153	}	1374	}
		1375
		1376	=head2 WATCHER STATES
		1377
		1378	There are various watcher states mentioned throughout this manual -
		1379	active, pending and so on. In this section these states and the rules to
		1380	transition between them will be described in more detail - and while these
		1381	rules might look complicated, they usually do "the right thing".
		1382
		1383	=over 4
		1384
		1385	=item initialiased
		1386
		1387	Before a watcher can be registered with the event looop it has to be
		1388	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1389	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1390
		1391	In this state it is simply some block of memory that is suitable for use
		1392	in an event loop. It can be moved around, freed, reused etc. at will.
		1393
		1394	=item started/running/active
		1395
		1396	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1397	property of the event loop, and is actively waiting for events. While in
		1398	this state it cannot be accessed (except in a few documented ways), moved,
		1399	freed or anything else - the only legal thing is to keep a pointer to it,
		1400	and call libev functions on it that are documented to work on active watchers.
		1401
		1402	=item pending
		1403
		1404	If a watcher is active and libev determines that an event it is interested
		1405	in has occurred (such as a timer expiring), it will become pending. It will
		1406	stay in this pending state until either it is stopped or its callback is
		1407	about to be invoked, so it is not normally pending inside the watcher
		1408	callback.
		1409
		1410	The watcher might or might not be active while it is pending (for example,
		1411	an expired non-repeating timer can be pending but no longer active). If it
		1412	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1413	but it is still property of the event loop at this time, so cannot be
		1414	moved, freed or reused. And if it is active the rules described in the
		1415	previous item still apply.
		1416
		1417	It is also possible to feed an event on a watcher that is not active (e.g.
		1418	via C<ev_feed_event>), in which case it becomes pending without being
		1419	active.
		1420
		1421	=item stopped
		1422
		1423	A watcher can be stopped implicitly by libev (in which case it might still
		1424	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1425	latter will clear any pending state the watcher might be in, regardless
		1426	of whether it was active or not, so stopping a watcher explicitly before
		1427	freeing it is often a good idea.
		1428
		1429	While stopped (and not pending) the watcher is essentially in the
		1430	initialised state, that is it can be reused, moved, modified in any way
		1431	you wish.
		1432
		1433	=back
		1434
		1435	=head2 WATCHER PRIORITY MODELS
		1436
		1437	Many event loops support I<watcher priorities>, which are usually small
		1438	integers that influence the ordering of event callback invocation
		1439	between watchers in some way, all else being equal.
		1440
		1441	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1442	description for the more technical details such as the actual priority
		1443	range.
		1444
		1445	There are two common ways how these these priorities are being interpreted
		1446	by event loops:
		1447
		1448	In the more common lock-out model, higher priorities "lock out" invocation
		1449	of lower priority watchers, which means as long as higher priority
		1450	watchers receive events, lower priority watchers are not being invoked.
		1451
		1452	The less common only-for-ordering model uses priorities solely to order
		1453	callback invocation within a single event loop iteration: Higher priority
		1454	watchers are invoked before lower priority ones, but they all get invoked
		1455	before polling for new events.
		1456
		1457	Libev uses the second (only-for-ordering) model for all its watchers
		1458	except for idle watchers (which use the lock-out model).
		1459
		1460	The rationale behind this is that implementing the lock-out model for
		1461	watchers is not well supported by most kernel interfaces, and most event
		1462	libraries will just poll for the same events again and again as long as
		1463	their callbacks have not been executed, which is very inefficient in the
		1464	common case of one high-priority watcher locking out a mass of lower
		1465	priority ones.
		1466
		1467	Static (ordering) priorities are most useful when you have two or more
		1468	watchers handling the same resource: a typical usage example is having an
		1469	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1470	timeouts. Under load, data might be received while the program handles
		1471	other jobs, but since timers normally get invoked first, the timeout
		1472	handler will be executed before checking for data. In that case, giving
		1473	the timer a lower priority than the I/O watcher ensures that I/O will be
		1474	handled first even under adverse conditions (which is usually, but not
		1475	always, what you want).
		1476
		1477	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1478	will only be executed when no same or higher priority watchers have
		1479	received events, they can be used to implement the "lock-out" model when
		1480	required.
		1481
		1482	For example, to emulate how many other event libraries handle priorities,
		1483	you can associate an C<ev_idle> watcher to each such watcher, and in
		1484	the normal watcher callback, you just start the idle watcher. The real
		1485	processing is done in the idle watcher callback. This causes libev to
		1486	continuously poll and process kernel event data for the watcher, but when
		1487	the lock-out case is known to be rare (which in turn is rare :), this is
		1488	workable.
		1489
		1490	Usually, however, the lock-out model implemented that way will perform
		1491	miserably under the type of load it was designed to handle. In that case,
		1492	it might be preferable to stop the real watcher before starting the
		1493	idle watcher, so the kernel will not have to process the event in case
		1494	the actual processing will be delayed for considerable time.
		1495
		1496	Here is an example of an I/O watcher that should run at a strictly lower
		1497	priority than the default, and which should only process data when no
		1498	other events are pending:
		1499
		1500	ev_idle idle; // actual processing watcher
		1501	ev_io io; // actual event watcher
		1502
		1503	static void
		1504	io_cb (EV_P_ ev_io *w, int revents)
		1505	{
		1506	// stop the I/O watcher, we received the event, but
		1507	// are not yet ready to handle it.
		1508	ev_io_stop (EV_A_ w);
		1509
		1510	// start the idle watcher to handle the actual event.
		1511	// it will not be executed as long as other watchers
		1512	// with the default priority are receiving events.
		1513	ev_idle_start (EV_A_ &idle);
		1514	}
		1515
		1516	static void
		1517	idle_cb (EV_P_ ev_idle *w, int revents)
		1518	{
		1519	// actual processing
		1520	read (STDIN_FILENO, ...);
		1521
		1522	// have to start the I/O watcher again, as
		1523	// we have handled the event
		1524	ev_io_start (EV_P_ &io);
		1525	}
		1526
		1527	// initialisation
		1528	ev_idle_init (&idle, idle_cb);
		1529	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1530	ev_io_start (EV_DEFAULT_ &io);
		1531
		1532	In the "real" world, it might also be beneficial to start a timer, so that
		1533	low-priority connections can not be locked out forever under load. This
		1534	enables your program to keep a lower latency for important connections
		1535	during short periods of high load, while not completely locking out less
		1536	important ones.
1154		1537
1155		1538
1156	=head1 WATCHER TYPES	1539	=head1 WATCHER TYPES
1157		1540
1158	This section describes each watcher in detail, but will not repeat	1541	This section describes each watcher in detail, but will not repeat
…		…
1184	descriptors to non-blocking mode is also usually a good idea (but not	1567	descriptors to non-blocking mode is also usually a good idea (but not
1185	required if you know what you are doing).	1568	required if you know what you are doing).
1186		1569
1187	If you cannot use non-blocking mode, then force the use of a	1570	If you cannot use non-blocking mode, then force the use of a
1188	known-to-be-good backend (at the time of this writing, this includes only	1571	known-to-be-good backend (at the time of this writing, this includes only
1189	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1572	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1573	descriptors for which non-blocking operation makes no sense (such as
		1574	files) - libev doesn't guarantee any specific behaviour in that case.
1190		1575
1191	Another thing you have to watch out for is that it is quite easy to	1576	Another thing you have to watch out for is that it is quite easy to
1192	receive "spurious" readiness notifications, that is your callback might	1577	receive "spurious" readiness notifications, that is your callback might
1193	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1194	because there is no data. Not only are some backends known to create a	1579	because there is no data. Not only are some backends known to create a
…		…
1259		1644
1260	So when you encounter spurious, unexplained daemon exits, make sure you	1645	So when you encounter spurious, unexplained daemon exits, make sure you
1261	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1646	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1262	somewhere, as that would have given you a big clue).	1647	somewhere, as that would have given you a big clue).
1263		1648
		1649	=head3 The special problem of accept()ing when you can't
		1650
		1651	Many implementations of the POSIX C<accept> function (for example,
		1652	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1653	connection from the pending queue in all error cases.
		1654
		1655	For example, larger servers often run out of file descriptors (because
		1656	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1657	rejecting the connection, leading to libev signalling readiness on
		1658	the next iteration again (the connection still exists after all), and
		1659	typically causing the program to loop at 100% CPU usage.
		1660
		1661	Unfortunately, the set of errors that cause this issue differs between
		1662	operating systems, there is usually little the app can do to remedy the
		1663	situation, and no known thread-safe method of removing the connection to
		1664	cope with overload is known (to me).
		1665
		1666	One of the easiest ways to handle this situation is to just ignore it
		1667	- when the program encounters an overload, it will just loop until the
		1668	situation is over. While this is a form of busy waiting, no OS offers an
		1669	event-based way to handle this situation, so it's the best one can do.
		1670
		1671	A better way to handle the situation is to log any errors other than
		1672	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1673	messages, and continue as usual, which at least gives the user an idea of
		1674	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1675	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1676	usage.
		1677
		1678	If your program is single-threaded, then you could also keep a dummy file
		1679	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1680	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1681	close that fd, and create a new dummy fd. This will gracefully refuse
		1682	clients under typical overload conditions.
		1683
		1684	The last way to handle it is to simply log the error and C<exit>, as
		1685	is often done with C<malloc> failures, but this results in an easy
		1686	opportunity for a DoS attack.
1264		1687
1265	=head3 Watcher-Specific Functions	1688	=head3 Watcher-Specific Functions
1266		1689
1267	=over 4	1690	=over 4
1268		1691
…		…
1300	...	1723	...
1301	struct ev_loop *loop = ev_default_init (0);	1724	struct ev_loop *loop = ev_default_init (0);
1302	ev_io stdin_readable;	1725	ev_io stdin_readable;
1303	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1726	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1304	ev_io_start (loop, &stdin_readable);	1727	ev_io_start (loop, &stdin_readable);
1305	ev_loop (loop, 0);	1728	ev_run (loop, 0);
1306		1729
1307		1730
1308	=head2 C<ev_timer> - relative and optionally repeating timeouts	1731	=head2 C<ev_timer> - relative and optionally repeating timeouts
1309		1732
1310	Timer watchers are simple relative timers that generate an event after a	1733	Timer watchers are simple relative timers that generate an event after a
…		…
1315	year, it will still time out after (roughly) one hour. "Roughly" because	1738	year, it will still time out after (roughly) one hour. "Roughly" because
1316	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1739	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1317	monotonic clock option helps a lot here).	1740	monotonic clock option helps a lot here).
1318		1741
1319	The callback is guaranteed to be invoked only I<after> its timeout has	1742	The callback is guaranteed to be invoked only I<after> its timeout has
1320	passed, but if multiple timers become ready during the same loop iteration	1743	passed (not I<at>, so on systems with very low-resolution clocks this
1321	then order of execution is undefined.	1744	might introduce a small delay). If multiple timers become ready during the
		1745	same loop iteration then the ones with earlier time-out values are invoked
		1746	before ones of the same priority with later time-out values (but this is
		1747	no longer true when a callback calls C<ev_run> recursively).
1322		1748
1323	=head3 Be smart about timeouts	1749	=head3 Be smart about timeouts
1324		1750
1325	Many real-world problems involve some kind of timeout, usually for error	1751	Many real-world problems involve some kind of timeout, usually for error
1326	recovery. A typical example is an HTTP request - if the other side hangs,	1752	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1370	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1796	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1371	member and C<ev_timer_again>.	1797	member and C<ev_timer_again>.
1372		1798
1373	At start:	1799	At start:
1374		1800
1375	ev_timer_init (timer, callback);	1801	ev_init (timer, callback);
1376	timer->repeat = 60.;	1802	timer->repeat = 60.;
1377	ev_timer_again (loop, timer);	1803	ev_timer_again (loop, timer);
1378		1804
1379	Each time there is some activity:	1805	Each time there is some activity:
1380		1806
…		…
1412	ev_tstamp timeout = last_activity + 60.;	1838	ev_tstamp timeout = last_activity + 60.;
1413		1839
1414	// if last_activity + 60. is older than now, we did time out	1840	// if last_activity + 60. is older than now, we did time out
1415	if (timeout < now)	1841	if (timeout < now)
1416	{	1842	{
1417	// timeout occured, take action	1843	// timeout occurred, take action
1418	}	1844	}
1419	else	1845	else
1420	{	1846	{
1421	// callback was invoked, but there was some activity, re-arm	1847	// callback was invoked, but there was some activity, re-arm
1422	// the watcher to fire in last_activity + 60, which is	1848	// the watcher to fire in last_activity + 60, which is
1423	// guaranteed to be in the future, so "again" is positive:	1849	// guaranteed to be in the future, so "again" is positive:
1424	w->again = timeout - now;	1850	w->repeat = timeout - now;
1425	ev_timer_again (EV_A_ w);	1851	ev_timer_again (EV_A_ w);
1426	}	1852	}
1427	}	1853	}
1428		1854
1429	To summarise the callback: first calculate the real timeout (defined	1855	To summarise the callback: first calculate the real timeout (defined
…		…
1442		1868
1443	To start the timer, simply initialise the watcher and set C<last_activity>	1869	To start the timer, simply initialise the watcher and set C<last_activity>
1444	to the current time (meaning we just have some activity :), then call the	1870	to the current time (meaning we just have some activity :), then call the
1445	callback, which will "do the right thing" and start the timer:	1871	callback, which will "do the right thing" and start the timer:
1446		1872
1447	ev_timer_init (timer, callback);	1873	ev_init (timer, callback);
1448	last_activity = ev_now (loop);	1874	last_activity = ev_now (loop);
1449	callback (loop, timer, EV_TIMEOUT);	1875	callback (loop, timer, EV_TIMER);
1450		1876
1451	And when there is some activity, simply store the current time in	1877	And when there is some activity, simply store the current time in
1452	C<last_activity>, no libev calls at all:	1878	C<last_activity>, no libev calls at all:
1453		1879
1454	last_actiivty = ev_now (loop);	1880	last_activity = ev_now (loop);
1455		1881
1456	This technique is slightly more complex, but in most cases where the	1882	This technique is slightly more complex, but in most cases where the
1457	time-out is unlikely to be triggered, much more efficient.	1883	time-out is unlikely to be triggered, much more efficient.
1458		1884
1459	Changing the timeout is trivial as well (if it isn't hard-coded in the	1885	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1497		1923
1498	=head3 The special problem of time updates	1924	=head3 The special problem of time updates
1499		1925
1500	Establishing the current time is a costly operation (it usually takes at	1926	Establishing the current time is a costly operation (it usually takes at
1501	least two system calls): EV therefore updates its idea of the current	1927	least two system calls): EV therefore updates its idea of the current
1502	time only before and after C<ev_loop> collects new events, which causes a	1928	time only before and after C<ev_run> collects new events, which causes a
1503	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1929	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1504	lots of events in one iteration.	1930	lots of events in one iteration.
1505		1931
1506	The relative timeouts are calculated relative to the C<ev_now ()>	1932	The relative timeouts are calculated relative to the C<ev_now ()>
1507	time. This is usually the right thing as this timestamp refers to the time	1933	time. This is usually the right thing as this timestamp refers to the time
…		…
1513		1939
1514	If the event loop is suspended for a long time, you can also force an	1940	If the event loop is suspended for a long time, you can also force an
1515	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1941	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1516	()>.	1942	()>.
1517		1943
		1944	=head3 The special problems of suspended animation
		1945
		1946	When you leave the server world it is quite customary to hit machines that
		1947	can suspend/hibernate - what happens to the clocks during such a suspend?
		1948
		1949	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1950	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1951	to run until the system is suspended, but they will not advance while the
		1952	system is suspended. That means, on resume, it will be as if the program
		1953	was frozen for a few seconds, but the suspend time will not be counted
		1954	towards C<ev_timer> when a monotonic clock source is used. The real time
		1955	clock advanced as expected, but if it is used as sole clocksource, then a
		1956	long suspend would be detected as a time jump by libev, and timers would
		1957	be adjusted accordingly.
		1958
		1959	I would not be surprised to see different behaviour in different between
		1960	operating systems, OS versions or even different hardware.
		1961
		1962	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1963	time jump in the monotonic clocks and the realtime clock. If the program
		1964	is suspended for a very long time, and monotonic clock sources are in use,
		1965	then you can expect C<ev_timer>s to expire as the full suspension time
		1966	will be counted towards the timers. When no monotonic clock source is in
		1967	use, then libev will again assume a timejump and adjust accordingly.
		1968
		1969	It might be beneficial for this latter case to call C<ev_suspend>
		1970	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1971	deterministic behaviour in this case (you can do nothing against
		1972	C<SIGSTOP>).
		1973
1518	=head3 Watcher-Specific Functions and Data Members	1974	=head3 Watcher-Specific Functions and Data Members
1519		1975
1520	=over 4	1976	=over 4
1521		1977
1522	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1978	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1545	If the timer is started but non-repeating, stop it (as if it timed out).	2001	If the timer is started but non-repeating, stop it (as if it timed out).
1546		2002
1547	If the timer is repeating, either start it if necessary (with the	2003	If the timer is repeating, either start it if necessary (with the
1548	C<repeat> value), or reset the running timer to the C<repeat> value.	2004	C<repeat> value), or reset the running timer to the C<repeat> value.
1549		2005
1550	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2006	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1551	usage example.	2007	usage example.
		2008
		2009	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2010
		2011	Returns the remaining time until a timer fires. If the timer is active,
		2012	then this time is relative to the current event loop time, otherwise it's
		2013	the timeout value currently configured.
		2014
		2015	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2016	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2017	will return C<4>. When the timer expires and is restarted, it will return
		2018	roughly C<7> (likely slightly less as callback invocation takes some time,
		2019	too), and so on.
1552		2020
1553	=item ev_tstamp repeat [read-write]	2021	=item ev_tstamp repeat [read-write]
1554		2022
1555	The current C<repeat> value. Will be used each time the watcher times out	2023	The current C<repeat> value. Will be used each time the watcher times out
1556	or C<ev_timer_again> is called, and determines the next timeout (if any),	2024	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1582	}	2050	}
1583		2051
1584	ev_timer mytimer;	2052	ev_timer mytimer;
1585	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2053	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1586	ev_timer_again (&mytimer); /* start timer */	2054	ev_timer_again (&mytimer); /* start timer */
1587	ev_loop (loop, 0);	2055	ev_run (loop, 0);
1588		2056
1589	// and in some piece of code that gets executed on any "activity":	2057	// and in some piece of code that gets executed on any "activity":
1590	// reset the timeout to start ticking again at 10 seconds	2058	// reset the timeout to start ticking again at 10 seconds
1591	ev_timer_again (&mytimer);	2059	ev_timer_again (&mytimer);
1592		2060
…		…
1594	=head2 C<ev_periodic> - to cron or not to cron?	2062	=head2 C<ev_periodic> - to cron or not to cron?
1595		2063
1596	Periodic watchers are also timers of a kind, but they are very versatile	2064	Periodic watchers are also timers of a kind, but they are very versatile
1597	(and unfortunately a bit complex).	2065	(and unfortunately a bit complex).
1598		2066
1599	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2067	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1600	but on wall clock time (absolute time). You can tell a periodic watcher	2068	relative time, the physical time that passes) but on wall clock time
1601	to trigger after some specific point in time. For example, if you tell a	2069	(absolute time, the thing you can read on your calender or clock). The
1602	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2070	difference is that wall clock time can run faster or slower than real
1603	+ 10.>, that is, an absolute time not a delay) and then reset your system	2071	time, and time jumps are not uncommon (e.g. when you adjust your
1604	clock to January of the previous year, then it will take more than year	2072	wrist-watch).
1605	to trigger the event (unlike an C<ev_timer>, which would still trigger
1606	roughly 10 seconds later as it uses a relative timeout).
1607		2073
		2074	You can tell a periodic watcher to trigger after some specific point
		2075	in time: for example, if you tell a periodic watcher to trigger "in 10
		2076	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2077	not a delay) and then reset your system clock to January of the previous
		2078	year, then it will take a year or more to trigger the event (unlike an
		2079	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2080	it, as it uses a relative timeout).
		2081
1608	C<ev_periodic>s can also be used to implement vastly more complex timers,	2082	C<ev_periodic> watchers can also be used to implement vastly more complex
1609	such as triggering an event on each "midnight, local time", or other	2083	timers, such as triggering an event on each "midnight, local time", or
1610	complicated rules.	2084	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2085	those cannot react to time jumps.
1611		2086
1612	As with timers, the callback is guaranteed to be invoked only when the	2087	As with timers, the callback is guaranteed to be invoked only when the
1613	time (C<at>) has passed, but if multiple periodic timers become ready	2088	point in time where it is supposed to trigger has passed. If multiple
1614	during the same loop iteration, then order of execution is undefined.	2089	timers become ready during the same loop iteration then the ones with
		2090	earlier time-out values are invoked before ones with later time-out values
		2091	(but this is no longer true when a callback calls C<ev_run> recursively).
1615		2092
1616	=head3 Watcher-Specific Functions and Data Members	2093	=head3 Watcher-Specific Functions and Data Members
1617		2094
1618	=over 4	2095	=over 4
1619		2096
1620	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2097	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1621		2098
1622	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2099	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2100
1624	Lots of arguments, lets sort it out... There are basically three modes of	2101	Lots of arguments, let's sort it out... There are basically three modes of
1625	operation, and we will explain them from simplest to most complex:	2102	operation, and we will explain them from simplest to most complex:
1626		2103
1627	=over 4	2104	=over 4
1628		2105
1629	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2106	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1630		2107
1631	In this configuration the watcher triggers an event after the wall clock	2108	In this configuration the watcher triggers an event after the wall clock
1632	time C<at> has passed. It will not repeat and will not adjust when a time	2109	time C<offset> has passed. It will not repeat and will not adjust when a
1633	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2110	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1634	only run when the system clock reaches or surpasses this time.	2111	will be stopped and invoked when the system clock reaches or surpasses
		2112	this point in time.
1635		2113
1636	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2114	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1637		2115
1638	In this mode the watcher will always be scheduled to time out at the next	2116	In this mode the watcher will always be scheduled to time out at the next
1639	C<at + N * interval> time (for some integer N, which can also be negative)	2117	C<offset + N * interval> time (for some integer N, which can also be
1640	and then repeat, regardless of any time jumps.	2118	negative) and then repeat, regardless of any time jumps. The C<offset>
		2119	argument is merely an offset into the C<interval> periods.
1641		2120
1642	This can be used to create timers that do not drift with respect to the	2121	This can be used to create timers that do not drift with respect to the
1643	system clock, for example, here is a C<ev_periodic> that triggers each	2122	system clock, for example, here is an C<ev_periodic> that triggers each
1644	hour, on the hour:	2123	hour, on the hour (with respect to UTC):
1645		2124
1646	ev_periodic_set (&periodic, 0., 3600., 0);	2125	ev_periodic_set (&periodic, 0., 3600., 0);
1647		2126
1648	This doesn't mean there will always be 3600 seconds in between triggers,	2127	This doesn't mean there will always be 3600 seconds in between triggers,
1649	but only that the callback will be called when the system time shows a	2128	but only that the callback will be called when the system time shows a
1650	full hour (UTC), or more correctly, when the system time is evenly divisible	2129	full hour (UTC), or more correctly, when the system time is evenly divisible
1651	by 3600.	2130	by 3600.
1652		2131
1653	Another way to think about it (for the mathematically inclined) is that	2132	Another way to think about it (for the mathematically inclined) is that
1654	C<ev_periodic> will try to run the callback in this mode at the next possible	2133	C<ev_periodic> will try to run the callback in this mode at the next possible
1655	time where C<time = at (mod interval)>, regardless of any time jumps.	2134	time where C<time = offset (mod interval)>, regardless of any time jumps.
1656		2135
1657	For numerical stability it is preferable that the C<at> value is near	2136	For numerical stability it is preferable that the C<offset> value is near
1658	C<ev_now ()> (the current time), but there is no range requirement for	2137	C<ev_now ()> (the current time), but there is no range requirement for
1659	this value, and in fact is often specified as zero.	2138	this value, and in fact is often specified as zero.
1660		2139
1661	Note also that there is an upper limit to how often a timer can fire (CPU	2140	Note also that there is an upper limit to how often a timer can fire (CPU
1662	speed for example), so if C<interval> is very small then timing stability	2141	speed for example), so if C<interval> is very small then timing stability
1663	will of course deteriorate. Libev itself tries to be exact to be about one	2142	will of course deteriorate. Libev itself tries to be exact to be about one
1664	millisecond (if the OS supports it and the machine is fast enough).	2143	millisecond (if the OS supports it and the machine is fast enough).
1665		2144
1666	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2145	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1667		2146
1668	In this mode the values for C<interval> and C<at> are both being	2147	In this mode the values for C<interval> and C<offset> are both being
1669	ignored. Instead, each time the periodic watcher gets scheduled, the	2148	ignored. Instead, each time the periodic watcher gets scheduled, the
1670	reschedule callback will be called with the watcher as first, and the	2149	reschedule callback will be called with the watcher as first, and the
1671	current time as second argument.	2150	current time as second argument.
1672		2151
1673	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2152	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1674	ever, or make ANY event loop modifications whatsoever>.	2153	or make ANY other event loop modifications whatsoever, unless explicitly
		2154	allowed by documentation here>.
1675		2155
1676	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2156	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1677	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2157	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1678	only event loop modification you are allowed to do).	2158	only event loop modification you are allowed to do).
1679		2159
…		…
1709	a different time than the last time it was called (e.g. in a crond like	2189	a different time than the last time it was called (e.g. in a crond like
1710	program when the crontabs have changed).	2190	program when the crontabs have changed).
1711		2191
1712	=item ev_tstamp ev_periodic_at (ev_periodic *)	2192	=item ev_tstamp ev_periodic_at (ev_periodic *)
1713		2193
1714	When active, returns the absolute time that the watcher is supposed to	2194	When active, returns the absolute time that the watcher is supposed
1715	trigger next.	2195	to trigger next. This is not the same as the C<offset> argument to
		2196	C<ev_periodic_set>, but indeed works even in interval and manual
		2197	rescheduling modes.
1716		2198
1717	=item ev_tstamp offset [read-write]	2199	=item ev_tstamp offset [read-write]
1718		2200
1719	When repeating, this contains the offset value, otherwise this is the	2201	When repeating, this contains the offset value, otherwise this is the
1720	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2202	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2203	although libev might modify this value for better numerical stability).
1721		2204
1722	Can be modified any time, but changes only take effect when the periodic	2205	Can be modified any time, but changes only take effect when the periodic
1723	timer fires or C<ev_periodic_again> is being called.	2206	timer fires or C<ev_periodic_again> is being called.
1724		2207
1725	=item ev_tstamp interval [read-write]	2208	=item ev_tstamp interval [read-write]
…		…
1741	Example: Call a callback every hour, or, more precisely, whenever the	2224	Example: Call a callback every hour, or, more precisely, whenever the
1742	system time is divisible by 3600. The callback invocation times have	2225	system time is divisible by 3600. The callback invocation times have
1743	potentially a lot of jitter, but good long-term stability.	2226	potentially a lot of jitter, but good long-term stability.
1744		2227
1745	static void	2228	static void
1746	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2229	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1747	{	2230	{
1748	... its now a full hour (UTC, or TAI or whatever your clock follows)	2231	... its now a full hour (UTC, or TAI or whatever your clock follows)
1749	}	2232	}
1750		2233
1751	ev_periodic hourly_tick;	2234	ev_periodic hourly_tick;
…		…
1777	Signal watchers will trigger an event when the process receives a specific	2260	Signal watchers will trigger an event when the process receives a specific
1778	signal one or more times. Even though signals are very asynchronous, libev	2261	signal one or more times. Even though signals are very asynchronous, libev
1779	will try it's best to deliver signals synchronously, i.e. as part of the	2262	will try it's best to deliver signals synchronously, i.e. as part of the
1780	normal event processing, like any other event.	2263	normal event processing, like any other event.
1781		2264
1782	If you want signals asynchronously, just use C<sigaction> as you would	2265	If you want signals to be delivered truly asynchronously, just use
1783	do without libev and forget about sharing the signal. You can even use	2266	C<sigaction> as you would do without libev and forget about sharing
1784	C<ev_async> from a signal handler to synchronously wake up an event loop.	2267	the signal. You can even use C<ev_async> from a signal handler to
		2268	synchronously wake up an event loop.
1785		2269
1786	You can configure as many watchers as you like per signal. Only when the	2270	You can configure as many watchers as you like for the same signal, but
		2271	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2272	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2273	C<SIGINT> in both the default loop and another loop at the same time. At
		2274	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2275
1787	first watcher gets started will libev actually register a signal handler	2276	When the first watcher gets started will libev actually register something
1788	with the kernel (thus it coexists with your own signal handlers as long as	2277	with the kernel (thus it coexists with your own signal handlers as long as
1789	you don't register any with libev for the same signal). Similarly, when	2278	you don't register any with libev for the same signal).
1790	the last signal watcher for a signal is stopped, libev will reset the
1791	signal handler to SIG_DFL (regardless of what it was set to before).
1792		2279
1793	If possible and supported, libev will install its handlers with	2280	If possible and supported, libev will install its handlers with
1794	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2281	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1795	interrupted. If you have a problem with system calls getting interrupted by	2282	not be unduly interrupted. If you have a problem with system calls getting
1796	signals you can block all signals in an C<ev_check> watcher and unblock	2283	interrupted by signals you can block all signals in an C<ev_check> watcher
1797	them in an C<ev_prepare> watcher.	2284	and unblock them in an C<ev_prepare> watcher.
		2285
		2286	=head3 The special problem of inheritance over fork/execve/pthread_create
		2287
		2288	Both the signal mask (C<sigprocmask>) and the signal disposition
		2289	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2290	stopping it again), that is, libev might or might not block the signal,
		2291	and might or might not set or restore the installed signal handler.
		2292
		2293	While this does not matter for the signal disposition (libev never
		2294	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2295	C<execve>), this matters for the signal mask: many programs do not expect
		2296	certain signals to be blocked.
		2297
		2298	This means that before calling C<exec> (from the child) you should reset
		2299	the signal mask to whatever "default" you expect (all clear is a good
		2300	choice usually).
		2301
		2302	The simplest way to ensure that the signal mask is reset in the child is
		2303	to install a fork handler with C<pthread_atfork> that resets it. That will
		2304	catch fork calls done by libraries (such as the libc) as well.
		2305
		2306	In current versions of libev, the signal will not be blocked indefinitely
		2307	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2308	the window of opportunity for problems, it will not go away, as libev
		2309	I<has> to modify the signal mask, at least temporarily.
		2310
		2311	So I can't stress this enough: I<If you do not reset your signal mask when
		2312	you expect it to be empty, you have a race condition in your code>. This
		2313	is not a libev-specific thing, this is true for most event libraries.
1798		2314
1799	=head3 Watcher-Specific Functions and Data Members	2315	=head3 Watcher-Specific Functions and Data Members
1800		2316
1801	=over 4	2317	=over 4
1802		2318
…		…
1818	Example: Try to exit cleanly on SIGINT.	2334	Example: Try to exit cleanly on SIGINT.
1819		2335
1820	static void	2336	static void
1821	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2337	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1822	{	2338	{
1823	ev_unloop (loop, EVUNLOOP_ALL);	2339	ev_break (loop, EVBREAK_ALL);
1824	}	2340	}
1825		2341
1826	ev_signal signal_watcher;	2342	ev_signal signal_watcher;
1827	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2343	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1828	ev_signal_start (loop, &signal_watcher);	2344	ev_signal_start (loop, &signal_watcher);
…		…
1834	some child status changes (most typically when a child of yours dies or	2350	some child status changes (most typically when a child of yours dies or
1835	exits). It is permissible to install a child watcher I<after> the child	2351	exits). It is permissible to install a child watcher I<after> the child
1836	has been forked (which implies it might have already exited), as long	2352	has been forked (which implies it might have already exited), as long
1837	as the event loop isn't entered (or is continued from a watcher), i.e.,	2353	as the event loop isn't entered (or is continued from a watcher), i.e.,
1838	forking and then immediately registering a watcher for the child is fine,	2354	forking and then immediately registering a watcher for the child is fine,
1839	but forking and registering a watcher a few event loop iterations later is	2355	but forking and registering a watcher a few event loop iterations later or
1840	not.	2356	in the next callback invocation is not.
1841		2357
1842	Only the default event loop is capable of handling signals, and therefore	2358	Only the default event loop is capable of handling signals, and therefore
1843	you can only register child watchers in the default event loop.	2359	you can only register child watchers in the default event loop.
1844		2360
		2361	Due to some design glitches inside libev, child watchers will always be
		2362	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2363	libev)
		2364
1845	=head3 Process Interaction	2365	=head3 Process Interaction
1846		2366
1847	Libev grabs C<SIGCHLD> as soon as the default event loop is	2367	Libev grabs C<SIGCHLD> as soon as the default event loop is
1848	initialised. This is necessary to guarantee proper behaviour even if	2368	initialised. This is necessary to guarantee proper behaviour even if the
1849	the first child watcher is started after the child exits. The occurrence	2369	first child watcher is started after the child exits. The occurrence
1850	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2370	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1851	synchronously as part of the event loop processing. Libev always reaps all	2371	synchronously as part of the event loop processing. Libev always reaps all
1852	children, even ones not watched.	2372	children, even ones not watched.
1853		2373
1854	=head3 Overriding the Built-In Processing	2374	=head3 Overriding the Built-In Processing
…		…
1864	=head3 Stopping the Child Watcher	2384	=head3 Stopping the Child Watcher
1865		2385
1866	Currently, the child watcher never gets stopped, even when the	2386	Currently, the child watcher never gets stopped, even when the
1867	child terminates, so normally one needs to stop the watcher in the	2387	child terminates, so normally one needs to stop the watcher in the
1868	callback. Future versions of libev might stop the watcher automatically	2388	callback. Future versions of libev might stop the watcher automatically
1869	when a child exit is detected.	2389	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2390	problem).
1870		2391
1871	=head3 Watcher-Specific Functions and Data Members	2392	=head3 Watcher-Specific Functions and Data Members
1872		2393
1873	=over 4	2394	=over 4
1874		2395
…		…
2010	the process. The exception are C<ev_stat> watchers - those call C<stat	2531	the process. The exception are C<ev_stat> watchers - those call C<stat
2011	()>, which is a synchronous operation.	2532	()>, which is a synchronous operation.
2012		2533
2013	For local paths, this usually doesn't matter: unless the system is very	2534	For local paths, this usually doesn't matter: unless the system is very
2014	busy or the intervals between stat's are large, a stat call will be fast,	2535	busy or the intervals between stat's are large, a stat call will be fast,
2015	as the path data is suually in memory already (except when starting the	2536	as the path data is usually in memory already (except when starting the
2016	watcher).	2537	watcher).
2017		2538
2018	For networked file systems, calling C<stat ()> can block an indefinite	2539	For networked file systems, calling C<stat ()> can block an indefinite
2019	time due to network issues, and even under good conditions, a stat call	2540	time due to network issues, and even under good conditions, a stat call
2020	often takes multiple milliseconds.	2541	often takes multiple milliseconds.
…		…
2177		2698
2178	=head3 Watcher-Specific Functions and Data Members	2699	=head3 Watcher-Specific Functions and Data Members
2179		2700
2180	=over 4	2701	=over 4
2181		2702
2182	=item ev_idle_init (ev_signal *, callback)	2703	=item ev_idle_init (ev_idle *, callback)
2183		2704
2184	Initialises and configures the idle watcher - it has no parameters of any	2705	Initialises and configures the idle watcher - it has no parameters of any
2185	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2706	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2186	believe me.	2707	believe me.
2187		2708
…		…
2200	// no longer anything immediate to do.	2721	// no longer anything immediate to do.
2201	}	2722	}
2202		2723
2203	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2724	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2204	ev_idle_init (idle_watcher, idle_cb);	2725	ev_idle_init (idle_watcher, idle_cb);
2205	ev_idle_start (loop, idle_cb);	2726	ev_idle_start (loop, idle_watcher);
2206		2727
2207		2728
2208	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2729	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2209		2730
2210	Prepare and check watchers are usually (but not always) used in pairs:	2731	Prepare and check watchers are usually (but not always) used in pairs:
2211	prepare watchers get invoked before the process blocks and check watchers	2732	prepare watchers get invoked before the process blocks and check watchers
2212	afterwards.	2733	afterwards.
2213		2734
2214	You I<must not> call C<ev_loop> or similar functions that enter	2735	You I<must not> call C<ev_run> or similar functions that enter
2215	the current event loop from either C<ev_prepare> or C<ev_check>	2736	the current event loop from either C<ev_prepare> or C<ev_check>
2216	watchers. Other loops than the current one are fine, however. The	2737	watchers. Other loops than the current one are fine, however. The
2217	rationale behind this is that you do not need to check for recursion in	2738	rationale behind this is that you do not need to check for recursion in
2218	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2739	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2219	C<ev_check> so if you have one watcher of each kind they will always be	2740	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2303	struct pollfd fds [nfd];	2824	struct pollfd fds [nfd];
2304	// actual code will need to loop here and realloc etc.	2825	// actual code will need to loop here and realloc etc.
2305	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2826	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2306		2827
2307	/* the callback is illegal, but won't be called as we stop during check */	2828	/* the callback is illegal, but won't be called as we stop during check */
2308	ev_timer_init (&tw, 0, timeout * 1e-3);	2829	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2309	ev_timer_start (loop, &tw);	2830	ev_timer_start (loop, &tw);
2310		2831
2311	// create one ev_io per pollfd	2832	// create one ev_io per pollfd
2312	for (int i = 0; i < nfd; ++i)	2833	for (int i = 0; i < nfd; ++i)
2313	{	2834	{
…		…
2387		2908
2388	if (timeout >= 0)	2909	if (timeout >= 0)
2389	// create/start timer	2910	// create/start timer
2390		2911
2391	// poll	2912	// poll
2392	ev_loop (EV_A_ 0);	2913	ev_run (EV_A_ 0);
2393		2914
2394	// stop timer again	2915	// stop timer again
2395	if (timeout >= 0)	2916	if (timeout >= 0)
2396	ev_timer_stop (EV_A_ &to);	2917	ev_timer_stop (EV_A_ &to);
2397		2918
…		…
2426	some fds have to be watched and handled very quickly (with low latency),	2947	some fds have to be watched and handled very quickly (with low latency),
2427	and even priorities and idle watchers might have too much overhead. In	2948	and even priorities and idle watchers might have too much overhead. In
2428	this case you would put all the high priority stuff in one loop and all	2949	this case you would put all the high priority stuff in one loop and all
2429	the rest in a second one, and embed the second one in the first.	2950	the rest in a second one, and embed the second one in the first.
2430		2951
2431	As long as the watcher is active, the callback will be invoked every time	2952	As long as the watcher is active, the callback will be invoked every
2432	there might be events pending in the embedded loop. The callback must then	2953	time there might be events pending in the embedded loop. The callback
2433	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2954	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2434	their callbacks (you could also start an idle watcher to give the embedded	2955	sweep and invoke their callbacks (the callback doesn't need to invoke the
2435	loop strictly lower priority for example). You can also set the callback	2956	C<ev_embed_sweep> function directly, it could also start an idle watcher
2436	to C<0>, in which case the embed watcher will automatically execute the	2957	to give the embedded loop strictly lower priority for example).
2437	embedded loop sweep.
2438		2958
2439	As long as the watcher is started it will automatically handle events. The	2959	You can also set the callback to C<0>, in which case the embed watcher
2440	callback will be invoked whenever some events have been handled. You can	2960	will automatically execute the embedded loop sweep whenever necessary.
2441	set the callback to C<0> to avoid having to specify one if you are not
2442	interested in that.
2443		2961
2444	Also, there have not currently been made special provisions for forking:	2962	Fork detection will be handled transparently while the C<ev_embed> watcher
2445	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2963	is active, i.e., the embedded loop will automatically be forked when the
2446	but you will also have to stop and restart any C<ev_embed> watchers	2964	embedding loop forks. In other cases, the user is responsible for calling
2447	yourself - but you can use a fork watcher to handle this automatically,	2965	C<ev_loop_fork> on the embedded loop.
2448	and future versions of libev might do just that.
2449		2966
2450	Unfortunately, not all backends are embeddable: only the ones returned by	2967	Unfortunately, not all backends are embeddable: only the ones returned by
2451	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2968	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2452	portable one.	2969	portable one.
2453		2970
…		…
2479	if you do not want that, you need to temporarily stop the embed watcher).	2996	if you do not want that, you need to temporarily stop the embed watcher).
2480		2997
2481	=item ev_embed_sweep (loop, ev_embed *)	2998	=item ev_embed_sweep (loop, ev_embed *)
2482		2999
2483	Make a single, non-blocking sweep over the embedded loop. This works	3000	Make a single, non-blocking sweep over the embedded loop. This works
2484	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3001	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2485	appropriate way for embedded loops.	3002	appropriate way for embedded loops.
2486		3003
2487	=item struct ev_loop *other [read-only]	3004	=item struct ev_loop *other [read-only]
2488		3005
2489	The embedded event loop.	3006	The embedded event loop.
…		…
2547	event loop blocks next and before C<ev_check> watchers are being called,	3064	event loop blocks next and before C<ev_check> watchers are being called,
2548	and only in the child after the fork. If whoever good citizen calling	3065	and only in the child after the fork. If whoever good citizen calling
2549	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3066	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2550	handlers will be invoked, too, of course.	3067	handlers will be invoked, too, of course.
2551		3068
		3069	=head3 The special problem of life after fork - how is it possible?
		3070
		3071	Most uses of C<fork()> consist of forking, then some simple calls to set
		3072	up/change the process environment, followed by a call to C<exec()>. This
		3073	sequence should be handled by libev without any problems.
		3074
		3075	This changes when the application actually wants to do event handling
		3076	in the child, or both parent in child, in effect "continuing" after the
		3077	fork.
		3078
		3079	The default mode of operation (for libev, with application help to detect
		3080	forks) is to duplicate all the state in the child, as would be expected
		3081	when I<either> the parent I<or> the child process continues.
		3082
		3083	When both processes want to continue using libev, then this is usually the
		3084	wrong result. In that case, usually one process (typically the parent) is
		3085	supposed to continue with all watchers in place as before, while the other
		3086	process typically wants to start fresh, i.e. without any active watchers.
		3087
		3088	The cleanest and most efficient way to achieve that with libev is to
		3089	simply create a new event loop, which of course will be "empty", and
		3090	use that for new watchers. This has the advantage of not touching more
		3091	memory than necessary, and thus avoiding the copy-on-write, and the
		3092	disadvantage of having to use multiple event loops (which do not support
		3093	signal watchers).
		3094
		3095	When this is not possible, or you want to use the default loop for
		3096	other reasons, then in the process that wants to start "fresh", call
		3097	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3098	Destroying the default loop will "orphan" (not stop) all registered
		3099	watchers, so you have to be careful not to execute code that modifies
		3100	those watchers. Note also that in that case, you have to re-register any
		3101	signal watchers.
		3102
2552	=head3 Watcher-Specific Functions and Data Members	3103	=head3 Watcher-Specific Functions and Data Members
2553		3104
2554	=over 4	3105	=over 4
2555		3106
2556	=item ev_fork_init (ev_signal *, callback)	3107	=item ev_fork_init (ev_fork *, callback)
2557		3108
2558	Initialises and configures the fork watcher - it has no parameters of any	3109	Initialises and configures the fork watcher - it has no parameters of any
2559	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3110	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2560	believe me.	3111	really.
2561		3112
2562	=back	3113	=back
2563		3114
2564		3115
		3116	=head2 C<ev_cleanup> - even the best things end
		3117
		3118	Cleanup watchers are called just before the event loop is being destroyed
		3119	by a call to C<ev_loop_destroy>.
		3120
		3121	While there is no guarantee that the event loop gets destroyed, cleanup
		3122	watchers provide a convenient method to install cleanup hooks for your
		3123	program, worker threads and so on - you just to make sure to destroy the
		3124	loop when you want them to be invoked.
		3125
		3126	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3127	all other watchers, they do not keep a reference to the event loop (which
		3128	makes a lot of sense if you think about it). Like all other watchers, you
		3129	can call libev functions in the callback, except C<ev_cleanup_start>.
		3130
		3131	=head3 Watcher-Specific Functions and Data Members
		3132
		3133	=over 4
		3134
		3135	=item ev_cleanup_init (ev_cleanup *, callback)
		3136
		3137	Initialises and configures the cleanup watcher - it has no parameters of
		3138	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3139	pointless, I assure you.
		3140
		3141	=back
		3142
		3143	Example: Register an atexit handler to destroy the default loop, so any
		3144	cleanup functions are called.
		3145
		3146	static void
		3147	program_exits (void)
		3148	{
		3149	ev_loop_destroy (EV_DEFAULT_UC);
		3150	}
		3151
		3152	...
		3153	atexit (program_exits);
		3154
		3155
2565	=head2 C<ev_async> - how to wake up another event loop	3156	=head2 C<ev_async> - how to wake up an event loop
2566		3157
2567	In general, you cannot use an C<ev_loop> from multiple threads or other	3158	In general, you cannot use an C<ev_run> from multiple threads or other
2568	asynchronous sources such as signal handlers (as opposed to multiple event	3159	asynchronous sources such as signal handlers (as opposed to multiple event
2569	loops - those are of course safe to use in different threads).	3160	loops - those are of course safe to use in different threads).
2570		3161
2571	Sometimes, however, you need to wake up another event loop you do not	3162	Sometimes, however, you need to wake up an event loop you do not control,
2572	control, for example because it belongs to another thread. This is what	3163	for example because it belongs to another thread. This is what C<ev_async>
2573	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3164	watchers do: as long as the C<ev_async> watcher is active, you can signal
2574	can signal it by calling C<ev_async_send>, which is thread- and signal	3165	it by calling C<ev_async_send>, which is thread- and signal safe.
2575	safe.
2576		3166
2577	This functionality is very similar to C<ev_signal> watchers, as signals,	3167	This functionality is very similar to C<ev_signal> watchers, as signals,
2578	too, are asynchronous in nature, and signals, too, will be compressed	3168	too, are asynchronous in nature, and signals, too, will be compressed
2579	(i.e. the number of callback invocations may be less than the number of	3169	(i.e. the number of callback invocations may be less than the number of
2580	C<ev_async_sent> calls).	3170	C<ev_async_sent> calls).
…		…
2585	=head3 Queueing	3175	=head3 Queueing
2586		3176
2587	C<ev_async> does not support queueing of data in any way. The reason	3177	C<ev_async> does not support queueing of data in any way. The reason
2588	is that the author does not know of a simple (or any) algorithm for a	3178	is that the author does not know of a simple (or any) algorithm for a
2589	multiple-writer-single-reader queue that works in all cases and doesn't	3179	multiple-writer-single-reader queue that works in all cases and doesn't
2590	need elaborate support such as pthreads.	3180	need elaborate support such as pthreads or unportable memory access
		3181	semantics.
2591		3182
2592	That means that if you want to queue data, you have to provide your own	3183	That means that if you want to queue data, you have to provide your own
2593	queue. But at least I can tell you how to implement locking around your	3184	queue. But at least I can tell you how to implement locking around your
2594	queue:	3185	queue:
2595		3186
…		…
2684	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3275	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2685	C<ev_feed_event>, this call is safe to do from other threads, signal or	3276	C<ev_feed_event>, this call is safe to do from other threads, signal or
2686	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3277	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2687	section below on what exactly this means).	3278	section below on what exactly this means).
2688		3279
		3280	Note that, as with other watchers in libev, multiple events might get
		3281	compressed into a single callback invocation (another way to look at this
		3282	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3283	reset when the event loop detects that).
		3284
2689	This call incurs the overhead of a system call only once per loop iteration,	3285	This call incurs the overhead of a system call only once per event loop
2690	so while the overhead might be noticeable, it doesn't apply to repeated	3286	iteration, so while the overhead might be noticeable, it doesn't apply to
2691	calls to C<ev_async_send>.	3287	repeated calls to C<ev_async_send> for the same event loop.
2692		3288
2693	=item bool = ev_async_pending (ev_async *)	3289	=item bool = ev_async_pending (ev_async *)
2694		3290
2695	Returns a non-zero value when C<ev_async_send> has been called on the	3291	Returns a non-zero value when C<ev_async_send> has been called on the
2696	watcher but the event has not yet been processed (or even noted) by the	3292	watcher but the event has not yet been processed (or even noted) by the
…		…
2699	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2700	the loop iterates next and checks for the watcher to have become active,	3296	the loop iterates next and checks for the watcher to have become active,
2701	it will reset the flag again. C<ev_async_pending> can be used to very	3297	it will reset the flag again. C<ev_async_pending> can be used to very
2702	quickly check whether invoking the loop might be a good idea.	3298	quickly check whether invoking the loop might be a good idea.
2703		3299
2704	Not that this does I<not> check whether the watcher itself is pending, only	3300	Not that this does I<not> check whether the watcher itself is pending,
2705	whether it has been requested to make this watcher pending.	3301	only whether it has been requested to make this watcher pending: there
		3302	is a time window between the event loop checking and resetting the async
		3303	notification, and the callback being invoked.
2706		3304
2707	=back	3305	=back
2708		3306
2709		3307
2710	=head1 OTHER FUNCTIONS	3308	=head1 OTHER FUNCTIONS
…		…
2727		3325
2728	If C<timeout> is less than 0, then no timeout watcher will be	3326	If C<timeout> is less than 0, then no timeout watcher will be
2729	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3327	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2730	repeat = 0) will be started. C<0> is a valid timeout.	3328	repeat = 0) will be started. C<0> is a valid timeout.
2731		3329
2732	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3330	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2733	passed an C<revents> set like normal event callbacks (a combination of	3331	passed an C<revents> set like normal event callbacks (a combination of
2734	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3332	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2735	value passed to C<ev_once>. Note that it is possible to receive I<both>	3333	value passed to C<ev_once>. Note that it is possible to receive I<both>
2736	a timeout and an io event at the same time - you probably should give io	3334	a timeout and an io event at the same time - you probably should give io
2737	events precedence.	3335	events precedence.
2738		3336
2739	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3337	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2740		3338
2741	static void stdin_ready (int revents, void *arg)	3339	static void stdin_ready (int revents, void *arg)
2742	{	3340	{
2743	if (revents & EV_READ)	3341	if (revents & EV_READ)
2744	/* stdin might have data for us, joy! */;	3342	/* stdin might have data for us, joy! */;
2745	else if (revents & EV_TIMEOUT)	3343	else if (revents & EV_TIMER)
2746	/* doh, nothing entered */;	3344	/* doh, nothing entered */;
2747	}	3345	}
2748		3346
2749	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3347	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2750		3348
2751	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2752
2753	Feeds the given event set into the event loop, as if the specified event
2754	had happened for the specified watcher (which must be a pointer to an
2755	initialised but not necessarily started event watcher).
2756
2757	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3349	=item ev_feed_fd_event (loop, int fd, int revents)
2758		3350
2759	Feed an event on the given fd, as if a file descriptor backend detected	3351	Feed an event on the given fd, as if a file descriptor backend detected
2760	the given events it.	3352	the given events it.
2761		3353
2762	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3354	=item ev_feed_signal_event (loop, int signum)
2763		3355
2764	Feed an event as if the given signal occurred (C<loop> must be the default	3356	Feed an event as if the given signal occurred (C<loop> must be the default
2765	loop!).	3357	loop!).
2766		3358
2767	=back	3359	=back
…		…
2847		3439
2848	=over 4	3440	=over 4
2849		3441
2850	=item ev::TYPE::TYPE ()	3442	=item ev::TYPE::TYPE ()
2851		3443
2852	=item ev::TYPE::TYPE (struct ev_loop *)	3444	=item ev::TYPE::TYPE (loop)
2853		3445
2854	=item ev::TYPE::~TYPE	3446	=item ev::TYPE::~TYPE
2855		3447
2856	The constructor (optionally) takes an event loop to associate the watcher	3448	The constructor (optionally) takes an event loop to associate the watcher
2857	with. If it is omitted, it will use C<EV_DEFAULT>.	3449	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2889		3481
2890	myclass obj;	3482	myclass obj;
2891	ev::io iow;	3483	ev::io iow;
2892	iow.set <myclass, &myclass::io_cb> (&obj);	3484	iow.set <myclass, &myclass::io_cb> (&obj);
2893		3485
		3486	=item w->set (object *)
		3487
		3488	This is a variation of a method callback - leaving out the method to call
		3489	will default the method to C<operator ()>, which makes it possible to use
		3490	functor objects without having to manually specify the C<operator ()> all
		3491	the time. Incidentally, you can then also leave out the template argument
		3492	list.
		3493
		3494	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3495	int revents)>.
		3496
		3497	See the method-C<set> above for more details.
		3498
		3499	Example: use a functor object as callback.
		3500
		3501	struct myfunctor
		3502	{
		3503	void operator() (ev::io &w, int revents)
		3504	{
		3505	...
		3506	}
		3507	}
		3508
		3509	myfunctor f;
		3510
		3511	ev::io w;
		3512	w.set (&f);
		3513
2894	=item w->set<function> (void *data = 0)	3514	=item w->set<function> (void *data = 0)
2895		3515
2896	Also sets a callback, but uses a static method or plain function as	3516	Also sets a callback, but uses a static method or plain function as
2897	callback. The optional C<data> argument will be stored in the watcher's	3517	callback. The optional C<data> argument will be stored in the watcher's
2898	C<data> member and is free for you to use.	3518	C<data> member and is free for you to use.
…		…
2904	Example: Use a plain function as callback.	3524	Example: Use a plain function as callback.
2905		3525
2906	static void io_cb (ev::io &w, int revents) { }	3526	static void io_cb (ev::io &w, int revents) { }
2907	iow.set <io_cb> ();	3527	iow.set <io_cb> ();
2908		3528
2909	=item w->set (struct ev_loop *)	3529	=item w->set (loop)
2910		3530
2911	Associates a different C<struct ev_loop> with this watcher. You can only	3531	Associates a different C<struct ev_loop> with this watcher. You can only
2912	do this when the watcher is inactive (and not pending either).	3532	do this when the watcher is inactive (and not pending either).
2913		3533
2914	=item w->set ([arguments])	3534	=item w->set ([arguments])
2915		3535
2916	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3536	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2917	called at least once. Unlike the C counterpart, an active watcher gets	3537	method or a suitable start method must be called at least once. Unlike the
2918	automatically stopped and restarted when reconfiguring it with this	3538	C counterpart, an active watcher gets automatically stopped and restarted
2919	method.	3539	when reconfiguring it with this method.
2920		3540
2921	=item w->start ()	3541	=item w->start ()
2922		3542
2923	Starts the watcher. Note that there is no C<loop> argument, as the	3543	Starts the watcher. Note that there is no C<loop> argument, as the
2924	constructor already stores the event loop.	3544	constructor already stores the event loop.
2925		3545
		3546	=item w->start ([arguments])
		3547
		3548	Instead of calling C<set> and C<start> methods separately, it is often
		3549	convenient to wrap them in one call. Uses the same type of arguments as
		3550	the configure C<set> method of the watcher.
		3551
2926	=item w->stop ()	3552	=item w->stop ()
2927		3553
2928	Stops the watcher if it is active. Again, no C<loop> argument.	3554	Stops the watcher if it is active. Again, no C<loop> argument.
2929		3555
2930	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3556	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2942		3568
2943	=back	3569	=back
2944		3570
2945	=back	3571	=back
2946		3572
2947	Example: Define a class with an IO and idle watcher, start one of them in	3573	Example: Define a class with two I/O and idle watchers, start the I/O
2948	the constructor.	3574	watchers in the constructor.
2949		3575
2950	class myclass	3576	class myclass
2951	{	3577	{
2952	ev::io io ; void io_cb (ev::io &w, int revents);	3578	ev::io io ; void io_cb (ev::io &w, int revents);
		3579	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2953	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3580	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2954		3581
2955	myclass (int fd)	3582	myclass (int fd)
2956	{	3583	{
2957	io .set <myclass, &myclass::io_cb > (this);	3584	io .set <myclass, &myclass::io_cb > (this);
		3585	io2 .set <myclass, &myclass::io2_cb > (this);
2958	idle.set <myclass, &myclass::idle_cb> (this);	3586	idle.set <myclass, &myclass::idle_cb> (this);
2959		3587
2960	io.start (fd, ev::READ);	3588	io.set (fd, ev::WRITE); // configure the watcher
		3589	io.start (); // start it whenever convenient
		3590
		3591	io2.start (fd, ev::READ); // set + start in one call
2961	}	3592	}
2962	};	3593	};
2963		3594
2964		3595
2965	=head1 OTHER LANGUAGE BINDINGS	3596	=head1 OTHER LANGUAGE BINDINGS
…		…
2984	L<http://software.schmorp.de/pkg/EV>.	3615	L<http://software.schmorp.de/pkg/EV>.
2985		3616
2986	=item Python	3617	=item Python
2987		3618
2988	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3619	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2989	seems to be quite complete and well-documented. Note, however, that the	3620	seems to be quite complete and well-documented.
2990	patch they require for libev is outright dangerous as it breaks the ABI
2991	for everybody else, and therefore, should never be applied in an installed
2992	libev (if python requires an incompatible ABI then it needs to embed
2993	libev).
2994		3621
2995	=item Ruby	3622	=item Ruby
2996		3623
2997	Tony Arcieri has written a ruby extension that offers access to a subset	3624	Tony Arcieri has written a ruby extension that offers access to a subset
2998	of the libev API and adds file handle abstractions, asynchronous DNS and	3625	of the libev API and adds file handle abstractions, asynchronous DNS and
2999	more on top of it. It can be found via gem servers. Its homepage is at	3626	more on top of it. It can be found via gem servers. Its homepage is at
3000	L<http://rev.rubyforge.org/>.	3627	L<http://rev.rubyforge.org/>.
3001		3628
		3629	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3630	makes rev work even on mingw.
		3631
		3632	=item Haskell
		3633
		3634	A haskell binding to libev is available at
		3635	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3636
3002	=item D	3637	=item D
3003		3638
3004	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3639	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3005	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3640	be found at L<http://proj.llucax.com.ar/wiki/evd>.
3006		3641
3007	=item Ocaml	3642	=item Ocaml
3008		3643
3009	Erkki Seppala has written Ocaml bindings for libev, to be found at	3644	Erkki Seppala has written Ocaml bindings for libev, to be found at
3010	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3645	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3646
		3647	=item Lua
		3648
		3649	Brian Maher has written a partial interface to libev for lua (at the
		3650	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3651	L<http://github.com/brimworks/lua-ev>.
3011		3652
3012	=back	3653	=back
3013		3654
3014		3655
3015	=head1 MACRO MAGIC	3656	=head1 MACRO MAGIC
…		…
3029	loop argument"). The C<EV_A> form is used when this is the sole argument,	3670	loop argument"). The C<EV_A> form is used when this is the sole argument,
3030	C<EV_A_> is used when other arguments are following. Example:	3671	C<EV_A_> is used when other arguments are following. Example:
3031		3672
3032	ev_unref (EV_A);	3673	ev_unref (EV_A);
3033	ev_timer_add (EV_A_ watcher);	3674	ev_timer_add (EV_A_ watcher);
3034	ev_loop (EV_A_ 0);	3675	ev_run (EV_A_ 0);
3035		3676
3036	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3677	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3037	which is often provided by the following macro.	3678	which is often provided by the following macro.
3038		3679
3039	=item C<EV_P>, C<EV_P_>	3680	=item C<EV_P>, C<EV_P_>
…		…
3079	}	3720	}
3080		3721
3081	ev_check check;	3722	ev_check check;
3082	ev_check_init (&check, check_cb);	3723	ev_check_init (&check, check_cb);
3083	ev_check_start (EV_DEFAULT_ &check);	3724	ev_check_start (EV_DEFAULT_ &check);
3084	ev_loop (EV_DEFAULT_ 0);	3725	ev_run (EV_DEFAULT_ 0);
3085		3726
3086	=head1 EMBEDDING	3727	=head1 EMBEDDING
3087		3728
3088	Libev can (and often is) directly embedded into host	3729	Libev can (and often is) directly embedded into host
3089	applications. Examples of applications that embed it include the Deliantra	3730	applications. Examples of applications that embed it include the Deliantra
…		…
3169	libev.m4	3810	libev.m4
3170		3811
3171	=head2 PREPROCESSOR SYMBOLS/MACROS	3812	=head2 PREPROCESSOR SYMBOLS/MACROS
3172		3813
3173	Libev can be configured via a variety of preprocessor symbols you have to	3814	Libev can be configured via a variety of preprocessor symbols you have to
3174	define before including any of its files. The default in the absence of	3815	define before including (or compiling) any of its files. The default in
3175	autoconf is documented for every option.	3816	the absence of autoconf is documented for every option.
		3817
		3818	Symbols marked with "(h)" do not change the ABI, and can have different
		3819	values when compiling libev vs. including F<ev.h>, so it is permissible
		3820	to redefine them before including F<ev.h> without breaking compatibility
		3821	to a compiled library. All other symbols change the ABI, which means all
		3822	users of libev and the libev code itself must be compiled with compatible
		3823	settings.
3176		3824
3177	=over 4	3825	=over 4
3178		3826
		3827	=item EV_COMPAT3 (h)
		3828
		3829	Backwards compatibility is a major concern for libev. This is why this
		3830	release of libev comes with wrappers for the functions and symbols that
		3831	have been renamed between libev version 3 and 4.
		3832
		3833	You can disable these wrappers (to test compatibility with future
		3834	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3835	sources. This has the additional advantage that you can drop the C<struct>
		3836	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3837	typedef in that case.
		3838
		3839	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3840	and in some even more future version the compatibility code will be
		3841	removed completely.
		3842
3179	=item EV_STANDALONE	3843	=item EV_STANDALONE (h)
3180		3844
3181	Must always be C<1> if you do not use autoconf configuration, which	3845	Must always be C<1> if you do not use autoconf configuration, which
3182	keeps libev from including F<config.h>, and it also defines dummy	3846	keeps libev from including F<config.h>, and it also defines dummy
3183	implementations for some libevent functions (such as logging, which is not	3847	implementations for some libevent functions (such as logging, which is not
3184	supported). It will also not define any of the structs usually found in	3848	supported). It will also not define any of the structs usually found in
3185	F<event.h> that are not directly supported by the libev core alone.	3849	F<event.h> that are not directly supported by the libev core alone.
3186		3850
		3851	In standalone mode, libev will still try to automatically deduce the
		3852	configuration, but has to be more conservative.
		3853
3187	=item EV_USE_MONOTONIC	3854	=item EV_USE_MONOTONIC
3188		3855
3189	If defined to be C<1>, libev will try to detect the availability of the	3856	If defined to be C<1>, libev will try to detect the availability of the
3190	monotonic clock option at both compile time and runtime. Otherwise no use	3857	monotonic clock option at both compile time and runtime. Otherwise no
3191	of the monotonic clock option will be attempted. If you enable this, you	3858	use of the monotonic clock option will be attempted. If you enable this,
3192	usually have to link against librt or something similar. Enabling it when	3859	you usually have to link against librt or something similar. Enabling it
3193	the functionality isn't available is safe, though, although you have	3860	when the functionality isn't available is safe, though, although you have
3194	to make sure you link against any libraries where the C<clock_gettime>	3861	to make sure you link against any libraries where the C<clock_gettime>
3195	function is hiding in (often F<-lrt>).	3862	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3196		3863
3197	=item EV_USE_REALTIME	3864	=item EV_USE_REALTIME
3198		3865
3199	If defined to be C<1>, libev will try to detect the availability of the	3866	If defined to be C<1>, libev will try to detect the availability of the
3200	real-time clock option at compile time (and assume its availability at	3867	real-time clock option at compile time (and assume its availability
3201	runtime if successful). Otherwise no use of the real-time clock option will	3868	at runtime if successful). Otherwise no use of the real-time clock
3202	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3869	option will be attempted. This effectively replaces C<gettimeofday>
3203	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3870	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3204	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3871	correctness. See the note about libraries in the description of
		3872	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3873	C<EV_USE_CLOCK_SYSCALL>.
		3874
		3875	=item EV_USE_CLOCK_SYSCALL
		3876
		3877	If defined to be C<1>, libev will try to use a direct syscall instead
		3878	of calling the system-provided C<clock_gettime> function. This option
		3879	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3880	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3881	programs needlessly. Using a direct syscall is slightly slower (in
		3882	theory), because no optimised vdso implementation can be used, but avoids
		3883	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3884	higher, as it simplifies linking (no need for C<-lrt>).
3205		3885
3206	=item EV_USE_NANOSLEEP	3886	=item EV_USE_NANOSLEEP
3207		3887
3208	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3888	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3209	and will use it for delays. Otherwise it will use C<select ()>.	3889	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3225		3905
3226	=item EV_SELECT_USE_FD_SET	3906	=item EV_SELECT_USE_FD_SET
3227		3907
3228	If defined to C<1>, then the select backend will use the system C<fd_set>	3908	If defined to C<1>, then the select backend will use the system C<fd_set>
3229	structure. This is useful if libev doesn't compile due to a missing	3909	structure. This is useful if libev doesn't compile due to a missing
3230	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3910	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3231	exotic systems. This usually limits the range of file descriptors to some	3911	on exotic systems. This usually limits the range of file descriptors to
3232	low limit such as 1024 or might have other limitations (winsocket only	3912	some low limit such as 1024 or might have other limitations (winsocket
3233	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3913	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3234	influence the size of the C<fd_set> used.	3914	configures the maximum size of the C<fd_set>.
3235		3915
3236	=item EV_SELECT_IS_WINSOCKET	3916	=item EV_SELECT_IS_WINSOCKET
3237		3917
3238	When defined to C<1>, the select backend will assume that	3918	When defined to C<1>, the select backend will assume that
3239	select/socket/connect etc. don't understand file descriptors but	3919	select/socket/connect etc. don't understand file descriptors but
…		…
3241	be used is the winsock select). This means that it will call	3921	be used is the winsock select). This means that it will call
3242	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3922	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3243	it is assumed that all these functions actually work on fds, even	3923	it is assumed that all these functions actually work on fds, even
3244	on win32. Should not be defined on non-win32 platforms.	3924	on win32. Should not be defined on non-win32 platforms.
3245		3925
3246	=item EV_FD_TO_WIN32_HANDLE	3926	=item EV_FD_TO_WIN32_HANDLE(fd)
3247		3927
3248	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3928	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3249	file descriptors to socket handles. When not defining this symbol (the	3929	file descriptors to socket handles. When not defining this symbol (the
3250	default), then libev will call C<_get_osfhandle>, which is usually	3930	default), then libev will call C<_get_osfhandle>, which is usually
3251	correct. In some cases, programs use their own file descriptor management,	3931	correct. In some cases, programs use their own file descriptor management,
3252	in which case they can provide this function to map fds to socket handles.	3932	in which case they can provide this function to map fds to socket handles.
		3933
		3934	=item EV_WIN32_HANDLE_TO_FD(handle)
		3935
		3936	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3937	using the standard C<_open_osfhandle> function. For programs implementing
		3938	their own fd to handle mapping, overwriting this function makes it easier
		3939	to do so. This can be done by defining this macro to an appropriate value.
		3940
		3941	=item EV_WIN32_CLOSE_FD(fd)
		3942
		3943	If programs implement their own fd to handle mapping on win32, then this
		3944	macro can be used to override the C<close> function, useful to unregister
		3945	file descriptors again. Note that the replacement function has to close
		3946	the underlying OS handle.
3253		3947
3254	=item EV_USE_POLL	3948	=item EV_USE_POLL
3255		3949
3256	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3950	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3257	backend. Otherwise it will be enabled on non-win32 platforms. It	3951	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3304	as well as for signal and thread safety in C<ev_async> watchers.	3998	as well as for signal and thread safety in C<ev_async> watchers.
3305		3999
3306	In the absence of this define, libev will use C<sig_atomic_t volatile>	4000	In the absence of this define, libev will use C<sig_atomic_t volatile>
3307	(from F<signal.h>), which is usually good enough on most platforms.	4001	(from F<signal.h>), which is usually good enough on most platforms.
3308		4002
3309	=item EV_H	4003	=item EV_H (h)
3310		4004
3311	The name of the F<ev.h> header file used to include it. The default if	4005	The name of the F<ev.h> header file used to include it. The default if
3312	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4006	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3313	used to virtually rename the F<ev.h> header file in case of conflicts.	4007	used to virtually rename the F<ev.h> header file in case of conflicts.
3314		4008
3315	=item EV_CONFIG_H	4009	=item EV_CONFIG_H (h)
3316		4010
3317	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4011	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3318	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4012	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3319	C<EV_H>, above.	4013	C<EV_H>, above.
3320		4014
3321	=item EV_EVENT_H	4015	=item EV_EVENT_H (h)
3322		4016
3323	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4017	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3324	of how the F<event.h> header can be found, the default is C<"event.h">.	4018	of how the F<event.h> header can be found, the default is C<"event.h">.
3325		4019
3326	=item EV_PROTOTYPES	4020	=item EV_PROTOTYPES (h)
3327		4021
3328	If defined to be C<0>, then F<ev.h> will not define any function	4022	If defined to be C<0>, then F<ev.h> will not define any function
3329	prototypes, but still define all the structs and other symbols. This is	4023	prototypes, but still define all the structs and other symbols. This is
3330	occasionally useful if you want to provide your own wrapper functions	4024	occasionally useful if you want to provide your own wrapper functions
3331	around libev functions.	4025	around libev functions.
…		…
3353	fine.	4047	fine.
3354		4048
3355	If your embedding application does not need any priorities, defining these	4049	If your embedding application does not need any priorities, defining these
3356	both to C<0> will save some memory and CPU.	4050	both to C<0> will save some memory and CPU.
3357		4051
3358	=item EV_PERIODIC_ENABLE	4052	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4053	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4054	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3359		4055
3360	If undefined or defined to be C<1>, then periodic timers are supported. If	4056	If undefined or defined to be C<1> (and the platform supports it), then
3361	defined to be C<0>, then they are not. Disabling them saves a few kB of	4057	the respective watcher type is supported. If defined to be C<0>, then it
3362	code.	4058	is not. Disabling watcher types mainly saves code size.
3363		4059
3364	=item EV_IDLE_ENABLE	4060	=item EV_FEATURES
3365
3366	If undefined or defined to be C<1>, then idle watchers are supported. If
3367	defined to be C<0>, then they are not. Disabling them saves a few kB of
3368	code.
3369
3370	=item EV_EMBED_ENABLE
3371
3372	If undefined or defined to be C<1>, then embed watchers are supported. If
3373	defined to be C<0>, then they are not. Embed watchers rely on most other
3374	watcher types, which therefore must not be disabled.
3375
3376	=item EV_STAT_ENABLE
3377
3378	If undefined or defined to be C<1>, then stat watchers are supported. If
3379	defined to be C<0>, then they are not.
3380
3381	=item EV_FORK_ENABLE
3382
3383	If undefined or defined to be C<1>, then fork watchers are supported. If
3384	defined to be C<0>, then they are not.
3385
3386	=item EV_ASYNC_ENABLE
3387
3388	If undefined or defined to be C<1>, then async watchers are supported. If
3389	defined to be C<0>, then they are not.
3390
3391	=item EV_MINIMAL
3392		4061
3393	If you need to shave off some kilobytes of code at the expense of some	4062	If you need to shave off some kilobytes of code at the expense of some
3394	speed, define this symbol to C<1>. Currently this is used to override some	4063	speed (but with the full API), you can define this symbol to request
3395	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4064	certain subsets of functionality. The default is to enable all features
3396	much smaller 2-heap for timer management over the default 4-heap.	4065	that can be enabled on the platform.
		4066
		4067	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4068	with some broad features you want) and then selectively re-enable
		4069	additional parts you want, for example if you want everything minimal,
		4070	but multiple event loop support, async and child watchers and the poll
		4071	backend, use this:
		4072
		4073	#define EV_FEATURES 0
		4074	#define EV_MULTIPLICITY 1
		4075	#define EV_USE_POLL 1
		4076	#define EV_CHILD_ENABLE 1
		4077	#define EV_ASYNC_ENABLE 1
		4078
		4079	The actual value is a bitset, it can be a combination of the following
		4080	values:
		4081
		4082	=over 4
		4083
		4084	=item C<1> - faster/larger code
		4085
		4086	Use larger code to speed up some operations.
		4087
		4088	Currently this is used to override some inlining decisions (enlarging the
		4089	code size by roughly 30% on amd64).
		4090
		4091	When optimising for size, use of compiler flags such as C<-Os> with
		4092	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4093	assertions.
		4094
		4095	=item C<2> - faster/larger data structures
		4096
		4097	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4098	hash table sizes and so on. This will usually further increase code size
		4099	and can additionally have an effect on the size of data structures at
		4100	runtime.
		4101
		4102	=item C<4> - full API configuration
		4103
		4104	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4105	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4106
		4107	=item C<8> - full API
		4108
		4109	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4110	details on which parts of the API are still available without this
		4111	feature, and do not complain if this subset changes over time.
		4112
		4113	=item C<16> - enable all optional watcher types
		4114
		4115	Enables all optional watcher types. If you want to selectively enable
		4116	only some watcher types other than I/O and timers (e.g. prepare,
		4117	embed, async, child...) you can enable them manually by defining
		4118	C<EV_watchertype_ENABLE> to C<1> instead.
		4119
		4120	=item C<32> - enable all backends
		4121
		4122	This enables all backends - without this feature, you need to enable at
		4123	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4124
		4125	=item C<64> - enable OS-specific "helper" APIs
		4126
		4127	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4128	default.
		4129
		4130	=back
		4131
		4132	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4133	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4134	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4135	watchers, timers and monotonic clock support.
		4136
		4137	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4138	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4139	your program might be left out as well - a binary starting a timer and an
		4140	I/O watcher then might come out at only 5Kb.
		4141
		4142	=item EV_AVOID_STDIO
		4143
		4144	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4145	functions (printf, scanf, perror etc.). This will increase the code size
		4146	somewhat, but if your program doesn't otherwise depend on stdio and your
		4147	libc allows it, this avoids linking in the stdio library which is quite
		4148	big.
		4149
		4150	Note that error messages might become less precise when this option is
		4151	enabled.
		4152
		4153	=item EV_NSIG
		4154
		4155	The highest supported signal number, +1 (or, the number of
		4156	signals): Normally, libev tries to deduce the maximum number of signals
		4157	automatically, but sometimes this fails, in which case it can be
		4158	specified. Also, using a lower number than detected (C<32> should be
		4159	good for about any system in existence) can save some memory, as libev
		4160	statically allocates some 12-24 bytes per signal number.
3397		4161
3398	=item EV_PID_HASHSIZE	4162	=item EV_PID_HASHSIZE
3399		4163
3400	C<ev_child> watchers use a small hash table to distribute workload by	4164	C<ev_child> watchers use a small hash table to distribute workload by
3401	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4165	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3402	than enough. If you need to manage thousands of children you might want to	4166	usually more than enough. If you need to manage thousands of children you
3403	increase this value (I<must> be a power of two).	4167	might want to increase this value (I<must> be a power of two).
3404		4168
3405	=item EV_INOTIFY_HASHSIZE	4169	=item EV_INOTIFY_HASHSIZE
3406		4170
3407	C<ev_stat> watchers use a small hash table to distribute workload by	4171	C<ev_stat> watchers use a small hash table to distribute workload by
3408	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4172	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3409	usually more than enough. If you need to manage thousands of C<ev_stat>	4173	disabled), usually more than enough. If you need to manage thousands of
3410	watchers you might want to increase this value (I<must> be a power of	4174	C<ev_stat> watchers you might want to increase this value (I<must> be a
3411	two).	4175	power of two).
3412		4176
3413	=item EV_USE_4HEAP	4177	=item EV_USE_4HEAP
3414		4178
3415	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4179	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3416	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4180	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3417	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4181	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3418	faster performance with many (thousands) of watchers.	4182	faster performance with many (thousands) of watchers.
3419		4183
3420	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4184	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3421	(disabled).	4185	will be C<0>.
3422		4186
3423	=item EV_HEAP_CACHE_AT	4187	=item EV_HEAP_CACHE_AT
3424		4188
3425	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4189	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3426	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4190	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3427	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4191	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3428	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4192	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3429	but avoids random read accesses on heap changes. This improves performance	4193	but avoids random read accesses on heap changes. This improves performance
3430	noticeably with many (hundreds) of watchers.	4194	noticeably with many (hundreds) of watchers.
3431		4195
3432	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4196	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3433	(disabled).	4197	will be C<0>.
3434		4198
3435	=item EV_VERIFY	4199	=item EV_VERIFY
3436		4200
3437	Controls how much internal verification (see C<ev_loop_verify ()>) will	4201	Controls how much internal verification (see C<ev_verify ()>) will
3438	be done: If set to C<0>, no internal verification code will be compiled	4202	be done: If set to C<0>, no internal verification code will be compiled
3439	in. If set to C<1>, then verification code will be compiled in, but not	4203	in. If set to C<1>, then verification code will be compiled in, but not
3440	called. If set to C<2>, then the internal verification code will be	4204	called. If set to C<2>, then the internal verification code will be
3441	called once per loop, which can slow down libev. If set to C<3>, then the	4205	called once per loop, which can slow down libev. If set to C<3>, then the
3442	verification code will be called very frequently, which will slow down	4206	verification code will be called very frequently, which will slow down
3443	libev considerably.	4207	libev considerably.
3444		4208
3445	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4209	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3446	C<0>.	4210	will be C<0>.
3447		4211
3448	=item EV_COMMON	4212	=item EV_COMMON
3449		4213
3450	By default, all watchers have a C<void *data> member. By redefining	4214	By default, all watchers have a C<void *data> member. By redefining
3451	this macro to a something else you can include more and other types of	4215	this macro to something else you can include more and other types of
3452	members. You have to define it each time you include one of the files,	4216	members. You have to define it each time you include one of the files,
3453	though, and it must be identical each time.	4217	though, and it must be identical each time.
3454		4218
3455	For example, the perl EV module uses something like this:	4219	For example, the perl EV module uses something like this:
3456		4220
…		…
3509	file.	4273	file.
3510		4274
3511	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4275	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3512	that everybody includes and which overrides some configure choices:	4276	that everybody includes and which overrides some configure choices:
3513		4277
3514	#define EV_MINIMAL 1	4278	#define EV_FEATURES 8
3515	#define EV_USE_POLL 0	4279	#define EV_USE_SELECT 1
3516	#define EV_MULTIPLICITY 0
3517	#define EV_PERIODIC_ENABLE 0	4280	#define EV_PREPARE_ENABLE 1
		4281	#define EV_IDLE_ENABLE 1
3518	#define EV_STAT_ENABLE 0	4282	#define EV_SIGNAL_ENABLE 1
3519	#define EV_FORK_ENABLE 0	4283	#define EV_CHILD_ENABLE 1
		4284	#define EV_USE_STDEXCEPT 0
3520	#define EV_CONFIG_H <config.h>	4285	#define EV_CONFIG_H <config.h>
3521	#define EV_MINPRI 0
3522	#define EV_MAXPRI 0
3523		4286
3524	#include "ev++.h"	4287	#include "ev++.h"
3525		4288
3526	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4289	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3527		4290
…		…
3587	default loop and triggering an C<ev_async> watcher from the default loop	4350	default loop and triggering an C<ev_async> watcher from the default loop
3588	watcher callback into the event loop interested in the signal.	4351	watcher callback into the event loop interested in the signal.
3589		4352
3590	=back	4353	=back
3591		4354
		4355	=head4 THREAD LOCKING EXAMPLE
		4356
		4357	Here is a fictitious example of how to run an event loop in a different
		4358	thread than where callbacks are being invoked and watchers are
		4359	created/added/removed.
		4360
		4361	For a real-world example, see the C<EV::Loop::Async> perl module,
		4362	which uses exactly this technique (which is suited for many high-level
		4363	languages).
		4364
		4365	The example uses a pthread mutex to protect the loop data, a condition
		4366	variable to wait for callback invocations, an async watcher to notify the
		4367	event loop thread and an unspecified mechanism to wake up the main thread.
		4368
		4369	First, you need to associate some data with the event loop:
		4370
		4371	typedef struct {
		4372	mutex_t lock; /* global loop lock */
		4373	ev_async async_w;
		4374	thread_t tid;
		4375	cond_t invoke_cv;
		4376	} userdata;
		4377
		4378	void prepare_loop (EV_P)
		4379	{
		4380	// for simplicity, we use a static userdata struct.
		4381	static userdata u;
		4382
		4383	ev_async_init (&u->async_w, async_cb);
		4384	ev_async_start (EV_A_ &u->async_w);
		4385
		4386	pthread_mutex_init (&u->lock, 0);
		4387	pthread_cond_init (&u->invoke_cv, 0);
		4388
		4389	// now associate this with the loop
		4390	ev_set_userdata (EV_A_ u);
		4391	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4392	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4393
		4394	// then create the thread running ev_loop
		4395	pthread_create (&u->tid, 0, l_run, EV_A);
		4396	}
		4397
		4398	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4399	solely to wake up the event loop so it takes notice of any new watchers
		4400	that might have been added:
		4401
		4402	static void
		4403	async_cb (EV_P_ ev_async *w, int revents)
		4404	{
		4405	// just used for the side effects
		4406	}
		4407
		4408	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4409	protecting the loop data, respectively.
		4410
		4411	static void
		4412	l_release (EV_P)
		4413	{
		4414	userdata *u = ev_userdata (EV_A);
		4415	pthread_mutex_unlock (&u->lock);
		4416	}
		4417
		4418	static void
		4419	l_acquire (EV_P)
		4420	{
		4421	userdata *u = ev_userdata (EV_A);
		4422	pthread_mutex_lock (&u->lock);
		4423	}
		4424
		4425	The event loop thread first acquires the mutex, and then jumps straight
		4426	into C<ev_run>:
		4427
		4428	void *
		4429	l_run (void *thr_arg)
		4430	{
		4431	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4432
		4433	l_acquire (EV_A);
		4434	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4435	ev_run (EV_A_ 0);
		4436	l_release (EV_A);
		4437
		4438	return 0;
		4439	}
		4440
		4441	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4442	signal the main thread via some unspecified mechanism (signals? pipe
		4443	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4444	have been called (in a while loop because a) spurious wakeups are possible
		4445	and b) skipping inter-thread-communication when there are no pending
		4446	watchers is very beneficial):
		4447
		4448	static void
		4449	l_invoke (EV_P)
		4450	{
		4451	userdata *u = ev_userdata (EV_A);
		4452
		4453	while (ev_pending_count (EV_A))
		4454	{
		4455	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4456	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4457	}
		4458	}
		4459
		4460	Now, whenever the main thread gets told to invoke pending watchers, it
		4461	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4462	thread to continue:
		4463
		4464	static void
		4465	real_invoke_pending (EV_P)
		4466	{
		4467	userdata *u = ev_userdata (EV_A);
		4468
		4469	pthread_mutex_lock (&u->lock);
		4470	ev_invoke_pending (EV_A);
		4471	pthread_cond_signal (&u->invoke_cv);
		4472	pthread_mutex_unlock (&u->lock);
		4473	}
		4474
		4475	Whenever you want to start/stop a watcher or do other modifications to an
		4476	event loop, you will now have to lock:
		4477
		4478	ev_timer timeout_watcher;
		4479	userdata *u = ev_userdata (EV_A);
		4480
		4481	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4482
		4483	pthread_mutex_lock (&u->lock);
		4484	ev_timer_start (EV_A_ &timeout_watcher);
		4485	ev_async_send (EV_A_ &u->async_w);
		4486	pthread_mutex_unlock (&u->lock);
		4487
		4488	Note that sending the C<ev_async> watcher is required because otherwise
		4489	an event loop currently blocking in the kernel will have no knowledge
		4490	about the newly added timer. By waking up the loop it will pick up any new
		4491	watchers in the next event loop iteration.
		4492
3592	=head3 COROUTINES	4493	=head3 COROUTINES
3593		4494
3594	Libev is very accommodating to coroutines ("cooperative threads"):	4495	Libev is very accommodating to coroutines ("cooperative threads"):
3595	libev fully supports nesting calls to its functions from different	4496	libev fully supports nesting calls to its functions from different
3596	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4497	coroutines (e.g. you can call C<ev_run> on the same loop from two
3597	different coroutines, and switch freely between both coroutines running the	4498	different coroutines, and switch freely between both coroutines running
3598	loop, as long as you don't confuse yourself). The only exception is that	4499	the loop, as long as you don't confuse yourself). The only exception is
3599	you must not do this from C<ev_periodic> reschedule callbacks.	4500	that you must not do this from C<ev_periodic> reschedule callbacks.
3600		4501
3601	Care has been taken to ensure that libev does not keep local state inside	4502	Care has been taken to ensure that libev does not keep local state inside
3602	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4503	C<ev_run>, and other calls do not usually allow for coroutine switches as
3603	they do not call any callbacks.	4504	they do not call any callbacks.
3604		4505
3605	=head2 COMPILER WARNINGS	4506	=head2 COMPILER WARNINGS
3606		4507
3607	Depending on your compiler and compiler settings, you might get no or a	4508	Depending on your compiler and compiler settings, you might get no or a
…		…
3618	maintainable.	4519	maintainable.
3619		4520
3620	And of course, some compiler warnings are just plain stupid, or simply	4521	And of course, some compiler warnings are just plain stupid, or simply
3621	wrong (because they don't actually warn about the condition their message	4522	wrong (because they don't actually warn about the condition their message
3622	seems to warn about). For example, certain older gcc versions had some	4523	seems to warn about). For example, certain older gcc versions had some
3623	warnings that resulted an extreme number of false positives. These have	4524	warnings that resulted in an extreme number of false positives. These have
3624	been fixed, but some people still insist on making code warn-free with	4525	been fixed, but some people still insist on making code warn-free with
3625	such buggy versions.	4526	such buggy versions.
3626		4527
3627	While libev is written to generate as few warnings as possible,	4528	While libev is written to generate as few warnings as possible,
3628	"warn-free" code is not a goal, and it is recommended not to build libev	4529	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3664	I suggest using suppression lists.	4565	I suggest using suppression lists.
3665		4566
3666		4567
3667	=head1 PORTABILITY NOTES	4568	=head1 PORTABILITY NOTES
3668		4569
		4570	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4571
		4572	GNU/Linux is the only common platform that supports 64 bit file/large file
		4573	interfaces but I<disables> them by default.
		4574
		4575	That means that libev compiled in the default environment doesn't support
		4576	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4577
		4578	Unfortunately, many programs try to work around this GNU/Linux issue
		4579	by enabling the large file API, which makes them incompatible with the
		4580	standard libev compiled for their system.
		4581
		4582	Likewise, libev cannot enable the large file API itself as this would
		4583	suddenly make it incompatible to the default compile time environment,
		4584	i.e. all programs not using special compile switches.
		4585
		4586	=head2 OS/X AND DARWIN BUGS
		4587
		4588	The whole thing is a bug if you ask me - basically any system interface
		4589	you touch is broken, whether it is locales, poll, kqueue or even the
		4590	OpenGL drivers.
		4591
		4592	=head3 C<kqueue> is buggy
		4593
		4594	The kqueue syscall is broken in all known versions - most versions support
		4595	only sockets, many support pipes.
		4596
		4597	Libev tries to work around this by not using C<kqueue> by default on this
		4598	rotten platform, but of course you can still ask for it when creating a
		4599	loop - embedding a socket-only kqueue loop into a select-based one is
		4600	probably going to work well.
		4601
		4602	=head3 C<poll> is buggy
		4603
		4604	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4605	implementation by something calling C<kqueue> internally around the 10.5.6
		4606	release, so now C<kqueue> I<and> C<poll> are broken.
		4607
		4608	Libev tries to work around this by not using C<poll> by default on
		4609	this rotten platform, but of course you can still ask for it when creating
		4610	a loop.
		4611
		4612	=head3 C<select> is buggy
		4613
		4614	All that's left is C<select>, and of course Apple found a way to fuck this
		4615	one up as well: On OS/X, C<select> actively limits the number of file
		4616	descriptors you can pass in to 1024 - your program suddenly crashes when
		4617	you use more.
		4618
		4619	There is an undocumented "workaround" for this - defining
		4620	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4621	work on OS/X.
		4622
		4623	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4624
		4625	=head3 C<errno> reentrancy
		4626
		4627	The default compile environment on Solaris is unfortunately so
		4628	thread-unsafe that you can't even use components/libraries compiled
		4629	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4630	defined by default. A valid, if stupid, implementation choice.
		4631
		4632	If you want to use libev in threaded environments you have to make sure
		4633	it's compiled with C<_REENTRANT> defined.
		4634
		4635	=head3 Event port backend
		4636
		4637	The scalable event interface for Solaris is called "event
		4638	ports". Unfortunately, this mechanism is very buggy in all major
		4639	releases. If you run into high CPU usage, your program freezes or you get
		4640	a large number of spurious wakeups, make sure you have all the relevant
		4641	and latest kernel patches applied. No, I don't know which ones, but there
		4642	are multiple ones to apply, and afterwards, event ports actually work
		4643	great.
		4644
		4645	If you can't get it to work, you can try running the program by setting
		4646	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4647	C<select> backends.
		4648
		4649	=head2 AIX POLL BUG
		4650
		4651	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4652	this by trying to avoid the poll backend altogether (i.e. it's not even
		4653	compiled in), which normally isn't a big problem as C<select> works fine
		4654	with large bitsets on AIX, and AIX is dead anyway.
		4655
3669	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4656	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4657
		4658	=head3 General issues
3670		4659
3671	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4660	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3672	requires, and its I/O model is fundamentally incompatible with the POSIX	4661	requires, and its I/O model is fundamentally incompatible with the POSIX
3673	model. Libev still offers limited functionality on this platform in	4662	model. Libev still offers limited functionality on this platform in
3674	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4663	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3675	descriptors. This only applies when using Win32 natively, not when using	4664	descriptors. This only applies when using Win32 natively, not when using
3676	e.g. cygwin.	4665	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4666	as every compielr comes with a slightly differently broken/incompatible
		4667	environment.
3677		4668
3678	Lifting these limitations would basically require the full	4669	Lifting these limitations would basically require the full
3679	re-implementation of the I/O system. If you are into these kinds of	4670	re-implementation of the I/O system. If you are into this kind of thing,
3680	things, then note that glib does exactly that for you in a very portable	4671	then note that glib does exactly that for you in a very portable way (note
3681	way (note also that glib is the slowest event library known to man).	4672	also that glib is the slowest event library known to man).
3682		4673
3683	There is no supported compilation method available on windows except	4674	There is no supported compilation method available on windows except
3684	embedding it into other applications.	4675	embedding it into other applications.
		4676
		4677	Sensible signal handling is officially unsupported by Microsoft - libev
		4678	tries its best, but under most conditions, signals will simply not work.
3685		4679
3686	Not a libev limitation but worth mentioning: windows apparently doesn't	4680	Not a libev limitation but worth mentioning: windows apparently doesn't
3687	accept large writes: instead of resulting in a partial write, windows will	4681	accept large writes: instead of resulting in a partial write, windows will
3688	either accept everything or return C<ENOBUFS> if the buffer is too large,	4682	either accept everything or return C<ENOBUFS> if the buffer is too large,
3689	so make sure you only write small amounts into your sockets (less than a	4683	so make sure you only write small amounts into your sockets (less than a
…		…
3694	the abysmal performance of winsockets, using a large number of sockets	4688	the abysmal performance of winsockets, using a large number of sockets
3695	is not recommended (and not reasonable). If your program needs to use	4689	is not recommended (and not reasonable). If your program needs to use
3696	more than a hundred or so sockets, then likely it needs to use a totally	4690	more than a hundred or so sockets, then likely it needs to use a totally
3697	different implementation for windows, as libev offers the POSIX readiness	4691	different implementation for windows, as libev offers the POSIX readiness
3698	notification model, which cannot be implemented efficiently on windows	4692	notification model, which cannot be implemented efficiently on windows
3699	(Microsoft monopoly games).	4693	(due to Microsoft monopoly games).
3700		4694
3701	A typical way to use libev under windows is to embed it (see the embedding	4695	A typical way to use libev under windows is to embed it (see the embedding
3702	section for details) and use the following F<evwrap.h> header file instead	4696	section for details) and use the following F<evwrap.h> header file instead
3703	of F<ev.h>:	4697	of F<ev.h>:
3704		4698
…		…
3711	you do I<not> compile the F<ev.c> or any other embedded source files!):	4705	you do I<not> compile the F<ev.c> or any other embedded source files!):
3712		4706
3713	#include "evwrap.h"	4707	#include "evwrap.h"
3714	#include "ev.c"	4708	#include "ev.c"
3715		4709
3716	=over 4
3717
3718	=item The winsocket select function	4710	=head3 The winsocket C<select> function
3719		4711
3720	The winsocket C<select> function doesn't follow POSIX in that it	4712	The winsocket C<select> function doesn't follow POSIX in that it
3721	requires socket I<handles> and not socket I<file descriptors> (it is	4713	requires socket I<handles> and not socket I<file descriptors> (it is
3722	also extremely buggy). This makes select very inefficient, and also	4714	also extremely buggy). This makes select very inefficient, and also
3723	requires a mapping from file descriptors to socket handles (the Microsoft	4715	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3732	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4724	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3733		4725
3734	Note that winsockets handling of fd sets is O(n), so you can easily get a	4726	Note that winsockets handling of fd sets is O(n), so you can easily get a
3735	complexity in the O(n²) range when using win32.	4727	complexity in the O(n²) range when using win32.
3736		4728
3737	=item Limited number of file descriptors	4729	=head3 Limited number of file descriptors
3738		4730
3739	Windows has numerous arbitrary (and low) limits on things.	4731	Windows has numerous arbitrary (and low) limits on things.
3740		4732
3741	Early versions of winsocket's select only supported waiting for a maximum	4733	Early versions of winsocket's select only supported waiting for a maximum
3742	of C<64> handles (probably owning to the fact that all windows kernels	4734	of C<64> handles (probably owning to the fact that all windows kernels
3743	can only wait for C<64> things at the same time internally; Microsoft	4735	can only wait for C<64> things at the same time internally; Microsoft
3744	recommends spawning a chain of threads and wait for 63 handles and the	4736	recommends spawning a chain of threads and wait for 63 handles and the
3745	previous thread in each. Great).	4737	previous thread in each. Sounds great!).
3746		4738
3747	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4739	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3748	to some high number (e.g. C<2048>) before compiling the winsocket select	4740	to some high number (e.g. C<2048>) before compiling the winsocket select
3749	call (which might be in libev or elsewhere, for example, perl does its own	4741	call (which might be in libev or elsewhere, for example, perl and many
3750	select emulation on windows).	4742	other interpreters do their own select emulation on windows).
3751		4743
3752	Another limit is the number of file descriptors in the Microsoft runtime	4744	Another limit is the number of file descriptors in the Microsoft runtime
3753	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4745	libraries, which by default is C<64> (there must be a hidden I<64>
3754	or something like this inside Microsoft). You can increase this by calling	4746	fetish or something like this inside Microsoft). You can increase this
3755	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4747	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3756	arbitrary limit), but is broken in many versions of the Microsoft runtime	4748	(another arbitrary limit), but is broken in many versions of the Microsoft
3757	libraries.
3758
3759	This might get you to about C<512> or C<2048> sockets (depending on	4749	runtime libraries. This might get you to about C<512> or C<2048> sockets
3760	windows version and/or the phase of the moon). To get more, you need to	4750	(depending on windows version and/or the phase of the moon). To get more,
3761	wrap all I/O functions and provide your own fd management, but the cost of	4751	you need to wrap all I/O functions and provide your own fd management, but
3762	calling select (O(n²)) will likely make this unworkable.	4752	the cost of calling select (O(n²)) will likely make this unworkable.
3763
3764	=back
3765		4753
3766	=head2 PORTABILITY REQUIREMENTS	4754	=head2 PORTABILITY REQUIREMENTS
3767		4755
3768	In addition to a working ISO-C implementation and of course the	4756	In addition to a working ISO-C implementation and of course the
3769	backend-specific APIs, libev relies on a few additional extensions:	4757	backend-specific APIs, libev relies on a few additional extensions:
…		…
3776	Libev assumes not only that all watcher pointers have the same internal	4764	Libev assumes not only that all watcher pointers have the same internal
3777	structure (guaranteed by POSIX but not by ISO C for example), but it also	4765	structure (guaranteed by POSIX but not by ISO C for example), but it also
3778	assumes that the same (machine) code can be used to call any watcher	4766	assumes that the same (machine) code can be used to call any watcher
3779	callback: The watcher callbacks have different type signatures, but libev	4767	callback: The watcher callbacks have different type signatures, but libev
3780	calls them using an C<ev_watcher *> internally.	4768	calls them using an C<ev_watcher *> internally.
		4769
		4770	=item pointer accesses must be thread-atomic
		4771
		4772	Accessing a pointer value must be atomic, it must both be readable and
		4773	writable in one piece - this is the case on all current architectures.
3781		4774
3782	=item C<sig_atomic_t volatile> must be thread-atomic as well	4775	=item C<sig_atomic_t volatile> must be thread-atomic as well
3783		4776
3784	The type C<sig_atomic_t volatile> (or whatever is defined as	4777	The type C<sig_atomic_t volatile> (or whatever is defined as
3785	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4778	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3808	watchers.	4801	watchers.
3809		4802
3810	=item C<double> must hold a time value in seconds with enough accuracy	4803	=item C<double> must hold a time value in seconds with enough accuracy
3811		4804
3812	The type C<double> is used to represent timestamps. It is required to	4805	The type C<double> is used to represent timestamps. It is required to
3813	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4806	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3814	enough for at least into the year 4000. This requirement is fulfilled by	4807	good enough for at least into the year 4000 with millisecond accuracy
		4808	(the design goal for libev). This requirement is overfulfilled by
3815	implementations implementing IEEE 754 (basically all existing ones).	4809	implementations using IEEE 754, which is basically all existing ones. With
		4810	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3816		4811
3817	=back	4812	=back
3818		4813
3819	If you know of other additional requirements drop me a note.	4814	If you know of other additional requirements drop me a note.
3820		4815
…		…
3888	involves iterating over all running async watchers or all signal numbers.	4883	involves iterating over all running async watchers or all signal numbers.
3889		4884
3890	=back	4885	=back
3891		4886
3892		4887
		4888	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4889
		4890	The major version 4 introduced some incompatible changes to the API.
		4891
		4892	At the moment, the C<ev.h> header file provides compatibility definitions
		4893	for all changes, so most programs should still compile. The compatibility
		4894	layer might be removed in later versions of libev, so better update to the
		4895	new API early than late.
		4896
		4897	=over 4
		4898
		4899	=item C<EV_COMPAT3> backwards compatibility mechanism
		4900
		4901	The backward compatibility mechanism can be controlled by
		4902	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4903	section.
		4904
		4905	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4906
		4907	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4908
		4909	ev_loop_destroy (EV_DEFAULT_UC);
		4910	ev_loop_fork (EV_DEFAULT);
		4911
		4912	=item function/symbol renames
		4913
		4914	A number of functions and symbols have been renamed:
		4915
		4916	ev_loop => ev_run
		4917	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4918	EVLOOP_ONESHOT => EVRUN_ONCE
		4919
		4920	ev_unloop => ev_break
		4921	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4922	EVUNLOOP_ONE => EVBREAK_ONE
		4923	EVUNLOOP_ALL => EVBREAK_ALL
		4924
		4925	EV_TIMEOUT => EV_TIMER
		4926
		4927	ev_loop_count => ev_iteration
		4928	ev_loop_depth => ev_depth
		4929	ev_loop_verify => ev_verify
		4930
		4931	Most functions working on C<struct ev_loop> objects don't have an
		4932	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4933	associated constants have been renamed to not collide with the C<struct
		4934	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4935	as all other watcher types. Note that C<ev_loop_fork> is still called
		4936	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4937	typedef.
		4938
		4939	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4940
		4941	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4942	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4943	and work, but the library code will of course be larger.
		4944
		4945	=back
		4946
		4947
		4948	=head1 GLOSSARY
		4949
		4950	=over 4
		4951
		4952	=item active
		4953
		4954	A watcher is active as long as it has been started and not yet stopped.
		4955	See L<WATCHER STATES> for details.
		4956
		4957	=item application
		4958
		4959	In this document, an application is whatever is using libev.
		4960
		4961	=item backend
		4962
		4963	The part of the code dealing with the operating system interfaces.
		4964
		4965	=item callback
		4966
		4967	The address of a function that is called when some event has been
		4968	detected. Callbacks are being passed the event loop, the watcher that
		4969	received the event, and the actual event bitset.
		4970
		4971	=item callback/watcher invocation
		4972
		4973	The act of calling the callback associated with a watcher.
		4974
		4975	=item event
		4976
		4977	A change of state of some external event, such as data now being available
		4978	for reading on a file descriptor, time having passed or simply not having
		4979	any other events happening anymore.
		4980
		4981	In libev, events are represented as single bits (such as C<EV_READ> or
		4982	C<EV_TIMER>).
		4983
		4984	=item event library
		4985
		4986	A software package implementing an event model and loop.
		4987
		4988	=item event loop
		4989
		4990	An entity that handles and processes external events and converts them
		4991	into callback invocations.
		4992
		4993	=item event model
		4994
		4995	The model used to describe how an event loop handles and processes
		4996	watchers and events.
		4997
		4998	=item pending
		4999
		5000	A watcher is pending as soon as the corresponding event has been
		5001	detected. See L<WATCHER STATES> for details.
		5002
		5003	=item real time
		5004
		5005	The physical time that is observed. It is apparently strictly monotonic :)
		5006
		5007	=item wall-clock time
		5008
		5009	The time and date as shown on clocks. Unlike real time, it can actually
		5010	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5011	clock.
		5012
		5013	=item watcher
		5014
		5015	A data structure that describes interest in certain events. Watchers need
		5016	to be started (attached to an event loop) before they can receive events.
		5017
		5018	=back
		5019
3893	=head1 AUTHOR	5020	=head1 AUTHOR
3894		5021
3895	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5022	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5023	Magnusson and Emanuele Giaquinta.
3896		5024

Diff Legend

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