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Revision 1.67 by root, Fri Dec 7 16:44:12 2007 UTC vs.
Revision 1.194 by root, Mon Oct 20 16:08:36 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
		67	The newest version of this document is also available as an html-formatted
		68	web page you might find easier to navigate when reading it for the first
		69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		70
53	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
54	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
55	these event sources and provide your program with events.	73	these event sources and provide your program with events.
56		74
57	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
58	(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
59	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
61	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
62	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
63	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
64	watcher.	82	watcher.
65		83
66	=head1 FEATURES	84	=head2 FEATURES
67		85
68	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
69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70	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
71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
78		96
79	It also is quite fast (see this	97	It also is quite fast (see this
80	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
81	for example).	99	for example).
82		100
83	=head1 CONVENTIONS	101	=head2 CONVENTIONS
84		102
85	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
86	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
87	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
88	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
89	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
90	(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.
91		110
92	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
93		112
94	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	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
97	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
98	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
99	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
100		142
101	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
102		144
103	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
104	library in any way.	146	library in any way.
…		…
109		151
110	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
111	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
112	you actually want to know.	154	you actually want to know.
113		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 ()>.
		161
114	=item int ev_version_major ()	162	=item int ev_version_major ()
115		163
116	=item int ev_version_minor ()	164	=item int ev_version_minor ()
117		165
118	You can find out the major and minor version numbers of the library	166	You can find out the major and minor ABI version numbers of the library
119	you linked against by calling the functions C<ev_version_major> and	167	you linked against by calling the functions C<ev_version_major> and
120	C<ev_version_minor>. If you want, you can compare against the global	168	C<ev_version_minor>. If you want, you can compare against the global
121	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	169	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
122	version of the library your program was compiled against.	170	version of the library your program was compiled against.
123		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
124	Usually, it's a good idea to terminate if the major versions mismatch,	175	Usually, it's a good idea to terminate if the major versions mismatch,
125	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
126	compatible to older versions, so a larger minor version alone is usually	177	compatible to older versions, so a larger minor version alone is usually
127	not a problem.	178	not a problem.
128		179
129	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
130	version.	181	version.
131		182
132	assert (("libev version mismatch",	183	assert (("libev version mismatch",
133	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
134	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
135		186
136	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
137		188
138	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_*>
139	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
141	a description of the set values.	192	a description of the set values.
142		193
143	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
144	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
145		196
146	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
147	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
148		199
149	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
150		201
151	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
152	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
153	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
154	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
155	(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
156	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
157		208
158	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
159		210
…		…
163	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
164	recommended ones.	215	recommended ones.
165		216
166	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
167		218
168	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
169		220
170	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
171	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
172	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
173	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
174	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
175	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.
176		230
177	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
178	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,
179	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.
180		234
181	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
182	retries).	236	retries (example requires a standards-compliant C<realloc>).
183		237
184	static void *	238	static void *
185	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
186	{	240	{
187	for (;;)	241	for (;;)
…		…
196	}	250	}
197		251
198	...	252	...
199	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
200		254
201	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
202		256
203	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
204	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
205	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
206	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
207	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
208	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
209	(such as abort).	263	(such as abort).
210		264
211	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.
…		…
226		280
227	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
228	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
229	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
230		284
231	If you use threads, a common model is to run the default event loop
232	in your main thread (or in a separate thread) and for each thread you
233	create, you also create another event loop. Libev itself does no locking
234	whatsoever, so if you mix calls to the same event loop in different
235	threads, make sure you lock (this is usually a bad idea, though, even if
236	done correctly, because it's hideous and inefficient).
237
238	=over 4	285	=over 4
239		286
240	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
241		288
242	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
…		…
245	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
246		293
247	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
248	function.	295	function.
249		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
250	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
251	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>).
252		310
253	The following flags are supported:	311	The following flags are supported:
254		312
…		…
259	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
260	thing, believe me).	318	thing, believe me).
261		319
262	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
263		321
264	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
265	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
266	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
267	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
268	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
269	around bugs.	327	around bugs.
…		…
275	enabling this flag.	333	enabling this flag.
276		334
277	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,
278	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
279	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
280	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
281	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
282	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
283		341
284	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
285	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
286	flag.	344	flag.
287		345
288	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>
289	environment variable.	347	environment variable.
290		348
291	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
292		350
293	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
294	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,
295	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
296	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
297	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).
298		367
299	=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)
300		369
301	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
302	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
303	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
304	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>.
305		379
306	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
307		381
308	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,
309	but it scales phenomenally better. While poll and select usually scale like	383	but it scales phenomenally better. While poll and select usually scale
310	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),
311	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.
312		389
313	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
314	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
315	(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
316	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
317	well if you register events for both fds.	394	very well if you register events for both fds.
318		395
319	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
320	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
321	(or space) is available.	398	(or space) is available.
322		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
323	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
324		413
325	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
326	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
327	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
328	completely useless). For this reason its not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
329	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
330	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.
331		424
332	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
333	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
334	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
335	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
336	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>.
337		444
338	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
339		446
340	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.
341		451
342	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
343		453
344	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,
345	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)).
346		456
347	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
348	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
349	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>.
350		473
351	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
352		475
353	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
354	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
355	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
356		479
		480	It is definitely not recommended to use this flag.
		481
357	=back	482	=back
358		483
359	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
360	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
361	specified, most compiled-in backend will be tried, usually in reverse	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
362	order of their flag values :)
363		487
364	The most typical usage is like this:	488	Example: This is the most typical usage.
365		489
366	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
368		492
369	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
370	environment settings to be taken into account:	494	environment settings to be taken into account:
371		495
372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
373		497
374	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
375	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
376	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):
377		502
378	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
379		504
380	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
381		506
382	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
383	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
384	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
385	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
386		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
387	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.
388		517
389	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
390	if (!epoller)	519	if (!epoller)
391	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
392		521
393	=item ev_default_destroy ()	522	=item ev_default_destroy ()
394		523
395	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
396	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
397	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
398	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
399	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
400	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
401	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>).
402		540
403	=item ev_loop_destroy (loop)	541	=item ev_loop_destroy (loop)
404		542
405	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
406	earlier call to C<ev_loop_new>.	544	earlier call to C<ev_loop_new>.
407		545
408	=item ev_default_fork ()	546	=item ev_default_fork ()
409		547
		548	This function sets a flag that causes subsequent C<ev_loop> iterations
410	This function reinitialises the kernel state for backends that have	549	to reinitialise the kernel state for backends that have one. Despite the
411	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
412	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
413	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.
414		554
415	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
416	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
417	fork+exec, you don't have to call it.	557	you just fork+exec, you don't have to call it at all.
418		558
419	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
420	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
421	quite nicely into a call to C<pthread_atfork>:	561	quite nicely into a call to C<pthread_atfork>:
422		562
423	pthread_atfork (0, 0, ev_default_fork);	563	pthread_atfork (0, 0, ev_default_fork);
424		564
425	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
426	without calling this function, so if you force one of those backends you
427	do not need to care.
428
429	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
430		566
431	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
432	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
433	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.
434		576
435	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
436		578
437	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
438	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
…		…
451		593
452	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
453	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
454	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
455	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
456	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.
457		611
458	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
459		613
460	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
461	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
…		…
464	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
465	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.
466		620
467	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
468	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
469	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
470	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
471	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.
472		627
473	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
474	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
475	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.
476		632
477	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
478	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
479	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
480	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
481	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
482	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
483	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
484		644
485	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
486		646
487	* If there are no active watchers (reference count is zero), return.	647	- Before the first iteration, call any pending watchers.
488	- Queue prepare watchers and then call all outstanding watchers.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
		649	- If a fork was detected (by any means), queue and call all fork watchers.
		650	- Queue and call all prepare watchers.
489	- 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.
490	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
491	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
492	- 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.
493	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
494	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
495	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
496	- Queue all outstanding timers.	662	- Queue all expired timers.
497	- Queue all outstanding periodics.	663	- Queue all expired periodics.
498	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
499	- Queue all check watchers.	665	- Queue all check watchers.
500	- 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).
501	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
502	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
503	- 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
504	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
505		672
506	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
507	anymore.	674	anymore.
508		675
509	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
510	... 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..)
511	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
512	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
513		680
514	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
515		682
516	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
517	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
518	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
519	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.
520		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
521	=item ev_ref (loop)	692	=item ev_ref (loop)
522		693
523	=item ev_unref (loop)	694	=item ev_unref (loop)
524		695
525	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
526	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
527	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
528	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>
529	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
530	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
531	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
532	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
533	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
534	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).
535		711
536	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>
537	running when nothing else is active.	713	running when nothing else is active.
538		714
539	struct ev_signal exitsig;	715	struct ev_signal exitsig;
540	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
541	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
542	evf_unref (loop);	718	evf_unref (loop);
543		719
544	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
545		721
546	ev_ref (loop);	722	ev_ref (loop);
547	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.
548		781
549	=back	782	=back
550		783
551		784
552	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
553		786
554	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
555	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
556	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:
557		790
558	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)
559	{	792	{
560	ev_io_stop (w);	793	ev_io_stop (w);
561	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
562	}	795	}
563		796
564	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
565	struct ev_io stdin_watcher;	798	struct ev_io stdin_watcher;
566	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
567	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
568	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
569	ev_loop (loop, 0);	802	ev_loop (loop, 0);
570		803
571	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
572	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,
573	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
574		807
575	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
576	(watcher *, callback)>, which expects a callback to be provided. This	809	(watcher *, callback)>, which expects a callback to be provided. This
577	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
578	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
579	is readable and/or writable).	812	is readable and/or writable).
580		813
581	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
582	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
…		…
652	=item C<EV_FORK>	885	=item C<EV_FORK>
653		886
654	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
655	C<ev_fork>).	888	C<ev_fork>).
656		889
		890	=item C<EV_ASYNC>
		891
		892	The given async watcher has been asynchronously notified (see C<ev_async>).
		893
657	=item C<EV_ERROR>	894	=item C<EV_ERROR>
658		895
659	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
660	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
661	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
662	problem. You best act on it by reporting the problem and somehow coping	899	problem. You best act on it by reporting the problem and somehow coping
663	with the watcher being stopped.	900	with the watcher being stopped.
664		901
665	Libev will usually signal a few "dummy" events together with an error,	902	Libev will usually signal a few "dummy" events together with an error, for
666	for example it might indicate that a fd is readable or writable, and if	903	example it might indicate that a fd is readable or writable, and if your
667	your callbacks is well-written it can just attempt the operation and cope	904	callbacks is well-written it can just attempt the operation and cope with
668	with the error from read() or write(). This will not work in multithreaded	905	the error from read() or write(). This will not work in multi-threaded
669	programs, though, so beware.	906	programs, though, as the fd could already be closed and reused for another
		907	thing, so beware.
670		908
671	=back	909	=back
672		910
673	=head2 GENERIC WATCHER FUNCTIONS	911	=head2 GENERIC WATCHER FUNCTIONS
674		912
…		…
690	(or never started) and there are no pending events outstanding.	928	(or never started) and there are no pending events outstanding.
691		929
692	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
693	int revents)>.	931	int revents)>.
694		932
		933	Example: Initialise an C<ev_io> watcher in two steps.
		934
		935	ev_io w;
		936	ev_init (&w, my_cb);
		937	ev_io_set (&w, STDIN_FILENO, EV_READ);
		938
695	=item C<ev_TYPE_set> (ev_TYPE *, [args])	939	=item C<ev_TYPE_set> (ev_TYPE *, [args])
696		940
697	This macro initialises the type-specific parts of a watcher. You need to	941	This macro initialises the type-specific parts of a watcher. You need to
698	call C<ev_init> at least once before you call this macro, but you can	942	call C<ev_init> at least once before you call this macro, but you can
699	call C<ev_TYPE_set> any number of times. You must not, however, call this	943	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
701	difference to the C<ev_init> macro).	945	difference to the C<ev_init> macro).
702		946
703	Although some watcher types do not have type-specific arguments	947	Although some watcher types do not have type-specific arguments
704	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	948	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
705		949
		950	See C<ev_init>, above, for an example.
		951
706	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	952	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
707		953
708	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	954	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
709	calls into a single call. This is the most convinient method to initialise	955	calls into a single call. This is the most convenient method to initialise
710	a watcher. The same limitations apply, of course.	956	a watcher. The same limitations apply, of course.
		957
		958	Example: Initialise and set an C<ev_io> watcher in one step.
		959
		960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
711		961
712	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
713		963
714	Starts (activates) the given watcher. Only active watchers will receive	964	Starts (activates) the given watcher. Only active watchers will receive
715	events. If the watcher is already active nothing will happen.	965	events. If the watcher is already active nothing will happen.
		966
		967	Example: Start the C<ev_io> watcher that is being abused as example in this
		968	whole section.
		969
		970	ev_io_start (EV_DEFAULT_UC, &w);
716		971
717	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
718		973
719	Stops the given watcher again (if active) and clears the pending	974	Stops the given watcher again (if active) and clears the pending
720	status. It is possible that stopped watchers are pending (for example,	975	status. It is possible that stopped watchers are pending (for example,
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	987	=item bool ev_is_pending (ev_TYPE *watcher)
733		988
734	Returns a true value iff the watcher is pending, (i.e. it has outstanding	989	Returns a true value iff the watcher is pending, (i.e. it has outstanding
735	events but its callback has not yet been invoked). As long as a watcher	990	events but its callback has not yet been invoked). As long as a watcher
736	is pending (but not active) you must not call an init function on it (but	991	is pending (but not active) you must not call an init function on it (but
737	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	992	C<ev_TYPE_set> is safe), you must not change its priority, and you must
738	libev (e.g. you cnanot C<free ()> it).	993	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		994	it).
739		995
740	=item callback ev_cb (ev_TYPE *watcher)	996	=item callback ev_cb (ev_TYPE *watcher)
741		997
742	Returns the callback currently set on the watcher.	998	Returns the callback currently set on the watcher.
743		999
…		…
762	watchers on the same event and make sure one is called first.	1018	watchers on the same event and make sure one is called first.
763		1019
764	If you need to suppress invocation when higher priority events are pending	1020	If you need to suppress invocation when higher priority events are pending
765	you need to look at C<ev_idle> watchers, which provide this functionality.	1021	you need to look at C<ev_idle> watchers, which provide this functionality.
766		1022
		1023	You I<must not> change the priority of a watcher as long as it is active or
		1024	pending.
		1025
767	The default priority used by watchers when no priority has been set is	1026	The default priority used by watchers when no priority has been set is
768	always C<0>, which is supposed to not be too high and not be too low :).	1027	always C<0>, which is supposed to not be too high and not be too low :).
769		1028
770	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1029	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
771	fine, as long as you do not mind that the priority value you query might	1030	fine, as long as you do not mind that the priority value you query might
772	or might not have been adjusted to be within valid range.	1031	or might not have been adjusted to be within valid range.
773		1032
		1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1034
		1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1036	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1037	can deal with that fact, as both are simply passed through to the
		1038	callback.
		1039
		1040	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1041
		1042	If the watcher is pending, this function clears its pending status and
		1043	returns its C<revents> bitset (as if its callback was invoked). If the
		1044	watcher isn't pending it does nothing and returns C<0>.
		1045
		1046	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1047	callback to be invoked, which can be accomplished with this function.
		1048
774	=back	1049	=back
775		1050
776		1051
777	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1052	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
778		1053
779	Each watcher has, by default, a member C<void *data> that you can change	1054	Each watcher has, by default, a member C<void *data> that you can change
780	and read at any time, libev will completely ignore it. This can be used	1055	and read at any time: libev will completely ignore it. This can be used
781	to associate arbitrary data with your watcher. If you need more data and	1056	to associate arbitrary data with your watcher. If you need more data and
782	don't want to allocate memory and store a pointer to it in that data	1057	don't want to allocate memory and store a pointer to it in that data
783	member, you can also "subclass" the watcher type and provide your own	1058	member, you can also "subclass" the watcher type and provide your own
784	data:	1059	data:
785		1060
786	struct my_io	1061	struct my_io
787	{	1062	{
788	struct ev_io io;	1063	struct ev_io io;
789	int otherfd;	1064	int otherfd;
790	void *somedata;	1065	void *somedata;
791	struct whatever *mostinteresting;	1066	struct whatever *mostinteresting;
792	}	1067	};
		1068
		1069	...
		1070	struct my_io w;
		1071	ev_io_init (&w.io, my_cb, fd, EV_READ);
793		1072
794	And since your callback will be called with a pointer to the watcher, you	1073	And since your callback will be called with a pointer to the watcher, you
795	can cast it back to your own type:	1074	can cast it back to your own type:
796		1075
797	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1076	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
798	{	1077	{
799	struct my_io *w = (struct my_io *)w_;	1078	struct my_io *w = (struct my_io *)w_;
800	...	1079	...
801	}	1080	}
802		1081
803	More interesting and less C-conformant ways of casting your callback type	1082	More interesting and less C-conformant ways of casting your callback type
804	instead have been omitted.	1083	instead have been omitted.
805		1084
806	Another common scenario is having some data structure with multiple	1085	Another common scenario is to use some data structure with multiple
807	watchers:	1086	embedded watchers:
808		1087
809	struct my_biggy	1088	struct my_biggy
810	{	1089	{
811	int some_data;	1090	int some_data;
812	ev_timer t1;	1091	ev_timer t1;
813	ev_timer t2;	1092	ev_timer t2;
814	}	1093	}
815		1094
816	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1095	In this case getting the pointer to C<my_biggy> is a bit more
817	you need to use C<offsetof>:	1096	complicated: Either you store the address of your C<my_biggy> struct
		1097	in the C<data> member of the watcher (for woozies), or you need to use
		1098	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1099	programmers):
818		1100
819	#include <stddef.h>	1101	#include <stddef.h>
820		1102
821	static void	1103	static void
822	t1_cb (EV_P_ struct ev_timer *w, int revents)	1104	t1_cb (EV_P_ struct ev_timer *w, int revents)
823	{	1105	{
824	struct my_biggy big = (struct my_biggy *	1106	struct my_biggy big = (struct my_biggy *
825	(((char *)w) - offsetof (struct my_biggy, t1));	1107	(((char *)w) - offsetof (struct my_biggy, t1));
826	}	1108	}
827		1109
828	static void	1110	static void
829	t2_cb (EV_P_ struct ev_timer *w, int revents)	1111	t2_cb (EV_P_ struct ev_timer *w, int revents)
830	{	1112	{
831	struct my_biggy big = (struct my_biggy *	1113	struct my_biggy big = (struct my_biggy *
832	(((char *)w) - offsetof (struct my_biggy, t2));	1114	(((char *)w) - offsetof (struct my_biggy, t2));
833	}	1115	}
834		1116
835		1117
836	=head1 WATCHER TYPES	1118	=head1 WATCHER TYPES
837		1119
838	This section describes each watcher in detail, but will not repeat	1120	This section describes each watcher in detail, but will not repeat
…		…
862	In general you can register as many read and/or write event watchers per	1144	In general you can register as many read and/or write event watchers per
863	fd as you want (as long as you don't confuse yourself). Setting all file	1145	fd as you want (as long as you don't confuse yourself). Setting all file
864	descriptors to non-blocking mode is also usually a good idea (but not	1146	descriptors to non-blocking mode is also usually a good idea (but not
865	required if you know what you are doing).	1147	required if you know what you are doing).
866		1148
867	You have to be careful with dup'ed file descriptors, though. Some backends	1149	If you cannot use non-blocking mode, then force the use of a
868	(the linux epoll backend is a notable example) cannot handle dup'ed file	1150	known-to-be-good backend (at the time of this writing, this includes only
869	descriptors correctly if you register interest in two or more fds pointing	1151	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
870	to the same underlying file/socket/etc. description (that is, they share
871	the same underlying "file open").
872
873	If you must do this, then force the use of a known-to-be-good backend
874	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
875	C<EVBACKEND_POLL>).
876		1152
877	Another thing you have to watch out for is that it is quite easy to	1153	Another thing you have to watch out for is that it is quite easy to
878	receive "spurious" readyness notifications, that is your callback might	1154	receive "spurious" readiness notifications, that is your callback might
879	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1155	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
880	because there is no data. Not only are some backends known to create a	1156	because there is no data. Not only are some backends known to create a
881	lot of those (for example solaris ports), it is very easy to get into	1157	lot of those (for example Solaris ports), it is very easy to get into
882	this situation even with a relatively standard program structure. Thus	1158	this situation even with a relatively standard program structure. Thus
883	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1159	it is best to always use non-blocking I/O: An extra C<read>(2) returning
884	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1160	C<EAGAIN> is far preferable to a program hanging until some data arrives.
885		1161
886	If you cannot run the fd in non-blocking mode (for example you should not	1162	If you cannot run the fd in non-blocking mode (for example you should
887	play around with an Xlib connection), then you have to seperately re-test	1163	not play around with an Xlib connection), then you have to separately
888	wether a file descriptor is really ready with a known-to-be good interface	1164	re-test whether a file descriptor is really ready with a known-to-be good
889	such as poll (fortunately in our Xlib example, Xlib already does this on	1165	interface such as poll (fortunately in our Xlib example, Xlib already
890	its own, so its quite safe to use).	1166	does this on its own, so its quite safe to use). Some people additionally
		1167	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1168	indefinitely.
		1169
		1170	But really, best use non-blocking mode.
		1171
		1172	=head3 The special problem of disappearing file descriptors
		1173
		1174	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1175	descriptor (either due to calling C<close> explicitly or any other means,
		1176	such as C<dup2>). The reason is that you register interest in some file
		1177	descriptor, but when it goes away, the operating system will silently drop
		1178	this interest. If another file descriptor with the same number then is
		1179	registered with libev, there is no efficient way to see that this is, in
		1180	fact, a different file descriptor.
		1181
		1182	To avoid having to explicitly tell libev about such cases, libev follows
		1183	the following policy: Each time C<ev_io_set> is being called, libev
		1184	will assume that this is potentially a new file descriptor, otherwise
		1185	it is assumed that the file descriptor stays the same. That means that
		1186	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1187	descriptor even if the file descriptor number itself did not change.
		1188
		1189	This is how one would do it normally anyway, the important point is that
		1190	the libev application should not optimise around libev but should leave
		1191	optimisations to libev.
		1192
		1193	=head3 The special problem of dup'ed file descriptors
		1194
		1195	Some backends (e.g. epoll), cannot register events for file descriptors,
		1196	but only events for the underlying file descriptions. That means when you
		1197	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1198	events for them, only one file descriptor might actually receive events.
		1199
		1200	There is no workaround possible except not registering events
		1201	for potentially C<dup ()>'ed file descriptors, or to resort to
		1202	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1203
		1204	=head3 The special problem of fork
		1205
		1206	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1207	useless behaviour. Libev fully supports fork, but needs to be told about
		1208	it in the child.
		1209
		1210	To support fork in your programs, you either have to call
		1211	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1212	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1213	C<EVBACKEND_POLL>.
		1214
		1215	=head3 The special problem of SIGPIPE
		1216
		1217	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1218	when writing to a pipe whose other end has been closed, your program gets
		1219	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1220	this is sensible behaviour, for daemons, this is usually undesirable.
		1221
		1222	So when you encounter spurious, unexplained daemon exits, make sure you
		1223	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1224	somewhere, as that would have given you a big clue).
		1225
		1226
		1227	=head3 Watcher-Specific Functions
891		1228
892	=over 4	1229	=over 4
893		1230
894	=item ev_io_init (ev_io *, callback, int fd, int events)	1231	=item ev_io_init (ev_io *, callback, int fd, int events)
895		1232
896	=item ev_io_set (ev_io *, int fd, int events)	1233	=item ev_io_set (ev_io *, int fd, int events)
897		1234
898	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1235	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
899	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1236	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
900	C<EV_READ | EV_WRITE> to receive the given events.	1237	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
901		1238
902	=item int fd [read-only]	1239	=item int fd [read-only]
903		1240
904	The file descriptor being watched.	1241	The file descriptor being watched.
905		1242
906	=item int events [read-only]	1243	=item int events [read-only]
907		1244
908	The events being watched.	1245	The events being watched.
909		1246
910	=back	1247	=back
		1248
		1249	=head3 Examples
911		1250
912	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1251	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
913	readable, but only once. Since it is likely line-buffered, you could	1252	readable, but only once. Since it is likely line-buffered, you could
914	attempt to read a whole line in the callback.	1253	attempt to read a whole line in the callback.
915		1254
916	static void	1255	static void
917	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1256	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
918	{	1257	{
919	ev_io_stop (loop, w);	1258	ev_io_stop (loop, w);
920	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1259	.. read from stdin here (or from w->fd) and handle any I/O errors
921	}	1260	}
922		1261
923	...	1262	...
924	struct ev_loop *loop = ev_default_init (0);	1263	struct ev_loop *loop = ev_default_init (0);
925	struct ev_io stdin_readable;	1264	struct ev_io stdin_readable;
926	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1265	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
927	ev_io_start (loop, &stdin_readable);	1266	ev_io_start (loop, &stdin_readable);
928	ev_loop (loop, 0);	1267	ev_loop (loop, 0);
929		1268
930		1269
931	=head2 C<ev_timer> - relative and optionally repeating timeouts	1270	=head2 C<ev_timer> - relative and optionally repeating timeouts
932		1271
933	Timer watchers are simple relative timers that generate an event after a	1272	Timer watchers are simple relative timers that generate an event after a
934	given time, and optionally repeating in regular intervals after that.	1273	given time, and optionally repeating in regular intervals after that.
935		1274
936	The timers are based on real time, that is, if you register an event that	1275	The timers are based on real time, that is, if you register an event that
937	times out after an hour and you reset your system clock to last years	1276	times out after an hour and you reset your system clock to January last
938	time, it will still time out after (roughly) and hour. "Roughly" because	1277	year, it will still time out after (roughly) one hour. "Roughly" because
939	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1278	detecting time jumps is hard, and some inaccuracies are unavoidable (the
940	monotonic clock option helps a lot here).	1279	monotonic clock option helps a lot here).
		1280
		1281	The callback is guaranteed to be invoked only I<after> its timeout has
		1282	passed, but if multiple timers become ready during the same loop iteration
		1283	then order of execution is undefined.
		1284
		1285	=head3 The special problem of time updates
		1286
		1287	Establishing the current time is a costly operation (it usually takes at
		1288	least two system calls): EV therefore updates its idea of the current
		1289	time only before and after C<ev_loop> collects new events, which causes a
		1290	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1291	lots of events in one iteration.
941		1292
942	The relative timeouts are calculated relative to the C<ev_now ()>	1293	The relative timeouts are calculated relative to the C<ev_now ()>
943	time. This is usually the right thing as this timestamp refers to the time	1294	time. This is usually the right thing as this timestamp refers to the time
944	of the event triggering whatever timeout you are modifying/starting. If	1295	of the event triggering whatever timeout you are modifying/starting. If
945	you suspect event processing to be delayed and you I<need> to base the timeout	1296	you suspect event processing to be delayed and you I<need> to base the
946	on the current time, use something like this to adjust for this:	1297	timeout on the current time, use something like this to adjust for this:
947		1298
948	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1299	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
949		1300
950	The callback is guarenteed to be invoked only when its timeout has passed,	1301	If the event loop is suspended for a long time, you can also force an
951	but if multiple timers become ready during the same loop iteration then	1302	update of the time returned by C<ev_now ()> by calling C<ev_now_update
952	order of execution is undefined.	1303	()>.
		1304
		1305	=head3 Watcher-Specific Functions and Data Members
953		1306
954	=over 4	1307	=over 4
955		1308
956	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1309	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
957		1310
958	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1311	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
959		1312
960	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1313	Configure the timer to trigger after C<after> seconds. If C<repeat>
961	C<0.>, then it will automatically be stopped. If it is positive, then the	1314	is C<0.>, then it will automatically be stopped once the timeout is
962	timer will automatically be configured to trigger again C<repeat> seconds	1315	reached. If it is positive, then the timer will automatically be
963	later, again, and again, until stopped manually.	1316	configured to trigger again C<repeat> seconds later, again, and again,
		1317	until stopped manually.
964		1318
965	The timer itself will do a best-effort at avoiding drift, that is, if you	1319	The timer itself will do a best-effort at avoiding drift, that is, if
966	configure a timer to trigger every 10 seconds, then it will trigger at	1320	you configure a timer to trigger every 10 seconds, then it will normally
967	exactly 10 second intervals. If, however, your program cannot keep up with	1321	trigger at exactly 10 second intervals. If, however, your program cannot
968	the timer (because it takes longer than those 10 seconds to do stuff) the	1322	keep up with the timer (because it takes longer than those 10 seconds to
969	timer will not fire more than once per event loop iteration.	1323	do stuff) the timer will not fire more than once per event loop iteration.
970		1324
971	=item ev_timer_again (loop)	1325	=item ev_timer_again (loop, ev_timer *)
972		1326
973	This will act as if the timer timed out and restart it again if it is	1327	This will act as if the timer timed out and restart it again if it is
974	repeating. The exact semantics are:	1328	repeating. The exact semantics are:
975		1329
976	If the timer is pending, its pending status is cleared.	1330	If the timer is pending, its pending status is cleared.
977		1331
978	If the timer is started but nonrepeating, stop it (as if it timed out).	1332	If the timer is started but non-repeating, stop it (as if it timed out).
979		1333
980	If the timer is repeating, either start it if necessary (with the	1334	If the timer is repeating, either start it if necessary (with the
981	C<repeat> value), or reset the running timer to the C<repeat> value.	1335	C<repeat> value), or reset the running timer to the C<repeat> value.
982		1336
983	This sounds a bit complicated, but here is a useful and typical	1337	This sounds a bit complicated, but here is a useful and typical
984	example: Imagine you have a tcp connection and you want a so-called idle	1338	example: Imagine you have a TCP connection and you want a so-called idle
985	timeout, that is, you want to be called when there have been, say, 60	1339	timeout, that is, you want to be called when there have been, say, 60
986	seconds of inactivity on the socket. The easiest way to do this is to	1340	seconds of inactivity on the socket. The easiest way to do this is to
987	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1341	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
988	C<ev_timer_again> each time you successfully read or write some data. If	1342	C<ev_timer_again> each time you successfully read or write some data. If
989	you go into an idle state where you do not expect data to travel on the	1343	you go into an idle state where you do not expect data to travel on the
…		…
1003	ev_timer_again (loop, timer);	1357	ev_timer_again (loop, timer);
1004		1358
1005	This is more slightly efficient then stopping/starting the timer each time	1359	This is more slightly efficient then stopping/starting the timer each time
1006	you want to modify its timeout value.	1360	you want to modify its timeout value.
1007		1361
		1362	Note, however, that it is often even more efficient to remember the
		1363	time of the last activity and let the timer time-out naturally. In the
		1364	callback, you then check whether the time-out is real, or, if there was
		1365	some activity, you reschedule the watcher to time-out in "last_activity +
		1366	timeout - ev_now ()" seconds.
		1367
1008	=item ev_tstamp repeat [read-write]	1368	=item ev_tstamp repeat [read-write]
1009		1369
1010	The current C<repeat> value. Will be used each time the watcher times out	1370	The current C<repeat> value. Will be used each time the watcher times out
1011	or C<ev_timer_again> is called and determines the next timeout (if any),	1371	or C<ev_timer_again> is called, and determines the next timeout (if any),
1012	which is also when any modifications are taken into account.	1372	which is also when any modifications are taken into account.
1013		1373
1014	=back	1374	=back
1015		1375
		1376	=head3 Examples
		1377
1016	Example: Create a timer that fires after 60 seconds.	1378	Example: Create a timer that fires after 60 seconds.
1017		1379
1018	static void	1380	static void
1019	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1381	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1020	{	1382	{
1021	.. one minute over, w is actually stopped right here	1383	.. one minute over, w is actually stopped right here
1022	}	1384	}
1023		1385
1024	struct ev_timer mytimer;	1386	struct ev_timer mytimer;
1025	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1387	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1026	ev_timer_start (loop, &mytimer);	1388	ev_timer_start (loop, &mytimer);
1027		1389
1028	Example: Create a timeout timer that times out after 10 seconds of	1390	Example: Create a timeout timer that times out after 10 seconds of
1029	inactivity.	1391	inactivity.
1030		1392
1031	static void	1393	static void
1032	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1394	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1033	{	1395	{
1034	.. ten seconds without any activity	1396	.. ten seconds without any activity
1035	}	1397	}
1036		1398
1037	struct ev_timer mytimer;	1399	struct ev_timer mytimer;
1038	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1400	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1039	ev_timer_again (&mytimer); /* start timer */	1401	ev_timer_again (&mytimer); /* start timer */
1040	ev_loop (loop, 0);	1402	ev_loop (loop, 0);
1041		1403
1042	// and in some piece of code that gets executed on any "activity":	1404	// and in some piece of code that gets executed on any "activity":
1043	// reset the timeout to start ticking again at 10 seconds	1405	// reset the timeout to start ticking again at 10 seconds
1044	ev_timer_again (&mytimer);	1406	ev_timer_again (&mytimer);
1045		1407
1046		1408
1047	=head2 C<ev_periodic> - to cron or not to cron?	1409	=head2 C<ev_periodic> - to cron or not to cron?
1048		1410
1049	Periodic watchers are also timers of a kind, but they are very versatile	1411	Periodic watchers are also timers of a kind, but they are very versatile
1050	(and unfortunately a bit complex).	1412	(and unfortunately a bit complex).
1051		1413
1052	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1414	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1053	but on wallclock time (absolute time). You can tell a periodic watcher	1415	but on wall clock time (absolute time). You can tell a periodic watcher
1054	to trigger "at" some specific point in time. For example, if you tell a	1416	to trigger after some specific point in time. For example, if you tell a
1055	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1417	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1056	+ 10.>) and then reset your system clock to the last year, then it will	1418	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1419	clock to January of the previous year, then it will take more than year
1057	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1420	to trigger the event (unlike an C<ev_timer>, which would still trigger
1058	roughly 10 seconds later and of course not if you reset your system time	1421	roughly 10 seconds later as it uses a relative timeout).
1059	again).
1060		1422
1061	They can also be used to implement vastly more complex timers, such as	1423	C<ev_periodic>s can also be used to implement vastly more complex timers,
1062	triggering an event on eahc midnight, local time.	1424	such as triggering an event on each "midnight, local time", or other
		1425	complicated rules.
1063		1426
1064	As with timers, the callback is guarenteed to be invoked only when the	1427	As with timers, the callback is guaranteed to be invoked only when the
1065	time (C<at>) has been passed, but if multiple periodic timers become ready	1428	time (C<at>) has passed, but if multiple periodic timers become ready
1066	during the same loop iteration then order of execution is undefined.	1429	during the same loop iteration, then order of execution is undefined.
		1430
		1431	=head3 Watcher-Specific Functions and Data Members
1067		1432
1068	=over 4	1433	=over 4
1069		1434
1070	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1435	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1071		1436
1072	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1437	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1073		1438
1074	Lots of arguments, lets sort it out... There are basically three modes of	1439	Lots of arguments, lets sort it out... There are basically three modes of
1075	operation, and we will explain them from simplest to complex:	1440	operation, and we will explain them from simplest to most complex:
1076		1441
1077	=over 4	1442	=over 4
1078		1443
1079	=item * absolute timer (interval = reschedule_cb = 0)	1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1080		1445
1081	In this configuration the watcher triggers an event at the wallclock time	1446	In this configuration the watcher triggers an event after the wall clock
1082	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1447	time C<at> has passed. It will not repeat and will not adjust when a time
1083	that is, if it is to be run at January 1st 2011 then it will run when the	1448	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1084	system time reaches or surpasses this time.	1449	only run when the system clock reaches or surpasses this time.
1085		1450
1086	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1087		1452
1088	In this mode the watcher will always be scheduled to time out at the next	1453	In this mode the watcher will always be scheduled to time out at the next
1089	C<at + N * interval> time (for some integer N) and then repeat, regardless	1454	C<at + N * interval> time (for some integer N, which can also be negative)
1090	of any time jumps.	1455	and then repeat, regardless of any time jumps.
1091		1456
1092	This can be used to create timers that do not drift with respect to system	1457	This can be used to create timers that do not drift with respect to the
1093	time:	1458	system clock, for example, here is a C<ev_periodic> that triggers each
		1459	hour, on the hour:
1094		1460
1095	ev_periodic_set (&periodic, 0., 3600., 0);	1461	ev_periodic_set (&periodic, 0., 3600., 0);
1096		1462
1097	This doesn't mean there will always be 3600 seconds in between triggers,	1463	This doesn't mean there will always be 3600 seconds in between triggers,
1098	but only that the the callback will be called when the system time shows a	1464	but only that the callback will be called when the system time shows a
1099	full hour (UTC), or more correctly, when the system time is evenly divisible	1465	full hour (UTC), or more correctly, when the system time is evenly divisible
1100	by 3600.	1466	by 3600.
1101		1467
1102	Another way to think about it (for the mathematically inclined) is that	1468	Another way to think about it (for the mathematically inclined) is that
1103	C<ev_periodic> will try to run the callback in this mode at the next possible	1469	C<ev_periodic> will try to run the callback in this mode at the next possible
1104	time where C<time = at (mod interval)>, regardless of any time jumps.	1470	time where C<time = at (mod interval)>, regardless of any time jumps.
1105		1471
		1472	For numerical stability it is preferable that the C<at> value is near
		1473	C<ev_now ()> (the current time), but there is no range requirement for
		1474	this value, and in fact is often specified as zero.
		1475
		1476	Note also that there is an upper limit to how often a timer can fire (CPU
		1477	speed for example), so if C<interval> is very small then timing stability
		1478	will of course deteriorate. Libev itself tries to be exact to be about one
		1479	millisecond (if the OS supports it and the machine is fast enough).
		1480
1106	=item * manual reschedule mode (reschedule_cb = callback)	1481	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1107		1482
1108	In this mode the values for C<interval> and C<at> are both being	1483	In this mode the values for C<interval> and C<at> are both being
1109	ignored. Instead, each time the periodic watcher gets scheduled, the	1484	ignored. Instead, each time the periodic watcher gets scheduled, the
1110	reschedule callback will be called with the watcher as first, and the	1485	reschedule callback will be called with the watcher as first, and the
1111	current time as second argument.	1486	current time as second argument.
1112		1487
1113	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1488	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1114	ever, or make any event loop modifications>. If you need to stop it,	1489	ever, or make ANY event loop modifications whatsoever>.
1115	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1116	starting a prepare watcher).
1117		1490
		1491	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1492	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1493	only event loop modification you are allowed to do).
		1494
1118	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1495	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1119	ev_tstamp now)>, e.g.:	1496	*w, ev_tstamp now)>, e.g.:
1120		1497
1121	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1498	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1122	{	1499	{
1123	return now + 60.;	1500	return now + 60.;
1124	}	1501	}
…		…
1126	It must return the next time to trigger, based on the passed time value	1503	It must return the next time to trigger, based on the passed time value
1127	(that is, the lowest time value larger than to the second argument). It	1504	(that is, the lowest time value larger than to the second argument). It
1128	will usually be called just before the callback will be triggered, but	1505	will usually be called just before the callback will be triggered, but
1129	might be called at other times, too.	1506	might be called at other times, too.
1130		1507
1131	NOTE: I<< This callback must always return a time that is later than the	1508	NOTE: I<< This callback must always return a time that is higher than or
1132	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1509	equal to the passed C<now> value >>.
1133		1510
1134	This can be used to create very complex timers, such as a timer that	1511	This can be used to create very complex timers, such as a timer that
1135	triggers on each midnight, local time. To do this, you would calculate the	1512	triggers on "next midnight, local time". To do this, you would calculate the
1136	next midnight after C<now> and return the timestamp value for this. How	1513	next midnight after C<now> and return the timestamp value for this. How
1137	you do this is, again, up to you (but it is not trivial, which is the main	1514	you do this is, again, up to you (but it is not trivial, which is the main
1138	reason I omitted it as an example).	1515	reason I omitted it as an example).
1139		1516
1140	=back	1517	=back
…		…
1144	Simply stops and restarts the periodic watcher again. This is only useful	1521	Simply stops and restarts the periodic watcher again. This is only useful
1145	when you changed some parameters or the reschedule callback would return	1522	when you changed some parameters or the reschedule callback would return
1146	a different time than the last time it was called (e.g. in a crond like	1523	a different time than the last time it was called (e.g. in a crond like
1147	program when the crontabs have changed).	1524	program when the crontabs have changed).
1148		1525
		1526	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1527
		1528	When active, returns the absolute time that the watcher is supposed to
		1529	trigger next.
		1530
		1531	=item ev_tstamp offset [read-write]
		1532
		1533	When repeating, this contains the offset value, otherwise this is the
		1534	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1535
		1536	Can be modified any time, but changes only take effect when the periodic
		1537	timer fires or C<ev_periodic_again> is being called.
		1538
1149	=item ev_tstamp interval [read-write]	1539	=item ev_tstamp interval [read-write]
1150		1540
1151	The current interval value. Can be modified any time, but changes only	1541	The current interval value. Can be modified any time, but changes only
1152	take effect when the periodic timer fires or C<ev_periodic_again> is being	1542	take effect when the periodic timer fires or C<ev_periodic_again> is being
1153	called.	1543	called.
…		…
1158	switched off. Can be changed any time, but changes only take effect when	1548	switched off. Can be changed any time, but changes only take effect when
1159	the periodic timer fires or C<ev_periodic_again> is being called.	1549	the periodic timer fires or C<ev_periodic_again> is being called.
1160		1550
1161	=back	1551	=back
1162		1552
		1553	=head3 Examples
		1554
1163	Example: Call a callback every hour, or, more precisely, whenever the	1555	Example: Call a callback every hour, or, more precisely, whenever the
1164	system clock is divisible by 3600. The callback invocation times have	1556	system time is divisible by 3600. The callback invocation times have
1165	potentially a lot of jittering, but good long-term stability.	1557	potentially a lot of jitter, but good long-term stability.
1166		1558
1167	static void	1559	static void
1168	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1560	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1169	{	1561	{
1170	... its now a full hour (UTC, or TAI or whatever your clock follows)	1562	... its now a full hour (UTC, or TAI or whatever your clock follows)
1171	}	1563	}
1172		1564
1173	struct ev_periodic hourly_tick;	1565	struct ev_periodic hourly_tick;
1174	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1566	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1175	ev_periodic_start (loop, &hourly_tick);	1567	ev_periodic_start (loop, &hourly_tick);
1176		1568
1177	Example: The same as above, but use a reschedule callback to do it:	1569	Example: The same as above, but use a reschedule callback to do it:
1178		1570
1179	#include <math.h>	1571	#include <math.h>
1180		1572
1181	static ev_tstamp	1573	static ev_tstamp
1182	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1183	{	1575	{
1184	return fmod (now, 3600.) + 3600.;	1576	return now + (3600. - fmod (now, 3600.));
1185	}	1577	}
1186		1578
1187	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1188		1580
1189	Example: Call a callback every hour, starting now:	1581	Example: Call a callback every hour, starting now:
1190		1582
1191	struct ev_periodic hourly_tick;	1583	struct ev_periodic hourly_tick;
1192	ev_periodic_init (&hourly_tick, clock_cb,	1584	ev_periodic_init (&hourly_tick, clock_cb,
1193	fmod (ev_now (loop), 3600.), 3600., 0);	1585	fmod (ev_now (loop), 3600.), 3600., 0);
1194	ev_periodic_start (loop, &hourly_tick);	1586	ev_periodic_start (loop, &hourly_tick);
1195		1587
1196		1588
1197	=head2 C<ev_signal> - signal me when a signal gets signalled!	1589	=head2 C<ev_signal> - signal me when a signal gets signalled!
1198		1590
1199	Signal watchers will trigger an event when the process receives a specific	1591	Signal watchers will trigger an event when the process receives a specific
1200	signal one or more times. Even though signals are very asynchronous, libev	1592	signal one or more times. Even though signals are very asynchronous, libev
1201	will try it's best to deliver signals synchronously, i.e. as part of the	1593	will try it's best to deliver signals synchronously, i.e. as part of the
1202	normal event processing, like any other event.	1594	normal event processing, like any other event.
1203		1595
		1596	If you want signals asynchronously, just use C<sigaction> as you would
		1597	do without libev and forget about sharing the signal. You can even use
		1598	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1599
1204	You can configure as many watchers as you like per signal. Only when the	1600	You can configure as many watchers as you like per signal. Only when the
1205	first watcher gets started will libev actually register a signal watcher	1601	first watcher gets started will libev actually register a signal handler
1206	with the kernel (thus it coexists with your own signal handlers as long	1602	with the kernel (thus it coexists with your own signal handlers as long as
1207	as you don't register any with libev). Similarly, when the last signal	1603	you don't register any with libev for the same signal). Similarly, when
1208	watcher for a signal is stopped libev will reset the signal handler to	1604	the last signal watcher for a signal is stopped, libev will reset the
1209	SIG_DFL (regardless of what it was set to before).	1605	signal handler to SIG_DFL (regardless of what it was set to before).
		1606
		1607	If possible and supported, libev will install its handlers with
		1608	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1609	interrupted. If you have a problem with system calls getting interrupted by
		1610	signals you can block all signals in an C<ev_check> watcher and unblock
		1611	them in an C<ev_prepare> watcher.
		1612
		1613	=head3 Watcher-Specific Functions and Data Members
1210		1614
1211	=over 4	1615	=over 4
1212		1616
1213	=item ev_signal_init (ev_signal *, callback, int signum)	1617	=item ev_signal_init (ev_signal *, callback, int signum)
1214		1618
…		…
1221		1625
1222	The signal the watcher watches out for.	1626	The signal the watcher watches out for.
1223		1627
1224	=back	1628	=back
1225		1629
		1630	=head3 Examples
		1631
		1632	Example: Try to exit cleanly on SIGINT.
		1633
		1634	static void
		1635	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1636	{
		1637	ev_unloop (loop, EVUNLOOP_ALL);
		1638	}
		1639
		1640	struct ev_signal signal_watcher;
		1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1642	ev_signal_start (loop, &signal_watcher);
		1643
1226		1644
1227	=head2 C<ev_child> - watch out for process status changes	1645	=head2 C<ev_child> - watch out for process status changes
1228		1646
1229	Child watchers trigger when your process receives a SIGCHLD in response to	1647	Child watchers trigger when your process receives a SIGCHLD in response to
1230	some child status changes (most typically when a child of yours dies).	1648	some child status changes (most typically when a child of yours dies or
		1649	exits). It is permissible to install a child watcher I<after> the child
		1650	has been forked (which implies it might have already exited), as long
		1651	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1652	forking and then immediately registering a watcher for the child is fine,
		1653	but forking and registering a watcher a few event loop iterations later is
		1654	not.
		1655
		1656	Only the default event loop is capable of handling signals, and therefore
		1657	you can only register child watchers in the default event loop.
		1658
		1659	=head3 Process Interaction
		1660
		1661	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1662	initialised. This is necessary to guarantee proper behaviour even if
		1663	the first child watcher is started after the child exits. The occurrence
		1664	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1665	synchronously as part of the event loop processing. Libev always reaps all
		1666	children, even ones not watched.
		1667
		1668	=head3 Overriding the Built-In Processing
		1669
		1670	Libev offers no special support for overriding the built-in child
		1671	processing, but if your application collides with libev's default child
		1672	handler, you can override it easily by installing your own handler for
		1673	C<SIGCHLD> after initialising the default loop, and making sure the
		1674	default loop never gets destroyed. You are encouraged, however, to use an
		1675	event-based approach to child reaping and thus use libev's support for
		1676	that, so other libev users can use C<ev_child> watchers freely.
		1677
		1678	=head3 Stopping the Child Watcher
		1679
		1680	Currently, the child watcher never gets stopped, even when the
		1681	child terminates, so normally one needs to stop the watcher in the
		1682	callback. Future versions of libev might stop the watcher automatically
		1683	when a child exit is detected.
		1684
		1685	=head3 Watcher-Specific Functions and Data Members
1231		1686
1232	=over 4	1687	=over 4
1233		1688
1234	=item ev_child_init (ev_child *, callback, int pid)	1689	=item ev_child_init (ev_child *, callback, int pid, int trace)
1235		1690
1236	=item ev_child_set (ev_child *, int pid)	1691	=item ev_child_set (ev_child *, int pid, int trace)
1237		1692
1238	Configures the watcher to wait for status changes of process C<pid> (or	1693	Configures the watcher to wait for status changes of process C<pid> (or
1239	I<any> process if C<pid> is specified as C<0>). The callback can look	1694	I<any> process if C<pid> is specified as C<0>). The callback can look
1240	at the C<rstatus> member of the C<ev_child> watcher structure to see	1695	at the C<rstatus> member of the C<ev_child> watcher structure to see
1241	the status word (use the macros from C<sys/wait.h> and see your systems	1696	the status word (use the macros from C<sys/wait.h> and see your systems
1242	C<waitpid> documentation). The C<rpid> member contains the pid of the	1697	C<waitpid> documentation). The C<rpid> member contains the pid of the
1243	process causing the status change.	1698	process causing the status change. C<trace> must be either C<0> (only
		1699	activate the watcher when the process terminates) or C<1> (additionally
		1700	activate the watcher when the process is stopped or continued).
1244		1701
1245	=item int pid [read-only]	1702	=item int pid [read-only]
1246		1703
1247	The process id this watcher watches out for, or C<0>, meaning any process id.	1704	The process id this watcher watches out for, or C<0>, meaning any process id.
1248		1705
…		…
1255	The process exit/trace status caused by C<rpid> (see your systems	1712	The process exit/trace status caused by C<rpid> (see your systems
1256	C<waitpid> and C<sys/wait.h> documentation for details).	1713	C<waitpid> and C<sys/wait.h> documentation for details).
1257		1714
1258	=back	1715	=back
1259		1716
1260	Example: Try to exit cleanly on SIGINT and SIGTERM.	1717	=head3 Examples
1261		1718
		1719	Example: C<fork()> a new process and install a child handler to wait for
		1720	its completion.
		1721
		1722	ev_child cw;
		1723
1262	static void	1724	static void
1263	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1725	child_cb (EV_P_ struct ev_child *w, int revents)
1264	{	1726	{
1265	ev_unloop (loop, EVUNLOOP_ALL);	1727	ev_child_stop (EV_A_ w);
		1728	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1266	}	1729	}
1267		1730
1268	struct ev_signal signal_watcher;	1731	pid_t pid = fork ();
1269	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1732
1270	ev_signal_start (loop, &sigint_cb);	1733	if (pid < 0)
		1734	// error
		1735	else if (pid == 0)
		1736	{
		1737	// the forked child executes here
		1738	exit (1);
		1739	}
		1740	else
		1741	{
		1742	ev_child_init (&cw, child_cb, pid, 0);
		1743	ev_child_start (EV_DEFAULT_ &cw);
		1744	}
1271		1745
1272		1746
1273	=head2 C<ev_stat> - did the file attributes just change?	1747	=head2 C<ev_stat> - did the file attributes just change?
1274		1748
1275	This watches a filesystem path for attribute changes. That is, it calls	1749	This watches a file system path for attribute changes. That is, it calls
1276	C<stat> regularly (or when the OS says it changed) and sees if it changed	1750	C<stat> regularly (or when the OS says it changed) and sees if it changed
1277	compared to the last time, invoking the callback if it did.	1751	compared to the last time, invoking the callback if it did.
1278		1752
1279	The path does not need to exist: changing from "path exists" to "path does	1753	The path does not need to exist: changing from "path exists" to "path does
1280	not exist" is a status change like any other. The condition "path does	1754	not exist" is a status change like any other. The condition "path does
…		…
1283	the stat buffer having unspecified contents.	1757	the stat buffer having unspecified contents.
1284		1758
1285	The path I<should> be absolute and I<must not> end in a slash. If it is	1759	The path I<should> be absolute and I<must not> end in a slash. If it is
1286	relative and your working directory changes, the behaviour is undefined.	1760	relative and your working directory changes, the behaviour is undefined.
1287		1761
1288	Since there is no standard to do this, the portable implementation simply	1762	Since there is no standard kernel interface to do this, the portable
1289	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1763	implementation simply calls C<stat (2)> regularly on the path to see if
1290	can specify a recommended polling interval for this case. If you specify	1764	it changed somehow. You can specify a recommended polling interval for
1291	a polling interval of C<0> (highly recommended!) then a I<suitable,	1765	this case. If you specify a polling interval of C<0> (highly recommended!)
1292	unspecified default> value will be used (which you can expect to be around	1766	then a I<suitable, unspecified default> value will be used (which
1293	five seconds, although this might change dynamically). Libev will also	1767	you can expect to be around five seconds, although this might change
1294	impose a minimum interval which is currently around C<0.1>, but thats	1768	dynamically). Libev will also impose a minimum interval which is currently
1295	usually overkill.	1769	around C<0.1>, but thats usually overkill.
1296		1770
1297	This watcher type is not meant for massive numbers of stat watchers,	1771	This watcher type is not meant for massive numbers of stat watchers,
1298	as even with OS-supported change notifications, this can be	1772	as even with OS-supported change notifications, this can be
1299	resource-intensive.	1773	resource-intensive.
1300		1774
1301	At the time of this writing, only the Linux inotify interface is	1775	At the time of this writing, the only OS-specific interface implemented
1302	implemented (implementing kqueue support is left as an exercise for the	1776	is the Linux inotify interface (implementing kqueue support is left as
1303	reader). Inotify will be used to give hints only and should not change the	1777	an exercise for the reader. Note, however, that the author sees no way
1304	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1778	of implementing C<ev_stat> semantics with kqueue).
1305	to fall back to regular polling again even with inotify, but changes are	1779
1306	usually detected immediately, and if the file exists there will be no	1780	=head3 ABI Issues (Largefile Support)
1307	polling.	1781
		1782	Libev by default (unless the user overrides this) uses the default
		1783	compilation environment, which means that on systems with large file
		1784	support disabled by default, you get the 32 bit version of the stat
		1785	structure. When using the library from programs that change the ABI to
		1786	use 64 bit file offsets the programs will fail. In that case you have to
		1787	compile libev with the same flags to get binary compatibility. This is
		1788	obviously the case with any flags that change the ABI, but the problem is
		1789	most noticeably disabled with ev_stat and large file support.
		1790
		1791	The solution for this is to lobby your distribution maker to make large
		1792	file interfaces available by default (as e.g. FreeBSD does) and not
		1793	optional. Libev cannot simply switch on large file support because it has
		1794	to exchange stat structures with application programs compiled using the
		1795	default compilation environment.
		1796
		1797	=head3 Inotify and Kqueue
		1798
		1799	When C<inotify (7)> support has been compiled into libev (generally only
		1800	available with Linux) and present at runtime, it will be used to speed up
		1801	change detection where possible. The inotify descriptor will be created lazily
		1802	when the first C<ev_stat> watcher is being started.
		1803
		1804	Inotify presence does not change the semantics of C<ev_stat> watchers
		1805	except that changes might be detected earlier, and in some cases, to avoid
		1806	making regular C<stat> calls. Even in the presence of inotify support
		1807	there are many cases where libev has to resort to regular C<stat> polling,
		1808	but as long as the path exists, libev usually gets away without polling.
		1809
		1810	There is no support for kqueue, as apparently it cannot be used to
		1811	implement this functionality, due to the requirement of having a file
		1812	descriptor open on the object at all times, and detecting renames, unlinks
		1813	etc. is difficult.
		1814
		1815	=head3 The special problem of stat time resolution
		1816
		1817	The C<stat ()> system call only supports full-second resolution portably, and
		1818	even on systems where the resolution is higher, most file systems still
		1819	only support whole seconds.
		1820
		1821	That means that, if the time is the only thing that changes, you can
		1822	easily miss updates: on the first update, C<ev_stat> detects a change and
		1823	calls your callback, which does something. When there is another update
		1824	within the same second, C<ev_stat> will be unable to detect unless the
		1825	stat data does change in other ways (e.g. file size).
		1826
		1827	The solution to this is to delay acting on a change for slightly more
		1828	than a second (or till slightly after the next full second boundary), using
		1829	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1830	ev_timer_again (loop, w)>).
		1831
		1832	The C<.02> offset is added to work around small timing inconsistencies
		1833	of some operating systems (where the second counter of the current time
		1834	might be be delayed. One such system is the Linux kernel, where a call to
		1835	C<gettimeofday> might return a timestamp with a full second later than
		1836	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1837	update file times then there will be a small window where the kernel uses
		1838	the previous second to update file times but libev might already execute
		1839	the timer callback).
		1840
		1841	=head3 Watcher-Specific Functions and Data Members
1308		1842
1309	=over 4	1843	=over 4
1310		1844
1311	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1845	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1312		1846
…		…
1316	C<path>. The C<interval> is a hint on how quickly a change is expected to	1850	C<path>. The C<interval> is a hint on how quickly a change is expected to
1317	be detected and should normally be specified as C<0> to let libev choose	1851	be detected and should normally be specified as C<0> to let libev choose
1318	a suitable value. The memory pointed to by C<path> must point to the same	1852	a suitable value. The memory pointed to by C<path> must point to the same
1319	path for as long as the watcher is active.	1853	path for as long as the watcher is active.
1320		1854
1321	The callback will be receive C<EV_STAT> when a change was detected,	1855	The callback will receive an C<EV_STAT> event when a change was detected,
1322	relative to the attributes at the time the watcher was started (or the	1856	relative to the attributes at the time the watcher was started (or the
1323	last change was detected).	1857	last change was detected).
1324		1858
1325	=item ev_stat_stat (ev_stat *)	1859	=item ev_stat_stat (loop, ev_stat *)
1326		1860
1327	Updates the stat buffer immediately with new values. If you change the	1861	Updates the stat buffer immediately with new values. If you change the
1328	watched path in your callback, you could call this fucntion to avoid	1862	watched path in your callback, you could call this function to avoid
1329	detecting this change (while introducing a race condition). Can also be	1863	detecting this change (while introducing a race condition if you are not
1330	useful simply to find out the new values.	1864	the only one changing the path). Can also be useful simply to find out the
		1865	new values.
1331		1866
1332	=item ev_statdata attr [read-only]	1867	=item ev_statdata attr [read-only]
1333		1868
1334	The most-recently detected attributes of the file. Although the type is of	1869	The most-recently detected attributes of the file. Although the type is
1335	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1870	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1336	suitable for your system. If the C<st_nlink> member is C<0>, then there	1871	suitable for your system, but you can only rely on the POSIX-standardised
		1872	members to be present. If the C<st_nlink> member is C<0>, then there was
1337	was some error while C<stat>ing the file.	1873	some error while C<stat>ing the file.
1338		1874
1339	=item ev_statdata prev [read-only]	1875	=item ev_statdata prev [read-only]
1340		1876
1341	The previous attributes of the file. The callback gets invoked whenever	1877	The previous attributes of the file. The callback gets invoked whenever
1342	C<prev> != C<attr>.	1878	C<prev> != C<attr>, or, more precisely, one or more of these members
		1879	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1880	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1343		1881
1344	=item ev_tstamp interval [read-only]	1882	=item ev_tstamp interval [read-only]
1345		1883
1346	The specified interval.	1884	The specified interval.
1347		1885
1348	=item const char *path [read-only]	1886	=item const char *path [read-only]
1349		1887
1350	The filesystem path that is being watched.	1888	The file system path that is being watched.
1351		1889
1352	=back	1890	=back
1353		1891
		1892	=head3 Examples
		1893
1354	Example: Watch C</etc/passwd> for attribute changes.	1894	Example: Watch C</etc/passwd> for attribute changes.
1355		1895
1356	static void	1896	static void
1357	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1897	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1358	{	1898	{
1359	/* /etc/passwd changed in some way */	1899	/* /etc/passwd changed in some way */
1360	if (w->attr.st_nlink)	1900	if (w->attr.st_nlink)
1361	{	1901	{
1362	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1902	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1363	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1903	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1364	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1904	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1365	}	1905	}
1366	else	1906	else
1367	/* you shalt not abuse printf for puts */	1907	/* you shalt not abuse printf for puts */
1368	puts ("wow, /etc/passwd is not there, expect problems. "	1908	puts ("wow, /etc/passwd is not there, expect problems. "
1369	"if this is windows, they already arrived\n");	1909	"if this is windows, they already arrived\n");
1370	}	1910	}
1371		1911
1372	...	1912	...
1373	ev_stat passwd;	1913	ev_stat passwd;
1374		1914
1375	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1915	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1376	ev_stat_start (loop, &passwd);	1916	ev_stat_start (loop, &passwd);
		1917
		1918	Example: Like above, but additionally use a one-second delay so we do not
		1919	miss updates (however, frequent updates will delay processing, too, so
		1920	one might do the work both on C<ev_stat> callback invocation I<and> on
		1921	C<ev_timer> callback invocation).
		1922
		1923	static ev_stat passwd;
		1924	static ev_timer timer;
		1925
		1926	static void
		1927	timer_cb (EV_P_ ev_timer *w, int revents)
		1928	{
		1929	ev_timer_stop (EV_A_ w);
		1930
		1931	/* now it's one second after the most recent passwd change */
		1932	}
		1933
		1934	static void
		1935	stat_cb (EV_P_ ev_stat *w, int revents)
		1936	{
		1937	/* reset the one-second timer */
		1938	ev_timer_again (EV_A_ &timer);
		1939	}
		1940
		1941	...
		1942	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1943	ev_stat_start (loop, &passwd);
		1944	ev_timer_init (&timer, timer_cb, 0., 1.02);
1377		1945
1378		1946
1379	=head2 C<ev_idle> - when you've got nothing better to do...	1947	=head2 C<ev_idle> - when you've got nothing better to do...
1380		1948
1381	Idle watchers trigger events when no other events of the same or higher	1949	Idle watchers trigger events when no other events of the same or higher
1382	priority are pending (prepare, check and other idle watchers do not	1950	priority are pending (prepare, check and other idle watchers do not count
1383	count).	1951	as receiving "events").
1384		1952
1385	That is, as long as your process is busy handling sockets or timeouts	1953	That is, as long as your process is busy handling sockets or timeouts
1386	(or even signals, imagine) of the same or higher priority it will not be	1954	(or even signals, imagine) of the same or higher priority it will not be
1387	triggered. But when your process is idle (or only lower-priority watchers	1955	triggered. But when your process is idle (or only lower-priority watchers
1388	are pending), the idle watchers are being called once per event loop	1956	are pending), the idle watchers are being called once per event loop
…		…
1395	Apart from keeping your process non-blocking (which is a useful	1963	Apart from keeping your process non-blocking (which is a useful
1396	effect on its own sometimes), idle watchers are a good place to do	1964	effect on its own sometimes), idle watchers are a good place to do
1397	"pseudo-background processing", or delay processing stuff to after the	1965	"pseudo-background processing", or delay processing stuff to after the
1398	event loop has handled all outstanding events.	1966	event loop has handled all outstanding events.
1399		1967
		1968	=head3 Watcher-Specific Functions and Data Members
		1969
1400	=over 4	1970	=over 4
1401		1971
1402	=item ev_idle_init (ev_signal *, callback)	1972	=item ev_idle_init (ev_signal *, callback)
1403		1973
1404	Initialises and configures the idle watcher - it has no parameters of any	1974	Initialises and configures the idle watcher - it has no parameters of any
1405	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1975	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1406	believe me.	1976	believe me.
1407		1977
1408	=back	1978	=back
1409		1979
		1980	=head3 Examples
		1981
1410	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1982	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1411	callback, free it. Also, use no error checking, as usual.	1983	callback, free it. Also, use no error checking, as usual.
1412		1984
1413	static void	1985	static void
1414	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1986	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1415	{	1987	{
1416	free (w);	1988	free (w);
1417	// now do something you wanted to do when the program has	1989	// now do something you wanted to do when the program has
1418	// no longer asnything immediate to do.	1990	// no longer anything immediate to do.
1419	}	1991	}
1420		1992
1421	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1993	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1422	ev_idle_init (idle_watcher, idle_cb);	1994	ev_idle_init (idle_watcher, idle_cb);
1423	ev_idle_start (loop, idle_cb);	1995	ev_idle_start (loop, idle_cb);
1424		1996
1425		1997
1426	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1427		1999
1428	Prepare and check watchers are usually (but not always) used in tandem:	2000	Prepare and check watchers are usually (but not always) used in pairs:
1429	prepare watchers get invoked before the process blocks and check watchers	2001	prepare watchers get invoked before the process blocks and check watchers
1430	afterwards.	2002	afterwards.
1431		2003
1432	You I<must not> call C<ev_loop> or similar functions that enter	2004	You I<must not> call C<ev_loop> or similar functions that enter
1433	the current event loop from either C<ev_prepare> or C<ev_check>	2005	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1436	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2008	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1437	C<ev_check> so if you have one watcher of each kind they will always be	2009	C<ev_check> so if you have one watcher of each kind they will always be
1438	called in pairs bracketing the blocking call.	2010	called in pairs bracketing the blocking call.
1439		2011
1440	Their main purpose is to integrate other event mechanisms into libev and	2012	Their main purpose is to integrate other event mechanisms into libev and
1441	their use is somewhat advanced. This could be used, for example, to track	2013	their use is somewhat advanced. They could be used, for example, to track
1442	variable changes, implement your own watchers, integrate net-snmp or a	2014	variable changes, implement your own watchers, integrate net-snmp or a
1443	coroutine library and lots more. They are also occasionally useful if	2015	coroutine library and lots more. They are also occasionally useful if
1444	you cache some data and want to flush it before blocking (for example,	2016	you cache some data and want to flush it before blocking (for example,
1445	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2017	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1446	watcher).	2018	watcher).
1447		2019
1448	This is done by examining in each prepare call which file descriptors need	2020	This is done by examining in each prepare call which file descriptors
1449	to be watched by the other library, registering C<ev_io> watchers for	2021	need to be watched by the other library, registering C<ev_io> watchers
1450	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2022	for them and starting an C<ev_timer> watcher for any timeouts (many
1451	provide just this functionality). Then, in the check watcher you check for	2023	libraries provide exactly this functionality). Then, in the check watcher,
1452	any events that occured (by checking the pending status of all watchers	2024	you check for any events that occurred (by checking the pending status
1453	and stopping them) and call back into the library. The I/O and timer	2025	of all watchers and stopping them) and call back into the library. The
1454	callbacks will never actually be called (but must be valid nevertheless,	2026	I/O and timer callbacks will never actually be called (but must be valid
1455	because you never know, you know?).	2027	nevertheless, because you never know, you know?).
1456		2028
1457	As another example, the Perl Coro module uses these hooks to integrate	2029	As another example, the Perl Coro module uses these hooks to integrate
1458	coroutines into libev programs, by yielding to other active coroutines	2030	coroutines into libev programs, by yielding to other active coroutines
1459	during each prepare and only letting the process block if no coroutines	2031	during each prepare and only letting the process block if no coroutines
1460	are ready to run (it's actually more complicated: it only runs coroutines	2032	are ready to run (it's actually more complicated: it only runs coroutines
1461	with priority higher than or equal to the event loop and one coroutine	2033	with priority higher than or equal to the event loop and one coroutine
1462	of lower priority, but only once, using idle watchers to keep the event	2034	of lower priority, but only once, using idle watchers to keep the event
1463	loop from blocking if lower-priority coroutines are active, thus mapping	2035	loop from blocking if lower-priority coroutines are active, thus mapping
1464	low-priority coroutines to idle/background tasks).	2036	low-priority coroutines to idle/background tasks).
1465		2037
		2038	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		2039	priority, to ensure that they are being run before any other watchers
		2040	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2041
		2042	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
		2043	activate ("feed") events into libev. While libev fully supports this, they
		2044	might get executed before other C<ev_check> watchers did their job. As
		2045	C<ev_check> watchers are often used to embed other (non-libev) event
		2046	loops those other event loops might be in an unusable state until their
		2047	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		2048	others).
		2049
		2050	=head3 Watcher-Specific Functions and Data Members
		2051
1466	=over 4	2052	=over 4
1467		2053
1468	=item ev_prepare_init (ev_prepare *, callback)	2054	=item ev_prepare_init (ev_prepare *, callback)
1469		2055
1470	=item ev_check_init (ev_check *, callback)	2056	=item ev_check_init (ev_check *, callback)
1471		2057
1472	Initialises and configures the prepare or check watcher - they have no	2058	Initialises and configures the prepare or check watcher - they have no
1473	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2059	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1474	macros, but using them is utterly, utterly and completely pointless.	2060	macros, but using them is utterly, utterly, utterly and completely
		2061	pointless.
1475		2062
1476	=back	2063	=back
1477		2064
1478	Example: To include a library such as adns, you would add IO watchers	2065	=head3 Examples
1479	and a timeout watcher in a prepare handler, as required by libadns, and	2066
		2067	There are a number of principal ways to embed other event loops or modules
		2068	into libev. Here are some ideas on how to include libadns into libev
		2069	(there is a Perl module named C<EV::ADNS> that does this, which you could
		2070	use as a working example. Another Perl module named C<EV::Glib> embeds a
		2071	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		2072	Glib event loop).
		2073
		2074	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1480	in a check watcher, destroy them and call into libadns. What follows is	2075	and in a check watcher, destroy them and call into libadns. What follows
1481	pseudo-code only of course:	2076	is pseudo-code only of course. This requires you to either use a low
		2077	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		2078	the callbacks for the IO/timeout watchers might not have been called yet.
1482		2079
1483	static ev_io iow [nfd];	2080	static ev_io iow [nfd];
1484	static ev_timer tw;	2081	static ev_timer tw;
1485		2082
1486	static void	2083	static void
1487	io_cb (ev_loop *loop, ev_io *w, int revents)	2084	io_cb (ev_loop *loop, ev_io *w, int revents)
1488	{	2085	{
1489	// set the relevant poll flags
1490	// could also call adns_processreadable etc. here
1491	struct pollfd *fd = (struct pollfd *)w->data;
1492	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1493	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1494	}	2086	}
1495		2087
1496	// create io watchers for each fd and a timer before blocking	2088	// create io watchers for each fd and a timer before blocking
1497	static void	2089	static void
1498	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2090	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1499	{	2091	{
1500	int timeout = 3600000;	2092	int timeout = 3600000;
1501	struct pollfd fds [nfd];	2093	struct pollfd fds [nfd];
1502	// actual code will need to loop here and realloc etc.	2094	// actual code will need to loop here and realloc etc.
1503	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2095	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1504		2096
1505	/* the callback is illegal, but won't be called as we stop during check */	2097	/* the callback is illegal, but won't be called as we stop during check */
1506	ev_timer_init (&tw, 0, timeout * 1e-3);	2098	ev_timer_init (&tw, 0, timeout * 1e-3);
1507	ev_timer_start (loop, &tw);	2099	ev_timer_start (loop, &tw);
1508		2100
1509	// create on ev_io per pollfd	2101	// create one ev_io per pollfd
1510	for (int i = 0; i < nfd; ++i)	2102	for (int i = 0; i < nfd; ++i)
1511	{	2103	{
1512	ev_io_init (iow + i, io_cb, fds [i].fd,	2104	ev_io_init (iow + i, io_cb, fds [i].fd,
1513	((fds [i].events & POLLIN ? EV_READ : 0)	2105	((fds [i].events & POLLIN ? EV_READ : 0)
1514	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2106	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1515		2107
1516	fds [i].revents = 0;	2108	fds [i].revents = 0;
1517	iow [i].data = fds + i;
1518	ev_io_start (loop, iow + i);	2109	ev_io_start (loop, iow + i);
1519	}	2110	}
1520	}	2111	}
1521		2112
1522	// stop all watchers after blocking	2113	// stop all watchers after blocking
1523	static void	2114	static void
1524	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2115	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1525	{	2116	{
1526	ev_timer_stop (loop, &tw);	2117	ev_timer_stop (loop, &tw);
1527		2118
1528	for (int i = 0; i < nfd; ++i)	2119	for (int i = 0; i < nfd; ++i)
		2120	{
		2121	// set the relevant poll flags
		2122	// could also call adns_processreadable etc. here
		2123	struct pollfd *fd = fds + i;
		2124	int revents = ev_clear_pending (iow + i);
		2125	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2126	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2127
		2128	// now stop the watcher
1529	ev_io_stop (loop, iow + i);	2129	ev_io_stop (loop, iow + i);
		2130	}
1530		2131
1531	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2132	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1532	}	2133	}
		2134
		2135	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2136	in the prepare watcher and would dispose of the check watcher.
		2137
		2138	Method 3: If the module to be embedded supports explicit event
		2139	notification (libadns does), you can also make use of the actual watcher
		2140	callbacks, and only destroy/create the watchers in the prepare watcher.
		2141
		2142	static void
		2143	timer_cb (EV_P_ ev_timer *w, int revents)
		2144	{
		2145	adns_state ads = (adns_state)w->data;
		2146	update_now (EV_A);
		2147
		2148	adns_processtimeouts (ads, &tv_now);
		2149	}
		2150
		2151	static void
		2152	io_cb (EV_P_ ev_io *w, int revents)
		2153	{
		2154	adns_state ads = (adns_state)w->data;
		2155	update_now (EV_A);
		2156
		2157	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2158	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2159	}
		2160
		2161	// do not ever call adns_afterpoll
		2162
		2163	Method 4: Do not use a prepare or check watcher because the module you
		2164	want to embed is not flexible enough to support it. Instead, you can
		2165	override their poll function. The drawback with this solution is that the
		2166	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
		2167	this approach, effectively embedding EV as a client into the horrible
		2168	libglib event loop.
		2169
		2170	static gint
		2171	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2172	{
		2173	int got_events = 0;
		2174
		2175	for (n = 0; n < nfds; ++n)
		2176	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2177
		2178	if (timeout >= 0)
		2179	// create/start timer
		2180
		2181	// poll
		2182	ev_loop (EV_A_ 0);
		2183
		2184	// stop timer again
		2185	if (timeout >= 0)
		2186	ev_timer_stop (EV_A_ &to);
		2187
		2188	// stop io watchers again - their callbacks should have set
		2189	for (n = 0; n < nfds; ++n)
		2190	ev_io_stop (EV_A_ iow [n]);
		2191
		2192	return got_events;
		2193	}
1533		2194
1534		2195
1535	=head2 C<ev_embed> - when one backend isn't enough...	2196	=head2 C<ev_embed> - when one backend isn't enough...
1536		2197
1537	This is a rather advanced watcher type that lets you embed one event loop	2198	This is a rather advanced watcher type that lets you embed one event loop
…		…
1543	prioritise I/O.	2204	prioritise I/O.
1544		2205
1545	As an example for a bug workaround, the kqueue backend might only support	2206	As an example for a bug workaround, the kqueue backend might only support
1546	sockets on some platform, so it is unusable as generic backend, but you	2207	sockets on some platform, so it is unusable as generic backend, but you
1547	still want to make use of it because you have many sockets and it scales	2208	still want to make use of it because you have many sockets and it scales
1548	so nicely. In this case, you would create a kqueue-based loop and embed it	2209	so nicely. In this case, you would create a kqueue-based loop and embed
1549	into your default loop (which might use e.g. poll). Overall operation will	2210	it into your default loop (which might use e.g. poll). Overall operation
1550	be a bit slower because first libev has to poll and then call kevent, but	2211	will be a bit slower because first libev has to call C<poll> and then
1551	at least you can use both at what they are best.	2212	C<kevent>, but at least you can use both mechanisms for what they are
		2213	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1552		2214
1553	As for prioritising I/O: rarely you have the case where some fds have	2215	As for prioritising I/O: under rare circumstances you have the case where
1554	to be watched and handled very quickly (with low latency), and even	2216	some fds have to be watched and handled very quickly (with low latency),
1555	priorities and idle watchers might have too much overhead. In this case	2217	and even priorities and idle watchers might have too much overhead. In
1556	you would put all the high priority stuff in one loop and all the rest in	2218	this case you would put all the high priority stuff in one loop and all
1557	a second one, and embed the second one in the first.	2219	the rest in a second one, and embed the second one in the first.
1558		2220
1559	As long as the watcher is active, the callback will be invoked every time	2221	As long as the watcher is active, the callback will be invoked every time
1560	there might be events pending in the embedded loop. The callback must then	2222	there might be events pending in the embedded loop. The callback must then
1561	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2223	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1562	their callbacks (you could also start an idle watcher to give the embedded	2224	their callbacks (you could also start an idle watcher to give the embedded
…		…
1570	interested in that.	2232	interested in that.
1571		2233
1572	Also, there have not currently been made special provisions for forking:	2234	Also, there have not currently been made special provisions for forking:
1573	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2235	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1574	but you will also have to stop and restart any C<ev_embed> watchers	2236	but you will also have to stop and restart any C<ev_embed> watchers
1575	yourself.	2237	yourself - but you can use a fork watcher to handle this automatically,
		2238	and future versions of libev might do just that.
1576		2239
1577	Unfortunately, not all backends are embeddable, only the ones returned by	2240	Unfortunately, not all backends are embeddable: only the ones returned by
1578	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1579	portable one.	2242	portable one.
1580		2243
1581	So when you want to use this feature you will always have to be prepared	2244	So when you want to use this feature you will always have to be prepared
1582	that you cannot get an embeddable loop. The recommended way to get around	2245	that you cannot get an embeddable loop. The recommended way to get around
1583	this is to have a separate variables for your embeddable loop, try to	2246	this is to have a separate variables for your embeddable loop, try to
1584	create it, and if that fails, use the normal loop for everything:	2247	create it, and if that fails, use the normal loop for everything.
1585		2248
1586	struct ev_loop *loop_hi = ev_default_init (0);	2249	=head3 C<ev_embed> and fork
1587	struct ev_loop *loop_lo = 0;
1588	struct ev_embed embed;
1589
1590	// see if there is a chance of getting one that works
1591	// (remember that a flags value of 0 means autodetection)
1592	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1593	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1594	: 0;
1595		2250
1596	// if we got one, then embed it, otherwise default to loop_hi	2251	While the C<ev_embed> watcher is running, forks in the embedding loop will
1597	if (loop_lo)	2252	automatically be applied to the embedded loop as well, so no special
1598	{	2253	fork handling is required in that case. When the watcher is not running,
1599	ev_embed_init (&embed, 0, loop_lo);	2254	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1600	ev_embed_start (loop_hi, &embed);	2255	as applicable.
1601	}	2256
1602	else	2257	=head3 Watcher-Specific Functions and Data Members
1603	loop_lo = loop_hi;
1604		2258
1605	=over 4	2259	=over 4
1606		2260
1607	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2261	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1608		2262
…		…
1610		2264
1611	Configures the watcher to embed the given loop, which must be	2265	Configures the watcher to embed the given loop, which must be
1612	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2266	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1613	invoked automatically, otherwise it is the responsibility of the callback	2267	invoked automatically, otherwise it is the responsibility of the callback
1614	to invoke it (it will continue to be called until the sweep has been done,	2268	to invoke it (it will continue to be called until the sweep has been done,
1615	if you do not want thta, you need to temporarily stop the embed watcher).	2269	if you do not want that, you need to temporarily stop the embed watcher).
1616		2270
1617	=item ev_embed_sweep (loop, ev_embed *)	2271	=item ev_embed_sweep (loop, ev_embed *)
1618		2272
1619	Make a single, non-blocking sweep over the embedded loop. This works	2273	Make a single, non-blocking sweep over the embedded loop. This works
1620	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2274	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1621	apropriate way for embedded loops.	2275	appropriate way for embedded loops.
1622		2276
1623	=item struct ev_loop *loop [read-only]	2277	=item struct ev_loop *other [read-only]
1624		2278
1625	The embedded event loop.	2279	The embedded event loop.
1626		2280
1627	=back	2281	=back
		2282
		2283	=head3 Examples
		2284
		2285	Example: Try to get an embeddable event loop and embed it into the default
		2286	event loop. If that is not possible, use the default loop. The default
		2287	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2288	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2289	used).
		2290
		2291	struct ev_loop *loop_hi = ev_default_init (0);
		2292	struct ev_loop *loop_lo = 0;
		2293	struct ev_embed embed;
		2294
		2295	// see if there is a chance of getting one that works
		2296	// (remember that a flags value of 0 means autodetection)
		2297	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2298	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2299	: 0;
		2300
		2301	// if we got one, then embed it, otherwise default to loop_hi
		2302	if (loop_lo)
		2303	{
		2304	ev_embed_init (&embed, 0, loop_lo);
		2305	ev_embed_start (loop_hi, &embed);
		2306	}
		2307	else
		2308	loop_lo = loop_hi;
		2309
		2310	Example: Check if kqueue is available but not recommended and create
		2311	a kqueue backend for use with sockets (which usually work with any
		2312	kqueue implementation). Store the kqueue/socket-only event loop in
		2313	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2314
		2315	struct ev_loop *loop = ev_default_init (0);
		2316	struct ev_loop *loop_socket = 0;
		2317	struct ev_embed embed;
		2318
		2319	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2320	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2321	{
		2322	ev_embed_init (&embed, 0, loop_socket);
		2323	ev_embed_start (loop, &embed);
		2324	}
		2325
		2326	if (!loop_socket)
		2327	loop_socket = loop;
		2328
		2329	// now use loop_socket for all sockets, and loop for everything else
1628		2330
1629		2331
1630	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2332	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1631		2333
1632	Fork watchers are called when a C<fork ()> was detected (usually because	2334	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1635	event loop blocks next and before C<ev_check> watchers are being called,	2337	event loop blocks next and before C<ev_check> watchers are being called,
1636	and only in the child after the fork. If whoever good citizen calling	2338	and only in the child after the fork. If whoever good citizen calling
1637	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2339	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1638	handlers will be invoked, too, of course.	2340	handlers will be invoked, too, of course.
1639		2341
		2342	=head3 Watcher-Specific Functions and Data Members
		2343
1640	=over 4	2344	=over 4
1641		2345
1642	=item ev_fork_init (ev_signal *, callback)	2346	=item ev_fork_init (ev_signal *, callback)
1643		2347
1644	Initialises and configures the fork watcher - it has no parameters of any	2348	Initialises and configures the fork watcher - it has no parameters of any
…		…
1646	believe me.	2350	believe me.
1647		2351
1648	=back	2352	=back
1649		2353
1650		2354
		2355	=head2 C<ev_async> - how to wake up another event loop
		2356
		2357	In general, you cannot use an C<ev_loop> from multiple threads or other
		2358	asynchronous sources such as signal handlers (as opposed to multiple event
		2359	loops - those are of course safe to use in different threads).
		2360
		2361	Sometimes, however, you need to wake up another event loop you do not
		2362	control, for example because it belongs to another thread. This is what
		2363	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2364	can signal it by calling C<ev_async_send>, which is thread- and signal
		2365	safe.
		2366
		2367	This functionality is very similar to C<ev_signal> watchers, as signals,
		2368	too, are asynchronous in nature, and signals, too, will be compressed
		2369	(i.e. the number of callback invocations may be less than the number of
		2370	C<ev_async_sent> calls).
		2371
		2372	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2373	just the default loop.
		2374
		2375	=head3 Queueing
		2376
		2377	C<ev_async> does not support queueing of data in any way. The reason
		2378	is that the author does not know of a simple (or any) algorithm for a
		2379	multiple-writer-single-reader queue that works in all cases and doesn't
		2380	need elaborate support such as pthreads.
		2381
		2382	That means that if you want to queue data, you have to provide your own
		2383	queue. But at least I can tell you how to implement locking around your
		2384	queue:
		2385
		2386	=over 4
		2387
		2388	=item queueing from a signal handler context
		2389
		2390	To implement race-free queueing, you simply add to the queue in the signal
		2391	handler but you block the signal handler in the watcher callback. Here is
		2392	an example that does that for some fictitious SIGUSR1 handler:
		2393
		2394	static ev_async mysig;
		2395
		2396	static void
		2397	sigusr1_handler (void)
		2398	{
		2399	sometype data;
		2400
		2401	// no locking etc.
		2402	queue_put (data);
		2403	ev_async_send (EV_DEFAULT_ &mysig);
		2404	}
		2405
		2406	static void
		2407	mysig_cb (EV_P_ ev_async *w, int revents)
		2408	{
		2409	sometype data;
		2410	sigset_t block, prev;
		2411
		2412	sigemptyset (&block);
		2413	sigaddset (&block, SIGUSR1);
		2414	sigprocmask (SIG_BLOCK, &block, &prev);
		2415
		2416	while (queue_get (&data))
		2417	process (data);
		2418
		2419	if (sigismember (&prev, SIGUSR1)
		2420	sigprocmask (SIG_UNBLOCK, &block, 0);
		2421	}
		2422
		2423	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2424	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2425	either...).
		2426
		2427	=item queueing from a thread context
		2428
		2429	The strategy for threads is different, as you cannot (easily) block
		2430	threads but you can easily preempt them, so to queue safely you need to
		2431	employ a traditional mutex lock, such as in this pthread example:
		2432
		2433	static ev_async mysig;
		2434	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2435
		2436	static void
		2437	otherthread (void)
		2438	{
		2439	// only need to lock the actual queueing operation
		2440	pthread_mutex_lock (&mymutex);
		2441	queue_put (data);
		2442	pthread_mutex_unlock (&mymutex);
		2443
		2444	ev_async_send (EV_DEFAULT_ &mysig);
		2445	}
		2446
		2447	static void
		2448	mysig_cb (EV_P_ ev_async *w, int revents)
		2449	{
		2450	pthread_mutex_lock (&mymutex);
		2451
		2452	while (queue_get (&data))
		2453	process (data);
		2454
		2455	pthread_mutex_unlock (&mymutex);
		2456	}
		2457
		2458	=back
		2459
		2460
		2461	=head3 Watcher-Specific Functions and Data Members
		2462
		2463	=over 4
		2464
		2465	=item ev_async_init (ev_async *, callback)
		2466
		2467	Initialises and configures the async watcher - it has no parameters of any
		2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2469	trust me.
		2470
		2471	=item ev_async_send (loop, ev_async *)
		2472
		2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2474	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2475	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2477	section below on what exactly this means).
		2478
		2479	This call incurs the overhead of a system call only once per loop iteration,
		2480	so while the overhead might be noticeable, it doesn't apply to repeated
		2481	calls to C<ev_async_send>.
		2482
		2483	=item bool = ev_async_pending (ev_async *)
		2484
		2485	Returns a non-zero value when C<ev_async_send> has been called on the
		2486	watcher but the event has not yet been processed (or even noted) by the
		2487	event loop.
		2488
		2489	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2490	the loop iterates next and checks for the watcher to have become active,
		2491	it will reset the flag again. C<ev_async_pending> can be used to very
		2492	quickly check whether invoking the loop might be a good idea.
		2493
		2494	Not that this does I<not> check whether the watcher itself is pending, only
		2495	whether it has been requested to make this watcher pending.
		2496
		2497	=back
		2498
		2499
1651	=head1 OTHER FUNCTIONS	2500	=head1 OTHER FUNCTIONS
1652		2501
1653	There are some other functions of possible interest. Described. Here. Now.	2502	There are some other functions of possible interest. Described. Here. Now.
1654		2503
1655	=over 4	2504	=over 4
1656		2505
1657	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2506	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1658		2507
1659	This function combines a simple timer and an I/O watcher, calls your	2508	This function combines a simple timer and an I/O watcher, calls your
1660	callback on whichever event happens first and automatically stop both	2509	callback on whichever event happens first and automatically stops both
1661	watchers. This is useful if you want to wait for a single event on an fd	2510	watchers. This is useful if you want to wait for a single event on an fd
1662	or timeout without having to allocate/configure/start/stop/free one or	2511	or timeout without having to allocate/configure/start/stop/free one or
1663	more watchers yourself.	2512	more watchers yourself.
1664		2513
1665	If C<fd> is less than 0, then no I/O watcher will be started and events	2514	If C<fd> is less than 0, then no I/O watcher will be started and the
1666	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2515	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1667	C<events> set will be craeted and started.	2516	the given C<fd> and C<events> set will be created and started.
1668		2517
1669	If C<timeout> is less than 0, then no timeout watcher will be	2518	If C<timeout> is less than 0, then no timeout watcher will be
1670	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2519	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1671	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2520	repeat = 0) will be started. C<0> is a valid timeout.
1672	dubious value.
1673		2521
1674	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2522	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1675	passed an C<revents> set like normal event callbacks (a combination of	2523	passed an C<revents> set like normal event callbacks (a combination of
1676	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2524	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1677	value passed to C<ev_once>:	2525	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2526	a timeout and an io event at the same time - you probably should give io
		2527	events precedence.
1678		2528
		2529	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2530
1679	static void stdin_ready (int revents, void *arg)	2531	static void stdin_ready (int revents, void *arg)
1680	{	2532	{
1681	if (revents & EV_TIMEOUT)
1682	/* doh, nothing entered */;
1683	else if (revents & EV_READ)	2533	if (revents & EV_READ)
1684	/* stdin might have data for us, joy! */;	2534	/* stdin might have data for us, joy! */;
		2535	else if (revents & EV_TIMEOUT)
		2536	/* doh, nothing entered */;
1685	}	2537	}
1686		2538
1687	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1688		2540
1689	=item ev_feed_event (ev_loop *, watcher *, int revents)	2541	=item ev_feed_event (ev_loop *, watcher *, int revents)
1690		2542
1691	Feeds the given event set into the event loop, as if the specified event	2543	Feeds the given event set into the event loop, as if the specified event
1692	had happened for the specified watcher (which must be a pointer to an	2544	had happened for the specified watcher (which must be a pointer to an
…		…
1697	Feed an event on the given fd, as if a file descriptor backend detected	2549	Feed an event on the given fd, as if a file descriptor backend detected
1698	the given events it.	2550	the given events it.
1699		2551
1700	=item ev_feed_signal_event (ev_loop *loop, int signum)	2552	=item ev_feed_signal_event (ev_loop *loop, int signum)
1701		2553
1702	Feed an event as if the given signal occured (C<loop> must be the default	2554	Feed an event as if the given signal occurred (C<loop> must be the default
1703	loop!).	2555	loop!).
1704		2556
1705	=back	2557	=back
1706		2558
1707		2559
…		…
1723		2575
1724	=item * Priorities are not currently supported. Initialising priorities	2576	=item * Priorities are not currently supported. Initialising priorities
1725	will fail and all watchers will have the same priority, even though there	2577	will fail and all watchers will have the same priority, even though there
1726	is an ev_pri field.	2578	is an ev_pri field.
1727		2579
		2580	=item * In libevent, the last base created gets the signals, in libev, the
		2581	first base created (== the default loop) gets the signals.
		2582
1728	=item * Other members are not supported.	2583	=item * Other members are not supported.
1729		2584
1730	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2585	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1731	to use the libev header file and library.	2586	to use the libev header file and library.
1732		2587
1733	=back	2588	=back
1734		2589
1735	=head1 C++ SUPPORT	2590	=head1 C++ SUPPORT
1736		2591
1737	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2592	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1738	you to use some convinience methods to start/stop watchers and also change	2593	you to use some convenience methods to start/stop watchers and also change
1739	the callback model to a model using method callbacks on objects.	2594	the callback model to a model using method callbacks on objects.
1740		2595
1741	To use it,	2596	To use it,
1742		2597
1743	#include <ev++.h>	2598	#include <ev++.h>
1744		2599
1745	(it is not installed by default). This automatically includes F<ev.h>	2600	This automatically includes F<ev.h> and puts all of its definitions (many
1746	and puts all of its definitions (many of them macros) into the global	2601	of them macros) into the global namespace. All C++ specific things are
1747	namespace. All C++ specific things are put into the C<ev> namespace.	2602	put into the C<ev> namespace. It should support all the same embedding
		2603	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1748		2604
1749	It should support all the same embedding options as F<ev.h>, most notably	2605	Care has been taken to keep the overhead low. The only data member the C++
1750	C<EV_MULTIPLICITY>.	2606	classes add (compared to plain C-style watchers) is the event loop pointer
		2607	that the watcher is associated with (or no additional members at all if
		2608	you disable C<EV_MULTIPLICITY> when embedding libev).
		2609
		2610	Currently, functions, and static and non-static member functions can be
		2611	used as callbacks. Other types should be easy to add as long as they only
		2612	need one additional pointer for context. If you need support for other
		2613	types of functors please contact the author (preferably after implementing
		2614	it).
1751		2615
1752	Here is a list of things available in the C<ev> namespace:	2616	Here is a list of things available in the C<ev> namespace:
1753		2617
1754	=over 4	2618	=over 4
1755		2619
…		…
1771		2635
1772	All of those classes have these methods:	2636	All of those classes have these methods:
1773		2637
1774	=over 4	2638	=over 4
1775		2639
1776	=item ev::TYPE::TYPE (object *, object::method *)	2640	=item ev::TYPE::TYPE ()
1777		2641
1778	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2642	=item ev::TYPE::TYPE (struct ev_loop *)
1779		2643
1780	=item ev::TYPE::~TYPE	2644	=item ev::TYPE::~TYPE
1781		2645
1782	The constructor takes a pointer to an object and a method pointer to	2646	The constructor (optionally) takes an event loop to associate the watcher
1783	the event handler callback to call in this class. The constructor calls	2647	with. If it is omitted, it will use C<EV_DEFAULT>.
1784	C<ev_init> for you, which means you have to call the C<set> method	2648
1785	before starting it. If you do not specify a loop then the constructor	2649	The constructor calls C<ev_init> for you, which means you have to call the
1786	automatically associates the default loop with this watcher.	2650	C<set> method before starting it.
		2651
		2652	It will not set a callback, however: You have to call the templated C<set>
		2653	method to set a callback before you can start the watcher.
		2654
		2655	(The reason why you have to use a method is a limitation in C++ which does
		2656	not allow explicit template arguments for constructors).
1787		2657
1788	The destructor automatically stops the watcher if it is active.	2658	The destructor automatically stops the watcher if it is active.
		2659
		2660	=item w->set<class, &class::method> (object *)
		2661
		2662	This method sets the callback method to call. The method has to have a
		2663	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2664	first argument and the C<revents> as second. The object must be given as
		2665	parameter and is stored in the C<data> member of the watcher.
		2666
		2667	This method synthesizes efficient thunking code to call your method from
		2668	the C callback that libev requires. If your compiler can inline your
		2669	callback (i.e. it is visible to it at the place of the C<set> call and
		2670	your compiler is good :), then the method will be fully inlined into the
		2671	thunking function, making it as fast as a direct C callback.
		2672
		2673	Example: simple class declaration and watcher initialisation
		2674
		2675	struct myclass
		2676	{
		2677	void io_cb (ev::io &w, int revents) { }
		2678	}
		2679
		2680	myclass obj;
		2681	ev::io iow;
		2682	iow.set <myclass, &myclass::io_cb> (&obj);
		2683
		2684	=item w->set<function> (void *data = 0)
		2685
		2686	Also sets a callback, but uses a static method or plain function as
		2687	callback. The optional C<data> argument will be stored in the watcher's
		2688	C<data> member and is free for you to use.
		2689
		2690	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2691
		2692	See the method-C<set> above for more details.
		2693
		2694	Example: Use a plain function as callback.
		2695
		2696	static void io_cb (ev::io &w, int revents) { }
		2697	iow.set <io_cb> ();
1789		2698
1790	=item w->set (struct ev_loop *)	2699	=item w->set (struct ev_loop *)
1791		2700
1792	Associates a different C<struct ev_loop> with this watcher. You can only	2701	Associates a different C<struct ev_loop> with this watcher. You can only
1793	do this when the watcher is inactive (and not pending either).	2702	do this when the watcher is inactive (and not pending either).
1794		2703
1795	=item w->set ([args])	2704	=item w->set ([arguments])
1796		2705
1797	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2706	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1798	called at least once. Unlike the C counterpart, an active watcher gets	2707	called at least once. Unlike the C counterpart, an active watcher gets
1799	automatically stopped and restarted.	2708	automatically stopped and restarted when reconfiguring it with this
		2709	method.
1800		2710
1801	=item w->start ()	2711	=item w->start ()
1802		2712
1803	Starts the watcher. Note that there is no C<loop> argument as the	2713	Starts the watcher. Note that there is no C<loop> argument, as the
1804	constructor already takes the loop.	2714	constructor already stores the event loop.
1805		2715
1806	=item w->stop ()	2716	=item w->stop ()
1807		2717
1808	Stops the watcher if it is active. Again, no C<loop> argument.	2718	Stops the watcher if it is active. Again, no C<loop> argument.
1809		2719
1810	=item w->again () C<ev::timer>, C<ev::periodic> only	2720	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1811		2721
1812	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2722	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1813	C<ev_TYPE_again> function.	2723	C<ev_TYPE_again> function.
1814		2724
1815	=item w->sweep () C<ev::embed> only	2725	=item w->sweep () (C<ev::embed> only)
1816		2726
1817	Invokes C<ev_embed_sweep>.	2727	Invokes C<ev_embed_sweep>.
1818		2728
1819	=item w->update () C<ev::stat> only	2729	=item w->update () (C<ev::stat> only)
1820		2730
1821	Invokes C<ev_stat_stat>.	2731	Invokes C<ev_stat_stat>.
1822		2732
1823	=back	2733	=back
1824		2734
1825	=back	2735	=back
1826		2736
1827	Example: Define a class with an IO and idle watcher, start one of them in	2737	Example: Define a class with an IO and idle watcher, start one of them in
1828	the constructor.	2738	the constructor.
1829		2739
1830	class myclass	2740	class myclass
1831	{	2741	{
1832	ev_io io; void io_cb (ev::io &w, int revents);	2742	ev::io io ; void io_cb (ev::io &w, int revents);
1833	ev_idle idle void idle_cb (ev::idle &w, int revents);	2743	ev::idle idle; void idle_cb (ev::idle &w, int revents);
1834		2744
1835	myclass ();	2745	myclass (int fd)
1836	}	2746	{
		2747	io .set <myclass, &myclass::io_cb > (this);
		2748	idle.set <myclass, &myclass::idle_cb> (this);
1837		2749
1838	myclass::myclass (int fd)
1839	: io (this, &myclass::io_cb),
1840	idle (this, &myclass::idle_cb)
1841	{
1842	io.start (fd, ev::READ);	2750	io.start (fd, ev::READ);
		2751	}
1843	}	2752	};
		2753
		2754
		2755	=head1 OTHER LANGUAGE BINDINGS
		2756
		2757	Libev does not offer other language bindings itself, but bindings for a
		2758	number of languages exist in the form of third-party packages. If you know
		2759	any interesting language binding in addition to the ones listed here, drop
		2760	me a note.
		2761
		2762	=over 4
		2763
		2764	=item Perl
		2765
		2766	The EV module implements the full libev API and is actually used to test
		2767	libev. EV is developed together with libev. Apart from the EV core module,
		2768	there are additional modules that implement libev-compatible interfaces
		2769	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2770	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2771	and C<EV::Glib>).
		2772
		2773	It can be found and installed via CPAN, its homepage is at
		2774	L<http://software.schmorp.de/pkg/EV>.
		2775
		2776	=item Python
		2777
		2778	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2779	seems to be quite complete and well-documented. Note, however, that the
		2780	patch they require for libev is outright dangerous as it breaks the ABI
		2781	for everybody else, and therefore, should never be applied in an installed
		2782	libev (if python requires an incompatible ABI then it needs to embed
		2783	libev).
		2784
		2785	=item Ruby
		2786
		2787	Tony Arcieri has written a ruby extension that offers access to a subset
		2788	of the libev API and adds file handle abstractions, asynchronous DNS and
		2789	more on top of it. It can be found via gem servers. Its homepage is at
		2790	L<http://rev.rubyforge.org/>.
		2791
		2792	=item D
		2793
		2794	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2795	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2796
		2797	=back
1844		2798
1845		2799
1846	=head1 MACRO MAGIC	2800	=head1 MACRO MAGIC
1847		2801
1848	Libev can be compiled with a variety of options, the most fundemantal is	2802	Libev can be compiled with a variety of options, the most fundamental
1849	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2803	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1850	callbacks have an initial C<struct ev_loop *> argument.	2804	functions and callbacks have an initial C<struct ev_loop *> argument.
1851		2805
1852	To make it easier to write programs that cope with either variant, the	2806	To make it easier to write programs that cope with either variant, the
1853	following macros are defined:	2807	following macros are defined:
1854		2808
1855	=over 4	2809	=over 4
…		…
1858		2812
1859	This provides the loop I<argument> for functions, if one is required ("ev	2813	This provides the loop I<argument> for functions, if one is required ("ev
1860	loop argument"). The C<EV_A> form is used when this is the sole argument,	2814	loop argument"). The C<EV_A> form is used when this is the sole argument,
1861	C<EV_A_> is used when other arguments are following. Example:	2815	C<EV_A_> is used when other arguments are following. Example:
1862		2816
1863	ev_unref (EV_A);	2817	ev_unref (EV_A);
1864	ev_timer_add (EV_A_ watcher);	2818	ev_timer_add (EV_A_ watcher);
1865	ev_loop (EV_A_ 0);	2819	ev_loop (EV_A_ 0);
1866		2820
1867	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2821	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1868	which is often provided by the following macro.	2822	which is often provided by the following macro.
1869		2823
1870	=item C<EV_P>, C<EV_P_>	2824	=item C<EV_P>, C<EV_P_>
1871		2825
1872	This provides the loop I<parameter> for functions, if one is required ("ev	2826	This provides the loop I<parameter> for functions, if one is required ("ev
1873	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2827	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1874	C<EV_P_> is used when other parameters are following. Example:	2828	C<EV_P_> is used when other parameters are following. Example:
1875		2829
1876	// this is how ev_unref is being declared	2830	// this is how ev_unref is being declared
1877	static void ev_unref (EV_P);	2831	static void ev_unref (EV_P);
1878		2832
1879	// this is how you can declare your typical callback	2833	// this is how you can declare your typical callback
1880	static void cb (EV_P_ ev_timer *w, int revents)	2834	static void cb (EV_P_ ev_timer *w, int revents)
1881		2835
1882	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2836	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1883	suitable for use with C<EV_A>.	2837	suitable for use with C<EV_A>.
1884		2838
1885	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2839	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1886		2840
1887	Similar to the other two macros, this gives you the value of the default	2841	Similar to the other two macros, this gives you the value of the default
1888	loop, if multiple loops are supported ("ev loop default").	2842	loop, if multiple loops are supported ("ev loop default").
1889		2843
		2844	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2845
		2846	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2847	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2848	is undefined when the default loop has not been initialised by a previous
		2849	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2850
		2851	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2852	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2853
1890	=back	2854	=back
1891		2855
1892	Example: Declare and initialise a check watcher, utilising the above	2856	Example: Declare and initialise a check watcher, utilising the above
1893	macros so it will work regardless of wether multiple loops are supported	2857	macros so it will work regardless of whether multiple loops are supported
1894	or not.	2858	or not.
1895		2859
1896	static void	2860	static void
1897	check_cb (EV_P_ ev_timer *w, int revents)	2861	check_cb (EV_P_ ev_timer *w, int revents)
1898	{	2862	{
1899	ev_check_stop (EV_A_ w);	2863	ev_check_stop (EV_A_ w);
1900	}	2864	}
1901		2865
1902	ev_check check;	2866	ev_check check;
1903	ev_check_init (&check, check_cb);	2867	ev_check_init (&check, check_cb);
1904	ev_check_start (EV_DEFAULT_ &check);	2868	ev_check_start (EV_DEFAULT_ &check);
1905	ev_loop (EV_DEFAULT_ 0);	2869	ev_loop (EV_DEFAULT_ 0);
1906		2870
1907	=head1 EMBEDDING	2871	=head1 EMBEDDING
1908		2872
1909	Libev can (and often is) directly embedded into host	2873	Libev can (and often is) directly embedded into host
1910	applications. Examples of applications that embed it include the Deliantra	2874	applications. Examples of applications that embed it include the Deliantra
1911	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2875	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1912	and rxvt-unicode.	2876	and rxvt-unicode.
1913		2877
1914	The goal is to enable you to just copy the neecssary files into your	2878	The goal is to enable you to just copy the necessary files into your
1915	source directory without having to change even a single line in them, so	2879	source directory without having to change even a single line in them, so
1916	you can easily upgrade by simply copying (or having a checked-out copy of	2880	you can easily upgrade by simply copying (or having a checked-out copy of
1917	libev somewhere in your source tree).	2881	libev somewhere in your source tree).
1918		2882
1919	=head2 FILESETS	2883	=head2 FILESETS
1920		2884
1921	Depending on what features you need you need to include one or more sets of files	2885	Depending on what features you need you need to include one or more sets of files
1922	in your app.	2886	in your application.
1923		2887
1924	=head3 CORE EVENT LOOP	2888	=head3 CORE EVENT LOOP
1925		2889
1926	To include only the libev core (all the C<ev_*> functions), with manual	2890	To include only the libev core (all the C<ev_*> functions), with manual
1927	configuration (no autoconf):	2891	configuration (no autoconf):
1928		2892
1929	#define EV_STANDALONE 1	2893	#define EV_STANDALONE 1
1930	#include "ev.c"	2894	#include "ev.c"
1931		2895
1932	This will automatically include F<ev.h>, too, and should be done in a	2896	This will automatically include F<ev.h>, too, and should be done in a
1933	single C source file only to provide the function implementations. To use	2897	single C source file only to provide the function implementations. To use
1934	it, do the same for F<ev.h> in all files wishing to use this API (best	2898	it, do the same for F<ev.h> in all files wishing to use this API (best
1935	done by writing a wrapper around F<ev.h> that you can include instead and	2899	done by writing a wrapper around F<ev.h> that you can include instead and
1936	where you can put other configuration options):	2900	where you can put other configuration options):
1937		2901
1938	#define EV_STANDALONE 1	2902	#define EV_STANDALONE 1
1939	#include "ev.h"	2903	#include "ev.h"
1940		2904
1941	Both header files and implementation files can be compiled with a C++	2905	Both header files and implementation files can be compiled with a C++
1942	compiler (at least, thats a stated goal, and breakage will be treated	2906	compiler (at least, thats a stated goal, and breakage will be treated
1943	as a bug).	2907	as a bug).
1944		2908
1945	You need the following files in your source tree, or in a directory	2909	You need the following files in your source tree, or in a directory
1946	in your include path (e.g. in libev/ when using -Ilibev):	2910	in your include path (e.g. in libev/ when using -Ilibev):
1947		2911
1948	ev.h	2912	ev.h
1949	ev.c	2913	ev.c
1950	ev_vars.h	2914	ev_vars.h
1951	ev_wrap.h	2915	ev_wrap.h
1952		2916
1953	ev_win32.c required on win32 platforms only	2917	ev_win32.c required on win32 platforms only
1954		2918
1955	ev_select.c only when select backend is enabled (which is enabled by default)	2919	ev_select.c only when select backend is enabled (which is enabled by default)
1956	ev_poll.c only when poll backend is enabled (disabled by default)	2920	ev_poll.c only when poll backend is enabled (disabled by default)
1957	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2921	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1958	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2922	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1959	ev_port.c only when the solaris port backend is enabled (disabled by default)	2923	ev_port.c only when the solaris port backend is enabled (disabled by default)
1960		2924
1961	F<ev.c> includes the backend files directly when enabled, so you only need	2925	F<ev.c> includes the backend files directly when enabled, so you only need
1962	to compile this single file.	2926	to compile this single file.
1963		2927
1964	=head3 LIBEVENT COMPATIBILITY API	2928	=head3 LIBEVENT COMPATIBILITY API
1965		2929
1966	To include the libevent compatibility API, also include:	2930	To include the libevent compatibility API, also include:
1967		2931
1968	#include "event.c"	2932	#include "event.c"
1969		2933
1970	in the file including F<ev.c>, and:	2934	in the file including F<ev.c>, and:
1971		2935
1972	#include "event.h"	2936	#include "event.h"
1973		2937
1974	in the files that want to use the libevent API. This also includes F<ev.h>.	2938	in the files that want to use the libevent API. This also includes F<ev.h>.
1975		2939
1976	You need the following additional files for this:	2940	You need the following additional files for this:
1977		2941
1978	event.h	2942	event.h
1979	event.c	2943	event.c
1980		2944
1981	=head3 AUTOCONF SUPPORT	2945	=head3 AUTOCONF SUPPORT
1982		2946
1983	Instead of using C<EV_STANDALONE=1> and providing your config in	2947	Instead of using C<EV_STANDALONE=1> and providing your configuration in
1984	whatever way you want, you can also C<m4_include([libev.m4])> in your	2948	whatever way you want, you can also C<m4_include([libev.m4])> in your
1985	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2949	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1986	include F<config.h> and configure itself accordingly.	2950	include F<config.h> and configure itself accordingly.
1987		2951
1988	For this of course you need the m4 file:	2952	For this of course you need the m4 file:
1989		2953
1990	libev.m4	2954	libev.m4
1991		2955
1992	=head2 PREPROCESSOR SYMBOLS/MACROS	2956	=head2 PREPROCESSOR SYMBOLS/MACROS
1993		2957
1994	Libev can be configured via a variety of preprocessor symbols you have to define	2958	Libev can be configured via a variety of preprocessor symbols you have to
1995	before including any of its files. The default is not to build for multiplicity	2959	define before including any of its files. The default in the absence of
1996	and only include the select backend.	2960	autoconf is documented for every option.
1997		2961
1998	=over 4	2962	=over 4
1999		2963
2000	=item EV_STANDALONE	2964	=item EV_STANDALONE
2001		2965
…		…
2006	F<event.h> that are not directly supported by the libev core alone.	2970	F<event.h> that are not directly supported by the libev core alone.
2007		2971
2008	=item EV_USE_MONOTONIC	2972	=item EV_USE_MONOTONIC
2009		2973
2010	If defined to be C<1>, libev will try to detect the availability of the	2974	If defined to be C<1>, libev will try to detect the availability of the
2011	monotonic clock option at both compiletime and runtime. Otherwise no use	2975	monotonic clock option at both compile time and runtime. Otherwise no use
2012	of the monotonic clock option will be attempted. If you enable this, you	2976	of the monotonic clock option will be attempted. If you enable this, you
2013	usually have to link against librt or something similar. Enabling it when	2977	usually have to link against librt or something similar. Enabling it when
2014	the functionality isn't available is safe, though, althoguh you have	2978	the functionality isn't available is safe, though, although you have
2015	to make sure you link against any libraries where the C<clock_gettime>	2979	to make sure you link against any libraries where the C<clock_gettime>
2016	function is hiding in (often F<-lrt>).	2980	function is hiding in (often F<-lrt>).
2017		2981
2018	=item EV_USE_REALTIME	2982	=item EV_USE_REALTIME
2019		2983
2020	If defined to be C<1>, libev will try to detect the availability of the	2984	If defined to be C<1>, libev will try to detect the availability of the
2021	realtime clock option at compiletime (and assume its availability at	2985	real-time clock option at compile time (and assume its availability at
2022	runtime if successful). Otherwise no use of the realtime clock option will	2986	runtime if successful). Otherwise no use of the real-time clock option will
2023	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2987	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2024	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2988	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2025	in the description of C<EV_USE_MONOTONIC>, though.	2989	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2990
		2991	=item EV_USE_NANOSLEEP
		2992
		2993	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2994	and will use it for delays. Otherwise it will use C<select ()>.
		2995
		2996	=item EV_USE_EVENTFD
		2997
		2998	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2999	available and will probe for kernel support at runtime. This will improve
		3000	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3001	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3002	2.7 or newer, otherwise disabled.
2026		3003
2027	=item EV_USE_SELECT	3004	=item EV_USE_SELECT
2028		3005
2029	If undefined or defined to be C<1>, libev will compile in support for the	3006	If undefined or defined to be C<1>, libev will compile in support for the
2030	C<select>(2) backend. No attempt at autodetection will be done: if no	3007	C<select>(2) backend. No attempt at auto-detection will be done: if no
2031	other method takes over, select will be it. Otherwise the select backend	3008	other method takes over, select will be it. Otherwise the select backend
2032	will not be compiled in.	3009	will not be compiled in.
2033		3010
2034	=item EV_SELECT_USE_FD_SET	3011	=item EV_SELECT_USE_FD_SET
2035		3012
2036	If defined to C<1>, then the select backend will use the system C<fd_set>	3013	If defined to C<1>, then the select backend will use the system C<fd_set>
2037	structure. This is useful if libev doesn't compile due to a missing	3014	structure. This is useful if libev doesn't compile due to a missing
2038	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3015	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2039	exotic systems. This usually limits the range of file descriptors to some	3016	exotic systems. This usually limits the range of file descriptors to some
2040	low limit such as 1024 or might have other limitations (winsocket only	3017	low limit such as 1024 or might have other limitations (winsocket only
2041	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3018	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2042	influence the size of the C<fd_set> used.	3019	influence the size of the C<fd_set> used.
2043		3020
…		…
2049	be used is the winsock select). This means that it will call	3026	be used is the winsock select). This means that it will call
2050	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3027	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2051	it is assumed that all these functions actually work on fds, even	3028	it is assumed that all these functions actually work on fds, even
2052	on win32. Should not be defined on non-win32 platforms.	3029	on win32. Should not be defined on non-win32 platforms.
2053		3030
		3031	=item EV_FD_TO_WIN32_HANDLE
		3032
		3033	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3034	file descriptors to socket handles. When not defining this symbol (the
		3035	default), then libev will call C<_get_osfhandle>, which is usually
		3036	correct. In some cases, programs use their own file descriptor management,
		3037	in which case they can provide this function to map fds to socket handles.
		3038
2054	=item EV_USE_POLL	3039	=item EV_USE_POLL
2055		3040
2056	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3041	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2057	backend. Otherwise it will be enabled on non-win32 platforms. It	3042	backend. Otherwise it will be enabled on non-win32 platforms. It
2058	takes precedence over select.	3043	takes precedence over select.
2059		3044
2060	=item EV_USE_EPOLL	3045	=item EV_USE_EPOLL
2061		3046
2062	If defined to be C<1>, libev will compile in support for the Linux	3047	If defined to be C<1>, libev will compile in support for the Linux
2063	C<epoll>(7) backend. Its availability will be detected at runtime,	3048	C<epoll>(7) backend. Its availability will be detected at runtime,
2064	otherwise another method will be used as fallback. This is the	3049	otherwise another method will be used as fallback. This is the preferred
2065	preferred backend for GNU/Linux systems.	3050	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3051	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2066		3052
2067	=item EV_USE_KQUEUE	3053	=item EV_USE_KQUEUE
2068		3054
2069	If defined to be C<1>, libev will compile in support for the BSD style	3055	If defined to be C<1>, libev will compile in support for the BSD style
2070	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3056	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2083	otherwise another method will be used as fallback. This is the preferred	3069	otherwise another method will be used as fallback. This is the preferred
2084	backend for Solaris 10 systems.	3070	backend for Solaris 10 systems.
2085		3071
2086	=item EV_USE_DEVPOLL	3072	=item EV_USE_DEVPOLL
2087		3073
2088	reserved for future expansion, works like the USE symbols above.	3074	Reserved for future expansion, works like the USE symbols above.
2089		3075
2090	=item EV_USE_INOTIFY	3076	=item EV_USE_INOTIFY
2091		3077
2092	If defined to be C<1>, libev will compile in support for the Linux inotify	3078	If defined to be C<1>, libev will compile in support for the Linux inotify
2093	interface to speed up C<ev_stat> watchers. Its actual availability will	3079	interface to speed up C<ev_stat> watchers. Its actual availability will
2094	be detected at runtime.	3080	be detected at runtime. If undefined, it will be enabled if the headers
		3081	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3082
		3083	=item EV_ATOMIC_T
		3084
		3085	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3086	access is atomic with respect to other threads or signal contexts. No such
		3087	type is easily found in the C language, so you can provide your own type
		3088	that you know is safe for your purposes. It is used both for signal handler "locking"
		3089	as well as for signal and thread safety in C<ev_async> watchers.
		3090
		3091	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3092	(from F<signal.h>), which is usually good enough on most platforms.
2095		3093
2096	=item EV_H	3094	=item EV_H
2097		3095
2098	The name of the F<ev.h> header file used to include it. The default if	3096	The name of the F<ev.h> header file used to include it. The default if
2099	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3097	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2100	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3098	used to virtually rename the F<ev.h> header file in case of conflicts.
2101		3099
2102	=item EV_CONFIG_H	3100	=item EV_CONFIG_H
2103		3101
2104	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3102	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2105	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3103	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2106	C<EV_H>, above.	3104	C<EV_H>, above.
2107		3105
2108	=item EV_EVENT_H	3106	=item EV_EVENT_H
2109		3107
2110	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3108	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2111	of how the F<event.h> header can be found.	3109	of how the F<event.h> header can be found, the default is C<"event.h">.
2112		3110
2113	=item EV_PROTOTYPES	3111	=item EV_PROTOTYPES
2114		3112
2115	If defined to be C<0>, then F<ev.h> will not define any function	3113	If defined to be C<0>, then F<ev.h> will not define any function
2116	prototypes, but still define all the structs and other symbols. This is	3114	prototypes, but still define all the structs and other symbols. This is
…		…
2123	will have the C<struct ev_loop *> as first argument, and you can create	3121	will have the C<struct ev_loop *> as first argument, and you can create
2124	additional independent event loops. Otherwise there will be no support	3122	additional independent event loops. Otherwise there will be no support
2125	for multiple event loops and there is no first event loop pointer	3123	for multiple event loops and there is no first event loop pointer
2126	argument. Instead, all functions act on the single default loop.	3124	argument. Instead, all functions act on the single default loop.
2127		3125
		3126	=item EV_MINPRI
		3127
		3128	=item EV_MAXPRI
		3129
		3130	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		3131	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		3132	provide for more priorities by overriding those symbols (usually defined
		3133	to be C<-2> and C<2>, respectively).
		3134
		3135	When doing priority-based operations, libev usually has to linearly search
		3136	all the priorities, so having many of them (hundreds) uses a lot of space
		3137	and time, so using the defaults of five priorities (-2 .. +2) is usually
		3138	fine.
		3139
		3140	If your embedding application does not need any priorities, defining these
		3141	both to C<0> will save some memory and CPU.
		3142
2128	=item EV_PERIODIC_ENABLE	3143	=item EV_PERIODIC_ENABLE
2129		3144
2130	If undefined or defined to be C<1>, then periodic timers are supported. If	3145	If undefined or defined to be C<1>, then periodic timers are supported. If
2131	defined to be C<0>, then they are not. Disabling them saves a few kB of	3146	defined to be C<0>, then they are not. Disabling them saves a few kB of
2132	code.	3147	code.
…		…
2138	code.	3153	code.
2139		3154
2140	=item EV_EMBED_ENABLE	3155	=item EV_EMBED_ENABLE
2141		3156
2142	If undefined or defined to be C<1>, then embed watchers are supported. If	3157	If undefined or defined to be C<1>, then embed watchers are supported. If
2143	defined to be C<0>, then they are not.	3158	defined to be C<0>, then they are not. Embed watchers rely on most other
		3159	watcher types, which therefore must not be disabled.
2144		3160
2145	=item EV_STAT_ENABLE	3161	=item EV_STAT_ENABLE
2146		3162
2147	If undefined or defined to be C<1>, then stat watchers are supported. If	3163	If undefined or defined to be C<1>, then stat watchers are supported. If
2148	defined to be C<0>, then they are not.	3164	defined to be C<0>, then they are not.
…		…
2150	=item EV_FORK_ENABLE	3166	=item EV_FORK_ENABLE
2151		3167
2152	If undefined or defined to be C<1>, then fork watchers are supported. If	3168	If undefined or defined to be C<1>, then fork watchers are supported. If
2153	defined to be C<0>, then they are not.	3169	defined to be C<0>, then they are not.
2154		3170
		3171	=item EV_ASYNC_ENABLE
		3172
		3173	If undefined or defined to be C<1>, then async watchers are supported. If
		3174	defined to be C<0>, then they are not.
		3175
2155	=item EV_MINIMAL	3176	=item EV_MINIMAL
2156		3177
2157	If you need to shave off some kilobytes of code at the expense of some	3178	If you need to shave off some kilobytes of code at the expense of some
2158	speed, define this symbol to C<1>. Currently only used for gcc to override	3179	speed, define this symbol to C<1>. Currently this is used to override some
2159	some inlining decisions, saves roughly 30% codesize of amd64.	3180	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3181	much smaller 2-heap for timer management over the default 4-heap.
2160		3182
2161	=item EV_PID_HASHSIZE	3183	=item EV_PID_HASHSIZE
2162		3184
2163	C<ev_child> watchers use a small hash table to distribute workload by	3185	C<ev_child> watchers use a small hash table to distribute workload by
2164	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3186	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2165	than enough. If you need to manage thousands of children you might want to	3187	than enough. If you need to manage thousands of children you might want to
2166	increase this value (I<must> be a power of two).	3188	increase this value (I<must> be a power of two).
2167		3189
2168	=item EV_INOTIFY_HASHSIZE	3190	=item EV_INOTIFY_HASHSIZE
2169		3191
2170	C<ev_staz> watchers use a small hash table to distribute workload by	3192	C<ev_stat> watchers use a small hash table to distribute workload by
2171	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3193	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2172	usually more than enough. If you need to manage thousands of C<ev_stat>	3194	usually more than enough. If you need to manage thousands of C<ev_stat>
2173	watchers you might want to increase this value (I<must> be a power of	3195	watchers you might want to increase this value (I<must> be a power of
2174	two).	3196	two).
2175		3197
		3198	=item EV_USE_4HEAP
		3199
		3200	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3201	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3202	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3203	faster performance with many (thousands) of watchers.
		3204
		3205	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3206	(disabled).
		3207
		3208	=item EV_HEAP_CACHE_AT
		3209
		3210	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3211	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3212	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3213	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3214	but avoids random read accesses on heap changes. This improves performance
		3215	noticeably with many (hundreds) of watchers.
		3216
		3217	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3218	(disabled).
		3219
		3220	=item EV_VERIFY
		3221
		3222	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3223	be done: If set to C<0>, no internal verification code will be compiled
		3224	in. If set to C<1>, then verification code will be compiled in, but not
		3225	called. If set to C<2>, then the internal verification code will be
		3226	called once per loop, which can slow down libev. If set to C<3>, then the
		3227	verification code will be called very frequently, which will slow down
		3228	libev considerably.
		3229
		3230	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3231	C<0>.
		3232
2176	=item EV_COMMON	3233	=item EV_COMMON
2177		3234
2178	By default, all watchers have a C<void *data> member. By redefining	3235	By default, all watchers have a C<void *data> member. By redefining
2179	this macro to a something else you can include more and other types of	3236	this macro to a something else you can include more and other types of
2180	members. You have to define it each time you include one of the files,	3237	members. You have to define it each time you include one of the files,
2181	though, and it must be identical each time.	3238	though, and it must be identical each time.
2182		3239
2183	For example, the perl EV module uses something like this:	3240	For example, the perl EV module uses something like this:
2184		3241
2185	#define EV_COMMON \	3242	#define EV_COMMON \
2186	SV *self; /* contains this struct */ \	3243	SV *self; /* contains this struct */ \
2187	SV *cb_sv, *fh /* note no trailing ";" */	3244	SV *cb_sv, *fh /* note no trailing ";" */
2188		3245
2189	=item EV_CB_DECLARE (type)	3246	=item EV_CB_DECLARE (type)
2190		3247
2191	=item EV_CB_INVOKE (watcher, revents)	3248	=item EV_CB_INVOKE (watcher, revents)
2192		3249
2193	=item ev_set_cb (ev, cb)	3250	=item ev_set_cb (ev, cb)
2194		3251
2195	Can be used to change the callback member declaration in each watcher,	3252	Can be used to change the callback member declaration in each watcher,
2196	and the way callbacks are invoked and set. Must expand to a struct member	3253	and the way callbacks are invoked and set. Must expand to a struct member
2197	definition and a statement, respectively. See the F<ev.v> header file for	3254	definition and a statement, respectively. See the F<ev.h> header file for
2198	their default definitions. One possible use for overriding these is to	3255	their default definitions. One possible use for overriding these is to
2199	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3256	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2200	method calls instead of plain function calls in C++.	3257	method calls instead of plain function calls in C++.
		3258
		3259	=back
		3260
		3261	=head2 EXPORTED API SYMBOLS
		3262
		3263	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3264	exported symbols, you can use the provided F<Symbol.*> files which list
		3265	all public symbols, one per line:
		3266
		3267	Symbols.ev for libev proper
		3268	Symbols.event for the libevent emulation
		3269
		3270	This can also be used to rename all public symbols to avoid clashes with
		3271	multiple versions of libev linked together (which is obviously bad in
		3272	itself, but sometimes it is inconvenient to avoid this).
		3273
		3274	A sed command like this will create wrapper C<#define>'s that you need to
		3275	include before including F<ev.h>:
		3276
		3277	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3278
		3279	This would create a file F<wrap.h> which essentially looks like this:
		3280
		3281	#define ev_backend myprefix_ev_backend
		3282	#define ev_check_start myprefix_ev_check_start
		3283	#define ev_check_stop myprefix_ev_check_stop
		3284	...
2201		3285
2202	=head2 EXAMPLES	3286	=head2 EXAMPLES
2203		3287
2204	For a real-world example of a program the includes libev	3288	For a real-world example of a program the includes libev
2205	verbatim, you can have a look at the EV perl module	3289	verbatim, you can have a look at the EV perl module
…		…
2210	file.	3294	file.
2211		3295
2212	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3296	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2213	that everybody includes and which overrides some configure choices:	3297	that everybody includes and which overrides some configure choices:
2214		3298
2215	#define EV_MINIMAL 1	3299	#define EV_MINIMAL 1
2216	#define EV_USE_POLL 0	3300	#define EV_USE_POLL 0
2217	#define EV_MULTIPLICITY 0	3301	#define EV_MULTIPLICITY 0
2218	#define EV_PERIODIC_ENABLE 0	3302	#define EV_PERIODIC_ENABLE 0
2219	#define EV_STAT_ENABLE 0	3303	#define EV_STAT_ENABLE 0
2220	#define EV_FORK_ENABLE 0	3304	#define EV_FORK_ENABLE 0
2221	#define EV_CONFIG_H <config.h>	3305	#define EV_CONFIG_H <config.h>
2222	#define EV_MINPRI 0	3306	#define EV_MINPRI 0
2223	#define EV_MAXPRI 0	3307	#define EV_MAXPRI 0
2224		3308
2225	#include "ev++.h"	3309	#include "ev++.h"
2226		3310
2227	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3311	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2228		3312
2229	#include "ev_cpp.h"	3313	#include "ev_cpp.h"
2230	#include "ev.c"	3314	#include "ev.c"
2231		3315
		3316	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2232		3317
		3318	=head2 THREADS AND COROUTINES
		3319
		3320	=head3 THREADS
		3321
		3322	All libev functions are reentrant and thread-safe unless explicitly
		3323	documented otherwise, but libev implements no locking itself. This means
		3324	that you can use as many loops as you want in parallel, as long as there
		3325	are no concurrent calls into any libev function with the same loop
		3326	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3327	of course): libev guarantees that different event loops share no data
		3328	structures that need any locking.
		3329
		3330	Or to put it differently: calls with different loop parameters can be done
		3331	concurrently from multiple threads, calls with the same loop parameter
		3332	must be done serially (but can be done from different threads, as long as
		3333	only one thread ever is inside a call at any point in time, e.g. by using
		3334	a mutex per loop).
		3335
		3336	Specifically to support threads (and signal handlers), libev implements
		3337	so-called C<ev_async> watchers, which allow some limited form of
		3338	concurrency on the same event loop, namely waking it up "from the
		3339	outside".
		3340
		3341	If you want to know which design (one loop, locking, or multiple loops
		3342	without or something else still) is best for your problem, then I cannot
		3343	help you, but here is some generic advice:
		3344
		3345	=over 4
		3346
		3347	=item * most applications have a main thread: use the default libev loop
		3348	in that thread, or create a separate thread running only the default loop.
		3349
		3350	This helps integrating other libraries or software modules that use libev
		3351	themselves and don't care/know about threading.
		3352
		3353	=item * one loop per thread is usually a good model.
		3354
		3355	Doing this is almost never wrong, sometimes a better-performance model
		3356	exists, but it is always a good start.
		3357
		3358	=item * other models exist, such as the leader/follower pattern, where one
		3359	loop is handed through multiple threads in a kind of round-robin fashion.
		3360
		3361	Choosing a model is hard - look around, learn, know that usually you can do
		3362	better than you currently do :-)
		3363
		3364	=item * often you need to talk to some other thread which blocks in the
		3365	event loop.
		3366
		3367	C<ev_async> watchers can be used to wake them up from other threads safely
		3368	(or from signal contexts...).
		3369
		3370	An example use would be to communicate signals or other events that only
		3371	work in the default loop by registering the signal watcher with the
		3372	default loop and triggering an C<ev_async> watcher from the default loop
		3373	watcher callback into the event loop interested in the signal.
		3374
		3375	=back
		3376
		3377	=head3 COROUTINES
		3378
		3379	Libev is very accommodating to coroutines ("cooperative threads"):
		3380	libev fully supports nesting calls to its functions from different
		3381	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3382	different coroutines, and switch freely between both coroutines running the
		3383	loop, as long as you don't confuse yourself). The only exception is that
		3384	you must not do this from C<ev_periodic> reschedule callbacks.
		3385
		3386	Care has been taken to ensure that libev does not keep local state inside
		3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3388	they do not clal any callbacks.
		3389
		3390	=head2 COMPILER WARNINGS
		3391
		3392	Depending on your compiler and compiler settings, you might get no or a
		3393	lot of warnings when compiling libev code. Some people are apparently
		3394	scared by this.
		3395
		3396	However, these are unavoidable for many reasons. For one, each compiler
		3397	has different warnings, and each user has different tastes regarding
		3398	warning options. "Warn-free" code therefore cannot be a goal except when
		3399	targeting a specific compiler and compiler-version.
		3400
		3401	Another reason is that some compiler warnings require elaborate
		3402	workarounds, or other changes to the code that make it less clear and less
		3403	maintainable.
		3404
		3405	And of course, some compiler warnings are just plain stupid, or simply
		3406	wrong (because they don't actually warn about the condition their message
		3407	seems to warn about). For example, certain older gcc versions had some
		3408	warnings that resulted an extreme number of false positives. These have
		3409	been fixed, but some people still insist on making code warn-free with
		3410	such buggy versions.
		3411
		3412	While libev is written to generate as few warnings as possible,
		3413	"warn-free" code is not a goal, and it is recommended not to build libev
		3414	with any compiler warnings enabled unless you are prepared to cope with
		3415	them (e.g. by ignoring them). Remember that warnings are just that:
		3416	warnings, not errors, or proof of bugs.
		3417
		3418
		3419	=head2 VALGRIND
		3420
		3421	Valgrind has a special section here because it is a popular tool that is
		3422	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3423
		3424	If you think you found a bug (memory leak, uninitialised data access etc.)
		3425	in libev, then check twice: If valgrind reports something like:
		3426
		3427	==2274== definitely lost: 0 bytes in 0 blocks.
		3428	==2274== possibly lost: 0 bytes in 0 blocks.
		3429	==2274== still reachable: 256 bytes in 1 blocks.
		3430
		3431	Then there is no memory leak, just as memory accounted to global variables
		3432	is not a memleak - the memory is still being refernced, and didn't leak.
		3433
		3434	Similarly, under some circumstances, valgrind might report kernel bugs
		3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3436	although an acceptable workaround has been found here), or it might be
		3437	confused.
		3438
		3439	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3440	make it into some kind of religion.
		3441
		3442	If you are unsure about something, feel free to contact the mailing list
		3443	with the full valgrind report and an explanation on why you think this
		3444	is a bug in libev (best check the archives, too :). However, don't be
		3445	annoyed when you get a brisk "this is no bug" answer and take the chance
		3446	of learning how to interpret valgrind properly.
		3447
		3448	If you need, for some reason, empty reports from valgrind for your project
		3449	I suggest using suppression lists.
		3450
		3451
		3452	=head1 PORTABILITY NOTES
		3453
		3454	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3455
		3456	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3457	requires, and its I/O model is fundamentally incompatible with the POSIX
		3458	model. Libev still offers limited functionality on this platform in
		3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3460	descriptors. This only applies when using Win32 natively, not when using
		3461	e.g. cygwin.
		3462
		3463	Lifting these limitations would basically require the full
		3464	re-implementation of the I/O system. If you are into these kinds of
		3465	things, then note that glib does exactly that for you in a very portable
		3466	way (note also that glib is the slowest event library known to man).
		3467
		3468	There is no supported compilation method available on windows except
		3469	embedding it into other applications.
		3470
		3471	Not a libev limitation but worth mentioning: windows apparently doesn't
		3472	accept large writes: instead of resulting in a partial write, windows will
		3473	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3474	so make sure you only write small amounts into your sockets (less than a
		3475	megabyte seems safe, but this apparently depends on the amount of memory
		3476	available).
		3477
		3478	Due to the many, low, and arbitrary limits on the win32 platform and
		3479	the abysmal performance of winsockets, using a large number of sockets
		3480	is not recommended (and not reasonable). If your program needs to use
		3481	more than a hundred or so sockets, then likely it needs to use a totally
		3482	different implementation for windows, as libev offers the POSIX readiness
		3483	notification model, which cannot be implemented efficiently on windows
		3484	(Microsoft monopoly games).
		3485
		3486	A typical way to use libev under windows is to embed it (see the embedding
		3487	section for details) and use the following F<evwrap.h> header file instead
		3488	of F<ev.h>:
		3489
		3490	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3491	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3492
		3493	#include "ev.h"
		3494
		3495	And compile the following F<evwrap.c> file into your project (make sure
		3496	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3497
		3498	#include "evwrap.h"
		3499	#include "ev.c"
		3500
		3501	=over 4
		3502
		3503	=item The winsocket select function
		3504
		3505	The winsocket C<select> function doesn't follow POSIX in that it
		3506	requires socket I<handles> and not socket I<file descriptors> (it is
		3507	also extremely buggy). This makes select very inefficient, and also
		3508	requires a mapping from file descriptors to socket handles (the Microsoft
		3509	C runtime provides the function C<_open_osfhandle> for this). See the
		3510	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3511	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3512
		3513	The configuration for a "naked" win32 using the Microsoft runtime
		3514	libraries and raw winsocket select is:
		3515
		3516	#define EV_USE_SELECT 1
		3517	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3518
		3519	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3520	complexity in the O(n²) range when using win32.
		3521
		3522	=item Limited number of file descriptors
		3523
		3524	Windows has numerous arbitrary (and low) limits on things.
		3525
		3526	Early versions of winsocket's select only supported waiting for a maximum
		3527	of C<64> handles (probably owning to the fact that all windows kernels
		3528	can only wait for C<64> things at the same time internally; Microsoft
		3529	recommends spawning a chain of threads and wait for 63 handles and the
		3530	previous thread in each. Great).
		3531
		3532	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3533	to some high number (e.g. C<2048>) before compiling the winsocket select
		3534	call (which might be in libev or elsewhere, for example, perl does its own
		3535	select emulation on windows).
		3536
		3537	Another limit is the number of file descriptors in the Microsoft runtime
		3538	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3539	or something like this inside Microsoft). You can increase this by calling
		3540	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3541	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3542	libraries.
		3543
		3544	This might get you to about C<512> or C<2048> sockets (depending on
		3545	windows version and/or the phase of the moon). To get more, you need to
		3546	wrap all I/O functions and provide your own fd management, but the cost of
		3547	calling select (O(n²)) will likely make this unworkable.
		3548
		3549	=back
		3550
		3551	=head2 PORTABILITY REQUIREMENTS
		3552
		3553	In addition to a working ISO-C implementation and of course the
		3554	backend-specific APIs, libev relies on a few additional extensions:
		3555
		3556	=over 4
		3557
		3558	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3559	calling conventions regardless of C<ev_watcher_type *>.
		3560
		3561	Libev assumes not only that all watcher pointers have the same internal
		3562	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3563	assumes that the same (machine) code can be used to call any watcher
		3564	callback: The watcher callbacks have different type signatures, but libev
		3565	calls them using an C<ev_watcher *> internally.
		3566
		3567	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3568
		3569	The type C<sig_atomic_t volatile> (or whatever is defined as
		3570	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3571	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3572	believed to be sufficiently portable.
		3573
		3574	=item C<sigprocmask> must work in a threaded environment
		3575
		3576	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3577	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3578	pthread implementations will either allow C<sigprocmask> in the "main
		3579	thread" or will block signals process-wide, both behaviours would
		3580	be compatible with libev. Interaction between C<sigprocmask> and
		3581	C<pthread_sigmask> could complicate things, however.
		3582
		3583	The most portable way to handle signals is to block signals in all threads
		3584	except the initial one, and run the default loop in the initial thread as
		3585	well.
		3586
		3587	=item C<long> must be large enough for common memory allocation sizes
		3588
		3589	To improve portability and simplify its API, libev uses C<long> internally
		3590	instead of C<size_t> when allocating its data structures. On non-POSIX
		3591	systems (Microsoft...) this might be unexpectedly low, but is still at
		3592	least 31 bits everywhere, which is enough for hundreds of millions of
		3593	watchers.
		3594
		3595	=item C<double> must hold a time value in seconds with enough accuracy
		3596
		3597	The type C<double> is used to represent timestamps. It is required to
		3598	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3599	enough for at least into the year 4000. This requirement is fulfilled by
		3600	implementations implementing IEEE 754 (basically all existing ones).
		3601
		3602	=back
		3603
		3604	If you know of other additional requirements drop me a note.
		3605
		3606
2233	=head1 COMPLEXITIES	3607	=head1 ALGORITHMIC COMPLEXITIES
2234		3608
2235	In this section the complexities of (many of) the algorithms used inside	3609	In this section the complexities of (many of) the algorithms used inside
2236	libev will be explained. For complexity discussions about backends see the	3610	libev will be documented. For complexity discussions about backends see
2237	documentation for C<ev_default_init>.	3611	the documentation for C<ev_default_init>.
		3612
		3613	All of the following are about amortised time: If an array needs to be
		3614	extended, libev needs to realloc and move the whole array, but this
		3615	happens asymptotically rarer with higher number of elements, so O(1) might
		3616	mean that libev does a lengthy realloc operation in rare cases, but on
		3617	average it is much faster and asymptotically approaches constant time.
2238		3618
2239	=over 4	3619	=over 4
2240		3620
2241	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3621	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2242		3622
		3623	This means that, when you have a watcher that triggers in one hour and
		3624	there are 100 watchers that would trigger before that, then inserting will
		3625	have to skip roughly seven (C<ld 100>) of these watchers.
		3626
2243	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3627	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2244		3628
		3629	That means that changing a timer costs less than removing/adding them,
		3630	as only the relative motion in the event queue has to be paid for.
		3631
2245	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3632	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2246		3633
		3634	These just add the watcher into an array or at the head of a list.
		3635
2247	=item Stopping check/prepare/idle watchers: O(1)	3636	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2248		3637
2249	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3638	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2250		3639
		3640	These watchers are stored in lists, so they need to be walked to find the
		3641	correct watcher to remove. The lists are usually short (you don't usually
		3642	have many watchers waiting for the same fd or signal: one is typical, two
		3643	is rare).
		3644
2251	=item Finding the next timer per loop iteration: O(1)	3645	=item Finding the next timer in each loop iteration: O(1)
		3646
		3647	By virtue of using a binary or 4-heap, the next timer is always found at a
		3648	fixed position in the storage array.
2252		3649
2253	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3650	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2254		3651
2255	=item Activating one watcher: O(1)	3652	A change means an I/O watcher gets started or stopped, which requires
		3653	libev to recalculate its status (and possibly tell the kernel, depending
		3654	on backend and whether C<ev_io_set> was used).
		3655
		3656	=item Activating one watcher (putting it into the pending state): O(1)
		3657
		3658	=item Priority handling: O(number_of_priorities)
		3659
		3660	Priorities are implemented by allocating some space for each
		3661	priority. When doing priority-based operations, libev usually has to
		3662	linearly search all the priorities, but starting/stopping and activating
		3663	watchers becomes O(1) with respect to priority handling.
		3664
		3665	=item Sending an ev_async: O(1)
		3666
		3667	=item Processing ev_async_send: O(number_of_async_watchers)
		3668
		3669	=item Processing signals: O(max_signal_number)
		3670
		3671	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3672	calls in the current loop iteration. Checking for async and signal events
		3673	involves iterating over all running async watchers or all signal numbers.
2256		3674
2257	=back	3675	=back
2258		3676
2259		3677
2260	=head1 AUTHOR	3678	=head1 AUTHOR

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