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Revision 1.84 by root, Wed Dec 12 22:26:37 2007 UTC vs.
Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
61	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
104		142
105	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
106		144
107	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
108	library in any way.	146	library in any way.
…		…
112	=item ev_tstamp ev_time ()	150	=item ev_tstamp ev_time ()
113		151
114	Returns the current time as libev would use it. Please note that the	152	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	153	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	154	you actually want to know.
		155
		156	=item ev_sleep (ev_tstamp interval)
		157
		158	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
		160	this is a sub-second-resolution C<sleep ()>.
117		161
118	=item int ev_version_major ()	162	=item int ev_version_major ()
119		163
120	=item int ev_version_minor ()	164	=item int ev_version_minor ()
121		165
…		…
134	not a problem.	178	not a problem.
135		179
136	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
137	version.	181	version.
138		182
139	assert (("libev version mismatch",	183	assert (("libev version mismatch",
140	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
141	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
142		186
143	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
144		188
145	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
146	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
148	a description of the set values.	192	a description of the set values.
149		193
150	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
151	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
152		196
153	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
154	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
155		199
156	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
157		201
158	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
159	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
160	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
161	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
162	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
163	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
164		208
165	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
166		210
…		…
170	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
171	recommended ones.	215	recommended ones.
172		216
173	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
174		218
175	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
176		220
177	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
178	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
179	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
180	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
181	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
182	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
183		230
184	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
185	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
186	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
187		234
188	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
189	retries).	236	retries (example requires a standards-compliant C<realloc>).
190		237
191	static void *	238	static void *
192	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
193	{	240	{
194	for (;;)	241	for (;;)
…		…
203	}	250	}
204		251
205	...	252	...
206	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
207		254
208	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
209		256
210	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
211	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
212	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
213	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
214	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
215	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
216	(such as abort).	263	(such as abort).
217		264
218	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
233		280
234	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
235	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
236	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
237		284
238	If you use threads, a common model is to run the default event loop
239	in your main thread (or in a separate thread) and for each thread you
240	create, you also create another event loop. Libev itself does no locking
241	whatsoever, so if you mix calls to the same event loop in different
242	threads, make sure you lock (this is usually a bad idea, though, even if
243	done correctly, because it's hideous and inefficient).
244
245	=over 4	285	=over 4
246		286
247	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
248		288
249	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
…		…
252	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
253		293
254	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
255	function.	295	function.
256		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your application you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
		307
257	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
258	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
259		310
260	The following flags are supported:	311	The following flags are supported:
261		312
…		…
266	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
267	thing, believe me).	318	thing, believe me).
268		319
269	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
270		321
271	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
272	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
273	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
274	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
275	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
276	around bugs.	327	around bugs.
…		…
282	enabling this flag.	333	enabling this flag.
283		334
284	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
285	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
286	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
287	Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
288	without a syscall and thus I<very> fast, but my Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
289	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
290		341
291	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
292	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
293	flag.	344	flag.
294		345
295	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
296	environment variable.	347	environment variable.
297		348
298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
299		350
300	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
301	libev tries to roll its own fd_set with no limits on the number of fds,	352	libev tries to roll its own fd_set with no limits on the number of fds,
302	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
303	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
304	the fastest backend for a low number of fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
305		367
306	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
307		369
308	And this is your standard poll(2) backend. It's more complicated than	370	And this is your standard poll(2) backend. It's more complicated
309	select, but handles sparse fds better and has no artificial limit on the	371	than select, but handles sparse fds better and has no artificial
310	number of fds you can use (except it will slow down considerably with a	372	limit on the number of fds you can use (except it will slow down
311	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	373	considerably with a lot of inactive fds). It scales similarly to select,
		374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		375	performance tips.
		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
312		379
313	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
314		381
315	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
316	but it scales phenomenally better. While poll and select usually scale like	383	but it scales phenomenally better. While poll and select usually scale
317	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	384	like O(total_fds) where n is the total number of fds (or the highest fd),
318	either O(1) or O(active_fds).	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
		386	of shortcomings, such as silently dropping events in some hard-to-detect
		387	cases and requiring a system call per fd change, no fork support and bad
		388	support for dup.
319		389
320	While stopping and starting an I/O watcher in the same iteration will	390	While stopping, setting and starting an I/O watcher in the same iteration
321	result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
322	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
323	best to avoid that. Also, dup()ed file descriptors might not work very	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
324	well if you register events for both fds.	394	very well if you register events for both fds.
325		395
326	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
327	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
328	(or space) is available.	398	(or space) is available.
329		399
		400	Best performance from this backend is achieved by not unregistering all
		401	watchers for a file descriptor until it has been closed, if possible,
		402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
		405
		406	While nominally embeddable in other event loops, this feature is broken in
		407	all kernel versions tested so far.
		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
330	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
331		413
332	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
333	was broken on all BSDs except NetBSD (usually it doesn't work with	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
334	anything but sockets and pipes, except on Darwin, where of course its	416	anything but sockets and pipes, except on Darwin, where of course it's
335	completely useless). For this reason its not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
336	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
337	C<EVBACKEND_KQUEUE>).	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
		420
		421	You still can embed kqueue into a normal poll or select backend and use it
		422	only for sockets (after having made sure that sockets work with kqueue on
		423	the target platform). See C<ev_embed> watchers for more info.
338		424
339	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
340	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
341	course). While starting and stopping an I/O watcher does not cause an	427	course). While stopping, setting and starting an I/O watcher does never
342	extra syscall as with epoll, it still adds up to four event changes per	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
343	incident, so its best to avoid that.	429	two event changes per incident. Support for C<fork ()> is very bad and it
		430	drops fds silently in similarly hard-to-detect cases.
		431
		432	This backend usually performs well under most conditions.
		433
		434	While nominally embeddable in other event loops, this doesn't work
		435	everywhere, so you might need to test for this. And since it is broken
		436	almost everywhere, you should only use it when you have a lot of sockets
		437	(for which it usually works), by embedding it into another event loop
		438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
		439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
344		444
345	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
346		446
347	This is not implemented yet (and might never be).	447	This is not implemented yet (and might never be, unless you send me an
		448	implementation). According to reports, C</dev/poll> only supports sockets
		449	and is not embeddable, which would limit the usefulness of this backend
		450	immensely.
348		451
349	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
350		453
351	This uses the Solaris 10 port mechanism. As with everything on Solaris,	454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
352	it's really slow, but it still scales very well (O(active_fds)).	455	it's really slow, but it still scales very well (O(active_fds)).
353		456
354	Please note that solaris ports can result in a lot of spurious	457	Please note that Solaris event ports can deliver a lot of spurious
355	notifications, so you need to use non-blocking I/O or other means to avoid	458	notifications, so you need to use non-blocking I/O or other means to avoid
356	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
		460
		461	While this backend scales well, it requires one system call per active
		462	file descriptor per loop iteration. For small and medium numbers of file
		463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		464	might perform better.
		465
		466	On the positive side, with the exception of the spurious readiness
		467	notifications, this backend actually performed fully to specification
		468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
357		473
358	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
359		475
360	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
361	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
362	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
363		479
		480	It is definitely not recommended to use this flag.
		481
364	=back	482	=back
365		483
366	If one or more of these are ored into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
367	backends will be tried (in the reverse order as given here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
368	specified, most compiled-in backend will be tried, usually in reverse	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
369	order of their flag values :)
370		487
371	The most typical usage is like this:	488	Example: This is the most typical usage.
372		489
373	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
374	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
375		492
376	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
377	environment settings to be taken into account:	494	environment settings to be taken into account:
378		495
379	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
380		497
381	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
382	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
383	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
384		502
385	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
386		504
387	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
388		506
389	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
390	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
391	handle signal and child watchers, and attempts to do so will be greeted by	509	handle signal and child watchers, and attempts to do so will be greeted by
392	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
393		511
		512	Note that this function I<is> thread-safe, and the recommended way to use
		513	libev with threads is indeed to create one loop per thread, and using the
		514	default loop in the "main" or "initial" thread.
		515
394	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
395		517
396	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
397	if (!epoller)	519	if (!epoller)
398	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
399		521
400	=item ev_default_destroy ()	522	=item ev_default_destroy ()
401		523
402	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
403	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
404	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
405	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
406	calling this function, or cope with the fact afterwards (which is usually	528	calling this function, or cope with the fact afterwards (which is usually
407	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
408	for example).	530	for example).
		531
		532	Note that certain global state, such as signal state, will not be freed by
		533	this function, and related watchers (such as signal and child watchers)
		534	would need to be stopped manually.
		535
		536	In general it is not advisable to call this function except in the
		537	rare occasion where you really need to free e.g. the signal handling
		538	pipe fds. If you need dynamically allocated loops it is better to use
		539	C<ev_loop_new> and C<ev_loop_destroy>).
409		540
410	=item ev_loop_destroy (loop)	541	=item ev_loop_destroy (loop)
411		542
412	Like C<ev_default_destroy>, but destroys an event loop created by an	543	Like C<ev_default_destroy>, but destroys an event loop created by an
413	earlier call to C<ev_loop_new>.	544	earlier call to C<ev_loop_new>.
414		545
415	=item ev_default_fork ()	546	=item ev_default_fork ()
416		547
		548	This function sets a flag that causes subsequent C<ev_loop> iterations
417	This function reinitialises the kernel state for backends that have	549	to reinitialise the kernel state for backends that have one. Despite the
418	one. Despite the name, you can call it anytime, but it makes most sense	550	name, you can call it anytime, but it makes most sense after forking, in
419	after forking, in either the parent or child process (or both, but that	551	the child process (or both child and parent, but that again makes little
420	again makes little sense).	552	sense). You I<must> call it in the child before using any of the libev
		553	functions, and it will only take effect at the next C<ev_loop> iteration.
421		554
422	You I<must> call this function in the child process after forking if and	555	On the other hand, you only need to call this function in the child
423	only if you want to use the event library in both processes. If you just	556	process if and only if you want to use the event library in the child. If
424	fork+exec, you don't have to call it.	557	you just fork+exec, you don't have to call it at all.
425		558
426	The function itself is quite fast and it's usually not a problem to call	559	The function itself is quite fast and it's usually not a problem to call
427	it just in case after a fork. To make this easy, the function will fit in	560	it just in case after a fork. To make this easy, the function will fit in
428	quite nicely into a call to C<pthread_atfork>:	561	quite nicely into a call to C<pthread_atfork>:
429		562
430	pthread_atfork (0, 0, ev_default_fork);	563	pthread_atfork (0, 0, ev_default_fork);
431		564
432	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
433	without calling this function, so if you force one of those backends you
434	do not need to care.
435
436	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
437		566
438	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
439	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
440	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
		571
		572	=item int ev_is_default_loop (loop)
		573
		574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
441		576
442	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
443		578
444	Returns the count of loop iterations for the loop, which is identical to	579	Returns the count of loop iterations for the loop, which is identical to
445	the number of times libev did poll for new events. It starts at C<0> and	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
458		593
459	Returns the current "event loop time", which is the time the event loop	594	Returns the current "event loop time", which is the time the event loop
460	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
461	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
462	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
463	event occuring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
464		611
465	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
466		613
467	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
468	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
…		…
471	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
472	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
473		620
474	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
475	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
476	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
477	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
478	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
479		627
480	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
481	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
482	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
483		632
484	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
485	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
486	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
487	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
488	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
490	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
491		644
492	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
493		646
494	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
495	* If there are no active watchers (reference count is zero), return.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
496	- Queue all prepare watchers and then call all outstanding watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
		650	- Queue and call all prepare watchers.
497	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
498	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
499	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
500	- Calculate for how long to block.	655	- Calculate for how long to sleep or block, if at all
		656	(active idle watchers, EVLOOP_NONBLOCK or not having
		657	any active watchers at all will result in not sleeping).
		658	- Sleep if the I/O and timer collect interval say so.
501	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
502	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
503	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
504	- Queue all outstanding timers.	662	- Queue all expired timers.
505	- Queue all outstanding periodics.	663	- Queue all expired periodics.
506	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
507	- Queue all check watchers.	665	- Queue all check watchers.
508	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
509	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
510	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
512	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
513		672
514	Example: Queue some jobs and then loop until no events are outsanding	673	Example: Queue some jobs and then loop until no events are outstanding
515	anymore.	674	anymore.
516		675
517	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
518	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
519	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
520	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
521		680
522	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
523		682
524	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
525	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
526	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
527	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
528		687
		688	This "unloop state" will be cleared when entering C<ev_loop> again.
		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
529	=item ev_ref (loop)	692	=item ev_ref (loop)
530		693
531	=item ev_unref (loop)	694	=item ev_unref (loop)
532		695
533	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
534	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
535	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
536	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
537	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
538	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
539	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
540	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
541	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
542	libraries. Just remember to I<unref after start> and I<ref before stop>.	708	libraries. Just remember to I<unref after start> and I<ref before stop>
		709	(but only if the watcher wasn't active before, or was active before,
		710	respectively).
543		711
544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
545	running when nothing else is active.	713	running when nothing else is active.
546		714
547	struct ev_signal exitsig;	715	struct ev_signal exitsig;
548	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
549	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
550	evf_unref (loop);	718	evf_unref (loop);
551		719
552	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
553		721
554	ev_ref (loop);	722	ev_ref (loop);
555	ev_signal_stop (loop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
		724
		725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		726
		727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		728
		729	These advanced functions influence the time that libev will spend waiting
		730	for events. Both time intervals are by default C<0>, meaning that libev
		731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
		733
		734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		735	allows libev to delay invocation of I/O and timer/periodic callbacks
		736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
		738
		739	The idea is that sometimes your program runs just fast enough to handle
		740	one (or very few) event(s) per loop iteration. While this makes the
		741	program responsive, it also wastes a lot of CPU time to poll for new
		742	events, especially with backends like C<select ()> which have a high
		743	overhead for the actual polling but can deliver many events at once.
		744
		745	By setting a higher I<io collect interval> you allow libev to spend more
		746	time collecting I/O events, so you can handle more events per iteration,
		747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		748	C<ev_timer>) will be not affected. Setting this to a non-null value will
		749	introduce an additional C<ev_sleep ()> call into most loop iterations.
		750
		751	Likewise, by setting a higher I<timeout collect interval> you allow libev
		752	to spend more time collecting timeouts, at the expense of increased
		753	latency/jitter/inexactness (the watcher callback will be called
		754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		755	value will not introduce any overhead in libev.
		756
		757	Many (busy) programs can usually benefit by setting the I/O collect
		758	interval to a value near C<0.1> or so, which is often enough for
		759	interactive servers (of course not for games), likewise for timeouts. It
		760	usually doesn't make much sense to set it to a lower value than C<0.01>,
		761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
556		781
557	=back	782	=back
558		783
559		784
560	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
561		786
562	A watcher is a structure that you create and register to record your	787	A watcher is a structure that you create and register to record your
563	interest in some event. For instance, if you want to wait for STDIN to	788	interest in some event. For instance, if you want to wait for STDIN to
564	become readable, you would create an C<ev_io> watcher for that:	789	become readable, you would create an C<ev_io> watcher for that:
565		790
566	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
567	{	792	{
568	ev_io_stop (w);	793	ev_io_stop (w);
569	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
570	}	795	}
571		796
572	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
573	struct ev_io stdin_watcher;	798	struct ev_io stdin_watcher;
574	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
575	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
576	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
577	ev_loop (loop, 0);	802	ev_loop (loop, 0);
578		803
579	As you can see, you are responsible for allocating the memory for your	804	As you can see, you are responsible for allocating the memory for your
580	watcher structures (and it is usually a bad idea to do this on the stack,	805	watcher structures (and it is usually a bad idea to do this on the stack,
581	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
582		807
583	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
584	(watcher *, callback)>, which expects a callback to be provided. This	809	(watcher *, callback)>, which expects a callback to be provided. This
585	callback gets invoked each time the event occurs (or, in the case of io	810	callback gets invoked each time the event occurs (or, in the case of I/O
586	watchers, each time the event loop detects that the file descriptor given	811	watchers, each time the event loop detects that the file descriptor given
587	is readable and/or writable).	812	is readable and/or writable).
588		813
589	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
590	with arguments specific to this watcher type. There is also a macro	815	with arguments specific to this watcher type. There is also a macro
…		…
660	=item C<EV_FORK>	885	=item C<EV_FORK>
661		886
662	The event loop has been resumed in the child process after fork (see	887	The event loop has been resumed in the child process after fork (see
663	C<ev_fork>).	888	C<ev_fork>).
664		889
		890	=item C<EV_ASYNC>
		891
		892	The given async watcher has been asynchronously notified (see C<ev_async>).
		893
665	=item C<EV_ERROR>	894	=item C<EV_ERROR>
666		895
667	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
668	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
669	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
670	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
671	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
672		905
673	Libev will usually signal a few "dummy" events together with an error,	906	Libev will usually signal a few "dummy" events together with an error, for
674	for example it might indicate that a fd is readable or writable, and if	907	example it might indicate that a fd is readable or writable, and if your
675	your callbacks is well-written it can just attempt the operation and cope	908	callbacks is well-written it can just attempt the operation and cope with
676	with the error from read() or write(). This will not work in multithreaded	909	the error from read() or write(). This will not work in multi-threaded
677	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
678		912
679	=back	913	=back
680		914
681	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
682		916
…		…
698	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
699		933
700	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
701	int revents)>.	935	int revents)>.
702		936
		937	Example: Initialise an C<ev_io> watcher in two steps.
		938
		939	ev_io w;
		940	ev_init (&w, my_cb);
		941	ev_io_set (&w, STDIN_FILENO, EV_READ);
		942
703	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
704		944
705	This macro initialises the type-specific parts of a watcher. You need to	945	This macro initialises the type-specific parts of a watcher. You need to
706	call C<ev_init> at least once before you call this macro, but you can	946	call C<ev_init> at least once before you call this macro, but you can
707	call C<ev_TYPE_set> any number of times. You must not, however, call this	947	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
709	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
710		950
711	Although some watcher types do not have type-specific arguments	951	Although some watcher types do not have type-specific arguments
712	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
713		953
		954	See C<ev_init>, above, for an example.
		955
714	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
715		957
716	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
717	calls into a single call. This is the most convinient method to initialise	959	calls into a single call. This is the most convenient method to initialise
718	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
719		965
720	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
721		967
722	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
723	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
724		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
725	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
726		977
727	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
728	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
729	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
730	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
731	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
732	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
733		986
734	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
735		988
736	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
737	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
785		1038
786	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
787		1040
788	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
789	C<loop> nor C<revents> need to be valid as long as the watcher callback	1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
790	can deal with that fact.	1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
791		1045
792	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
793		1047
794	If the watcher is pending, this function returns clears its pending status	1048	If the watcher is pending, this function clears its pending status and
795	and returns its C<revents> bitset (as if its callback was invoked). If the	1049	returns its C<revents> bitset (as if its callback was invoked). If the
796	watcher isn't pending it does nothing and returns C<0>.	1050	watcher isn't pending it does nothing and returns C<0>.
797		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
798	=back	1055	=back
799		1056
800		1057
801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
802		1059
803	Each watcher has, by default, a member C<void *data> that you can change	1060	Each watcher has, by default, a member C<void *data> that you can change
804	and read at any time, libev will completely ignore it. This can be used	1061	and read at any time: libev will completely ignore it. This can be used
805	to associate arbitrary data with your watcher. If you need more data and	1062	to associate arbitrary data with your watcher. If you need more data and
806	don't want to allocate memory and store a pointer to it in that data	1063	don't want to allocate memory and store a pointer to it in that data
807	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
808	data:	1065	data:
809		1066
810	struct my_io	1067	struct my_io
811	{	1068	{
812	struct ev_io io;	1069	struct ev_io io;
813	int otherfd;	1070	int otherfd;
814	void *somedata;	1071	void *somedata;
815	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
816	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
817		1078
818	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
819	can cast it back to your own type:	1080	can cast it back to your own type:
820		1081
821	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
822	{	1083	{
823	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
824	...	1085	...
825	}	1086	}
826		1087
827	More interesting and less C-conformant ways of casting your callback type	1088	More interesting and less C-conformant ways of casting your callback type
828	instead have been omitted.	1089	instead have been omitted.
829		1090
830	Another common scenario is having some data structure with multiple	1091	Another common scenario is to use some data structure with multiple
831	watchers:	1092	embedded watchers:
832		1093
833	struct my_biggy	1094	struct my_biggy
834	{	1095	{
835	int some_data;	1096	int some_data;
836	ev_timer t1;	1097	ev_timer t1;
837	ev_timer t2;	1098	ev_timer t2;
838	}	1099	}
839		1100
840	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1101	In this case getting the pointer to C<my_biggy> is a bit more
841	you need to use C<offsetof>:	1102	complicated: Either you store the address of your C<my_biggy> struct
		1103	in the C<data> member of the watcher (for woozies), or you need to use
		1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
842		1106
843	#include <stddef.h>	1107	#include <stddef.h>
844		1108
845	static void	1109	static void
846	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ struct ev_timer *w, int revents)
847	{	1111	{
848	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
849	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
850	}	1114	}
851		1115
852	static void	1116	static void
853	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ struct ev_timer *w, int revents)
854	{	1118	{
855	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
856	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
857	}	1121	}
858		1122
859		1123
860	=head1 WATCHER TYPES	1124	=head1 WATCHER TYPES
861		1125
862	This section describes each watcher in detail, but will not repeat	1126	This section describes each watcher in detail, but will not repeat
…		…
886	In general you can register as many read and/or write event watchers per	1150	In general you can register as many read and/or write event watchers per
887	fd as you want (as long as you don't confuse yourself). Setting all file	1151	fd as you want (as long as you don't confuse yourself). Setting all file
888	descriptors to non-blocking mode is also usually a good idea (but not	1152	descriptors to non-blocking mode is also usually a good idea (but not
889	required if you know what you are doing).	1153	required if you know what you are doing).
890		1154
891	You have to be careful with dup'ed file descriptors, though. Some backends	1155	If you cannot use non-blocking mode, then force the use of a
892	(the linux epoll backend is a notable example) cannot handle dup'ed file	1156	known-to-be-good backend (at the time of this writing, this includes only
893	descriptors correctly if you register interest in two or more fds pointing	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
894	to the same underlying file/socket/etc. description (that is, they share
895	the same underlying "file open").
896
897	If you must do this, then force the use of a known-to-be-good backend
898	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
899	C<EVBACKEND_POLL>).
900		1158
901	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
902	receive "spurious" readyness notifications, that is your callback might	1160	receive "spurious" readiness notifications, that is your callback might
903	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
904	because there is no data. Not only are some backends known to create a	1162	because there is no data. Not only are some backends known to create a
905	lot of those (for example solaris ports), it is very easy to get into	1163	lot of those (for example Solaris ports), it is very easy to get into
906	this situation even with a relatively standard program structure. Thus	1164	this situation even with a relatively standard program structure. Thus
907	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
908	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
909		1167
910	If you cannot run the fd in non-blocking mode (for example you should not	1168	If you cannot run the fd in non-blocking mode (for example you should
911	play around with an Xlib connection), then you have to seperately re-test	1169	not play around with an Xlib connection), then you have to separately
912	whether a file descriptor is really ready with a known-to-be good interface	1170	re-test whether a file descriptor is really ready with a known-to-be good
913	such as poll (fortunately in our Xlib example, Xlib already does this on	1171	interface such as poll (fortunately in our Xlib example, Xlib already
914	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
915		1177
916	=head3 The special problem of disappearing file descriptors	1178	=head3 The special problem of disappearing file descriptors
917		1179
918	Some backends (e.g kqueue, epoll) need to be told about closing a file	1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file
919	descriptor (either by calling C<close> explicitly or by any other means,	1181	descriptor (either due to calling C<close> explicitly or any other means,
920	such as C<dup>). The reason is that you register interest in some file	1182	such as C<dup2>). The reason is that you register interest in some file
921	descriptor, but when it goes away, the operating system will silently drop	1183	descriptor, but when it goes away, the operating system will silently drop
922	this interest. If another file descriptor with the same number then is	1184	this interest. If another file descriptor with the same number then is
923	registered with libev, there is no efficient way to see that this is, in	1185	registered with libev, there is no efficient way to see that this is, in
924	fact, a different file descriptor.	1186	fact, a different file descriptor.
925		1187
…		…
932		1194
933	This is how one would do it normally anyway, the important point is that	1195	This is how one would do it normally anyway, the important point is that
934	the libev application should not optimise around libev but should leave	1196	the libev application should not optimise around libev but should leave
935	optimisations to libev.	1197	optimisations to libev.
936		1198
		1199	=head3 The special problem of dup'ed file descriptors
		1200
		1201	Some backends (e.g. epoll), cannot register events for file descriptors,
		1202	but only events for the underlying file descriptions. That means when you
		1203	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1204	events for them, only one file descriptor might actually receive events.
		1205
		1206	There is no workaround possible except not registering events
		1207	for potentially C<dup ()>'ed file descriptors, or to resort to
		1208	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1209
		1210	=head3 The special problem of fork
		1211
		1212	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1213	useless behaviour. Libev fully supports fork, but needs to be told about
		1214	it in the child.
		1215
		1216	To support fork in your programs, you either have to call
		1217	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1219	C<EVBACKEND_POLL>.
		1220
		1221	=head3 The special problem of SIGPIPE
		1222
		1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1224	when writing to a pipe whose other end has been closed, your program gets
		1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1226	this is sensible behaviour, for daemons, this is usually undesirable.
		1227
		1228	So when you encounter spurious, unexplained daemon exits, make sure you
		1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1230	somewhere, as that would have given you a big clue).
		1231
937		1232
938	=head3 Watcher-Specific Functions	1233	=head3 Watcher-Specific Functions
939		1234
940	=over 4	1235	=over 4
941		1236
942	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
943		1238
944	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
945		1240
946	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1241	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
947	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1242	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
948	C<EV_READ | EV_WRITE> to receive the given events.	1243	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
949		1244
950	=item int fd [read-only]	1245	=item int fd [read-only]
951		1246
952	The file descriptor being watched.	1247	The file descriptor being watched.
953		1248
954	=item int events [read-only]	1249	=item int events [read-only]
955		1250
956	The events being watched.	1251	The events being watched.
957		1252
958	=back	1253	=back
		1254
		1255	=head3 Examples
959		1256
960	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
961	readable, but only once. Since it is likely line-buffered, you could	1258	readable, but only once. Since it is likely line-buffered, you could
962	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
963		1260
964	static void	1261	static void
965	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
966	{	1263	{
967	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
968	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
969	}	1266	}
970		1267
971	...	1268	...
972	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
973	struct ev_io stdin_readable;	1270	struct ev_io stdin_readable;
974	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
975	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
976	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
977		1274
978		1275
979	=head2 C<ev_timer> - relative and optionally repeating timeouts	1276	=head2 C<ev_timer> - relative and optionally repeating timeouts
980		1277
981	Timer watchers are simple relative timers that generate an event after a	1278	Timer watchers are simple relative timers that generate an event after a
982	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
983		1280
984	The timers are based on real time, that is, if you register an event that	1281	The timers are based on real time, that is, if you register an event that
985	times out after an hour and you reset your system clock to last years	1282	times out after an hour and you reset your system clock to January last
986	time, it will still time out after (roughly) and hour. "Roughly" because	1283	year, it will still time out after (roughly) one hour. "Roughly" because
987	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
988	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
		1286
		1287	The callback is guaranteed to be invoked only I<after> its timeout has
		1288	passed, but if multiple timers become ready during the same loop iteration
		1289	then order of execution is undefined.
		1290
		1291	=head3 The special problem of time updates
		1292
		1293	Establishing the current time is a costly operation (it usually takes at
		1294	least two system calls): EV therefore updates its idea of the current
		1295	time only before and after C<ev_loop> collects new events, which causes a
		1296	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1297	lots of events in one iteration.
989		1298
990	The relative timeouts are calculated relative to the C<ev_now ()>	1299	The relative timeouts are calculated relative to the C<ev_now ()>
991	time. This is usually the right thing as this timestamp refers to the time	1300	time. This is usually the right thing as this timestamp refers to the time
992	of the event triggering whatever timeout you are modifying/starting. If	1301	of the event triggering whatever timeout you are modifying/starting. If
993	you suspect event processing to be delayed and you I<need> to base the timeout	1302	you suspect event processing to be delayed and you I<need> to base the
994	on the current time, use something like this to adjust for this:	1303	timeout on the current time, use something like this to adjust for this:
995		1304
996	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1305	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
997		1306
998	The callback is guarenteed to be invoked only when its timeout has passed,	1307	If the event loop is suspended for a long time, you can also force an
999	but if multiple timers become ready during the same loop iteration then	1308	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1000	order of execution is undefined.	1309	()>.
1001		1310
1002	=head3 Watcher-Specific Functions and Data Members	1311	=head3 Watcher-Specific Functions and Data Members
1003		1312
1004	=over 4	1313	=over 4
1005		1314
1006	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1315	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1007		1316
1008	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1317	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1009		1318
1010	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1319	Configure the timer to trigger after C<after> seconds. If C<repeat>
1011	C<0.>, then it will automatically be stopped. If it is positive, then the	1320	is C<0.>, then it will automatically be stopped once the timeout is
1012	timer will automatically be configured to trigger again C<repeat> seconds	1321	reached. If it is positive, then the timer will automatically be
1013	later, again, and again, until stopped manually.	1322	configured to trigger again C<repeat> seconds later, again, and again,
		1323	until stopped manually.
1014		1324
1015	The timer itself will do a best-effort at avoiding drift, that is, if you	1325	The timer itself will do a best-effort at avoiding drift, that is, if
1016	configure a timer to trigger every 10 seconds, then it will trigger at	1326	you configure a timer to trigger every 10 seconds, then it will normally
1017	exactly 10 second intervals. If, however, your program cannot keep up with	1327	trigger at exactly 10 second intervals. If, however, your program cannot
1018	the timer (because it takes longer than those 10 seconds to do stuff) the	1328	keep up with the timer (because it takes longer than those 10 seconds to
1019	timer will not fire more than once per event loop iteration.	1329	do stuff) the timer will not fire more than once per event loop iteration.
1020		1330
1021	=item ev_timer_again (loop)	1331	=item ev_timer_again (loop, ev_timer *)
1022		1332
1023	This will act as if the timer timed out and restart it again if it is	1333	This will act as if the timer timed out and restart it again if it is
1024	repeating. The exact semantics are:	1334	repeating. The exact semantics are:
1025		1335
1026	If the timer is pending, its pending status is cleared.	1336	If the timer is pending, its pending status is cleared.
1027		1337
1028	If the timer is started but nonrepeating, stop it (as if it timed out).	1338	If the timer is started but non-repeating, stop it (as if it timed out).
1029		1339
1030	If the timer is repeating, either start it if necessary (with the	1340	If the timer is repeating, either start it if necessary (with the
1031	C<repeat> value), or reset the running timer to the C<repeat> value.	1341	C<repeat> value), or reset the running timer to the C<repeat> value.
1032		1342
1033	This sounds a bit complicated, but here is a useful and typical	1343	This sounds a bit complicated, but here is a useful and typical
1034	example: Imagine you have a tcp connection and you want a so-called idle	1344	example: Imagine you have a TCP connection and you want a so-called idle
1035	timeout, that is, you want to be called when there have been, say, 60	1345	timeout, that is, you want to be called when there have been, say, 60
1036	seconds of inactivity on the socket. The easiest way to do this is to	1346	seconds of inactivity on the socket. The easiest way to do this is to
1037	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1347	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1038	C<ev_timer_again> each time you successfully read or write some data. If	1348	C<ev_timer_again> each time you successfully read or write some data. If
1039	you go into an idle state where you do not expect data to travel on the	1349	you go into an idle state where you do not expect data to travel on the
…		…
1053	ev_timer_again (loop, timer);	1363	ev_timer_again (loop, timer);
1054		1364
1055	This is more slightly efficient then stopping/starting the timer each time	1365	This is more slightly efficient then stopping/starting the timer each time
1056	you want to modify its timeout value.	1366	you want to modify its timeout value.
1057		1367
		1368	Note, however, that it is often even more efficient to remember the
		1369	time of the last activity and let the timer time-out naturally. In the
		1370	callback, you then check whether the time-out is real, or, if there was
		1371	some activity, you reschedule the watcher to time-out in "last_activity +
		1372	timeout - ev_now ()" seconds.
		1373
1058	=item ev_tstamp repeat [read-write]	1374	=item ev_tstamp repeat [read-write]
1059		1375
1060	The current C<repeat> value. Will be used each time the watcher times out	1376	The current C<repeat> value. Will be used each time the watcher times out
1061	or C<ev_timer_again> is called and determines the next timeout (if any),	1377	or C<ev_timer_again> is called, and determines the next timeout (if any),
1062	which is also when any modifications are taken into account.	1378	which is also when any modifications are taken into account.
1063		1379
1064	=back	1380	=back
1065		1381
		1382	=head3 Examples
		1383
1066	Example: Create a timer that fires after 60 seconds.	1384	Example: Create a timer that fires after 60 seconds.
1067		1385
1068	static void	1386	static void
1069	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1387	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1070	{	1388	{
1071	.. one minute over, w is actually stopped right here	1389	.. one minute over, w is actually stopped right here
1072	}	1390	}
1073		1391
1074	struct ev_timer mytimer;	1392	struct ev_timer mytimer;
1075	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1393	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1076	ev_timer_start (loop, &mytimer);	1394	ev_timer_start (loop, &mytimer);
1077		1395
1078	Example: Create a timeout timer that times out after 10 seconds of	1396	Example: Create a timeout timer that times out after 10 seconds of
1079	inactivity.	1397	inactivity.
1080		1398
1081	static void	1399	static void
1082	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1400	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1083	{	1401	{
1084	.. ten seconds without any activity	1402	.. ten seconds without any activity
1085	}	1403	}
1086		1404
1087	struct ev_timer mytimer;	1405	struct ev_timer mytimer;
1088	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1406	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1089	ev_timer_again (&mytimer); /* start timer */	1407	ev_timer_again (&mytimer); /* start timer */
1090	ev_loop (loop, 0);	1408	ev_loop (loop, 0);
1091		1409
1092	// and in some piece of code that gets executed on any "activity":	1410	// and in some piece of code that gets executed on any "activity":
1093	// reset the timeout to start ticking again at 10 seconds	1411	// reset the timeout to start ticking again at 10 seconds
1094	ev_timer_again (&mytimer);	1412	ev_timer_again (&mytimer);
1095		1413
1096		1414
1097	=head2 C<ev_periodic> - to cron or not to cron?	1415	=head2 C<ev_periodic> - to cron or not to cron?
1098		1416
1099	Periodic watchers are also timers of a kind, but they are very versatile	1417	Periodic watchers are also timers of a kind, but they are very versatile
1100	(and unfortunately a bit complex).	1418	(and unfortunately a bit complex).
1101		1419
1102	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1420	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1103	but on wallclock time (absolute time). You can tell a periodic watcher	1421	but on wall clock time (absolute time). You can tell a periodic watcher
1104	to trigger "at" some specific point in time. For example, if you tell a	1422	to trigger after some specific point in time. For example, if you tell a
1105	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1423	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1106	+ 10.>) and then reset your system clock to the last year, then it will	1424	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1425	clock to January of the previous year, then it will take more than year
1107	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1426	to trigger the event (unlike an C<ev_timer>, which would still trigger
1108	roughly 10 seconds later).	1427	roughly 10 seconds later as it uses a relative timeout).
1109		1428
1110	They can also be used to implement vastly more complex timers, such as	1429	C<ev_periodic>s can also be used to implement vastly more complex timers,
1111	triggering an event on each midnight, local time or other, complicated,	1430	such as triggering an event on each "midnight, local time", or other
1112	rules.	1431	complicated rules.
1113		1432
1114	As with timers, the callback is guarenteed to be invoked only when the	1433	As with timers, the callback is guaranteed to be invoked only when the
1115	time (C<at>) has been passed, but if multiple periodic timers become ready	1434	time (C<at>) has passed, but if multiple periodic timers become ready
1116	during the same loop iteration then order of execution is undefined.	1435	during the same loop iteration, then order of execution is undefined.
1117		1436
1118	=head3 Watcher-Specific Functions and Data Members	1437	=head3 Watcher-Specific Functions and Data Members
1119		1438
1120	=over 4	1439	=over 4
1121		1440
1122	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1441	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1123		1442
1124	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1443	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1125		1444
1126	Lots of arguments, lets sort it out... There are basically three modes of	1445	Lots of arguments, lets sort it out... There are basically three modes of
1127	operation, and we will explain them from simplest to complex:	1446	operation, and we will explain them from simplest to most complex:
1128		1447
1129	=over 4	1448	=over 4
1130		1449
1131	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1450	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1132		1451
1133	In this configuration the watcher triggers an event at the wallclock time	1452	In this configuration the watcher triggers an event after the wall clock
1134	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1453	time C<at> has passed. It will not repeat and will not adjust when a time
1135	that is, if it is to be run at January 1st 2011 then it will run when the	1454	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1136	system time reaches or surpasses this time.	1455	only run when the system clock reaches or surpasses this time.
1137		1456
1138	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1457	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1139		1458
1140	In this mode the watcher will always be scheduled to time out at the next	1459	In this mode the watcher will always be scheduled to time out at the next
1141	C<at + N * interval> time (for some integer N, which can also be negative)	1460	C<at + N * interval> time (for some integer N, which can also be negative)
1142	and then repeat, regardless of any time jumps.	1461	and then repeat, regardless of any time jumps.
1143		1462
1144	This can be used to create timers that do not drift with respect to system	1463	This can be used to create timers that do not drift with respect to the
1145	time:	1464	system clock, for example, here is a C<ev_periodic> that triggers each
		1465	hour, on the hour:
1146		1466
1147	ev_periodic_set (&periodic, 0., 3600., 0);	1467	ev_periodic_set (&periodic, 0., 3600., 0);
1148		1468
1149	This doesn't mean there will always be 3600 seconds in between triggers,	1469	This doesn't mean there will always be 3600 seconds in between triggers,
1150	but only that the the callback will be called when the system time shows a	1470	but only that the callback will be called when the system time shows a
1151	full hour (UTC), or more correctly, when the system time is evenly divisible	1471	full hour (UTC), or more correctly, when the system time is evenly divisible
1152	by 3600.	1472	by 3600.
1153		1473
1154	Another way to think about it (for the mathematically inclined) is that	1474	Another way to think about it (for the mathematically inclined) is that
1155	C<ev_periodic> will try to run the callback in this mode at the next possible	1475	C<ev_periodic> will try to run the callback in this mode at the next possible
1156	time where C<time = at (mod interval)>, regardless of any time jumps.	1476	time where C<time = at (mod interval)>, regardless of any time jumps.
1157		1477
1158	For numerical stability it is preferable that the C<at> value is near	1478	For numerical stability it is preferable that the C<at> value is near
1159	C<ev_now ()> (the current time), but there is no range requirement for	1479	C<ev_now ()> (the current time), but there is no range requirement for
1160	this value.	1480	this value, and in fact is often specified as zero.
		1481
		1482	Note also that there is an upper limit to how often a timer can fire (CPU
		1483	speed for example), so if C<interval> is very small then timing stability
		1484	will of course deteriorate. Libev itself tries to be exact to be about one
		1485	millisecond (if the OS supports it and the machine is fast enough).
1161		1486
1162	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1487	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1163		1488
1164	In this mode the values for C<interval> and C<at> are both being	1489	In this mode the values for C<interval> and C<at> are both being
1165	ignored. Instead, each time the periodic watcher gets scheduled, the	1490	ignored. Instead, each time the periodic watcher gets scheduled, the
1166	reschedule callback will be called with the watcher as first, and the	1491	reschedule callback will be called with the watcher as first, and the
1167	current time as second argument.	1492	current time as second argument.
1168		1493
1169	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1494	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1170	ever, or make any event loop modifications>. If you need to stop it,	1495	ever, or make ANY event loop modifications whatsoever>.
1171	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1172	starting an C<ev_prepare> watcher, which is legal).
1173		1496
		1497	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1498	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1499	only event loop modification you are allowed to do).
		1500
1174	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1501	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1175	ev_tstamp now)>, e.g.:	1502	*w, ev_tstamp now)>, e.g.:
1176		1503
1177	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1504	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1178	{	1505	{
1179	return now + 60.;	1506	return now + 60.;
1180	}	1507	}
…		…
1182	It must return the next time to trigger, based on the passed time value	1509	It must return the next time to trigger, based on the passed time value
1183	(that is, the lowest time value larger than to the second argument). It	1510	(that is, the lowest time value larger than to the second argument). It
1184	will usually be called just before the callback will be triggered, but	1511	will usually be called just before the callback will be triggered, but
1185	might be called at other times, too.	1512	might be called at other times, too.
1186		1513
1187	NOTE: I<< This callback must always return a time that is later than the	1514	NOTE: I<< This callback must always return a time that is higher than or
1188	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1515	equal to the passed C<now> value >>.
1189		1516
1190	This can be used to create very complex timers, such as a timer that	1517	This can be used to create very complex timers, such as a timer that
1191	triggers on each midnight, local time. To do this, you would calculate the	1518	triggers on "next midnight, local time". To do this, you would calculate the
1192	next midnight after C<now> and return the timestamp value for this. How	1519	next midnight after C<now> and return the timestamp value for this. How
1193	you do this is, again, up to you (but it is not trivial, which is the main	1520	you do this is, again, up to you (but it is not trivial, which is the main
1194	reason I omitted it as an example).	1521	reason I omitted it as an example).
1195		1522
1196	=back	1523	=back
…		…
1200	Simply stops and restarts the periodic watcher again. This is only useful	1527	Simply stops and restarts the periodic watcher again. This is only useful
1201	when you changed some parameters or the reschedule callback would return	1528	when you changed some parameters or the reschedule callback would return
1202	a different time than the last time it was called (e.g. in a crond like	1529	a different time than the last time it was called (e.g. in a crond like
1203	program when the crontabs have changed).	1530	program when the crontabs have changed).
1204		1531
		1532	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1533
		1534	When active, returns the absolute time that the watcher is supposed to
		1535	trigger next.
		1536
1205	=item ev_tstamp offset [read-write]	1537	=item ev_tstamp offset [read-write]
1206		1538
1207	When repeating, this contains the offset value, otherwise this is the	1539	When repeating, this contains the offset value, otherwise this is the
1208	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1540	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1209		1541
…		…
1222	switched off. Can be changed any time, but changes only take effect when	1554	switched off. Can be changed any time, but changes only take effect when
1223	the periodic timer fires or C<ev_periodic_again> is being called.	1555	the periodic timer fires or C<ev_periodic_again> is being called.
1224		1556
1225	=back	1557	=back
1226		1558
		1559	=head3 Examples
		1560
1227	Example: Call a callback every hour, or, more precisely, whenever the	1561	Example: Call a callback every hour, or, more precisely, whenever the
1228	system clock is divisible by 3600. The callback invocation times have	1562	system time is divisible by 3600. The callback invocation times have
1229	potentially a lot of jittering, but good long-term stability.	1563	potentially a lot of jitter, but good long-term stability.
1230		1564
1231	static void	1565	static void
1232	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1566	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1233	{	1567	{
1234	... its now a full hour (UTC, or TAI or whatever your clock follows)	1568	... its now a full hour (UTC, or TAI or whatever your clock follows)
1235	}	1569	}
1236		1570
1237	struct ev_periodic hourly_tick;	1571	struct ev_periodic hourly_tick;
1238	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1572	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1239	ev_periodic_start (loop, &hourly_tick);	1573	ev_periodic_start (loop, &hourly_tick);
1240		1574
1241	Example: The same as above, but use a reschedule callback to do it:	1575	Example: The same as above, but use a reschedule callback to do it:
1242		1576
1243	#include <math.h>	1577	#include <math.h>
1244		1578
1245	static ev_tstamp	1579	static ev_tstamp
1246	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1580	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1247	{	1581	{
1248	return fmod (now, 3600.) + 3600.;	1582	return now + (3600. - fmod (now, 3600.));
1249	}	1583	}
1250		1584
1251	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1585	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1252		1586
1253	Example: Call a callback every hour, starting now:	1587	Example: Call a callback every hour, starting now:
1254		1588
1255	struct ev_periodic hourly_tick;	1589	struct ev_periodic hourly_tick;
1256	ev_periodic_init (&hourly_tick, clock_cb,	1590	ev_periodic_init (&hourly_tick, clock_cb,
1257	fmod (ev_now (loop), 3600.), 3600., 0);	1591	fmod (ev_now (loop), 3600.), 3600., 0);
1258	ev_periodic_start (loop, &hourly_tick);	1592	ev_periodic_start (loop, &hourly_tick);
1259		1593
1260		1594
1261	=head2 C<ev_signal> - signal me when a signal gets signalled!	1595	=head2 C<ev_signal> - signal me when a signal gets signalled!
1262		1596
1263	Signal watchers will trigger an event when the process receives a specific	1597	Signal watchers will trigger an event when the process receives a specific
1264	signal one or more times. Even though signals are very asynchronous, libev	1598	signal one or more times. Even though signals are very asynchronous, libev
1265	will try it's best to deliver signals synchronously, i.e. as part of the	1599	will try it's best to deliver signals synchronously, i.e. as part of the
1266	normal event processing, like any other event.	1600	normal event processing, like any other event.
1267		1601
		1602	If you want signals asynchronously, just use C<sigaction> as you would
		1603	do without libev and forget about sharing the signal. You can even use
		1604	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1605
1268	You can configure as many watchers as you like per signal. Only when the	1606	You can configure as many watchers as you like per signal. Only when the
1269	first watcher gets started will libev actually register a signal watcher	1607	first watcher gets started will libev actually register a signal handler
1270	with the kernel (thus it coexists with your own signal handlers as long	1608	with the kernel (thus it coexists with your own signal handlers as long as
1271	as you don't register any with libev). Similarly, when the last signal	1609	you don't register any with libev for the same signal). Similarly, when
1272	watcher for a signal is stopped libev will reset the signal handler to	1610	the last signal watcher for a signal is stopped, libev will reset the
1273	SIG_DFL (regardless of what it was set to before).	1611	signal handler to SIG_DFL (regardless of what it was set to before).
		1612
		1613	If possible and supported, libev will install its handlers with
		1614	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1615	interrupted. If you have a problem with system calls getting interrupted by
		1616	signals you can block all signals in an C<ev_check> watcher and unblock
		1617	them in an C<ev_prepare> watcher.
1274		1618
1275	=head3 Watcher-Specific Functions and Data Members	1619	=head3 Watcher-Specific Functions and Data Members
1276		1620
1277	=over 4	1621	=over 4
1278		1622
…		…
1287		1631
1288	The signal the watcher watches out for.	1632	The signal the watcher watches out for.
1289		1633
1290	=back	1634	=back
1291		1635
		1636	=head3 Examples
		1637
		1638	Example: Try to exit cleanly on SIGINT.
		1639
		1640	static void
		1641	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1642	{
		1643	ev_unloop (loop, EVUNLOOP_ALL);
		1644	}
		1645
		1646	struct ev_signal signal_watcher;
		1647	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1648	ev_signal_start (loop, &signal_watcher);
		1649
1292		1650
1293	=head2 C<ev_child> - watch out for process status changes	1651	=head2 C<ev_child> - watch out for process status changes
1294		1652
1295	Child watchers trigger when your process receives a SIGCHLD in response to	1653	Child watchers trigger when your process receives a SIGCHLD in response to
1296	some child status changes (most typically when a child of yours dies).	1654	some child status changes (most typically when a child of yours dies or
		1655	exits). It is permissible to install a child watcher I<after> the child
		1656	has been forked (which implies it might have already exited), as long
		1657	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1658	forking and then immediately registering a watcher for the child is fine,
		1659	but forking and registering a watcher a few event loop iterations later is
		1660	not.
		1661
		1662	Only the default event loop is capable of handling signals, and therefore
		1663	you can only register child watchers in the default event loop.
		1664
		1665	=head3 Process Interaction
		1666
		1667	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1668	initialised. This is necessary to guarantee proper behaviour even if
		1669	the first child watcher is started after the child exits. The occurrence
		1670	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1671	synchronously as part of the event loop processing. Libev always reaps all
		1672	children, even ones not watched.
		1673
		1674	=head3 Overriding the Built-In Processing
		1675
		1676	Libev offers no special support for overriding the built-in child
		1677	processing, but if your application collides with libev's default child
		1678	handler, you can override it easily by installing your own handler for
		1679	C<SIGCHLD> after initialising the default loop, and making sure the
		1680	default loop never gets destroyed. You are encouraged, however, to use an
		1681	event-based approach to child reaping and thus use libev's support for
		1682	that, so other libev users can use C<ev_child> watchers freely.
		1683
		1684	=head3 Stopping the Child Watcher
		1685
		1686	Currently, the child watcher never gets stopped, even when the
		1687	child terminates, so normally one needs to stop the watcher in the
		1688	callback. Future versions of libev might stop the watcher automatically
		1689	when a child exit is detected.
1297		1690
1298	=head3 Watcher-Specific Functions and Data Members	1691	=head3 Watcher-Specific Functions and Data Members
1299		1692
1300	=over 4	1693	=over 4
1301		1694
1302	=item ev_child_init (ev_child *, callback, int pid)	1695	=item ev_child_init (ev_child *, callback, int pid, int trace)
1303		1696
1304	=item ev_child_set (ev_child *, int pid)	1697	=item ev_child_set (ev_child *, int pid, int trace)
1305		1698
1306	Configures the watcher to wait for status changes of process C<pid> (or	1699	Configures the watcher to wait for status changes of process C<pid> (or
1307	I<any> process if C<pid> is specified as C<0>). The callback can look	1700	I<any> process if C<pid> is specified as C<0>). The callback can look
1308	at the C<rstatus> member of the C<ev_child> watcher structure to see	1701	at the C<rstatus> member of the C<ev_child> watcher structure to see
1309	the status word (use the macros from C<sys/wait.h> and see your systems	1702	the status word (use the macros from C<sys/wait.h> and see your systems
1310	C<waitpid> documentation). The C<rpid> member contains the pid of the	1703	C<waitpid> documentation). The C<rpid> member contains the pid of the
1311	process causing the status change.	1704	process causing the status change. C<trace> must be either C<0> (only
		1705	activate the watcher when the process terminates) or C<1> (additionally
		1706	activate the watcher when the process is stopped or continued).
1312		1707
1313	=item int pid [read-only]	1708	=item int pid [read-only]
1314		1709
1315	The process id this watcher watches out for, or C<0>, meaning any process id.	1710	The process id this watcher watches out for, or C<0>, meaning any process id.
1316		1711
…		…
1323	The process exit/trace status caused by C<rpid> (see your systems	1718	The process exit/trace status caused by C<rpid> (see your systems
1324	C<waitpid> and C<sys/wait.h> documentation for details).	1719	C<waitpid> and C<sys/wait.h> documentation for details).
1325		1720
1326	=back	1721	=back
1327		1722
1328	Example: Try to exit cleanly on SIGINT and SIGTERM.	1723	=head3 Examples
1329		1724
		1725	Example: C<fork()> a new process and install a child handler to wait for
		1726	its completion.
		1727
		1728	ev_child cw;
		1729
1330	static void	1730	static void
1331	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1731	child_cb (EV_P_ struct ev_child *w, int revents)
1332	{	1732	{
1333	ev_unloop (loop, EVUNLOOP_ALL);	1733	ev_child_stop (EV_A_ w);
		1734	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1334	}	1735	}
1335		1736
1336	struct ev_signal signal_watcher;	1737	pid_t pid = fork ();
1337	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1738
1338	ev_signal_start (loop, &sigint_cb);	1739	if (pid < 0)
		1740	// error
		1741	else if (pid == 0)
		1742	{
		1743	// the forked child executes here
		1744	exit (1);
		1745	}
		1746	else
		1747	{
		1748	ev_child_init (&cw, child_cb, pid, 0);
		1749	ev_child_start (EV_DEFAULT_ &cw);
		1750	}
1339		1751
1340		1752
1341	=head2 C<ev_stat> - did the file attributes just change?	1753	=head2 C<ev_stat> - did the file attributes just change?
1342		1754
1343	This watches a filesystem path for attribute changes. That is, it calls	1755	This watches a file system path for attribute changes. That is, it calls
1344	C<stat> regularly (or when the OS says it changed) and sees if it changed	1756	C<stat> regularly (or when the OS says it changed) and sees if it changed
1345	compared to the last time, invoking the callback if it did.	1757	compared to the last time, invoking the callback if it did.
1346		1758
1347	The path does not need to exist: changing from "path exists" to "path does	1759	The path does not need to exist: changing from "path exists" to "path does
1348	not exist" is a status change like any other. The condition "path does	1760	not exist" is a status change like any other. The condition "path does
…		…
1351	the stat buffer having unspecified contents.	1763	the stat buffer having unspecified contents.
1352		1764
1353	The path I<should> be absolute and I<must not> end in a slash. If it is	1765	The path I<should> be absolute and I<must not> end in a slash. If it is
1354	relative and your working directory changes, the behaviour is undefined.	1766	relative and your working directory changes, the behaviour is undefined.
1355		1767
1356	Since there is no standard to do this, the portable implementation simply	1768	Since there is no standard kernel interface to do this, the portable
1357	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1769	implementation simply calls C<stat (2)> regularly on the path to see if
1358	can specify a recommended polling interval for this case. If you specify	1770	it changed somehow. You can specify a recommended polling interval for
1359	a polling interval of C<0> (highly recommended!) then a I<suitable,	1771	this case. If you specify a polling interval of C<0> (highly recommended!)
1360	unspecified default> value will be used (which you can expect to be around	1772	then a I<suitable, unspecified default> value will be used (which
1361	five seconds, although this might change dynamically). Libev will also	1773	you can expect to be around five seconds, although this might change
1362	impose a minimum interval which is currently around C<0.1>, but thats	1774	dynamically). Libev will also impose a minimum interval which is currently
1363	usually overkill.	1775	around C<0.1>, but thats usually overkill.
1364		1776
1365	This watcher type is not meant for massive numbers of stat watchers,	1777	This watcher type is not meant for massive numbers of stat watchers,
1366	as even with OS-supported change notifications, this can be	1778	as even with OS-supported change notifications, this can be
1367	resource-intensive.	1779	resource-intensive.
1368		1780
1369	At the time of this writing, only the Linux inotify interface is	1781	At the time of this writing, the only OS-specific interface implemented
1370	implemented (implementing kqueue support is left as an exercise for the	1782	is the Linux inotify interface (implementing kqueue support is left as
1371	reader). Inotify will be used to give hints only and should not change the	1783	an exercise for the reader. Note, however, that the author sees no way
1372	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1784	of implementing C<ev_stat> semantics with kqueue).
1373	to fall back to regular polling again even with inotify, but changes are	1785
1374	usually detected immediately, and if the file exists there will be no	1786	=head3 ABI Issues (Largefile Support)
1375	polling.	1787
		1788	Libev by default (unless the user overrides this) uses the default
		1789	compilation environment, which means that on systems with large file
		1790	support disabled by default, you get the 32 bit version of the stat
		1791	structure. When using the library from programs that change the ABI to
		1792	use 64 bit file offsets the programs will fail. In that case you have to
		1793	compile libev with the same flags to get binary compatibility. This is
		1794	obviously the case with any flags that change the ABI, but the problem is
		1795	most noticeably disabled with ev_stat and large file support.
		1796
		1797	The solution for this is to lobby your distribution maker to make large
		1798	file interfaces available by default (as e.g. FreeBSD does) and not
		1799	optional. Libev cannot simply switch on large file support because it has
		1800	to exchange stat structures with application programs compiled using the
		1801	default compilation environment.
		1802
		1803	=head3 Inotify and Kqueue
		1804
		1805	When C<inotify (7)> support has been compiled into libev (generally
		1806	only available with Linux 2.6.25 or above due to bugs in earlier
		1807	implementations) and present at runtime, it will be used to speed up
		1808	change detection where possible. The inotify descriptor will be created
		1809	lazily when the first C<ev_stat> watcher is being started.
		1810
		1811	Inotify presence does not change the semantics of C<ev_stat> watchers
		1812	except that changes might be detected earlier, and in some cases, to avoid
		1813	making regular C<stat> calls. Even in the presence of inotify support
		1814	there are many cases where libev has to resort to regular C<stat> polling,
		1815	but as long as the path exists, libev usually gets away without polling.
		1816
		1817	There is no support for kqueue, as apparently it cannot be used to
		1818	implement this functionality, due to the requirement of having a file
		1819	descriptor open on the object at all times, and detecting renames, unlinks
		1820	etc. is difficult.
		1821
		1822	=head3 The special problem of stat time resolution
		1823
		1824	The C<stat ()> system call only supports full-second resolution portably, and
		1825	even on systems where the resolution is higher, most file systems still
		1826	only support whole seconds.
		1827
		1828	That means that, if the time is the only thing that changes, you can
		1829	easily miss updates: on the first update, C<ev_stat> detects a change and
		1830	calls your callback, which does something. When there is another update
		1831	within the same second, C<ev_stat> will be unable to detect unless the
		1832	stat data does change in other ways (e.g. file size).
		1833
		1834	The solution to this is to delay acting on a change for slightly more
		1835	than a second (or till slightly after the next full second boundary), using
		1836	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1837	ev_timer_again (loop, w)>).
		1838
		1839	The C<.02> offset is added to work around small timing inconsistencies
		1840	of some operating systems (where the second counter of the current time
		1841	might be be delayed. One such system is the Linux kernel, where a call to
		1842	C<gettimeofday> might return a timestamp with a full second later than
		1843	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1844	update file times then there will be a small window where the kernel uses
		1845	the previous second to update file times but libev might already execute
		1846	the timer callback).
1376		1847
1377	=head3 Watcher-Specific Functions and Data Members	1848	=head3 Watcher-Specific Functions and Data Members
1378		1849
1379	=over 4	1850	=over 4
1380		1851
…		…
1386	C<path>. The C<interval> is a hint on how quickly a change is expected to	1857	C<path>. The C<interval> is a hint on how quickly a change is expected to
1387	be detected and should normally be specified as C<0> to let libev choose	1858	be detected and should normally be specified as C<0> to let libev choose
1388	a suitable value. The memory pointed to by C<path> must point to the same	1859	a suitable value. The memory pointed to by C<path> must point to the same
1389	path for as long as the watcher is active.	1860	path for as long as the watcher is active.
1390		1861
1391	The callback will be receive C<EV_STAT> when a change was detected,	1862	The callback will receive an C<EV_STAT> event when a change was detected,
1392	relative to the attributes at the time the watcher was started (or the	1863	relative to the attributes at the time the watcher was started (or the
1393	last change was detected).	1864	last change was detected).
1394		1865
1395	=item ev_stat_stat (ev_stat *)	1866	=item ev_stat_stat (loop, ev_stat *)
1396		1867
1397	Updates the stat buffer immediately with new values. If you change the	1868	Updates the stat buffer immediately with new values. If you change the
1398	watched path in your callback, you could call this fucntion to avoid	1869	watched path in your callback, you could call this function to avoid
1399	detecting this change (while introducing a race condition). Can also be	1870	detecting this change (while introducing a race condition if you are not
1400	useful simply to find out the new values.	1871	the only one changing the path). Can also be useful simply to find out the
		1872	new values.
1401		1873
1402	=item ev_statdata attr [read-only]	1874	=item ev_statdata attr [read-only]
1403		1875
1404	The most-recently detected attributes of the file. Although the type is of	1876	The most-recently detected attributes of the file. Although the type is
1405	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1877	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1406	suitable for your system. If the C<st_nlink> member is C<0>, then there	1878	suitable for your system, but you can only rely on the POSIX-standardised
		1879	members to be present. If the C<st_nlink> member is C<0>, then there was
1407	was some error while C<stat>ing the file.	1880	some error while C<stat>ing the file.
1408		1881
1409	=item ev_statdata prev [read-only]	1882	=item ev_statdata prev [read-only]
1410		1883
1411	The previous attributes of the file. The callback gets invoked whenever	1884	The previous attributes of the file. The callback gets invoked whenever
1412	C<prev> != C<attr>.	1885	C<prev> != C<attr>, or, more precisely, one or more of these members
		1886	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1887	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1413		1888
1414	=item ev_tstamp interval [read-only]	1889	=item ev_tstamp interval [read-only]
1415		1890
1416	The specified interval.	1891	The specified interval.
1417		1892
1418	=item const char *path [read-only]	1893	=item const char *path [read-only]
1419		1894
1420	The filesystem path that is being watched.	1895	The file system path that is being watched.
1421		1896
1422	=back	1897	=back
1423		1898
		1899	=head3 Examples
		1900
1424	Example: Watch C</etc/passwd> for attribute changes.	1901	Example: Watch C</etc/passwd> for attribute changes.
1425		1902
1426	static void	1903	static void
1427	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1904	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1428	{	1905	{
1429	/* /etc/passwd changed in some way */	1906	/* /etc/passwd changed in some way */
1430	if (w->attr.st_nlink)	1907	if (w->attr.st_nlink)
1431	{	1908	{
1432	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1909	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1433	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1910	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1434	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1911	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1435	}	1912	}
1436	else	1913	else
1437	/* you shalt not abuse printf for puts */	1914	/* you shalt not abuse printf for puts */
1438	puts ("wow, /etc/passwd is not there, expect problems. "	1915	puts ("wow, /etc/passwd is not there, expect problems. "
1439	"if this is windows, they already arrived\n");	1916	"if this is windows, they already arrived\n");
1440	}	1917	}
1441		1918
1442	...	1919	...
1443	ev_stat passwd;	1920	ev_stat passwd;
1444		1921
1445	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1922	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1446	ev_stat_start (loop, &passwd);	1923	ev_stat_start (loop, &passwd);
		1924
		1925	Example: Like above, but additionally use a one-second delay so we do not
		1926	miss updates (however, frequent updates will delay processing, too, so
		1927	one might do the work both on C<ev_stat> callback invocation I<and> on
		1928	C<ev_timer> callback invocation).
		1929
		1930	static ev_stat passwd;
		1931	static ev_timer timer;
		1932
		1933	static void
		1934	timer_cb (EV_P_ ev_timer *w, int revents)
		1935	{
		1936	ev_timer_stop (EV_A_ w);
		1937
		1938	/* now it's one second after the most recent passwd change */
		1939	}
		1940
		1941	static void
		1942	stat_cb (EV_P_ ev_stat *w, int revents)
		1943	{
		1944	/* reset the one-second timer */
		1945	ev_timer_again (EV_A_ &timer);
		1946	}
		1947
		1948	...
		1949	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1950	ev_stat_start (loop, &passwd);
		1951	ev_timer_init (&timer, timer_cb, 0., 1.02);
1447		1952
1448		1953
1449	=head2 C<ev_idle> - when you've got nothing better to do...	1954	=head2 C<ev_idle> - when you've got nothing better to do...
1450		1955
1451	Idle watchers trigger events when no other events of the same or higher	1956	Idle watchers trigger events when no other events of the same or higher
1452	priority are pending (prepare, check and other idle watchers do not	1957	priority are pending (prepare, check and other idle watchers do not count
1453	count).	1958	as receiving "events").
1454		1959
1455	That is, as long as your process is busy handling sockets or timeouts	1960	That is, as long as your process is busy handling sockets or timeouts
1456	(or even signals, imagine) of the same or higher priority it will not be	1961	(or even signals, imagine) of the same or higher priority it will not be
1457	triggered. But when your process is idle (or only lower-priority watchers	1962	triggered. But when your process is idle (or only lower-priority watchers
1458	are pending), the idle watchers are being called once per event loop	1963	are pending), the idle watchers are being called once per event loop
…		…
1477	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1982	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1478	believe me.	1983	believe me.
1479		1984
1480	=back	1985	=back
1481		1986
		1987	=head3 Examples
		1988
1482	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1989	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1483	callback, free it. Also, use no error checking, as usual.	1990	callback, free it. Also, use no error checking, as usual.
1484		1991
1485	static void	1992	static void
1486	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1993	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1487	{	1994	{
1488	free (w);	1995	free (w);
1489	// now do something you wanted to do when the program has	1996	// now do something you wanted to do when the program has
1490	// no longer asnything immediate to do.	1997	// no longer anything immediate to do.
1491	}	1998	}
1492		1999
1493	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2000	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1494	ev_idle_init (idle_watcher, idle_cb);	2001	ev_idle_init (idle_watcher, idle_cb);
1495	ev_idle_start (loop, idle_cb);	2002	ev_idle_start (loop, idle_cb);
1496		2003
1497		2004
1498	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1499		2006
1500	Prepare and check watchers are usually (but not always) used in tandem:	2007	Prepare and check watchers are usually (but not always) used in pairs:
1501	prepare watchers get invoked before the process blocks and check watchers	2008	prepare watchers get invoked before the process blocks and check watchers
1502	afterwards.	2009	afterwards.
1503		2010
1504	You I<must not> call C<ev_loop> or similar functions that enter	2011	You I<must not> call C<ev_loop> or similar functions that enter
1505	the current event loop from either C<ev_prepare> or C<ev_check>	2012	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1508	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2015	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1509	C<ev_check> so if you have one watcher of each kind they will always be	2016	C<ev_check> so if you have one watcher of each kind they will always be
1510	called in pairs bracketing the blocking call.	2017	called in pairs bracketing the blocking call.
1511		2018
1512	Their main purpose is to integrate other event mechanisms into libev and	2019	Their main purpose is to integrate other event mechanisms into libev and
1513	their use is somewhat advanced. This could be used, for example, to track	2020	their use is somewhat advanced. They could be used, for example, to track
1514	variable changes, implement your own watchers, integrate net-snmp or a	2021	variable changes, implement your own watchers, integrate net-snmp or a
1515	coroutine library and lots more. They are also occasionally useful if	2022	coroutine library and lots more. They are also occasionally useful if
1516	you cache some data and want to flush it before blocking (for example,	2023	you cache some data and want to flush it before blocking (for example,
1517	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2024	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1518	watcher).	2025	watcher).
1519		2026
1520	This is done by examining in each prepare call which file descriptors need	2027	This is done by examining in each prepare call which file descriptors
1521	to be watched by the other library, registering C<ev_io> watchers for	2028	need to be watched by the other library, registering C<ev_io> watchers
1522	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2029	for them and starting an C<ev_timer> watcher for any timeouts (many
1523	provide just this functionality). Then, in the check watcher you check for	2030	libraries provide exactly this functionality). Then, in the check watcher,
1524	any events that occured (by checking the pending status of all watchers	2031	you check for any events that occurred (by checking the pending status
1525	and stopping them) and call back into the library. The I/O and timer	2032	of all watchers and stopping them) and call back into the library. The
1526	callbacks will never actually be called (but must be valid nevertheless,	2033	I/O and timer callbacks will never actually be called (but must be valid
1527	because you never know, you know?).	2034	nevertheless, because you never know, you know?).
1528		2035
1529	As another example, the Perl Coro module uses these hooks to integrate	2036	As another example, the Perl Coro module uses these hooks to integrate
1530	coroutines into libev programs, by yielding to other active coroutines	2037	coroutines into libev programs, by yielding to other active coroutines
1531	during each prepare and only letting the process block if no coroutines	2038	during each prepare and only letting the process block if no coroutines
1532	are ready to run (it's actually more complicated: it only runs coroutines	2039	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1535	loop from blocking if lower-priority coroutines are active, thus mapping	2042	loop from blocking if lower-priority coroutines are active, thus mapping
1536	low-priority coroutines to idle/background tasks).	2043	low-priority coroutines to idle/background tasks).
1537		2044
1538	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2045	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1539	priority, to ensure that they are being run before any other watchers	2046	priority, to ensure that they are being run before any other watchers
		2047	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2048
1540	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2049	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1541	too) should not activate ("feed") events into libev. While libev fully	2050	activate ("feed") events into libev. While libev fully supports this, they
1542	supports this, they will be called before other C<ev_check> watchers did	2051	might get executed before other C<ev_check> watchers did their job. As
1543	their job. As C<ev_check> watchers are often used to embed other event	2052	C<ev_check> watchers are often used to embed other (non-libev) event
1544	loops those other event loops might be in an unusable state until their	2053	loops those other event loops might be in an unusable state until their
1545	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2054	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1546	others).	2055	others).
1547		2056
1548	=head3 Watcher-Specific Functions and Data Members	2057	=head3 Watcher-Specific Functions and Data Members
…		…
1553		2062
1554	=item ev_check_init (ev_check *, callback)	2063	=item ev_check_init (ev_check *, callback)
1555		2064
1556	Initialises and configures the prepare or check watcher - they have no	2065	Initialises and configures the prepare or check watcher - they have no
1557	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2066	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1558	macros, but using them is utterly, utterly and completely pointless.	2067	macros, but using them is utterly, utterly, utterly and completely
		2068	pointless.
1559		2069
1560	=back	2070	=back
		2071
		2072	=head3 Examples
1561		2073
1562	There are a number of principal ways to embed other event loops or modules	2074	There are a number of principal ways to embed other event loops or modules
1563	into libev. Here are some ideas on how to include libadns into libev	2075	into libev. Here are some ideas on how to include libadns into libev
1564	(there is a Perl module named C<EV::ADNS> that does this, which you could	2076	(there is a Perl module named C<EV::ADNS> that does this, which you could
1565	use for an actually working example. Another Perl module named C<EV::Glib>	2077	use as a working example. Another Perl module named C<EV::Glib> embeds a
1566	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2078	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1567	into the Glib event loop).	2079	Glib event loop).
1568		2080
1569	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2081	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1570	and in a check watcher, destroy them and call into libadns. What follows	2082	and in a check watcher, destroy them and call into libadns. What follows
1571	is pseudo-code only of course. This requires you to either use a low	2083	is pseudo-code only of course. This requires you to either use a low
1572	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2084	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1573	the callbacks for the IO/timeout watchers might not have been called yet.	2085	the callbacks for the IO/timeout watchers might not have been called yet.
1574		2086
1575	static ev_io iow [nfd];	2087	static ev_io iow [nfd];
1576	static ev_timer tw;	2088	static ev_timer tw;
1577		2089
1578	static void	2090	static void
1579	io_cb (ev_loop *loop, ev_io *w, int revents)	2091	io_cb (ev_loop *loop, ev_io *w, int revents)
1580	{	2092	{
1581	}	2093	}
1582		2094
1583	// create io watchers for each fd and a timer before blocking	2095	// create io watchers for each fd and a timer before blocking
1584	static void	2096	static void
1585	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2097	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1586	{	2098	{
1587	int timeout = 3600000;	2099	int timeout = 3600000;
1588	struct pollfd fds [nfd];	2100	struct pollfd fds [nfd];
1589	// actual code will need to loop here and realloc etc.	2101	// actual code will need to loop here and realloc etc.
1590	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2102	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1591		2103
1592	/* the callback is illegal, but won't be called as we stop during check */	2104	/* the callback is illegal, but won't be called as we stop during check */
1593	ev_timer_init (&tw, 0, timeout * 1e-3);	2105	ev_timer_init (&tw, 0, timeout * 1e-3);
1594	ev_timer_start (loop, &tw);	2106	ev_timer_start (loop, &tw);
1595		2107
1596	// create one ev_io per pollfd	2108	// create one ev_io per pollfd
1597	for (int i = 0; i < nfd; ++i)	2109	for (int i = 0; i < nfd; ++i)
1598	{	2110	{
1599	ev_io_init (iow + i, io_cb, fds [i].fd,	2111	ev_io_init (iow + i, io_cb, fds [i].fd,
1600	((fds [i].events & POLLIN ? EV_READ : 0)	2112	((fds [i].events & POLLIN ? EV_READ : 0)
1601	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2113	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1602		2114
1603	fds [i].revents = 0;	2115	fds [i].revents = 0;
1604	ev_io_start (loop, iow + i);	2116	ev_io_start (loop, iow + i);
1605	}	2117	}
1606	}	2118	}
1607		2119
1608	// stop all watchers after blocking	2120	// stop all watchers after blocking
1609	static void	2121	static void
1610	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2122	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1611	{	2123	{
1612	ev_timer_stop (loop, &tw);	2124	ev_timer_stop (loop, &tw);
1613		2125
1614	for (int i = 0; i < nfd; ++i)	2126	for (int i = 0; i < nfd; ++i)
1615	{	2127	{
1616	// set the relevant poll flags	2128	// set the relevant poll flags
1617	// could also call adns_processreadable etc. here	2129	// could also call adns_processreadable etc. here
1618	struct pollfd *fd = fds + i;	2130	struct pollfd *fd = fds + i;
1619	int revents = ev_clear_pending (iow + i);	2131	int revents = ev_clear_pending (iow + i);
1620	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2132	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1621	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2133	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1622		2134
1623	// now stop the watcher	2135	// now stop the watcher
1624	ev_io_stop (loop, iow + i);	2136	ev_io_stop (loop, iow + i);
1625	}	2137	}
1626		2138
1627	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2139	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1628	}	2140	}
1629		2141
1630	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2142	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1631	in the prepare watcher and would dispose of the check watcher.	2143	in the prepare watcher and would dispose of the check watcher.
1632		2144
1633	Method 3: If the module to be embedded supports explicit event	2145	Method 3: If the module to be embedded supports explicit event
1634	notification (adns does), you can also make use of the actual watcher	2146	notification (libadns does), you can also make use of the actual watcher
1635	callbacks, and only destroy/create the watchers in the prepare watcher.	2147	callbacks, and only destroy/create the watchers in the prepare watcher.
1636		2148
1637	static void	2149	static void
1638	timer_cb (EV_P_ ev_timer *w, int revents)	2150	timer_cb (EV_P_ ev_timer *w, int revents)
1639	{	2151	{
1640	adns_state ads = (adns_state)w->data;	2152	adns_state ads = (adns_state)w->data;
1641	update_now (EV_A);	2153	update_now (EV_A);
1642		2154
1643	adns_processtimeouts (ads, &tv_now);	2155	adns_processtimeouts (ads, &tv_now);
1644	}	2156	}
1645		2157
1646	static void	2158	static void
1647	io_cb (EV_P_ ev_io *w, int revents)	2159	io_cb (EV_P_ ev_io *w, int revents)
1648	{	2160	{
1649	adns_state ads = (adns_state)w->data;	2161	adns_state ads = (adns_state)w->data;
1650	update_now (EV_A);	2162	update_now (EV_A);
1651		2163
1652	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2164	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1653	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2165	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1654	}	2166	}
1655		2167
1656	// do not ever call adns_afterpoll	2168	// do not ever call adns_afterpoll
1657		2169
1658	Method 4: Do not use a prepare or check watcher because the module you	2170	Method 4: Do not use a prepare or check watcher because the module you
1659	want to embed is too inflexible to support it. Instead, youc na override	2171	want to embed is not flexible enough to support it. Instead, you can
1660	their poll function. The drawback with this solution is that the main	2172	override their poll function. The drawback with this solution is that the
1661	loop is now no longer controllable by EV. The C<Glib::EV> module does	2173	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1662	this.	2174	this approach, effectively embedding EV as a client into the horrible
		2175	libglib event loop.
1663		2176
1664	static gint	2177	static gint
1665	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2178	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1666	{	2179	{
1667	int got_events = 0;	2180	int got_events = 0;
1668		2181
1669	for (n = 0; n < nfds; ++n)	2182	for (n = 0; n < nfds; ++n)
1670	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2183	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1671		2184
1672	if (timeout >= 0)	2185	if (timeout >= 0)
1673	// create/start timer	2186	// create/start timer
1674		2187
1675	// poll	2188	// poll
1676	ev_loop (EV_A_ 0);	2189	ev_loop (EV_A_ 0);
1677		2190
1678	// stop timer again	2191	// stop timer again
1679	if (timeout >= 0)	2192	if (timeout >= 0)
1680	ev_timer_stop (EV_A_ &to);	2193	ev_timer_stop (EV_A_ &to);
1681		2194
1682	// stop io watchers again - their callbacks should have set	2195	// stop io watchers again - their callbacks should have set
1683	for (n = 0; n < nfds; ++n)	2196	for (n = 0; n < nfds; ++n)
1684	ev_io_stop (EV_A_ iow [n]);	2197	ev_io_stop (EV_A_ iow [n]);
1685		2198
1686	return got_events;	2199	return got_events;
1687	}	2200	}
1688		2201
1689		2202
1690	=head2 C<ev_embed> - when one backend isn't enough...	2203	=head2 C<ev_embed> - when one backend isn't enough...
1691		2204
1692	This is a rather advanced watcher type that lets you embed one event loop	2205	This is a rather advanced watcher type that lets you embed one event loop
…		…
1698	prioritise I/O.	2211	prioritise I/O.
1699		2212
1700	As an example for a bug workaround, the kqueue backend might only support	2213	As an example for a bug workaround, the kqueue backend might only support
1701	sockets on some platform, so it is unusable as generic backend, but you	2214	sockets on some platform, so it is unusable as generic backend, but you
1702	still want to make use of it because you have many sockets and it scales	2215	still want to make use of it because you have many sockets and it scales
1703	so nicely. In this case, you would create a kqueue-based loop and embed it	2216	so nicely. In this case, you would create a kqueue-based loop and embed
1704	into your default loop (which might use e.g. poll). Overall operation will	2217	it into your default loop (which might use e.g. poll). Overall operation
1705	be a bit slower because first libev has to poll and then call kevent, but	2218	will be a bit slower because first libev has to call C<poll> and then
1706	at least you can use both at what they are best.	2219	C<kevent>, but at least you can use both mechanisms for what they are
		2220	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1707		2221
1708	As for prioritising I/O: rarely you have the case where some fds have	2222	As for prioritising I/O: under rare circumstances you have the case where
1709	to be watched and handled very quickly (with low latency), and even	2223	some fds have to be watched and handled very quickly (with low latency),
1710	priorities and idle watchers might have too much overhead. In this case	2224	and even priorities and idle watchers might have too much overhead. In
1711	you would put all the high priority stuff in one loop and all the rest in	2225	this case you would put all the high priority stuff in one loop and all
1712	a second one, and embed the second one in the first.	2226	the rest in a second one, and embed the second one in the first.
1713		2227
1714	As long as the watcher is active, the callback will be invoked every time	2228	As long as the watcher is active, the callback will be invoked every time
1715	there might be events pending in the embedded loop. The callback must then	2229	there might be events pending in the embedded loop. The callback must then
1716	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2230	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1717	their callbacks (you could also start an idle watcher to give the embedded	2231	their callbacks (you could also start an idle watcher to give the embedded
…		…
1725	interested in that.	2239	interested in that.
1726		2240
1727	Also, there have not currently been made special provisions for forking:	2241	Also, there have not currently been made special provisions for forking:
1728	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2242	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1729	but you will also have to stop and restart any C<ev_embed> watchers	2243	but you will also have to stop and restart any C<ev_embed> watchers
1730	yourself.	2244	yourself - but you can use a fork watcher to handle this automatically,
		2245	and future versions of libev might do just that.
1731		2246
1732	Unfortunately, not all backends are embeddable, only the ones returned by	2247	Unfortunately, not all backends are embeddable: only the ones returned by
1733	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2248	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1734	portable one.	2249	portable one.
1735		2250
1736	So when you want to use this feature you will always have to be prepared	2251	So when you want to use this feature you will always have to be prepared
1737	that you cannot get an embeddable loop. The recommended way to get around	2252	that you cannot get an embeddable loop. The recommended way to get around
1738	this is to have a separate variables for your embeddable loop, try to	2253	this is to have a separate variables for your embeddable loop, try to
1739	create it, and if that fails, use the normal loop for everything:	2254	create it, and if that fails, use the normal loop for everything.
1740		2255
1741	struct ev_loop *loop_hi = ev_default_init (0);	2256	=head3 C<ev_embed> and fork
1742	struct ev_loop *loop_lo = 0;
1743	struct ev_embed embed;
1744
1745	// see if there is a chance of getting one that works
1746	// (remember that a flags value of 0 means autodetection)
1747	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1748	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1749	: 0;
1750		2257
1751	// if we got one, then embed it, otherwise default to loop_hi	2258	While the C<ev_embed> watcher is running, forks in the embedding loop will
1752	if (loop_lo)	2259	automatically be applied to the embedded loop as well, so no special
1753	{	2260	fork handling is required in that case. When the watcher is not running,
1754	ev_embed_init (&embed, 0, loop_lo);	2261	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1755	ev_embed_start (loop_hi, &embed);	2262	as applicable.
1756	}
1757	else
1758	loop_lo = loop_hi;
1759		2263
1760	=head3 Watcher-Specific Functions and Data Members	2264	=head3 Watcher-Specific Functions and Data Members
1761		2265
1762	=over 4	2266	=over 4
1763		2267
…		…
1767		2271
1768	Configures the watcher to embed the given loop, which must be	2272	Configures the watcher to embed the given loop, which must be
1769	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2273	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1770	invoked automatically, otherwise it is the responsibility of the callback	2274	invoked automatically, otherwise it is the responsibility of the callback
1771	to invoke it (it will continue to be called until the sweep has been done,	2275	to invoke it (it will continue to be called until the sweep has been done,
1772	if you do not want thta, you need to temporarily stop the embed watcher).	2276	if you do not want that, you need to temporarily stop the embed watcher).
1773		2277
1774	=item ev_embed_sweep (loop, ev_embed *)	2278	=item ev_embed_sweep (loop, ev_embed *)
1775		2279
1776	Make a single, non-blocking sweep over the embedded loop. This works	2280	Make a single, non-blocking sweep over the embedded loop. This works
1777	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2281	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1778	apropriate way for embedded loops.	2282	appropriate way for embedded loops.
1779		2283
1780	=item struct ev_loop *loop [read-only]	2284	=item struct ev_loop *other [read-only]
1781		2285
1782	The embedded event loop.	2286	The embedded event loop.
1783		2287
1784	=back	2288	=back
		2289
		2290	=head3 Examples
		2291
		2292	Example: Try to get an embeddable event loop and embed it into the default
		2293	event loop. If that is not possible, use the default loop. The default
		2294	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2295	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2296	used).
		2297
		2298	struct ev_loop *loop_hi = ev_default_init (0);
		2299	struct ev_loop *loop_lo = 0;
		2300	struct ev_embed embed;
		2301
		2302	// see if there is a chance of getting one that works
		2303	// (remember that a flags value of 0 means autodetection)
		2304	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2305	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2306	: 0;
		2307
		2308	// if we got one, then embed it, otherwise default to loop_hi
		2309	if (loop_lo)
		2310	{
		2311	ev_embed_init (&embed, 0, loop_lo);
		2312	ev_embed_start (loop_hi, &embed);
		2313	}
		2314	else
		2315	loop_lo = loop_hi;
		2316
		2317	Example: Check if kqueue is available but not recommended and create
		2318	a kqueue backend for use with sockets (which usually work with any
		2319	kqueue implementation). Store the kqueue/socket-only event loop in
		2320	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2321
		2322	struct ev_loop *loop = ev_default_init (0);
		2323	struct ev_loop *loop_socket = 0;
		2324	struct ev_embed embed;
		2325
		2326	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2327	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2328	{
		2329	ev_embed_init (&embed, 0, loop_socket);
		2330	ev_embed_start (loop, &embed);
		2331	}
		2332
		2333	if (!loop_socket)
		2334	loop_socket = loop;
		2335
		2336	// now use loop_socket for all sockets, and loop for everything else
1785		2337
1786		2338
1787	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2339	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1788		2340
1789	Fork watchers are called when a C<fork ()> was detected (usually because	2341	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1805	believe me.	2357	believe me.
1806		2358
1807	=back	2359	=back
1808		2360
1809		2361
		2362	=head2 C<ev_async> - how to wake up another event loop
		2363
		2364	In general, you cannot use an C<ev_loop> from multiple threads or other
		2365	asynchronous sources such as signal handlers (as opposed to multiple event
		2366	loops - those are of course safe to use in different threads).
		2367
		2368	Sometimes, however, you need to wake up another event loop you do not
		2369	control, for example because it belongs to another thread. This is what
		2370	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2371	can signal it by calling C<ev_async_send>, which is thread- and signal
		2372	safe.
		2373
		2374	This functionality is very similar to C<ev_signal> watchers, as signals,
		2375	too, are asynchronous in nature, and signals, too, will be compressed
		2376	(i.e. the number of callback invocations may be less than the number of
		2377	C<ev_async_sent> calls).
		2378
		2379	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2380	just the default loop.
		2381
		2382	=head3 Queueing
		2383
		2384	C<ev_async> does not support queueing of data in any way. The reason
		2385	is that the author does not know of a simple (or any) algorithm for a
		2386	multiple-writer-single-reader queue that works in all cases and doesn't
		2387	need elaborate support such as pthreads.
		2388
		2389	That means that if you want to queue data, you have to provide your own
		2390	queue. But at least I can tell you how to implement locking around your
		2391	queue:
		2392
		2393	=over 4
		2394
		2395	=item queueing from a signal handler context
		2396
		2397	To implement race-free queueing, you simply add to the queue in the signal
		2398	handler but you block the signal handler in the watcher callback. Here is
		2399	an example that does that for some fictitious SIGUSR1 handler:
		2400
		2401	static ev_async mysig;
		2402
		2403	static void
		2404	sigusr1_handler (void)
		2405	{
		2406	sometype data;
		2407
		2408	// no locking etc.
		2409	queue_put (data);
		2410	ev_async_send (EV_DEFAULT_ &mysig);
		2411	}
		2412
		2413	static void
		2414	mysig_cb (EV_P_ ev_async *w, int revents)
		2415	{
		2416	sometype data;
		2417	sigset_t block, prev;
		2418
		2419	sigemptyset (&block);
		2420	sigaddset (&block, SIGUSR1);
		2421	sigprocmask (SIG_BLOCK, &block, &prev);
		2422
		2423	while (queue_get (&data))
		2424	process (data);
		2425
		2426	if (sigismember (&prev, SIGUSR1)
		2427	sigprocmask (SIG_UNBLOCK, &block, 0);
		2428	}
		2429
		2430	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2431	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2432	either...).
		2433
		2434	=item queueing from a thread context
		2435
		2436	The strategy for threads is different, as you cannot (easily) block
		2437	threads but you can easily preempt them, so to queue safely you need to
		2438	employ a traditional mutex lock, such as in this pthread example:
		2439
		2440	static ev_async mysig;
		2441	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2442
		2443	static void
		2444	otherthread (void)
		2445	{
		2446	// only need to lock the actual queueing operation
		2447	pthread_mutex_lock (&mymutex);
		2448	queue_put (data);
		2449	pthread_mutex_unlock (&mymutex);
		2450
		2451	ev_async_send (EV_DEFAULT_ &mysig);
		2452	}
		2453
		2454	static void
		2455	mysig_cb (EV_P_ ev_async *w, int revents)
		2456	{
		2457	pthread_mutex_lock (&mymutex);
		2458
		2459	while (queue_get (&data))
		2460	process (data);
		2461
		2462	pthread_mutex_unlock (&mymutex);
		2463	}
		2464
		2465	=back
		2466
		2467
		2468	=head3 Watcher-Specific Functions and Data Members
		2469
		2470	=over 4
		2471
		2472	=item ev_async_init (ev_async *, callback)
		2473
		2474	Initialises and configures the async watcher - it has no parameters of any
		2475	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2476	trust me.
		2477
		2478	=item ev_async_send (loop, ev_async *)
		2479
		2480	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2481	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2482	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2483	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2484	section below on what exactly this means).
		2485
		2486	This call incurs the overhead of a system call only once per loop iteration,
		2487	so while the overhead might be noticeable, it doesn't apply to repeated
		2488	calls to C<ev_async_send>.
		2489
		2490	=item bool = ev_async_pending (ev_async *)
		2491
		2492	Returns a non-zero value when C<ev_async_send> has been called on the
		2493	watcher but the event has not yet been processed (or even noted) by the
		2494	event loop.
		2495
		2496	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2497	the loop iterates next and checks for the watcher to have become active,
		2498	it will reset the flag again. C<ev_async_pending> can be used to very
		2499	quickly check whether invoking the loop might be a good idea.
		2500
		2501	Not that this does I<not> check whether the watcher itself is pending, only
		2502	whether it has been requested to make this watcher pending.
		2503
		2504	=back
		2505
		2506
1810	=head1 OTHER FUNCTIONS	2507	=head1 OTHER FUNCTIONS
1811		2508
1812	There are some other functions of possible interest. Described. Here. Now.	2509	There are some other functions of possible interest. Described. Here. Now.
1813		2510
1814	=over 4	2511	=over 4
1815		2512
1816	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2513	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1817		2514
1818	This function combines a simple timer and an I/O watcher, calls your	2515	This function combines a simple timer and an I/O watcher, calls your
1819	callback on whichever event happens first and automatically stop both	2516	callback on whichever event happens first and automatically stops both
1820	watchers. This is useful if you want to wait for a single event on an fd	2517	watchers. This is useful if you want to wait for a single event on an fd
1821	or timeout without having to allocate/configure/start/stop/free one or	2518	or timeout without having to allocate/configure/start/stop/free one or
1822	more watchers yourself.	2519	more watchers yourself.
1823		2520
1824	If C<fd> is less than 0, then no I/O watcher will be started and events	2521	If C<fd> is less than 0, then no I/O watcher will be started and the
1825	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2522	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1826	C<events> set will be craeted and started.	2523	the given C<fd> and C<events> set will be created and started.
1827		2524
1828	If C<timeout> is less than 0, then no timeout watcher will be	2525	If C<timeout> is less than 0, then no timeout watcher will be
1829	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2526	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1830	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2527	repeat = 0) will be started. C<0> is a valid timeout.
1831	dubious value.
1832		2528
1833	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2529	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1834	passed an C<revents> set like normal event callbacks (a combination of	2530	passed an C<revents> set like normal event callbacks (a combination of
1835	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2531	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1836	value passed to C<ev_once>:	2532	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2533	a timeout and an io event at the same time - you probably should give io
		2534	events precedence.
1837		2535
		2536	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2537
1838	static void stdin_ready (int revents, void *arg)	2538	static void stdin_ready (int revents, void *arg)
1839	{	2539	{
1840	if (revents & EV_TIMEOUT)
1841	/* doh, nothing entered */;
1842	else if (revents & EV_READ)	2540	if (revents & EV_READ)
1843	/* stdin might have data for us, joy! */;	2541	/* stdin might have data for us, joy! */;
		2542	else if (revents & EV_TIMEOUT)
		2543	/* doh, nothing entered */;
1844	}	2544	}
1845		2545
1846	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1847		2547
1848	=item ev_feed_event (ev_loop *, watcher *, int revents)	2548	=item ev_feed_event (ev_loop *, watcher *, int revents)
1849		2549
1850	Feeds the given event set into the event loop, as if the specified event	2550	Feeds the given event set into the event loop, as if the specified event
1851	had happened for the specified watcher (which must be a pointer to an	2551	had happened for the specified watcher (which must be a pointer to an
…		…
1856	Feed an event on the given fd, as if a file descriptor backend detected	2556	Feed an event on the given fd, as if a file descriptor backend detected
1857	the given events it.	2557	the given events it.
1858		2558
1859	=item ev_feed_signal_event (ev_loop *loop, int signum)	2559	=item ev_feed_signal_event (ev_loop *loop, int signum)
1860		2560
1861	Feed an event as if the given signal occured (C<loop> must be the default	2561	Feed an event as if the given signal occurred (C<loop> must be the default
1862	loop!).	2562	loop!).
1863		2563
1864	=back	2564	=back
1865		2565
1866		2566
…		…
1882		2582
1883	=item * Priorities are not currently supported. Initialising priorities	2583	=item * Priorities are not currently supported. Initialising priorities
1884	will fail and all watchers will have the same priority, even though there	2584	will fail and all watchers will have the same priority, even though there
1885	is an ev_pri field.	2585	is an ev_pri field.
1886		2586
		2587	=item * In libevent, the last base created gets the signals, in libev, the
		2588	first base created (== the default loop) gets the signals.
		2589
1887	=item * Other members are not supported.	2590	=item * Other members are not supported.
1888		2591
1889	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2592	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1890	to use the libev header file and library.	2593	to use the libev header file and library.
1891		2594
1892	=back	2595	=back
1893		2596
1894	=head1 C++ SUPPORT	2597	=head1 C++ SUPPORT
1895		2598
1896	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2599	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1897	you to use some convinience methods to start/stop watchers and also change	2600	you to use some convenience methods to start/stop watchers and also change
1898	the callback model to a model using method callbacks on objects.	2601	the callback model to a model using method callbacks on objects.
1899		2602
1900	To use it,	2603	To use it,
1901		2604
1902	#include <ev++.h>	2605	#include <ev++.h>
1903		2606
1904	This automatically includes F<ev.h> and puts all of its definitions (many	2607	This automatically includes F<ev.h> and puts all of its definitions (many
1905	of them macros) into the global namespace. All C++ specific things are	2608	of them macros) into the global namespace. All C++ specific things are
1906	put into the C<ev> namespace. It should support all the same embedding	2609	put into the C<ev> namespace. It should support all the same embedding
1907	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2610	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1974	your compiler is good :), then the method will be fully inlined into the	2677	your compiler is good :), then the method will be fully inlined into the
1975	thunking function, making it as fast as a direct C callback.	2678	thunking function, making it as fast as a direct C callback.
1976		2679
1977	Example: simple class declaration and watcher initialisation	2680	Example: simple class declaration and watcher initialisation
1978		2681
1979	struct myclass	2682	struct myclass
1980	{	2683	{
1981	void io_cb (ev::io &w, int revents) { }	2684	void io_cb (ev::io &w, int revents) { }
1982	}	2685	}
1983		2686
1984	myclass obj;	2687	myclass obj;
1985	ev::io iow;	2688	ev::io iow;
1986	iow.set <myclass, &myclass::io_cb> (&obj);	2689	iow.set <myclass, &myclass::io_cb> (&obj);
1987		2690
1988	=item w->set<function> (void *data = 0)	2691	=item w->set<function> (void *data = 0)
1989		2692
1990	Also sets a callback, but uses a static method or plain function as	2693	Also sets a callback, but uses a static method or plain function as
1991	callback. The optional C<data> argument will be stored in the watcher's	2694	callback. The optional C<data> argument will be stored in the watcher's
…		…
1993		2696
1994	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2697	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
1995		2698
1996	See the method-C<set> above for more details.	2699	See the method-C<set> above for more details.
1997		2700
1998	Example:	2701	Example: Use a plain function as callback.
1999		2702
2000	static void io_cb (ev::io &w, int revents) { }	2703	static void io_cb (ev::io &w, int revents) { }
2001	iow.set <io_cb> ();	2704	iow.set <io_cb> ();
2002		2705
2003	=item w->set (struct ev_loop *)	2706	=item w->set (struct ev_loop *)
2004		2707
2005	Associates a different C<struct ev_loop> with this watcher. You can only	2708	Associates a different C<struct ev_loop> with this watcher. You can only
2006	do this when the watcher is inactive (and not pending either).	2709	do this when the watcher is inactive (and not pending either).
2007		2710
2008	=item w->set ([args])	2711	=item w->set ([arguments])
2009		2712
2010	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2713	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2011	called at least once. Unlike the C counterpart, an active watcher gets	2714	called at least once. Unlike the C counterpart, an active watcher gets
2012	automatically stopped and restarted when reconfiguring it with this	2715	automatically stopped and restarted when reconfiguring it with this
2013	method.	2716	method.
2014		2717
2015	=item w->start ()	2718	=item w->start ()
…		…
2039	=back	2742	=back
2040		2743
2041	Example: Define a class with an IO and idle watcher, start one of them in	2744	Example: Define a class with an IO and idle watcher, start one of them in
2042	the constructor.	2745	the constructor.
2043		2746
2044	class myclass	2747	class myclass
2045	{	2748	{
2046	ev_io io; void io_cb (ev::io &w, int revents);	2749	ev::io io ; void io_cb (ev::io &w, int revents);
2047	ev_idle idle void idle_cb (ev::idle &w, int revents);	2750	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2048		2751
2049	myclass ();	2752	myclass (int fd)
2050	}	2753	{
2051
2052	myclass::myclass (int fd)
2053	{
2054	io .set <myclass, &myclass::io_cb > (this);	2754	io .set <myclass, &myclass::io_cb > (this);
2055	idle.set <myclass, &myclass::idle_cb> (this);	2755	idle.set <myclass, &myclass::idle_cb> (this);
2056		2756
2057	io.start (fd, ev::READ);	2757	io.start (fd, ev::READ);
		2758	}
2058	}	2759	};
		2760
		2761
		2762	=head1 OTHER LANGUAGE BINDINGS
		2763
		2764	Libev does not offer other language bindings itself, but bindings for a
		2765	number of languages exist in the form of third-party packages. If you know
		2766	any interesting language binding in addition to the ones listed here, drop
		2767	me a note.
		2768
		2769	=over 4
		2770
		2771	=item Perl
		2772
		2773	The EV module implements the full libev API and is actually used to test
		2774	libev. EV is developed together with libev. Apart from the EV core module,
		2775	there are additional modules that implement libev-compatible interfaces
		2776	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2777	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2778	and C<EV::Glib>).
		2779
		2780	It can be found and installed via CPAN, its homepage is at
		2781	L<http://software.schmorp.de/pkg/EV>.
		2782
		2783	=item Python
		2784
		2785	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2786	seems to be quite complete and well-documented. Note, however, that the
		2787	patch they require for libev is outright dangerous as it breaks the ABI
		2788	for everybody else, and therefore, should never be applied in an installed
		2789	libev (if python requires an incompatible ABI then it needs to embed
		2790	libev).
		2791
		2792	=item Ruby
		2793
		2794	Tony Arcieri has written a ruby extension that offers access to a subset
		2795	of the libev API and adds file handle abstractions, asynchronous DNS and
		2796	more on top of it. It can be found via gem servers. Its homepage is at
		2797	L<http://rev.rubyforge.org/>.
		2798
		2799	=item D
		2800
		2801	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2802	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2803
		2804	=back
2059		2805
2060		2806
2061	=head1 MACRO MAGIC	2807	=head1 MACRO MAGIC
2062		2808
2063	Libev can be compiled with a variety of options, the most fundamantal	2809	Libev can be compiled with a variety of options, the most fundamental
2064	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2810	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2065	functions and callbacks have an initial C<struct ev_loop *> argument.	2811	functions and callbacks have an initial C<struct ev_loop *> argument.
2066		2812
2067	To make it easier to write programs that cope with either variant, the	2813	To make it easier to write programs that cope with either variant, the
2068	following macros are defined:	2814	following macros are defined:
…		…
2073		2819
2074	This provides the loop I<argument> for functions, if one is required ("ev	2820	This provides the loop I<argument> for functions, if one is required ("ev
2075	loop argument"). The C<EV_A> form is used when this is the sole argument,	2821	loop argument"). The C<EV_A> form is used when this is the sole argument,
2076	C<EV_A_> is used when other arguments are following. Example:	2822	C<EV_A_> is used when other arguments are following. Example:
2077		2823
2078	ev_unref (EV_A);	2824	ev_unref (EV_A);
2079	ev_timer_add (EV_A_ watcher);	2825	ev_timer_add (EV_A_ watcher);
2080	ev_loop (EV_A_ 0);	2826	ev_loop (EV_A_ 0);
2081		2827
2082	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2828	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2083	which is often provided by the following macro.	2829	which is often provided by the following macro.
2084		2830
2085	=item C<EV_P>, C<EV_P_>	2831	=item C<EV_P>, C<EV_P_>
2086		2832
2087	This provides the loop I<parameter> for functions, if one is required ("ev	2833	This provides the loop I<parameter> for functions, if one is required ("ev
2088	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2834	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2089	C<EV_P_> is used when other parameters are following. Example:	2835	C<EV_P_> is used when other parameters are following. Example:
2090		2836
2091	// this is how ev_unref is being declared	2837	// this is how ev_unref is being declared
2092	static void ev_unref (EV_P);	2838	static void ev_unref (EV_P);
2093		2839
2094	// this is how you can declare your typical callback	2840	// this is how you can declare your typical callback
2095	static void cb (EV_P_ ev_timer *w, int revents)	2841	static void cb (EV_P_ ev_timer *w, int revents)
2096		2842
2097	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2843	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2098	suitable for use with C<EV_A>.	2844	suitable for use with C<EV_A>.
2099		2845
2100	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2846	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2101		2847
2102	Similar to the other two macros, this gives you the value of the default	2848	Similar to the other two macros, this gives you the value of the default
2103	loop, if multiple loops are supported ("ev loop default").	2849	loop, if multiple loops are supported ("ev loop default").
		2850
		2851	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2852
		2853	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2854	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2855	is undefined when the default loop has not been initialised by a previous
		2856	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2857
		2858	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2859	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2104		2860
2105	=back	2861	=back
2106		2862
2107	Example: Declare and initialise a check watcher, utilising the above	2863	Example: Declare and initialise a check watcher, utilising the above
2108	macros so it will work regardless of whether multiple loops are supported	2864	macros so it will work regardless of whether multiple loops are supported
2109	or not.	2865	or not.
2110		2866
2111	static void	2867	static void
2112	check_cb (EV_P_ ev_timer *w, int revents)	2868	check_cb (EV_P_ ev_timer *w, int revents)
2113	{	2869	{
2114	ev_check_stop (EV_A_ w);	2870	ev_check_stop (EV_A_ w);
2115	}	2871	}
2116		2872
2117	ev_check check;	2873	ev_check check;
2118	ev_check_init (&check, check_cb);	2874	ev_check_init (&check, check_cb);
2119	ev_check_start (EV_DEFAULT_ &check);	2875	ev_check_start (EV_DEFAULT_ &check);
2120	ev_loop (EV_DEFAULT_ 0);	2876	ev_loop (EV_DEFAULT_ 0);
2121		2877
2122	=head1 EMBEDDING	2878	=head1 EMBEDDING
2123		2879
2124	Libev can (and often is) directly embedded into host	2880	Libev can (and often is) directly embedded into host
2125	applications. Examples of applications that embed it include the Deliantra	2881	applications. Examples of applications that embed it include the Deliantra
2126	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2882	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2127	and rxvt-unicode.	2883	and rxvt-unicode.
2128		2884
2129	The goal is to enable you to just copy the neecssary files into your	2885	The goal is to enable you to just copy the necessary files into your
2130	source directory without having to change even a single line in them, so	2886	source directory without having to change even a single line in them, so
2131	you can easily upgrade by simply copying (or having a checked-out copy of	2887	you can easily upgrade by simply copying (or having a checked-out copy of
2132	libev somewhere in your source tree).	2888	libev somewhere in your source tree).
2133		2889
2134	=head2 FILESETS	2890	=head2 FILESETS
2135		2891
2136	Depending on what features you need you need to include one or more sets of files	2892	Depending on what features you need you need to include one or more sets of files
2137	in your app.	2893	in your application.
2138		2894
2139	=head3 CORE EVENT LOOP	2895	=head3 CORE EVENT LOOP
2140		2896
2141	To include only the libev core (all the C<ev_*> functions), with manual	2897	To include only the libev core (all the C<ev_*> functions), with manual
2142	configuration (no autoconf):	2898	configuration (no autoconf):
2143		2899
2144	#define EV_STANDALONE 1	2900	#define EV_STANDALONE 1
2145	#include "ev.c"	2901	#include "ev.c"
2146		2902
2147	This will automatically include F<ev.h>, too, and should be done in a	2903	This will automatically include F<ev.h>, too, and should be done in a
2148	single C source file only to provide the function implementations. To use	2904	single C source file only to provide the function implementations. To use
2149	it, do the same for F<ev.h> in all files wishing to use this API (best	2905	it, do the same for F<ev.h> in all files wishing to use this API (best
2150	done by writing a wrapper around F<ev.h> that you can include instead and	2906	done by writing a wrapper around F<ev.h> that you can include instead and
2151	where you can put other configuration options):	2907	where you can put other configuration options):
2152		2908
2153	#define EV_STANDALONE 1	2909	#define EV_STANDALONE 1
2154	#include "ev.h"	2910	#include "ev.h"
2155		2911
2156	Both header files and implementation files can be compiled with a C++	2912	Both header files and implementation files can be compiled with a C++
2157	compiler (at least, thats a stated goal, and breakage will be treated	2913	compiler (at least, thats a stated goal, and breakage will be treated
2158	as a bug).	2914	as a bug).
2159		2915
2160	You need the following files in your source tree, or in a directory	2916	You need the following files in your source tree, or in a directory
2161	in your include path (e.g. in libev/ when using -Ilibev):	2917	in your include path (e.g. in libev/ when using -Ilibev):
2162		2918
2163	ev.h	2919	ev.h
2164	ev.c	2920	ev.c
2165	ev_vars.h	2921	ev_vars.h
2166	ev_wrap.h	2922	ev_wrap.h
2167		2923
2168	ev_win32.c required on win32 platforms only	2924	ev_win32.c required on win32 platforms only
2169		2925
2170	ev_select.c only when select backend is enabled (which is enabled by default)	2926	ev_select.c only when select backend is enabled (which is enabled by default)
2171	ev_poll.c only when poll backend is enabled (disabled by default)	2927	ev_poll.c only when poll backend is enabled (disabled by default)
2172	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2928	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2173	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2929	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2174	ev_port.c only when the solaris port backend is enabled (disabled by default)	2930	ev_port.c only when the solaris port backend is enabled (disabled by default)
2175		2931
2176	F<ev.c> includes the backend files directly when enabled, so you only need	2932	F<ev.c> includes the backend files directly when enabled, so you only need
2177	to compile this single file.	2933	to compile this single file.
2178		2934
2179	=head3 LIBEVENT COMPATIBILITY API	2935	=head3 LIBEVENT COMPATIBILITY API
2180		2936
2181	To include the libevent compatibility API, also include:	2937	To include the libevent compatibility API, also include:
2182		2938
2183	#include "event.c"	2939	#include "event.c"
2184		2940
2185	in the file including F<ev.c>, and:	2941	in the file including F<ev.c>, and:
2186		2942
2187	#include "event.h"	2943	#include "event.h"
2188		2944
2189	in the files that want to use the libevent API. This also includes F<ev.h>.	2945	in the files that want to use the libevent API. This also includes F<ev.h>.
2190		2946
2191	You need the following additional files for this:	2947	You need the following additional files for this:
2192		2948
2193	event.h	2949	event.h
2194	event.c	2950	event.c
2195		2951
2196	=head3 AUTOCONF SUPPORT	2952	=head3 AUTOCONF SUPPORT
2197		2953
2198	Instead of using C<EV_STANDALONE=1> and providing your config in	2954	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2199	whatever way you want, you can also C<m4_include([libev.m4])> in your	2955	whatever way you want, you can also C<m4_include([libev.m4])> in your
2200	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2956	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2201	include F<config.h> and configure itself accordingly.	2957	include F<config.h> and configure itself accordingly.
2202		2958
2203	For this of course you need the m4 file:	2959	For this of course you need the m4 file:
2204		2960
2205	libev.m4	2961	libev.m4
2206		2962
2207	=head2 PREPROCESSOR SYMBOLS/MACROS	2963	=head2 PREPROCESSOR SYMBOLS/MACROS
2208		2964
2209	Libev can be configured via a variety of preprocessor symbols you have to define	2965	Libev can be configured via a variety of preprocessor symbols you have to
2210	before including any of its files. The default is not to build for multiplicity	2966	define before including any of its files. The default in the absence of
2211	and only include the select backend.	2967	autoconf is documented for every option.
2212		2968
2213	=over 4	2969	=over 4
2214		2970
2215	=item EV_STANDALONE	2971	=item EV_STANDALONE
2216		2972
…		…
2221	F<event.h> that are not directly supported by the libev core alone.	2977	F<event.h> that are not directly supported by the libev core alone.
2222		2978
2223	=item EV_USE_MONOTONIC	2979	=item EV_USE_MONOTONIC
2224		2980
2225	If defined to be C<1>, libev will try to detect the availability of the	2981	If defined to be C<1>, libev will try to detect the availability of the
2226	monotonic clock option at both compiletime and runtime. Otherwise no use	2982	monotonic clock option at both compile time and runtime. Otherwise no use
2227	of the monotonic clock option will be attempted. If you enable this, you	2983	of the monotonic clock option will be attempted. If you enable this, you
2228	usually have to link against librt or something similar. Enabling it when	2984	usually have to link against librt or something similar. Enabling it when
2229	the functionality isn't available is safe, though, althoguh you have	2985	the functionality isn't available is safe, though, although you have
2230	to make sure you link against any libraries where the C<clock_gettime>	2986	to make sure you link against any libraries where the C<clock_gettime>
2231	function is hiding in (often F<-lrt>).	2987	function is hiding in (often F<-lrt>).
2232		2988
2233	=item EV_USE_REALTIME	2989	=item EV_USE_REALTIME
2234		2990
2235	If defined to be C<1>, libev will try to detect the availability of the	2991	If defined to be C<1>, libev will try to detect the availability of the
2236	realtime clock option at compiletime (and assume its availability at	2992	real-time clock option at compile time (and assume its availability at
2237	runtime if successful). Otherwise no use of the realtime clock option will	2993	runtime if successful). Otherwise no use of the real-time clock option will
2238	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2994	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2239	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2995	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2240	in the description of C<EV_USE_MONOTONIC>, though.	2996	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2997
		2998	=item EV_USE_NANOSLEEP
		2999
		3000	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		3001	and will use it for delays. Otherwise it will use C<select ()>.
		3002
		3003	=item EV_USE_EVENTFD
		3004
		3005	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3006	available and will probe for kernel support at runtime. This will improve
		3007	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3008	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3009	2.7 or newer, otherwise disabled.
2241		3010
2242	=item EV_USE_SELECT	3011	=item EV_USE_SELECT
2243		3012
2244	If undefined or defined to be C<1>, libev will compile in support for the	3013	If undefined or defined to be C<1>, libev will compile in support for the
2245	C<select>(2) backend. No attempt at autodetection will be done: if no	3014	C<select>(2) backend. No attempt at auto-detection will be done: if no
2246	other method takes over, select will be it. Otherwise the select backend	3015	other method takes over, select will be it. Otherwise the select backend
2247	will not be compiled in.	3016	will not be compiled in.
2248		3017
2249	=item EV_SELECT_USE_FD_SET	3018	=item EV_SELECT_USE_FD_SET
2250		3019
2251	If defined to C<1>, then the select backend will use the system C<fd_set>	3020	If defined to C<1>, then the select backend will use the system C<fd_set>
2252	structure. This is useful if libev doesn't compile due to a missing	3021	structure. This is useful if libev doesn't compile due to a missing
2253	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3022	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2254	exotic systems. This usually limits the range of file descriptors to some	3023	exotic systems. This usually limits the range of file descriptors to some
2255	low limit such as 1024 or might have other limitations (winsocket only	3024	low limit such as 1024 or might have other limitations (winsocket only
2256	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3025	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2257	influence the size of the C<fd_set> used.	3026	influence the size of the C<fd_set> used.
2258		3027
…		…
2264	be used is the winsock select). This means that it will call	3033	be used is the winsock select). This means that it will call
2265	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3034	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2266	it is assumed that all these functions actually work on fds, even	3035	it is assumed that all these functions actually work on fds, even
2267	on win32. Should not be defined on non-win32 platforms.	3036	on win32. Should not be defined on non-win32 platforms.
2268		3037
		3038	=item EV_FD_TO_WIN32_HANDLE
		3039
		3040	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3041	file descriptors to socket handles. When not defining this symbol (the
		3042	default), then libev will call C<_get_osfhandle>, which is usually
		3043	correct. In some cases, programs use their own file descriptor management,
		3044	in which case they can provide this function to map fds to socket handles.
		3045
2269	=item EV_USE_POLL	3046	=item EV_USE_POLL
2270		3047
2271	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3048	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2272	backend. Otherwise it will be enabled on non-win32 platforms. It	3049	backend. Otherwise it will be enabled on non-win32 platforms. It
2273	takes precedence over select.	3050	takes precedence over select.
2274		3051
2275	=item EV_USE_EPOLL	3052	=item EV_USE_EPOLL
2276		3053
2277	If defined to be C<1>, libev will compile in support for the Linux	3054	If defined to be C<1>, libev will compile in support for the Linux
2278	C<epoll>(7) backend. Its availability will be detected at runtime,	3055	C<epoll>(7) backend. Its availability will be detected at runtime,
2279	otherwise another method will be used as fallback. This is the	3056	otherwise another method will be used as fallback. This is the preferred
2280	preferred backend for GNU/Linux systems.	3057	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3058	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2281		3059
2282	=item EV_USE_KQUEUE	3060	=item EV_USE_KQUEUE
2283		3061
2284	If defined to be C<1>, libev will compile in support for the BSD style	3062	If defined to be C<1>, libev will compile in support for the BSD style
2285	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3063	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2298	otherwise another method will be used as fallback. This is the preferred	3076	otherwise another method will be used as fallback. This is the preferred
2299	backend for Solaris 10 systems.	3077	backend for Solaris 10 systems.
2300		3078
2301	=item EV_USE_DEVPOLL	3079	=item EV_USE_DEVPOLL
2302		3080
2303	reserved for future expansion, works like the USE symbols above.	3081	Reserved for future expansion, works like the USE symbols above.
2304		3082
2305	=item EV_USE_INOTIFY	3083	=item EV_USE_INOTIFY
2306		3084
2307	If defined to be C<1>, libev will compile in support for the Linux inotify	3085	If defined to be C<1>, libev will compile in support for the Linux inotify
2308	interface to speed up C<ev_stat> watchers. Its actual availability will	3086	interface to speed up C<ev_stat> watchers. Its actual availability will
2309	be detected at runtime.	3087	be detected at runtime. If undefined, it will be enabled if the headers
		3088	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3089
		3090	=item EV_ATOMIC_T
		3091
		3092	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3093	access is atomic with respect to other threads or signal contexts. No such
		3094	type is easily found in the C language, so you can provide your own type
		3095	that you know is safe for your purposes. It is used both for signal handler "locking"
		3096	as well as for signal and thread safety in C<ev_async> watchers.
		3097
		3098	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3099	(from F<signal.h>), which is usually good enough on most platforms.
2310		3100
2311	=item EV_H	3101	=item EV_H
2312		3102
2313	The name of the F<ev.h> header file used to include it. The default if	3103	The name of the F<ev.h> header file used to include it. The default if
2314	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3104	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2315	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3105	used to virtually rename the F<ev.h> header file in case of conflicts.
2316		3106
2317	=item EV_CONFIG_H	3107	=item EV_CONFIG_H
2318		3108
2319	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3109	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2320	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3110	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2321	C<EV_H>, above.	3111	C<EV_H>, above.
2322		3112
2323	=item EV_EVENT_H	3113	=item EV_EVENT_H
2324		3114
2325	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3115	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2326	of how the F<event.h> header can be found.	3116	of how the F<event.h> header can be found, the default is C<"event.h">.
2327		3117
2328	=item EV_PROTOTYPES	3118	=item EV_PROTOTYPES
2329		3119
2330	If defined to be C<0>, then F<ev.h> will not define any function	3120	If defined to be C<0>, then F<ev.h> will not define any function
2331	prototypes, but still define all the structs and other symbols. This is	3121	prototypes, but still define all the structs and other symbols. This is
…		…
2352	When doing priority-based operations, libev usually has to linearly search	3142	When doing priority-based operations, libev usually has to linearly search
2353	all the priorities, so having many of them (hundreds) uses a lot of space	3143	all the priorities, so having many of them (hundreds) uses a lot of space
2354	and time, so using the defaults of five priorities (-2 .. +2) is usually	3144	and time, so using the defaults of five priorities (-2 .. +2) is usually
2355	fine.	3145	fine.
2356		3146
2357	If your embedding app does not need any priorities, defining these both to	3147	If your embedding application does not need any priorities, defining these
2358	C<0> will save some memory and cpu.	3148	both to C<0> will save some memory and CPU.
2359		3149
2360	=item EV_PERIODIC_ENABLE	3150	=item EV_PERIODIC_ENABLE
2361		3151
2362	If undefined or defined to be C<1>, then periodic timers are supported. If	3152	If undefined or defined to be C<1>, then periodic timers are supported. If
2363	defined to be C<0>, then they are not. Disabling them saves a few kB of	3153	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2370	code.	3160	code.
2371		3161
2372	=item EV_EMBED_ENABLE	3162	=item EV_EMBED_ENABLE
2373		3163
2374	If undefined or defined to be C<1>, then embed watchers are supported. If	3164	If undefined or defined to be C<1>, then embed watchers are supported. If
2375	defined to be C<0>, then they are not.	3165	defined to be C<0>, then they are not. Embed watchers rely on most other
		3166	watcher types, which therefore must not be disabled.
2376		3167
2377	=item EV_STAT_ENABLE	3168	=item EV_STAT_ENABLE
2378		3169
2379	If undefined or defined to be C<1>, then stat watchers are supported. If	3170	If undefined or defined to be C<1>, then stat watchers are supported. If
2380	defined to be C<0>, then they are not.	3171	defined to be C<0>, then they are not.
…		…
2382	=item EV_FORK_ENABLE	3173	=item EV_FORK_ENABLE
2383		3174
2384	If undefined or defined to be C<1>, then fork watchers are supported. If	3175	If undefined or defined to be C<1>, then fork watchers are supported. If
2385	defined to be C<0>, then they are not.	3176	defined to be C<0>, then they are not.
2386		3177
		3178	=item EV_ASYNC_ENABLE
		3179
		3180	If undefined or defined to be C<1>, then async watchers are supported. If
		3181	defined to be C<0>, then they are not.
		3182
2387	=item EV_MINIMAL	3183	=item EV_MINIMAL
2388		3184
2389	If you need to shave off some kilobytes of code at the expense of some	3185	If you need to shave off some kilobytes of code at the expense of some
2390	speed, define this symbol to C<1>. Currently only used for gcc to override	3186	speed, define this symbol to C<1>. Currently this is used to override some
2391	some inlining decisions, saves roughly 30% codesize of amd64.	3187	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3188	much smaller 2-heap for timer management over the default 4-heap.
2392		3189
2393	=item EV_PID_HASHSIZE	3190	=item EV_PID_HASHSIZE
2394		3191
2395	C<ev_child> watchers use a small hash table to distribute workload by	3192	C<ev_child> watchers use a small hash table to distribute workload by
2396	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3193	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2397	than enough. If you need to manage thousands of children you might want to	3194	than enough. If you need to manage thousands of children you might want to
2398	increase this value (I<must> be a power of two).	3195	increase this value (I<must> be a power of two).
2399		3196
2400	=item EV_INOTIFY_HASHSIZE	3197	=item EV_INOTIFY_HASHSIZE
2401		3198
2402	C<ev_staz> watchers use a small hash table to distribute workload by	3199	C<ev_stat> watchers use a small hash table to distribute workload by
2403	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3200	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2404	usually more than enough. If you need to manage thousands of C<ev_stat>	3201	usually more than enough. If you need to manage thousands of C<ev_stat>
2405	watchers you might want to increase this value (I<must> be a power of	3202	watchers you might want to increase this value (I<must> be a power of
2406	two).	3203	two).
2407		3204
		3205	=item EV_USE_4HEAP
		3206
		3207	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3208	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3209	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3210	faster performance with many (thousands) of watchers.
		3211
		3212	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3213	(disabled).
		3214
		3215	=item EV_HEAP_CACHE_AT
		3216
		3217	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3218	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3219	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3220	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3221	but avoids random read accesses on heap changes. This improves performance
		3222	noticeably with many (hundreds) of watchers.
		3223
		3224	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3225	(disabled).
		3226
		3227	=item EV_VERIFY
		3228
		3229	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3230	be done: If set to C<0>, no internal verification code will be compiled
		3231	in. If set to C<1>, then verification code will be compiled in, but not
		3232	called. If set to C<2>, then the internal verification code will be
		3233	called once per loop, which can slow down libev. If set to C<3>, then the
		3234	verification code will be called very frequently, which will slow down
		3235	libev considerably.
		3236
		3237	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3238	C<0>.
		3239
2408	=item EV_COMMON	3240	=item EV_COMMON
2409		3241
2410	By default, all watchers have a C<void *data> member. By redefining	3242	By default, all watchers have a C<void *data> member. By redefining
2411	this macro to a something else you can include more and other types of	3243	this macro to a something else you can include more and other types of
2412	members. You have to define it each time you include one of the files,	3244	members. You have to define it each time you include one of the files,
2413	though, and it must be identical each time.	3245	though, and it must be identical each time.
2414		3246
2415	For example, the perl EV module uses something like this:	3247	For example, the perl EV module uses something like this:
2416		3248
2417	#define EV_COMMON \	3249	#define EV_COMMON \
2418	SV *self; /* contains this struct */ \	3250	SV *self; /* contains this struct */ \
2419	SV *cb_sv, *fh /* note no trailing ";" */	3251	SV *cb_sv, *fh /* note no trailing ";" */
2420		3252
2421	=item EV_CB_DECLARE (type)	3253	=item EV_CB_DECLARE (type)
2422		3254
2423	=item EV_CB_INVOKE (watcher, revents)	3255	=item EV_CB_INVOKE (watcher, revents)
2424		3256
2425	=item ev_set_cb (ev, cb)	3257	=item ev_set_cb (ev, cb)
2426		3258
2427	Can be used to change the callback member declaration in each watcher,	3259	Can be used to change the callback member declaration in each watcher,
2428	and the way callbacks are invoked and set. Must expand to a struct member	3260	and the way callbacks are invoked and set. Must expand to a struct member
2429	definition and a statement, respectively. See the F<ev.v> header file for	3261	definition and a statement, respectively. See the F<ev.h> header file for
2430	their default definitions. One possible use for overriding these is to	3262	their default definitions. One possible use for overriding these is to
2431	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3263	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2432	method calls instead of plain function calls in C++.	3264	method calls instead of plain function calls in C++.
		3265
		3266	=back
		3267
		3268	=head2 EXPORTED API SYMBOLS
		3269
		3270	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3271	exported symbols, you can use the provided F<Symbol.*> files which list
		3272	all public symbols, one per line:
		3273
		3274	Symbols.ev for libev proper
		3275	Symbols.event for the libevent emulation
		3276
		3277	This can also be used to rename all public symbols to avoid clashes with
		3278	multiple versions of libev linked together (which is obviously bad in
		3279	itself, but sometimes it is inconvenient to avoid this).
		3280
		3281	A sed command like this will create wrapper C<#define>'s that you need to
		3282	include before including F<ev.h>:
		3283
		3284	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3285
		3286	This would create a file F<wrap.h> which essentially looks like this:
		3287
		3288	#define ev_backend myprefix_ev_backend
		3289	#define ev_check_start myprefix_ev_check_start
		3290	#define ev_check_stop myprefix_ev_check_stop
		3291	...
2433		3292
2434	=head2 EXAMPLES	3293	=head2 EXAMPLES
2435		3294
2436	For a real-world example of a program the includes libev	3295	For a real-world example of a program the includes libev
2437	verbatim, you can have a look at the EV perl module	3296	verbatim, you can have a look at the EV perl module
…		…
2442	file.	3301	file.
2443		3302
2444	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3303	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2445	that everybody includes and which overrides some configure choices:	3304	that everybody includes and which overrides some configure choices:
2446		3305
2447	#define EV_MINIMAL 1	3306	#define EV_MINIMAL 1
2448	#define EV_USE_POLL 0	3307	#define EV_USE_POLL 0
2449	#define EV_MULTIPLICITY 0	3308	#define EV_MULTIPLICITY 0
2450	#define EV_PERIODIC_ENABLE 0	3309	#define EV_PERIODIC_ENABLE 0
2451	#define EV_STAT_ENABLE 0	3310	#define EV_STAT_ENABLE 0
2452	#define EV_FORK_ENABLE 0	3311	#define EV_FORK_ENABLE 0
2453	#define EV_CONFIG_H <config.h>	3312	#define EV_CONFIG_H <config.h>
2454	#define EV_MINPRI 0	3313	#define EV_MINPRI 0
2455	#define EV_MAXPRI 0	3314	#define EV_MAXPRI 0
2456		3315
2457	#include "ev++.h"	3316	#include "ev++.h"
2458		3317
2459	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3318	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2460		3319
2461	#include "ev_cpp.h"	3320	#include "ev_cpp.h"
2462	#include "ev.c"	3321	#include "ev.c"
2463		3322
		3323	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2464		3324
		3325	=head2 THREADS AND COROUTINES
		3326
		3327	=head3 THREADS
		3328
		3329	All libev functions are reentrant and thread-safe unless explicitly
		3330	documented otherwise, but libev implements no locking itself. This means
		3331	that you can use as many loops as you want in parallel, as long as there
		3332	are no concurrent calls into any libev function with the same loop
		3333	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3334	of course): libev guarantees that different event loops share no data
		3335	structures that need any locking.
		3336
		3337	Or to put it differently: calls with different loop parameters can be done
		3338	concurrently from multiple threads, calls with the same loop parameter
		3339	must be done serially (but can be done from different threads, as long as
		3340	only one thread ever is inside a call at any point in time, e.g. by using
		3341	a mutex per loop).
		3342
		3343	Specifically to support threads (and signal handlers), libev implements
		3344	so-called C<ev_async> watchers, which allow some limited form of
		3345	concurrency on the same event loop, namely waking it up "from the
		3346	outside".
		3347
		3348	If you want to know which design (one loop, locking, or multiple loops
		3349	without or something else still) is best for your problem, then I cannot
		3350	help you, but here is some generic advice:
		3351
		3352	=over 4
		3353
		3354	=item * most applications have a main thread: use the default libev loop
		3355	in that thread, or create a separate thread running only the default loop.
		3356
		3357	This helps integrating other libraries or software modules that use libev
		3358	themselves and don't care/know about threading.
		3359
		3360	=item * one loop per thread is usually a good model.
		3361
		3362	Doing this is almost never wrong, sometimes a better-performance model
		3363	exists, but it is always a good start.
		3364
		3365	=item * other models exist, such as the leader/follower pattern, where one
		3366	loop is handed through multiple threads in a kind of round-robin fashion.
		3367
		3368	Choosing a model is hard - look around, learn, know that usually you can do
		3369	better than you currently do :-)
		3370
		3371	=item * often you need to talk to some other thread which blocks in the
		3372	event loop.
		3373
		3374	C<ev_async> watchers can be used to wake them up from other threads safely
		3375	(or from signal contexts...).
		3376
		3377	An example use would be to communicate signals or other events that only
		3378	work in the default loop by registering the signal watcher with the
		3379	default loop and triggering an C<ev_async> watcher from the default loop
		3380	watcher callback into the event loop interested in the signal.
		3381
		3382	=back
		3383
		3384	=head3 COROUTINES
		3385
		3386	Libev is very accommodating to coroutines ("cooperative threads"):
		3387	libev fully supports nesting calls to its functions from different
		3388	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3389	different coroutines, and switch freely between both coroutines running the
		3390	loop, as long as you don't confuse yourself). The only exception is that
		3391	you must not do this from C<ev_periodic> reschedule callbacks.
		3392
		3393	Care has been taken to ensure that libev does not keep local state inside
		3394	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3395	they do not clal any callbacks.
		3396
		3397	=head2 COMPILER WARNINGS
		3398
		3399	Depending on your compiler and compiler settings, you might get no or a
		3400	lot of warnings when compiling libev code. Some people are apparently
		3401	scared by this.
		3402
		3403	However, these are unavoidable for many reasons. For one, each compiler
		3404	has different warnings, and each user has different tastes regarding
		3405	warning options. "Warn-free" code therefore cannot be a goal except when
		3406	targeting a specific compiler and compiler-version.
		3407
		3408	Another reason is that some compiler warnings require elaborate
		3409	workarounds, or other changes to the code that make it less clear and less
		3410	maintainable.
		3411
		3412	And of course, some compiler warnings are just plain stupid, or simply
		3413	wrong (because they don't actually warn about the condition their message
		3414	seems to warn about). For example, certain older gcc versions had some
		3415	warnings that resulted an extreme number of false positives. These have
		3416	been fixed, but some people still insist on making code warn-free with
		3417	such buggy versions.
		3418
		3419	While libev is written to generate as few warnings as possible,
		3420	"warn-free" code is not a goal, and it is recommended not to build libev
		3421	with any compiler warnings enabled unless you are prepared to cope with
		3422	them (e.g. by ignoring them). Remember that warnings are just that:
		3423	warnings, not errors, or proof of bugs.
		3424
		3425
		3426	=head2 VALGRIND
		3427
		3428	Valgrind has a special section here because it is a popular tool that is
		3429	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3430
		3431	If you think you found a bug (memory leak, uninitialised data access etc.)
		3432	in libev, then check twice: If valgrind reports something like:
		3433
		3434	==2274== definitely lost: 0 bytes in 0 blocks.
		3435	==2274== possibly lost: 0 bytes in 0 blocks.
		3436	==2274== still reachable: 256 bytes in 1 blocks.
		3437
		3438	Then there is no memory leak, just as memory accounted to global variables
		3439	is not a memleak - the memory is still being refernced, and didn't leak.
		3440
		3441	Similarly, under some circumstances, valgrind might report kernel bugs
		3442	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3443	although an acceptable workaround has been found here), or it might be
		3444	confused.
		3445
		3446	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3447	make it into some kind of religion.
		3448
		3449	If you are unsure about something, feel free to contact the mailing list
		3450	with the full valgrind report and an explanation on why you think this
		3451	is a bug in libev (best check the archives, too :). However, don't be
		3452	annoyed when you get a brisk "this is no bug" answer and take the chance
		3453	of learning how to interpret valgrind properly.
		3454
		3455	If you need, for some reason, empty reports from valgrind for your project
		3456	I suggest using suppression lists.
		3457
		3458
		3459	=head1 PORTABILITY NOTES
		3460
		3461	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3462
		3463	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3464	requires, and its I/O model is fundamentally incompatible with the POSIX
		3465	model. Libev still offers limited functionality on this platform in
		3466	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3467	descriptors. This only applies when using Win32 natively, not when using
		3468	e.g. cygwin.
		3469
		3470	Lifting these limitations would basically require the full
		3471	re-implementation of the I/O system. If you are into these kinds of
		3472	things, then note that glib does exactly that for you in a very portable
		3473	way (note also that glib is the slowest event library known to man).
		3474
		3475	There is no supported compilation method available on windows except
		3476	embedding it into other applications.
		3477
		3478	Not a libev limitation but worth mentioning: windows apparently doesn't
		3479	accept large writes: instead of resulting in a partial write, windows will
		3480	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3481	so make sure you only write small amounts into your sockets (less than a
		3482	megabyte seems safe, but this apparently depends on the amount of memory
		3483	available).
		3484
		3485	Due to the many, low, and arbitrary limits on the win32 platform and
		3486	the abysmal performance of winsockets, using a large number of sockets
		3487	is not recommended (and not reasonable). If your program needs to use
		3488	more than a hundred or so sockets, then likely it needs to use a totally
		3489	different implementation for windows, as libev offers the POSIX readiness
		3490	notification model, which cannot be implemented efficiently on windows
		3491	(Microsoft monopoly games).
		3492
		3493	A typical way to use libev under windows is to embed it (see the embedding
		3494	section for details) and use the following F<evwrap.h> header file instead
		3495	of F<ev.h>:
		3496
		3497	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3498	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3499
		3500	#include "ev.h"
		3501
		3502	And compile the following F<evwrap.c> file into your project (make sure
		3503	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3504
		3505	#include "evwrap.h"
		3506	#include "ev.c"
		3507
		3508	=over 4
		3509
		3510	=item The winsocket select function
		3511
		3512	The winsocket C<select> function doesn't follow POSIX in that it
		3513	requires socket I<handles> and not socket I<file descriptors> (it is
		3514	also extremely buggy). This makes select very inefficient, and also
		3515	requires a mapping from file descriptors to socket handles (the Microsoft
		3516	C runtime provides the function C<_open_osfhandle> for this). See the
		3517	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3518	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3519
		3520	The configuration for a "naked" win32 using the Microsoft runtime
		3521	libraries and raw winsocket select is:
		3522
		3523	#define EV_USE_SELECT 1
		3524	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3525
		3526	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3527	complexity in the O(n²) range when using win32.
		3528
		3529	=item Limited number of file descriptors
		3530
		3531	Windows has numerous arbitrary (and low) limits on things.
		3532
		3533	Early versions of winsocket's select only supported waiting for a maximum
		3534	of C<64> handles (probably owning to the fact that all windows kernels
		3535	can only wait for C<64> things at the same time internally; Microsoft
		3536	recommends spawning a chain of threads and wait for 63 handles and the
		3537	previous thread in each. Great).
		3538
		3539	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3540	to some high number (e.g. C<2048>) before compiling the winsocket select
		3541	call (which might be in libev or elsewhere, for example, perl does its own
		3542	select emulation on windows).
		3543
		3544	Another limit is the number of file descriptors in the Microsoft runtime
		3545	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3546	or something like this inside Microsoft). You can increase this by calling
		3547	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3548	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3549	libraries.
		3550
		3551	This might get you to about C<512> or C<2048> sockets (depending on
		3552	windows version and/or the phase of the moon). To get more, you need to
		3553	wrap all I/O functions and provide your own fd management, but the cost of
		3554	calling select (O(n²)) will likely make this unworkable.
		3555
		3556	=back
		3557
		3558	=head2 PORTABILITY REQUIREMENTS
		3559
		3560	In addition to a working ISO-C implementation and of course the
		3561	backend-specific APIs, libev relies on a few additional extensions:
		3562
		3563	=over 4
		3564
		3565	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3566	calling conventions regardless of C<ev_watcher_type *>.
		3567
		3568	Libev assumes not only that all watcher pointers have the same internal
		3569	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3570	assumes that the same (machine) code can be used to call any watcher
		3571	callback: The watcher callbacks have different type signatures, but libev
		3572	calls them using an C<ev_watcher *> internally.
		3573
		3574	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3575
		3576	The type C<sig_atomic_t volatile> (or whatever is defined as
		3577	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3578	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3579	believed to be sufficiently portable.
		3580
		3581	=item C<sigprocmask> must work in a threaded environment
		3582
		3583	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3584	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3585	pthread implementations will either allow C<sigprocmask> in the "main
		3586	thread" or will block signals process-wide, both behaviours would
		3587	be compatible with libev. Interaction between C<sigprocmask> and
		3588	C<pthread_sigmask> could complicate things, however.
		3589
		3590	The most portable way to handle signals is to block signals in all threads
		3591	except the initial one, and run the default loop in the initial thread as
		3592	well.
		3593
		3594	=item C<long> must be large enough for common memory allocation sizes
		3595
		3596	To improve portability and simplify its API, libev uses C<long> internally
		3597	instead of C<size_t> when allocating its data structures. On non-POSIX
		3598	systems (Microsoft...) this might be unexpectedly low, but is still at
		3599	least 31 bits everywhere, which is enough for hundreds of millions of
		3600	watchers.
		3601
		3602	=item C<double> must hold a time value in seconds with enough accuracy
		3603
		3604	The type C<double> is used to represent timestamps. It is required to
		3605	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3606	enough for at least into the year 4000. This requirement is fulfilled by
		3607	implementations implementing IEEE 754 (basically all existing ones).
		3608
		3609	=back
		3610
		3611	If you know of other additional requirements drop me a note.
		3612
		3613
2465	=head1 COMPLEXITIES	3614	=head1 ALGORITHMIC COMPLEXITIES
2466		3615
2467	In this section the complexities of (many of) the algorithms used inside	3616	In this section the complexities of (many of) the algorithms used inside
2468	libev will be explained. For complexity discussions about backends see the	3617	libev will be documented. For complexity discussions about backends see
2469	documentation for C<ev_default_init>.	3618	the documentation for C<ev_default_init>.
2470		3619
2471	All of the following are about amortised time: If an array needs to be	3620	All of the following are about amortised time: If an array needs to be
2472	extended, libev needs to realloc and move the whole array, but this	3621	extended, libev needs to realloc and move the whole array, but this
2473	happens asymptotically never with higher number of elements, so O(1) might	3622	happens asymptotically rarer with higher number of elements, so O(1) might
2474	mean it might do a lengthy realloc operation in rare cases, but on average	3623	mean that libev does a lengthy realloc operation in rare cases, but on
2475	it is much faster and asymptotically approaches constant time.	3624	average it is much faster and asymptotically approaches constant time.
2476		3625
2477	=over 4	3626	=over 4
2478		3627
2479	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3628	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2480		3629
2481	This means that, when you have a watcher that triggers in one hour and	3630	This means that, when you have a watcher that triggers in one hour and
2482	there are 100 watchers that would trigger before that then inserting will	3631	there are 100 watchers that would trigger before that, then inserting will
2483	have to skip those 100 watchers.	3632	have to skip roughly seven (C<ld 100>) of these watchers.
2484		3633
2485	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3634	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2486		3635
2487	That means that for changing a timer costs less than removing/adding them	3636	That means that changing a timer costs less than removing/adding them,
2488	as only the relative motion in the event queue has to be paid for.	3637	as only the relative motion in the event queue has to be paid for.
2489		3638
2490	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3639	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2491		3640
2492	These just add the watcher into an array or at the head of a list.	3641	These just add the watcher into an array or at the head of a list.
		3642
2493	=item Stopping check/prepare/idle watchers: O(1)	3643	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2494		3644
2495	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3645	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2496		3646
2497	These watchers are stored in lists then need to be walked to find the	3647	These watchers are stored in lists, so they need to be walked to find the
2498	correct watcher to remove. The lists are usually short (you don't usually	3648	correct watcher to remove. The lists are usually short (you don't usually
2499	have many watchers waiting for the same fd or signal).	3649	have many watchers waiting for the same fd or signal: one is typical, two
		3650	is rare).
2500		3651
2501	=item Finding the next timer per loop iteration: O(1)	3652	=item Finding the next timer in each loop iteration: O(1)
		3653
		3654	By virtue of using a binary or 4-heap, the next timer is always found at a
		3655	fixed position in the storage array.
2502		3656
2503	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3657	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2504		3658
2505	A change means an I/O watcher gets started or stopped, which requires	3659	A change means an I/O watcher gets started or stopped, which requires
2506	libev to recalculate its status (and possibly tell the kernel).	3660	libev to recalculate its status (and possibly tell the kernel, depending
		3661	on backend and whether C<ev_io_set> was used).
2507		3662
2508	=item Activating one watcher: O(1)	3663	=item Activating one watcher (putting it into the pending state): O(1)
2509		3664
2510	=item Priority handling: O(number_of_priorities)	3665	=item Priority handling: O(number_of_priorities)
2511		3666
2512	Priorities are implemented by allocating some space for each	3667	Priorities are implemented by allocating some space for each
2513	priority. When doing priority-based operations, libev usually has to	3668	priority. When doing priority-based operations, libev usually has to
2514	linearly search all the priorities.	3669	linearly search all the priorities, but starting/stopping and activating
		3670	watchers becomes O(1) with respect to priority handling.
		3671
		3672	=item Sending an ev_async: O(1)
		3673
		3674	=item Processing ev_async_send: O(number_of_async_watchers)
		3675
		3676	=item Processing signals: O(max_signal_number)
		3677
		3678	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3679	calls in the current loop iteration. Checking for async and signal events
		3680	involves iterating over all running async watchers or all signal numbers.
2515		3681
2516	=back	3682	=back
2517		3683
2518		3684
2519	=head1 AUTHOR	3685	=head1 AUTHOR

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