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Revision 1.61 by root, Thu Nov 29 12:21:05 2007 UTC vs.
Revision 1.198 by root, Thu Oct 23 06:30:48 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_ 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_ 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	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<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.
…		…
222		276
223	=back	277	=back
224		278
225	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
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<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
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		284
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
…		…
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.
270		328
		329	=item C<EVFLAG_FORKCHECK>
		330
		331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		332	a fork, you can also make libev check for a fork in each iteration by
		333	enabling this flag.
		334
		335	This works by calling C<getpid ()> on every iteration of the loop,
		336	and thus this might slow down your event loop if you do a lot of loop
		337	iterations and little real work, but is usually not noticeable (on my
		338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		339	without a system call and thus I<very> fast, but my GNU/Linux system also has
		340	C<pthread_atfork> which is even faster).
		341
		342	The big advantage of this flag is that you can forget about fork (and
		343	forget about forgetting to tell libev about forking) when you use this
		344	flag.
		345
		346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
		347	environment variable.
		348
271	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
272		350
273	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
274	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,
275	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
276	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
277	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).
278		367
279	=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)
280		369
281	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
282	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
283	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
284	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>.
285		379
286	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
287		381
288	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,
289	but it scales phenomenally better. While poll and select usually scale like	383	but it scales phenomenally better. While poll and select usually scale
290	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),
291	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.
292		389
293	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
294	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
295	(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
296	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
297	well if you register events for both fds.	394	very well if you register events for both fds.
298		395
299	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
300	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
301	(or space) is available.	398	(or space) is available.
302		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
303	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
304		413
305	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
306	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
307	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
308	completely useless). For this reason its not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
309	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
310	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.
311		424
312	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
313	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
314	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
315	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
316	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>.
317		444
318	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
319		446
320	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.
321		451
322	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
323		453
324	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,
325	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)).
326		456
327	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
328	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
329	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>.
330		473
331	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
332		475
333	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
334	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
335	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
336		479
		480	It is definitely not recommended to use this flag.
		481
337	=back	482	=back
338		483
339	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
340	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
341	specified, most compiled-in backend will be tried, usually in reverse	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
342	order of their flag values :)
343		487
344	The most typical usage is like this:	488	Example: This is the most typical usage.
345		489
346	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
347	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
348		492
349	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
350	environment settings to be taken into account:	494	environment settings to be taken into account:
351		495
352	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
353		497
354	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
355	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
356	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):
357		502
358	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
359		504
360	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
361		506
362	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
363	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
364	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
365	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
366		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
367	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.
368		517
369	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
370	if (!epoller)	519	if (!epoller)
371	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
372		521
373	=item ev_default_destroy ()	522	=item ev_default_destroy ()
374		523
375	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
376	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
377	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
378	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
379	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
380	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
381	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>).
382		540
383	=item ev_loop_destroy (loop)	541	=item ev_loop_destroy (loop)
384		542
385	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
386	earlier call to C<ev_loop_new>.	544	earlier call to C<ev_loop_new>.
387		545
388	=item ev_default_fork ()	546	=item ev_default_fork ()
389		547
		548	This function sets a flag that causes subsequent C<ev_loop> iterations
390	This function reinitialises the kernel state for backends that have	549	to reinitialise the kernel state for backends that have one. Despite the
391	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
392	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
393	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.
394		554
395	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
396	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
397	fork+exec, you don't have to call it.	557	you just fork+exec, you don't have to call it at all.
398		558
399	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
400	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
401	quite nicely into a call to C<pthread_atfork>:	561	quite nicely into a call to C<pthread_atfork>:
402		562
403	pthread_atfork (0, 0, ev_default_fork);	563	pthread_atfork (0, 0, ev_default_fork);
404		564
405	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
406	without calling this function, so if you force one of those backends you
407	do not need to care.
408
409	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
410		566
411	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
412	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
413	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.
		576
		577	=item unsigned int ev_loop_count (loop)
		578
		579	Returns the count of loop iterations for the loop, which is identical to
		580	the number of times libev did poll for new events. It starts at C<0> and
		581	happily wraps around with enough iterations.
		582
		583	This value can sometimes be useful as a generation counter of sorts (it
		584	"ticks" the number of loop iterations), as it roughly corresponds with
		585	C<ev_prepare> and C<ev_check> calls.
414		586
415	=item unsigned int ev_backend (loop)	587	=item unsigned int ev_backend (loop)
416		588
417	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
418	use.	590	use.
…		…
421		593
422	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
423	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
424	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
425	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
426	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.
427		611
428	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
429		613
430	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
431	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
…		…
434	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
435	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.
436		620
437	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
438	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
439	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
440	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
441	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.
442		627
443	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
444	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
445	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.
446		632
447	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
448	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
449	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
450	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
451	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
452	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
453	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
454		644
455	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
456		646
457	* If there are no active watchers (reference count is zero), return.	647	- Before the first iteration, call any pending watchers.
458	- 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.
459	- 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.
460	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
461	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
462	- 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.
463	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
464	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
465	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
466	- Queue all outstanding timers.	662	- Queue all expired timers.
467	- Queue all outstanding periodics.	663	- Queue all expired periodics.
468	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
469	- Queue all check watchers.	665	- Queue all check watchers.
470	- 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).
471	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
472	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
473	- 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
474	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
475		672
476	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
477	anymore.	674	anymore.
478		675
479	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
480	... 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..)
481	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
482	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
483		680
484	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
485		682
486	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
487	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
488	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
489	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.
490		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
491	=item ev_ref (loop)	692	=item ev_ref (loop)
492		693
493	=item ev_unref (loop)	694	=item ev_unref (loop)
494		695
495	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
496	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
497	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
498	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>
499	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
500	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
501	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
502	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
503	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
504	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).
505		711
506	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>
507	running when nothing else is active.	713	running when nothing else is active.
508		714
509	struct ev_signal exitsig;	715	ev_signal exitsig;
510	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
511	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
512	evf_unref (loop);	718	evf_unref (loop);
513		719
514	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
515		721
516	ev_ref (loop);	722	ev_ref (loop);
517	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.
518		781
519	=back	782	=back
520		783
521		784
522	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
523		786
524	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
525	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
526	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:
527		790
528	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
529	{	792	{
530	ev_io_stop (w);	793	ev_io_stop (w);
531	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
532	}	795	}
533		796
534	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
535	struct ev_io stdin_watcher;	798	ev_io stdin_watcher;
536	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
537	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
538	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
539	ev_loop (loop, 0);	802	ev_loop (loop, 0);
540		803
541	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
542	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,
543	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
544		807
545	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
546	(watcher *, callback)>, which expects a callback to be provided. This	809	(watcher *, callback)>, which expects a callback to be provided. This
547	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
548	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
549	is readable and/or writable).	812	is readable and/or writable).
550		813
551	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
552	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
…		…
622	=item C<EV_FORK>	885	=item C<EV_FORK>
623		886
624	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
625	C<ev_fork>).	888	C<ev_fork>).
626		889
		890	=item C<EV_ASYNC>
		891
		892	The given async watcher has been asynchronously notified (see C<ev_async>).
		893
627	=item C<EV_ERROR>	894	=item C<EV_ERROR>
628		895
629	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
630	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
631	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
632	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
633	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
634		905
635	Libev will usually signal a few "dummy" events together with an error,	906	Libev will usually signal a few "dummy" events together with an error, for
636	for example it might indicate that a fd is readable or writable, and if	907	example it might indicate that a fd is readable or writable, and if your
637	your callbacks is well-written it can just attempt the operation and cope	908	callbacks is well-written it can just attempt the operation and cope with
638	with the error from read() or write(). This will not work in multithreaded	909	the error from read() or write(). This will not work in multi-threaded
639	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
640		912
641	=back	913	=back
642		914
643	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
644		916
…		…
657	which rolls both calls into one.	929	which rolls both calls into one.
658		930
659	You can reinitialise a watcher at any time as long as it has been stopped	931	You can reinitialise a watcher at any time as long as it has been stopped
660	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
661		933
662	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
663	int revents)>.	935	int revents)>.
		936
		937	Example: Initialise an C<ev_io> watcher in two steps.
		938
		939	ev_io w;
		940	ev_init (&w, my_cb);
		941	ev_io_set (&w, STDIN_FILENO, EV_READ);
664		942
665	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
666		944
667	This macro initialises the type-specific parts of a watcher. You need to	945	This macro initialises the type-specific parts of a watcher. You need to
668	call C<ev_init> at least once before you call this macro, but you can	946	call C<ev_init> at least once before you call this macro, but you can
…		…
671	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
672		950
673	Although some watcher types do not have type-specific arguments	951	Although some watcher types do not have type-specific arguments
674	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
675		953
		954	See C<ev_init>, above, for an example.
		955
676	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
677		957
678	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
679	calls into a single call. This is the most convinient method to initialise	959	calls into a single call. This is the most convenient method to initialise
680	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
681		965
682	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
683		967
684	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
685	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
686		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
687	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
688		977
689	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
690	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
691	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
692	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
693	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
694	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
695		986
696	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
697		988
698	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
699	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
702	=item bool ev_is_pending (ev_TYPE *watcher)	993	=item bool ev_is_pending (ev_TYPE *watcher)
703		994
704	Returns a true value iff the watcher is pending, (i.e. it has outstanding	995	Returns a true value iff the watcher is pending, (i.e. it has outstanding
705	events but its callback has not yet been invoked). As long as a watcher	996	events but its callback has not yet been invoked). As long as a watcher
706	is pending (but not active) you must not call an init function on it (but	997	is pending (but not active) you must not call an init function on it (but
707	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	998	C<ev_TYPE_set> is safe), you must not change its priority, and you must
708	libev (e.g. you cnanot C<free ()> it).	999	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1000	it).
709		1001
710	=item callback ev_cb (ev_TYPE *watcher)	1002	=item callback ev_cb (ev_TYPE *watcher)
711		1003
712	Returns the callback currently set on the watcher.	1004	Returns the callback currently set on the watcher.
713		1005
714	=item ev_cb_set (ev_TYPE *watcher, callback)	1006	=item ev_cb_set (ev_TYPE *watcher, callback)
715		1007
716	Change the callback. You can change the callback at virtually any time	1008	Change the callback. You can change the callback at virtually any time
717	(modulo threads).	1009	(modulo threads).
718		1010
		1011	=item ev_set_priority (ev_TYPE *watcher, priority)
		1012
		1013	=item int ev_priority (ev_TYPE *watcher)
		1014
		1015	Set and query the priority of the watcher. The priority is a small
		1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1017	(default: C<-2>). Pending watchers with higher priority will be invoked
		1018	before watchers with lower priority, but priority will not keep watchers
		1019	from being executed (except for C<ev_idle> watchers).
		1020
		1021	This means that priorities are I<only> used for ordering callback
		1022	invocation after new events have been received. This is useful, for
		1023	example, to reduce latency after idling, or more often, to bind two
		1024	watchers on the same event and make sure one is called first.
		1025
		1026	If you need to suppress invocation when higher priority events are pending
		1027	you need to look at C<ev_idle> watchers, which provide this functionality.
		1028
		1029	You I<must not> change the priority of a watcher as long as it is active or
		1030	pending.
		1031
		1032	The default priority used by watchers when no priority has been set is
		1033	always C<0>, which is supposed to not be too high and not be too low :).
		1034
		1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1036	fine, as long as you do not mind that the priority value you query might
		1037	or might not have been adjusted to be within valid range.
		1038
		1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1040
		1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
		1045
		1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1047
		1048	If the watcher is pending, this function clears its pending status and
		1049	returns its C<revents> bitset (as if its callback was invoked). If the
		1050	watcher isn't pending it does nothing and returns C<0>.
		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
719	=back	1055	=back
720		1056
721		1057
722	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
723		1059
724	Each watcher has, by default, a member C<void *data> that you can change	1060	Each watcher has, by default, a member C<void *data> that you can change
725	and read at any time, libev will completely ignore it. This can be used	1061	and read at any time: libev will completely ignore it. This can be used
726	to associate arbitrary data with your watcher. If you need more data and	1062	to associate arbitrary data with your watcher. If you need more data and
727	don't want to allocate memory and store a pointer to it in that data	1063	don't want to allocate memory and store a pointer to it in that data
728	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
729	data:	1065	data:
730		1066
731	struct my_io	1067	struct my_io
732	{	1068	{
733	struct ev_io io;	1069	ev_io io;
734	int otherfd;	1070	int otherfd;
735	void *somedata;	1071	void *somedata;
736	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
737	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
738		1078
739	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
740	can cast it back to your own type:	1080	can cast it back to your own type:
741		1081
742	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
743	{	1083	{
744	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
745	...	1085	...
746	}	1086	}
747		1087
748	More interesting and less C-conformant ways of casting your callback type	1088	More interesting and less C-conformant ways of casting your callback type
749	instead have been omitted.	1089	instead have been omitted.
750		1090
751	Another common scenario is having some data structure with multiple	1091	Another common scenario is to use some data structure with multiple
752	watchers:	1092	embedded watchers:
753		1093
754	struct my_biggy	1094	struct my_biggy
755	{	1095	{
756	int some_data;	1096	int some_data;
757	ev_timer t1;	1097	ev_timer t1;
758	ev_timer t2;	1098	ev_timer t2;
759	}	1099	}
760		1100
761	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1101	In this case getting the pointer to C<my_biggy> is a bit more
762	you need to use C<offsetof>:	1102	complicated: Either you store the address of your C<my_biggy> struct
		1103	in the C<data> member of the watcher (for woozies), or you need to use
		1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
763		1106
764	#include <stddef.h>	1107	#include <stddef.h>
765		1108
766	static void	1109	static void
767	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ ev_timer *w, int revents)
768	{	1111	{
769	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
770	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
771	}	1114	}
772		1115
773	static void	1116	static void
774	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ ev_timer *w, int revents)
775	{	1118	{
776	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
777	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
778	}	1121	}
779		1122
780		1123
781	=head1 WATCHER TYPES	1124	=head1 WATCHER TYPES
782		1125
783	This section describes each watcher in detail, but will not repeat	1126	This section describes each watcher in detail, but will not repeat
…		…
807	In general you can register as many read and/or write event watchers per	1150	In general you can register as many read and/or write event watchers per
808	fd as you want (as long as you don't confuse yourself). Setting all file	1151	fd as you want (as long as you don't confuse yourself). Setting all file
809	descriptors to non-blocking mode is also usually a good idea (but not	1152	descriptors to non-blocking mode is also usually a good idea (but not
810	required if you know what you are doing).	1153	required if you know what you are doing).
811		1154
812	You have to be careful with dup'ed file descriptors, though. Some backends	1155	If you cannot use non-blocking mode, then force the use of a
813	(the linux epoll backend is a notable example) cannot handle dup'ed file	1156	known-to-be-good backend (at the time of this writing, this includes only
814	descriptors correctly if you register interest in two or more fds pointing	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
815	to the same underlying file/socket/etc. description (that is, they share
816	the same underlying "file open").
817
818	If you must do this, then force the use of a known-to-be-good backend
819	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
820	C<EVBACKEND_POLL>).
821		1158
822	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
823	receive "spurious" readyness notifications, that is your callback might	1160	receive "spurious" readiness notifications, that is your callback might
824	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
825	because there is no data. Not only are some backends known to create a	1162	because there is no data. Not only are some backends known to create a
826	lot of those (for example solaris ports), it is very easy to get into	1163	lot of those (for example Solaris ports), it is very easy to get into
827	this situation even with a relatively standard program structure. Thus	1164	this situation even with a relatively standard program structure. Thus
828	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
829	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
830		1167
831	If you cannot run the fd in non-blocking mode (for example you should not	1168	If you cannot run the fd in non-blocking mode (for example you should
832	play around with an Xlib connection), then you have to seperately re-test	1169	not play around with an Xlib connection), then you have to separately
833	wether a file descriptor is really ready with a known-to-be good interface	1170	re-test whether a file descriptor is really ready with a known-to-be good
834	such as poll (fortunately in our Xlib example, Xlib already does this on	1171	interface such as poll (fortunately in our Xlib example, Xlib already
835	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
		1177
		1178	=head3 The special problem of disappearing file descriptors
		1179
		1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1181	descriptor (either due to calling C<close> explicitly or any other means,
		1182	such as C<dup2>). The reason is that you register interest in some file
		1183	descriptor, but when it goes away, the operating system will silently drop
		1184	this interest. If another file descriptor with the same number then is
		1185	registered with libev, there is no efficient way to see that this is, in
		1186	fact, a different file descriptor.
		1187
		1188	To avoid having to explicitly tell libev about such cases, libev follows
		1189	the following policy: Each time C<ev_io_set> is being called, libev
		1190	will assume that this is potentially a new file descriptor, otherwise
		1191	it is assumed that the file descriptor stays the same. That means that
		1192	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1193	descriptor even if the file descriptor number itself did not change.
		1194
		1195	This is how one would do it normally anyway, the important point is that
		1196	the libev application should not optimise around libev but should leave
		1197	optimisations to libev.
		1198
		1199	=head3 The special problem of dup'ed file descriptors
		1200
		1201	Some backends (e.g. epoll), cannot register events for file descriptors,
		1202	but only events for the underlying file descriptions. That means when you
		1203	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1204	events for them, only one file descriptor might actually receive events.
		1205
		1206	There is no workaround possible except not registering events
		1207	for potentially C<dup ()>'ed file descriptors, or to resort to
		1208	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1209
		1210	=head3 The special problem of fork
		1211
		1212	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1213	useless behaviour. Libev fully supports fork, but needs to be told about
		1214	it in the child.
		1215
		1216	To support fork in your programs, you either have to call
		1217	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1219	C<EVBACKEND_POLL>.
		1220
		1221	=head3 The special problem of SIGPIPE
		1222
		1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1224	when writing to a pipe whose other end has been closed, your program gets
		1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1226	this is sensible behaviour, for daemons, this is usually undesirable.
		1227
		1228	So when you encounter spurious, unexplained daemon exits, make sure you
		1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1230	somewhere, as that would have given you a big clue).
		1231
		1232
		1233	=head3 Watcher-Specific Functions
836		1234
837	=over 4	1235	=over 4
838		1236
839	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
840		1238
841	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
842		1240
843	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1241	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
844	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1242	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
845	C<EV_READ | EV_WRITE> to receive the given events.	1243	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
846		1244
847	=item int fd [read-only]	1245	=item int fd [read-only]
848		1246
849	The file descriptor being watched.	1247	The file descriptor being watched.
850		1248
851	=item int events [read-only]	1249	=item int events [read-only]
852		1250
853	The events being watched.	1251	The events being watched.
854		1252
855	=back	1253	=back
		1254
		1255	=head3 Examples
856		1256
857	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
858	readable, but only once. Since it is likely line-buffered, you could	1258	readable, but only once. Since it is likely line-buffered, you could
859	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
860		1260
861	static void	1261	static void
862	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
863	{	1263	{
864	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
865	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
866	}	1266	}
867		1267
868	...	1268	...
869	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
870	struct ev_io stdin_readable;	1270	ev_io stdin_readable;
871	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
872	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
873	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
874		1274
875		1275
876	=head2 C<ev_timer> - relative and optionally repeating timeouts	1276	=head2 C<ev_timer> - relative and optionally repeating timeouts
877		1277
878	Timer watchers are simple relative timers that generate an event after a	1278	Timer watchers are simple relative timers that generate an event after a
879	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
880		1280
881	The timers are based on real time, that is, if you register an event that	1281	The timers are based on real time, that is, if you register an event that
882	times out after an hour and you reset your system clock to last years	1282	times out after an hour and you reset your system clock to January last
883	time, it will still time out after (roughly) and hour. "Roughly" because	1283	year, it will still time out after (roughly) one hour. "Roughly" because
884	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
885	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
		1286
		1287	The callback is guaranteed to be invoked only I<after> its timeout has
		1288	passed, but if multiple timers become ready during the same loop iteration
		1289	then order of execution is undefined.
		1290
		1291	=head3 Be smart about timeouts
		1292
		1293	Many real-world problems invole some kind of time-out, usually for error
		1294	recovery. A typical example is an HTTP request - if the other side hangs,
		1295	you want to raise some error after a while.
		1296
		1297	Here are some ways on how to handle this problem, from simple and
		1298	inefficient to very efficient.
		1299
		1300	In the following examples a 60 second activity timeout is assumed - a
		1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")
		1302	was received.
		1303
		1304	=over 4
		1305
		1306	=item 1. Use a timer and stop, reinitialise, start it on activity.
		1307
		1308	This is the most obvious, but not the most simple way: In the beginning,
		1309	start the watcher:
		1310
		1311	ev_timer_init (timer, callback, 60., 0.);
		1312	ev_timer_start (loop, timer);
		1313
		1314	Then, each time there is some activity, C<ev_timer_stop> the timer,
		1315	initialise it again, and start it:
		1316
		1317	ev_timer_stop (loop, timer);
		1318	ev_timer_set (timer, 60., 0.);
		1319	ev_timer_start (loop, timer);
		1320
		1321	This is relatively simple to implement, but means that each time there
		1322	is some activity, libev will first have to remove the timer from it's
		1323	internal data strcuture and then add it again.
		1324
		1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1326
		1327	This is the easiest way, and involves using C<ev_timer_again> instead of
		1328	C<ev_timer_start>.
		1329
		1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and
		1331	then call C<ev_timer_again> at start and each time you successfully read
		1332	or write some data. If you go into an idle state where you do not expect
		1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and
		1334	C<ev_timer_again> will automatically restart it if need be.
		1335
		1336	That means you can ignore the C<after> value and C<ev_timer_start>
		1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.
		1338
		1339	At start:
		1340
		1341	ev_timer_init (timer, callback, 0., 60.);
		1342	ev_timer_again (loop, timer);
		1343
		1344	Each time you receive some data:
		1345
		1346	ev_timer_again (loop, timer);
		1347
		1348	It is even possible to change the time-out on the fly:
		1349
		1350	timer->repeat = 30.;
		1351	ev_timer_again (loop, timer);
		1352
		1353	This is slightly more efficient then stopping/starting the timer each time
		1354	you want to modify its timeout value, as libev does not have to completely
		1355	remove and re-insert the timer from/into it's internal data structure.
		1356
		1357	=item 3. Let the timer time out, but then re-arm it as required.
		1358
		1359	This method is more tricky, but usually most efficient: Most timeouts are
		1360	relatively long compared to the loop iteration time - in our example,
		1361	within 60 seconds, there are usually many I/O events with associated
		1362	activity resets.
		1363
		1364	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1365	but remember the time of last activity, and check for a real timeout only
		1366	within the callback:
		1367
		1368	ev_tstamp last_activity; // time of last activity
		1369
		1370	static void
		1371	callback (EV_P_ ev_timer *w, int revents)
		1372	{
		1373	ev_tstamp now = ev_now (EV_A);
		1374	ev_tstamp timeout = last_activity + 60.;
		1375
		1376	// if last_activity is older than now - timeout, we did time out
		1377	if (timeout < now)
		1378	{
		1379	// timeout occured, take action
		1380	}
		1381	else
		1382	{
		1383	// callback was invoked, but there was some activity, re-arm
		1384	// to fire in last_activity + 60.
		1385	w->again = timeout - now;
		1386	ev_timer_again (EV_A_ w);
		1387	}
		1388	}
		1389
		1390	To summarise the callback: first calculate the real time-out (defined as
		1391	"60 seconds after the last activity"), then check if that time has been
		1392	reached, which means there was a real timeout. Otherwise the callback was
		1393	invoked too early (timeout is in the future), so re-schedule the timer to
		1394	fire at that future time.
		1395
		1396	Note how C<ev_timer_again> is used, taking advantage of the
		1397	C<ev_timer_again> optimisation when the timer is already running.
		1398
		1399	This scheme causes more callback invocations (about one every 60 seconds),
		1400	but virtually no calls to libev to change the timeout.
		1401
		1402	To start the timer, simply intiialise the watcher and C<last_activity>,
		1403	then call the callback:
		1404
		1405	ev_timer_init (timer, callback);
		1406	last_activity = ev_now (loop);
		1407	callback (loop, timer, EV_TIMEOUT);
		1408
		1409	And when there is some activity, simply remember the time in
		1410	C<last_activity>:
		1411
		1412	last_actiivty = ev_now (loop);
		1413
		1414	This technique is slightly more complex, but in most cases where the
		1415	time-out is unlikely to be triggered, much more efficient.
		1416
		1417	=back
		1418
		1419	=head3 The special problem of time updates
		1420
		1421	Establishing the current time is a costly operation (it usually takes at
		1422	least two system calls): EV therefore updates its idea of the current
		1423	time only before and after C<ev_loop> collects new events, which causes a
		1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1425	lots of events in one iteration.
886		1426
887	The relative timeouts are calculated relative to the C<ev_now ()>	1427	The relative timeouts are calculated relative to the C<ev_now ()>
888	time. This is usually the right thing as this timestamp refers to the time	1428	time. This is usually the right thing as this timestamp refers to the time
889	of the event triggering whatever timeout you are modifying/starting. If	1429	of the event triggering whatever timeout you are modifying/starting. If
890	you suspect event processing to be delayed and you I<need> to base the timeout	1430	you suspect event processing to be delayed and you I<need> to base the
891	on the current time, use something like this to adjust for this:	1431	timeout on the current time, use something like this to adjust for this:
892		1432
893	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1433	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
894		1434
895	The callback is guarenteed to be invoked only when its timeout has passed,	1435	If the event loop is suspended for a long time, you can also force an
896	but if multiple timers become ready during the same loop iteration then	1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update
897	order of execution is undefined.	1437	()>.
		1438
		1439	=head3 Watcher-Specific Functions and Data Members
898		1440
899	=over 4	1441	=over 4
900		1442
901	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
902		1444
903	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1445	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
904		1446
905	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1447	Configure the timer to trigger after C<after> seconds. If C<repeat>
906	C<0.>, then it will automatically be stopped. If it is positive, then the	1448	is C<0.>, then it will automatically be stopped once the timeout is
907	timer will automatically be configured to trigger again C<repeat> seconds	1449	reached. If it is positive, then the timer will automatically be
908	later, again, and again, until stopped manually.	1450	configured to trigger again C<repeat> seconds later, again, and again,
		1451	until stopped manually.
909		1452
910	The timer itself will do a best-effort at avoiding drift, that is, if you	1453	The timer itself will do a best-effort at avoiding drift, that is, if
911	configure a timer to trigger every 10 seconds, then it will trigger at	1454	you configure a timer to trigger every 10 seconds, then it will normally
912	exactly 10 second intervals. If, however, your program cannot keep up with	1455	trigger at exactly 10 second intervals. If, however, your program cannot
913	the timer (because it takes longer than those 10 seconds to do stuff) the	1456	keep up with the timer (because it takes longer than those 10 seconds to
914	timer will not fire more than once per event loop iteration.	1457	do stuff) the timer will not fire more than once per event loop iteration.
915		1458
916	=item ev_timer_again (loop)	1459	=item ev_timer_again (loop, ev_timer *)
917		1460
918	This will act as if the timer timed out and restart it again if it is	1461	This will act as if the timer timed out and restart it again if it is
919	repeating. The exact semantics are:	1462	repeating. The exact semantics are:
920		1463
921	If the timer is pending, its pending status is cleared.	1464	If the timer is pending, its pending status is cleared.
922		1465
923	If the timer is started but nonrepeating, stop it (as if it timed out).	1466	If the timer is started but non-repeating, stop it (as if it timed out).
924		1467
925	If the timer is repeating, either start it if necessary (with the	1468	If the timer is repeating, either start it if necessary (with the
926	C<repeat> value), or reset the running timer to the C<repeat> value.	1469	C<repeat> value), or reset the running timer to the C<repeat> value.
927		1470
928	This sounds a bit complicated, but here is a useful and typical	1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a
929	example: Imagine you have a tcp connection and you want a so-called idle	1472	usage example.
930	timeout, that is, you want to be called when there have been, say, 60
931	seconds of inactivity on the socket. The easiest way to do this is to
932	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
933	C<ev_timer_again> each time you successfully read or write some data. If
934	you go into an idle state where you do not expect data to travel on the
935	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
936	automatically restart it if need be.
937
938	That means you can ignore the C<after> value and C<ev_timer_start>
939	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
940
941	ev_timer_init (timer, callback, 0., 5.);
942	ev_timer_again (loop, timer);
943	...
944	timer->again = 17.;
945	ev_timer_again (loop, timer);
946	...
947	timer->again = 10.;
948	ev_timer_again (loop, timer);
949
950	This is more slightly efficient then stopping/starting the timer each time
951	you want to modify its timeout value.
952		1473
953	=item ev_tstamp repeat [read-write]	1474	=item ev_tstamp repeat [read-write]
954		1475
955	The current C<repeat> value. Will be used each time the watcher times out	1476	The current C<repeat> value. Will be used each time the watcher times out
956	or C<ev_timer_again> is called and determines the next timeout (if any),	1477	or C<ev_timer_again> is called, and determines the next timeout (if any),
957	which is also when any modifications are taken into account.	1478	which is also when any modifications are taken into account.
958		1479
959	=back	1480	=back
960		1481
		1482	=head3 Examples
		1483
961	Example: Create a timer that fires after 60 seconds.	1484	Example: Create a timer that fires after 60 seconds.
962		1485
963	static void	1486	static void
964	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1487	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
965	{	1488	{
966	.. one minute over, w is actually stopped right here	1489	.. one minute over, w is actually stopped right here
967	}	1490	}
968		1491
969	struct ev_timer mytimer;	1492	ev_timer mytimer;
970	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1493	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
971	ev_timer_start (loop, &mytimer);	1494	ev_timer_start (loop, &mytimer);
972		1495
973	Example: Create a timeout timer that times out after 10 seconds of	1496	Example: Create a timeout timer that times out after 10 seconds of
974	inactivity.	1497	inactivity.
975		1498
976	static void	1499	static void
977	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1500	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
978	{	1501	{
979	.. ten seconds without any activity	1502	.. ten seconds without any activity
980	}	1503	}
981		1504
982	struct ev_timer mytimer;	1505	ev_timer mytimer;
983	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
984	ev_timer_again (&mytimer); /* start timer */	1507	ev_timer_again (&mytimer); /* start timer */
985	ev_loop (loop, 0);	1508	ev_loop (loop, 0);
986		1509
987	// and in some piece of code that gets executed on any "activity":	1510	// and in some piece of code that gets executed on any "activity":
988	// reset the timeout to start ticking again at 10 seconds	1511	// reset the timeout to start ticking again at 10 seconds
989	ev_timer_again (&mytimer);	1512	ev_timer_again (&mytimer);
990		1513
991		1514
992	=head2 C<ev_periodic> - to cron or not to cron?	1515	=head2 C<ev_periodic> - to cron or not to cron?
993		1516
994	Periodic watchers are also timers of a kind, but they are very versatile	1517	Periodic watchers are also timers of a kind, but they are very versatile
995	(and unfortunately a bit complex).	1518	(and unfortunately a bit complex).
996		1519
997	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
998	but on wallclock time (absolute time). You can tell a periodic watcher	1521	but on wall clock time (absolute time). You can tell a periodic watcher
999	to trigger "at" some specific point in time. For example, if you tell a	1522	to trigger after some specific point in time. For example, if you tell a
1000	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1001	+ 10.>) and then reset your system clock to the last year, then it will	1524	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1525	clock to January of the previous year, then it will take more than year
1002	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1003	roughly 10 seconds later and of course not if you reset your system time	1527	roughly 10 seconds later as it uses a relative timeout).
1004	again).
1005		1528
1006	They can also be used to implement vastly more complex timers, such as	1529	C<ev_periodic>s can also be used to implement vastly more complex timers,
1007	triggering an event on eahc midnight, local time.	1530	such as triggering an event on each "midnight, local time", or other
		1531	complicated rules.
1008		1532
1009	As with timers, the callback is guarenteed to be invoked only when the	1533	As with timers, the callback is guaranteed to be invoked only when the
1010	time (C<at>) has been passed, but if multiple periodic timers become ready	1534	time (C<at>) has passed, but if multiple periodic timers become ready
1011	during the same loop iteration then order of execution is undefined.	1535	during the same loop iteration, then order of execution is undefined.
		1536
		1537	=head3 Watcher-Specific Functions and Data Members
1012		1538
1013	=over 4	1539	=over 4
1014		1540
1015	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1016		1542
1017	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1018		1544
1019	Lots of arguments, lets sort it out... There are basically three modes of	1545	Lots of arguments, lets sort it out... There are basically three modes of
1020	operation, and we will explain them from simplest to complex:	1546	operation, and we will explain them from simplest to most complex:
1021		1547
1022	=over 4	1548	=over 4
1023		1549
1024	=item * absolute timer (interval = reschedule_cb = 0)	1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1025		1551
1026	In this configuration the watcher triggers an event at the wallclock time	1552	In this configuration the watcher triggers an event after the wall clock
1027	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1553	time C<at> has passed. It will not repeat and will not adjust when a time
1028	that is, if it is to be run at January 1st 2011 then it will run when the	1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1029	system time reaches or surpasses this time.	1555	only run when the system clock reaches or surpasses this time.
1030		1556
1031	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1032		1558
1033	In this mode the watcher will always be scheduled to time out at the next	1559	In this mode the watcher will always be scheduled to time out at the next
1034	C<at + N * interval> time (for some integer N) and then repeat, regardless	1560	C<at + N * interval> time (for some integer N, which can also be negative)
1035	of any time jumps.	1561	and then repeat, regardless of any time jumps.
1036		1562
1037	This can be used to create timers that do not drift with respect to system	1563	This can be used to create timers that do not drift with respect to the
1038	time:	1564	system clock, for example, here is a C<ev_periodic> that triggers each
		1565	hour, on the hour:
1039		1566
1040	ev_periodic_set (&periodic, 0., 3600., 0);	1567	ev_periodic_set (&periodic, 0., 3600., 0);
1041		1568
1042	This doesn't mean there will always be 3600 seconds in between triggers,	1569	This doesn't mean there will always be 3600 seconds in between triggers,
1043	but only that the the callback will be called when the system time shows a	1570	but only that the callback will be called when the system time shows a
1044	full hour (UTC), or more correctly, when the system time is evenly divisible	1571	full hour (UTC), or more correctly, when the system time is evenly divisible
1045	by 3600.	1572	by 3600.
1046		1573
1047	Another way to think about it (for the mathematically inclined) is that	1574	Another way to think about it (for the mathematically inclined) is that
1048	C<ev_periodic> will try to run the callback in this mode at the next possible	1575	C<ev_periodic> will try to run the callback in this mode at the next possible
1049	time where C<time = at (mod interval)>, regardless of any time jumps.	1576	time where C<time = at (mod interval)>, regardless of any time jumps.
1050		1577
		1578	For numerical stability it is preferable that the C<at> value is near
		1579	C<ev_now ()> (the current time), but there is no range requirement for
		1580	this value, and in fact is often specified as zero.
		1581
		1582	Note also that there is an upper limit to how often a timer can fire (CPU
		1583	speed for example), so if C<interval> is very small then timing stability
		1584	will of course deteriorate. Libev itself tries to be exact to be about one
		1585	millisecond (if the OS supports it and the machine is fast enough).
		1586
1051	=item * manual reschedule mode (reschedule_cb = callback)	1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1052		1588
1053	In this mode the values for C<interval> and C<at> are both being	1589	In this mode the values for C<interval> and C<at> are both being
1054	ignored. Instead, each time the periodic watcher gets scheduled, the	1590	ignored. Instead, each time the periodic watcher gets scheduled, the
1055	reschedule callback will be called with the watcher as first, and the	1591	reschedule callback will be called with the watcher as first, and the
1056	current time as second argument.	1592	current time as second argument.
1057		1593
1058	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1059	ever, or make any event loop modifications>. If you need to stop it,	1595	ever, or make ANY event loop modifications whatsoever>.
1060	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1061	starting a prepare watcher).
1062		1596
		1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1599	only event loop modification you are allowed to do).
		1600
1063	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1601	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1064	ev_tstamp now)>, e.g.:	1602	*w, ev_tstamp now)>, e.g.:
1065		1603
		1604	static ev_tstamp
1066	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1605	my_rescheduler (ev_periodic *w, ev_tstamp now)
1067	{	1606	{
1068	return now + 60.;	1607	return now + 60.;
1069	}	1608	}
1070		1609
1071	It must return the next time to trigger, based on the passed time value	1610	It must return the next time to trigger, based on the passed time value
1072	(that is, the lowest time value larger than to the second argument). It	1611	(that is, the lowest time value larger than to the second argument). It
1073	will usually be called just before the callback will be triggered, but	1612	will usually be called just before the callback will be triggered, but
1074	might be called at other times, too.	1613	might be called at other times, too.
1075		1614
1076	NOTE: I<< This callback must always return a time that is later than the	1615	NOTE: I<< This callback must always return a time that is higher than or
1077	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1616	equal to the passed C<now> value >>.
1078		1617
1079	This can be used to create very complex timers, such as a timer that	1618	This can be used to create very complex timers, such as a timer that
1080	triggers on each midnight, local time. To do this, you would calculate the	1619	triggers on "next midnight, local time". To do this, you would calculate the
1081	next midnight after C<now> and return the timestamp value for this. How	1620	next midnight after C<now> and return the timestamp value for this. How
1082	you do this is, again, up to you (but it is not trivial, which is the main	1621	you do this is, again, up to you (but it is not trivial, which is the main
1083	reason I omitted it as an example).	1622	reason I omitted it as an example).
1084		1623
1085	=back	1624	=back
…		…
1089	Simply stops and restarts the periodic watcher again. This is only useful	1628	Simply stops and restarts the periodic watcher again. This is only useful
1090	when you changed some parameters or the reschedule callback would return	1629	when you changed some parameters or the reschedule callback would return
1091	a different time than the last time it was called (e.g. in a crond like	1630	a different time than the last time it was called (e.g. in a crond like
1092	program when the crontabs have changed).	1631	program when the crontabs have changed).
1093		1632
		1633	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1634
		1635	When active, returns the absolute time that the watcher is supposed to
		1636	trigger next.
		1637
		1638	=item ev_tstamp offset [read-write]
		1639
		1640	When repeating, this contains the offset value, otherwise this is the
		1641	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1642
		1643	Can be modified any time, but changes only take effect when the periodic
		1644	timer fires or C<ev_periodic_again> is being called.
		1645
1094	=item ev_tstamp interval [read-write]	1646	=item ev_tstamp interval [read-write]
1095		1647
1096	The current interval value. Can be modified any time, but changes only	1648	The current interval value. Can be modified any time, but changes only
1097	take effect when the periodic timer fires or C<ev_periodic_again> is being	1649	take effect when the periodic timer fires or C<ev_periodic_again> is being
1098	called.	1650	called.
1099		1651
1100	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1652	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1101		1653
1102	The current reschedule callback, or C<0>, if this functionality is	1654	The current reschedule callback, or C<0>, if this functionality is
1103	switched off. Can be changed any time, but changes only take effect when	1655	switched off. Can be changed any time, but changes only take effect when
1104	the periodic timer fires or C<ev_periodic_again> is being called.	1656	the periodic timer fires or C<ev_periodic_again> is being called.
1105		1657
1106	=back	1658	=back
1107		1659
		1660	=head3 Examples
		1661
1108	Example: Call a callback every hour, or, more precisely, whenever the	1662	Example: Call a callback every hour, or, more precisely, whenever the
1109	system clock is divisible by 3600. The callback invocation times have	1663	system time is divisible by 3600. The callback invocation times have
1110	potentially a lot of jittering, but good long-term stability.	1664	potentially a lot of jitter, but good long-term stability.
1111		1665
1112	static void	1666	static void
1113	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1114	{	1668	{
1115	... its now a full hour (UTC, or TAI or whatever your clock follows)	1669	... its now a full hour (UTC, or TAI or whatever your clock follows)
1116	}	1670	}
1117		1671
1118	struct ev_periodic hourly_tick;	1672	ev_periodic hourly_tick;
1119	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1673	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1120	ev_periodic_start (loop, &hourly_tick);	1674	ev_periodic_start (loop, &hourly_tick);
1121		1675
1122	Example: The same as above, but use a reschedule callback to do it:	1676	Example: The same as above, but use a reschedule callback to do it:
1123		1677
1124	#include <math.h>	1678	#include <math.h>
1125		1679
1126	static ev_tstamp	1680	static ev_tstamp
1127	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1681	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1128	{	1682	{
1129	return fmod (now, 3600.) + 3600.;	1683	return now + (3600. - fmod (now, 3600.));
1130	}	1684	}
1131		1685
1132	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1686	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1133		1687
1134	Example: Call a callback every hour, starting now:	1688	Example: Call a callback every hour, starting now:
1135		1689
1136	struct ev_periodic hourly_tick;	1690	ev_periodic hourly_tick;
1137	ev_periodic_init (&hourly_tick, clock_cb,	1691	ev_periodic_init (&hourly_tick, clock_cb,
1138	fmod (ev_now (loop), 3600.), 3600., 0);	1692	fmod (ev_now (loop), 3600.), 3600., 0);
1139	ev_periodic_start (loop, &hourly_tick);	1693	ev_periodic_start (loop, &hourly_tick);
1140		1694
1141		1695
1142	=head2 C<ev_signal> - signal me when a signal gets signalled!	1696	=head2 C<ev_signal> - signal me when a signal gets signalled!
1143		1697
1144	Signal watchers will trigger an event when the process receives a specific	1698	Signal watchers will trigger an event when the process receives a specific
1145	signal one or more times. Even though signals are very asynchronous, libev	1699	signal one or more times. Even though signals are very asynchronous, libev
1146	will try it's best to deliver signals synchronously, i.e. as part of the	1700	will try it's best to deliver signals synchronously, i.e. as part of the
1147	normal event processing, like any other event.	1701	normal event processing, like any other event.
1148		1702
		1703	If you want signals asynchronously, just use C<sigaction> as you would
		1704	do without libev and forget about sharing the signal. You can even use
		1705	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1706
1149	You can configure as many watchers as you like per signal. Only when the	1707	You can configure as many watchers as you like per signal. Only when the
1150	first watcher gets started will libev actually register a signal watcher	1708	first watcher gets started will libev actually register a signal handler
1151	with the kernel (thus it coexists with your own signal handlers as long	1709	with the kernel (thus it coexists with your own signal handlers as long as
1152	as you don't register any with libev). Similarly, when the last signal	1710	you don't register any with libev for the same signal). Similarly, when
1153	watcher for a signal is stopped libev will reset the signal handler to	1711	the last signal watcher for a signal is stopped, libev will reset the
1154	SIG_DFL (regardless of what it was set to before).	1712	signal handler to SIG_DFL (regardless of what it was set to before).
		1713
		1714	If possible and supported, libev will install its handlers with
		1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1716	interrupted. If you have a problem with system calls getting interrupted by
		1717	signals you can block all signals in an C<ev_check> watcher and unblock
		1718	them in an C<ev_prepare> watcher.
		1719
		1720	=head3 Watcher-Specific Functions and Data Members
1155		1721
1156	=over 4	1722	=over 4
1157		1723
1158	=item ev_signal_init (ev_signal *, callback, int signum)	1724	=item ev_signal_init (ev_signal *, callback, int signum)
1159		1725
…		…
1166		1732
1167	The signal the watcher watches out for.	1733	The signal the watcher watches out for.
1168		1734
1169	=back	1735	=back
1170		1736
		1737	=head3 Examples
		1738
		1739	Example: Try to exit cleanly on SIGINT.
		1740
		1741	static void
		1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		1743	{
		1744	ev_unloop (loop, EVUNLOOP_ALL);
		1745	}
		1746
		1747	ev_signal signal_watcher;
		1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1749	ev_signal_start (loop, &signal_watcher);
		1750
1171		1751
1172	=head2 C<ev_child> - watch out for process status changes	1752	=head2 C<ev_child> - watch out for process status changes
1173		1753
1174	Child watchers trigger when your process receives a SIGCHLD in response to	1754	Child watchers trigger when your process receives a SIGCHLD in response to
1175	some child status changes (most typically when a child of yours dies).	1755	some child status changes (most typically when a child of yours dies or
		1756	exits). It is permissible to install a child watcher I<after> the child
		1757	has been forked (which implies it might have already exited), as long
		1758	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1759	forking and then immediately registering a watcher for the child is fine,
		1760	but forking and registering a watcher a few event loop iterations later is
		1761	not.
		1762
		1763	Only the default event loop is capable of handling signals, and therefore
		1764	you can only register child watchers in the default event loop.
		1765
		1766	=head3 Process Interaction
		1767
		1768	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1769	initialised. This is necessary to guarantee proper behaviour even if
		1770	the first child watcher is started after the child exits. The occurrence
		1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1772	synchronously as part of the event loop processing. Libev always reaps all
		1773	children, even ones not watched.
		1774
		1775	=head3 Overriding the Built-In Processing
		1776
		1777	Libev offers no special support for overriding the built-in child
		1778	processing, but if your application collides with libev's default child
		1779	handler, you can override it easily by installing your own handler for
		1780	C<SIGCHLD> after initialising the default loop, and making sure the
		1781	default loop never gets destroyed. You are encouraged, however, to use an
		1782	event-based approach to child reaping and thus use libev's support for
		1783	that, so other libev users can use C<ev_child> watchers freely.
		1784
		1785	=head3 Stopping the Child Watcher
		1786
		1787	Currently, the child watcher never gets stopped, even when the
		1788	child terminates, so normally one needs to stop the watcher in the
		1789	callback. Future versions of libev might stop the watcher automatically
		1790	when a child exit is detected.
		1791
		1792	=head3 Watcher-Specific Functions and Data Members
1176		1793
1177	=over 4	1794	=over 4
1178		1795
1179	=item ev_child_init (ev_child *, callback, int pid)	1796	=item ev_child_init (ev_child *, callback, int pid, int trace)
1180		1797
1181	=item ev_child_set (ev_child *, int pid)	1798	=item ev_child_set (ev_child *, int pid, int trace)
1182		1799
1183	Configures the watcher to wait for status changes of process C<pid> (or	1800	Configures the watcher to wait for status changes of process C<pid> (or
1184	I<any> process if C<pid> is specified as C<0>). The callback can look	1801	I<any> process if C<pid> is specified as C<0>). The callback can look
1185	at the C<rstatus> member of the C<ev_child> watcher structure to see	1802	at the C<rstatus> member of the C<ev_child> watcher structure to see
1186	the status word (use the macros from C<sys/wait.h> and see your systems	1803	the status word (use the macros from C<sys/wait.h> and see your systems
1187	C<waitpid> documentation). The C<rpid> member contains the pid of the	1804	C<waitpid> documentation). The C<rpid> member contains the pid of the
1188	process causing the status change.	1805	process causing the status change. C<trace> must be either C<0> (only
		1806	activate the watcher when the process terminates) or C<1> (additionally
		1807	activate the watcher when the process is stopped or continued).
1189		1808
1190	=item int pid [read-only]	1809	=item int pid [read-only]
1191		1810
1192	The process id this watcher watches out for, or C<0>, meaning any process id.	1811	The process id this watcher watches out for, or C<0>, meaning any process id.
1193		1812
…		…
1200	The process exit/trace status caused by C<rpid> (see your systems	1819	The process exit/trace status caused by C<rpid> (see your systems
1201	C<waitpid> and C<sys/wait.h> documentation for details).	1820	C<waitpid> and C<sys/wait.h> documentation for details).
1202		1821
1203	=back	1822	=back
1204		1823
1205	Example: Try to exit cleanly on SIGINT and SIGTERM.	1824	=head3 Examples
1206		1825
		1826	Example: C<fork()> a new process and install a child handler to wait for
		1827	its completion.
		1828
		1829	ev_child cw;
		1830
1207	static void	1831	static void
1208	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1832	child_cb (EV_P_ ev_child *w, int revents)
1209	{	1833	{
1210	ev_unloop (loop, EVUNLOOP_ALL);	1834	ev_child_stop (EV_A_ w);
		1835	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1211	}	1836	}
1212		1837
1213	struct ev_signal signal_watcher;	1838	pid_t pid = fork ();
1214	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1839
1215	ev_signal_start (loop, &sigint_cb);	1840	if (pid < 0)
		1841	// error
		1842	else if (pid == 0)
		1843	{
		1844	// the forked child executes here
		1845	exit (1);
		1846	}
		1847	else
		1848	{
		1849	ev_child_init (&cw, child_cb, pid, 0);
		1850	ev_child_start (EV_DEFAULT_ &cw);
		1851	}
1216		1852
1217		1853
1218	=head2 C<ev_stat> - did the file attributes just change?	1854	=head2 C<ev_stat> - did the file attributes just change?
1219		1855
1220	This watches a filesystem path for attribute changes. That is, it calls	1856	This watches a file system path for attribute changes. That is, it calls
1221	C<stat> regularly (or when the OS says it changed) and sees if it changed	1857	C<stat> regularly (or when the OS says it changed) and sees if it changed
1222	compared to the last time, invoking the callback if it did.	1858	compared to the last time, invoking the callback if it did.
1223		1859
1224	The path does not need to exist: changing from "path exists" to "path does	1860	The path does not need to exist: changing from "path exists" to "path does
1225	not exist" is a status change like any other. The condition "path does	1861	not exist" is a status change like any other. The condition "path does
…		…
1228	the stat buffer having unspecified contents.	1864	the stat buffer having unspecified contents.
1229		1865
1230	The path I<should> be absolute and I<must not> end in a slash. If it is	1866	The path I<should> be absolute and I<must not> end in a slash. If it is
1231	relative and your working directory changes, the behaviour is undefined.	1867	relative and your working directory changes, the behaviour is undefined.
1232		1868
1233	Since there is no standard to do this, the portable implementation simply	1869	Since there is no standard kernel interface to do this, the portable
1234	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1870	implementation simply calls C<stat (2)> regularly on the path to see if
1235	can specify a recommended polling interval for this case. If you specify	1871	it changed somehow. You can specify a recommended polling interval for
1236	a polling interval of C<0> (highly recommended!) then a I<suitable,	1872	this case. If you specify a polling interval of C<0> (highly recommended!)
1237	unspecified default> value will be used (which you can expect to be around	1873	then a I<suitable, unspecified default> value will be used (which
1238	five seconds, although this might change dynamically). Libev will also	1874	you can expect to be around five seconds, although this might change
1239	impose a minimum interval which is currently around C<0.1>, but thats	1875	dynamically). Libev will also impose a minimum interval which is currently
1240	usually overkill.	1876	around C<0.1>, but thats usually overkill.
1241		1877
1242	This watcher type is not meant for massive numbers of stat watchers,	1878	This watcher type is not meant for massive numbers of stat watchers,
1243	as even with OS-supported change notifications, this can be	1879	as even with OS-supported change notifications, this can be
1244	resource-intensive.	1880	resource-intensive.
1245		1881
1246	At the time of this writing, only the Linux inotify interface is	1882	At the time of this writing, the only OS-specific interface implemented
1247	implemented (implementing kqueue support is left as an exercise for the	1883	is the Linux inotify interface (implementing kqueue support is left as
1248	reader). Inotify will be used to give hints only and should not change the	1884	an exercise for the reader. Note, however, that the author sees no way
1249	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1885	of implementing C<ev_stat> semantics with kqueue).
1250	to fall back to regular polling again even with inotify, but changes are	1886
1251	usually detected immediately, and if the file exists there will be no	1887	=head3 ABI Issues (Largefile Support)
1252	polling.	1888
		1889	Libev by default (unless the user overrides this) uses the default
		1890	compilation environment, which means that on systems with large file
		1891	support disabled by default, you get the 32 bit version of the stat
		1892	structure. When using the library from programs that change the ABI to
		1893	use 64 bit file offsets the programs will fail. In that case you have to
		1894	compile libev with the same flags to get binary compatibility. This is
		1895	obviously the case with any flags that change the ABI, but the problem is
		1896	most noticeably disabled with ev_stat and large file support.
		1897
		1898	The solution for this is to lobby your distribution maker to make large
		1899	file interfaces available by default (as e.g. FreeBSD does) and not
		1900	optional. Libev cannot simply switch on large file support because it has
		1901	to exchange stat structures with application programs compiled using the
		1902	default compilation environment.
		1903
		1904	=head3 Inotify and Kqueue
		1905
		1906	When C<inotify (7)> support has been compiled into libev (generally
		1907	only available with Linux 2.6.25 or above due to bugs in earlier
		1908	implementations) and present at runtime, it will be used to speed up
		1909	change detection where possible. The inotify descriptor will be created
		1910	lazily when the first C<ev_stat> watcher is being started.
		1911
		1912	Inotify presence does not change the semantics of C<ev_stat> watchers
		1913	except that changes might be detected earlier, and in some cases, to avoid
		1914	making regular C<stat> calls. Even in the presence of inotify support
		1915	there are many cases where libev has to resort to regular C<stat> polling,
		1916	but as long as the path exists, libev usually gets away without polling.
		1917
		1918	There is no support for kqueue, as apparently it cannot be used to
		1919	implement this functionality, due to the requirement of having a file
		1920	descriptor open on the object at all times, and detecting renames, unlinks
		1921	etc. is difficult.
		1922
		1923	=head3 The special problem of stat time resolution
		1924
		1925	The C<stat ()> system call only supports full-second resolution portably, and
		1926	even on systems where the resolution is higher, most file systems still
		1927	only support whole seconds.
		1928
		1929	That means that, if the time is the only thing that changes, you can
		1930	easily miss updates: on the first update, C<ev_stat> detects a change and
		1931	calls your callback, which does something. When there is another update
		1932	within the same second, C<ev_stat> will be unable to detect unless the
		1933	stat data does change in other ways (e.g. file size).
		1934
		1935	The solution to this is to delay acting on a change for slightly more
		1936	than a second (or till slightly after the next full second boundary), using
		1937	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1938	ev_timer_again (loop, w)>).
		1939
		1940	The C<.02> offset is added to work around small timing inconsistencies
		1941	of some operating systems (where the second counter of the current time
		1942	might be be delayed. One such system is the Linux kernel, where a call to
		1943	C<gettimeofday> might return a timestamp with a full second later than
		1944	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1945	update file times then there will be a small window where the kernel uses
		1946	the previous second to update file times but libev might already execute
		1947	the timer callback).
		1948
		1949	=head3 Watcher-Specific Functions and Data Members
1253		1950
1254	=over 4	1951	=over 4
1255		1952
1256	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1953	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1257		1954
…		…
1261	C<path>. The C<interval> is a hint on how quickly a change is expected to	1958	C<path>. The C<interval> is a hint on how quickly a change is expected to
1262	be detected and should normally be specified as C<0> to let libev choose	1959	be detected and should normally be specified as C<0> to let libev choose
1263	a suitable value. The memory pointed to by C<path> must point to the same	1960	a suitable value. The memory pointed to by C<path> must point to the same
1264	path for as long as the watcher is active.	1961	path for as long as the watcher is active.
1265		1962
1266	The callback will be receive C<EV_STAT> when a change was detected,	1963	The callback will receive an C<EV_STAT> event when a change was detected,
1267	relative to the attributes at the time the watcher was started (or the	1964	relative to the attributes at the time the watcher was started (or the
1268	last change was detected).	1965	last change was detected).
1269		1966
1270	=item ev_stat_stat (ev_stat *)	1967	=item ev_stat_stat (loop, ev_stat *)
1271		1968
1272	Updates the stat buffer immediately with new values. If you change the	1969	Updates the stat buffer immediately with new values. If you change the
1273	watched path in your callback, you could call this fucntion to avoid	1970	watched path in your callback, you could call this function to avoid
1274	detecting this change (while introducing a race condition). Can also be	1971	detecting this change (while introducing a race condition if you are not
1275	useful simply to find out the new values.	1972	the only one changing the path). Can also be useful simply to find out the
		1973	new values.
1276		1974
1277	=item ev_statdata attr [read-only]	1975	=item ev_statdata attr [read-only]
1278		1976
1279	The most-recently detected attributes of the file. Although the type is of	1977	The most-recently detected attributes of the file. Although the type is
1280	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1978	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1281	suitable for your system. If the C<st_nlink> member is C<0>, then there	1979	suitable for your system, but you can only rely on the POSIX-standardised
		1980	members to be present. If the C<st_nlink> member is C<0>, then there was
1282	was some error while C<stat>ing the file.	1981	some error while C<stat>ing the file.
1283		1982
1284	=item ev_statdata prev [read-only]	1983	=item ev_statdata prev [read-only]
1285		1984
1286	The previous attributes of the file. The callback gets invoked whenever	1985	The previous attributes of the file. The callback gets invoked whenever
1287	C<prev> != C<attr>.	1986	C<prev> != C<attr>, or, more precisely, one or more of these members
		1987	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1988	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1288		1989
1289	=item ev_tstamp interval [read-only]	1990	=item ev_tstamp interval [read-only]
1290		1991
1291	The specified interval.	1992	The specified interval.
1292		1993
1293	=item const char *path [read-only]	1994	=item const char *path [read-only]
1294		1995
1295	The filesystem path that is being watched.	1996	The file system path that is being watched.
1296		1997
1297	=back	1998	=back
1298		1999
		2000	=head3 Examples
		2001
1299	Example: Watch C</etc/passwd> for attribute changes.	2002	Example: Watch C</etc/passwd> for attribute changes.
1300		2003
1301	static void	2004	static void
1302	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2005	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1303	{	2006	{
1304	/* /etc/passwd changed in some way */	2007	/* /etc/passwd changed in some way */
1305	if (w->attr.st_nlink)	2008	if (w->attr.st_nlink)
1306	{	2009	{
1307	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2010	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1308	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2011	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1309	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2012	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1310	}	2013	}
1311	else	2014	else
1312	/* you shalt not abuse printf for puts */	2015	/* you shalt not abuse printf for puts */
1313	puts ("wow, /etc/passwd is not there, expect problems. "	2016	puts ("wow, /etc/passwd is not there, expect problems. "
1314	"if this is windows, they already arrived\n");	2017	"if this is windows, they already arrived\n");
1315	}	2018	}
1316		2019
1317	...	2020	...
1318	ev_stat passwd;	2021	ev_stat passwd;
1319		2022
1320	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2023	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1321	ev_stat_start (loop, &passwd);	2024	ev_stat_start (loop, &passwd);
		2025
		2026	Example: Like above, but additionally use a one-second delay so we do not
		2027	miss updates (however, frequent updates will delay processing, too, so
		2028	one might do the work both on C<ev_stat> callback invocation I<and> on
		2029	C<ev_timer> callback invocation).
		2030
		2031	static ev_stat passwd;
		2032	static ev_timer timer;
		2033
		2034	static void
		2035	timer_cb (EV_P_ ev_timer *w, int revents)
		2036	{
		2037	ev_timer_stop (EV_A_ w);
		2038
		2039	/* now it's one second after the most recent passwd change */
		2040	}
		2041
		2042	static void
		2043	stat_cb (EV_P_ ev_stat *w, int revents)
		2044	{
		2045	/* reset the one-second timer */
		2046	ev_timer_again (EV_A_ &timer);
		2047	}
		2048
		2049	...
		2050	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		2051	ev_stat_start (loop, &passwd);
		2052	ev_timer_init (&timer, timer_cb, 0., 1.02);
1322		2053
1323		2054
1324	=head2 C<ev_idle> - when you've got nothing better to do...	2055	=head2 C<ev_idle> - when you've got nothing better to do...
1325		2056
1326	Idle watchers trigger events when there are no other events are pending	2057	Idle watchers trigger events when no other events of the same or higher
1327	(prepare, check and other idle watchers do not count). That is, as long	2058	priority are pending (prepare, check and other idle watchers do not count
1328	as your process is busy handling sockets or timeouts (or even signals,	2059	as receiving "events").
1329	imagine) it will not be triggered. But when your process is idle all idle	2060
1330	watchers are being called again and again, once per event loop iteration -	2061	That is, as long as your process is busy handling sockets or timeouts
		2062	(or even signals, imagine) of the same or higher priority it will not be
		2063	triggered. But when your process is idle (or only lower-priority watchers
		2064	are pending), the idle watchers are being called once per event loop
1331	until stopped, that is, or your process receives more events and becomes	2065	iteration - until stopped, that is, or your process receives more events
1332	busy.	2066	and becomes busy again with higher priority stuff.
1333		2067
1334	The most noteworthy effect is that as long as any idle watchers are	2068	The most noteworthy effect is that as long as any idle watchers are
1335	active, the process will not block when waiting for new events.	2069	active, the process will not block when waiting for new events.
1336		2070
1337	Apart from keeping your process non-blocking (which is a useful	2071	Apart from keeping your process non-blocking (which is a useful
1338	effect on its own sometimes), idle watchers are a good place to do	2072	effect on its own sometimes), idle watchers are a good place to do
1339	"pseudo-background processing", or delay processing stuff to after the	2073	"pseudo-background processing", or delay processing stuff to after the
1340	event loop has handled all outstanding events.	2074	event loop has handled all outstanding events.
1341		2075
		2076	=head3 Watcher-Specific Functions and Data Members
		2077
1342	=over 4	2078	=over 4
1343		2079
1344	=item ev_idle_init (ev_signal *, callback)	2080	=item ev_idle_init (ev_signal *, callback)
1345		2081
1346	Initialises and configures the idle watcher - it has no parameters of any	2082	Initialises and configures the idle watcher - it has no parameters of any
1347	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1348	believe me.	2084	believe me.
1349		2085
1350	=back	2086	=back
1351		2087
		2088	=head3 Examples
		2089
1352	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2090	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1353	callback, free it. Also, use no error checking, as usual.	2091	callback, free it. Also, use no error checking, as usual.
1354		2092
1355	static void	2093	static void
1356	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2094	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1357	{	2095	{
1358	free (w);	2096	free (w);
1359	// now do something you wanted to do when the program has	2097	// now do something you wanted to do when the program has
1360	// no longer asnything immediate to do.	2098	// no longer anything immediate to do.
1361	}	2099	}
1362		2100
1363	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1364	ev_idle_init (idle_watcher, idle_cb);	2102	ev_idle_init (idle_watcher, idle_cb);
1365	ev_idle_start (loop, idle_cb);	2103	ev_idle_start (loop, idle_cb);
1366		2104
1367		2105
1368	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1369		2107
1370	Prepare and check watchers are usually (but not always) used in tandem:	2108	Prepare and check watchers are usually (but not always) used in pairs:
1371	prepare watchers get invoked before the process blocks and check watchers	2109	prepare watchers get invoked before the process blocks and check watchers
1372	afterwards.	2110	afterwards.
1373		2111
1374	You I<must not> call C<ev_loop> or similar functions that enter	2112	You I<must not> call C<ev_loop> or similar functions that enter
1375	the current event loop from either C<ev_prepare> or C<ev_check>	2113	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1378	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1379	C<ev_check> so if you have one watcher of each kind they will always be	2117	C<ev_check> so if you have one watcher of each kind they will always be
1380	called in pairs bracketing the blocking call.	2118	called in pairs bracketing the blocking call.
1381		2119
1382	Their main purpose is to integrate other event mechanisms into libev and	2120	Their main purpose is to integrate other event mechanisms into libev and
1383	their use is somewhat advanced. This could be used, for example, to track	2121	their use is somewhat advanced. They could be used, for example, to track
1384	variable changes, implement your own watchers, integrate net-snmp or a	2122	variable changes, implement your own watchers, integrate net-snmp or a
1385	coroutine library and lots more. They are also occasionally useful if	2123	coroutine library and lots more. They are also occasionally useful if
1386	you cache some data and want to flush it before blocking (for example,	2124	you cache some data and want to flush it before blocking (for example,
1387	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2125	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1388	watcher).	2126	watcher).
1389		2127
1390	This is done by examining in each prepare call which file descriptors need	2128	This is done by examining in each prepare call which file descriptors
1391	to be watched by the other library, registering C<ev_io> watchers for	2129	need to be watched by the other library, registering C<ev_io> watchers
1392	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2130	for them and starting an C<ev_timer> watcher for any timeouts (many
1393	provide just this functionality). Then, in the check watcher you check for	2131	libraries provide exactly this functionality). Then, in the check watcher,
1394	any events that occured (by checking the pending status of all watchers	2132	you check for any events that occurred (by checking the pending status
1395	and stopping them) and call back into the library. The I/O and timer	2133	of all watchers and stopping them) and call back into the library. The
1396	callbacks will never actually be called (but must be valid nevertheless,	2134	I/O and timer callbacks will never actually be called (but must be valid
1397	because you never know, you know?).	2135	nevertheless, because you never know, you know?).
1398		2136
1399	As another example, the Perl Coro module uses these hooks to integrate	2137	As another example, the Perl Coro module uses these hooks to integrate
1400	coroutines into libev programs, by yielding to other active coroutines	2138	coroutines into libev programs, by yielding to other active coroutines
1401	during each prepare and only letting the process block if no coroutines	2139	during each prepare and only letting the process block if no coroutines
1402	are ready to run (it's actually more complicated: it only runs coroutines	2140	are ready to run (it's actually more complicated: it only runs coroutines
1403	with priority higher than or equal to the event loop and one coroutine	2141	with priority higher than or equal to the event loop and one coroutine
1404	of lower priority, but only once, using idle watchers to keep the event	2142	of lower priority, but only once, using idle watchers to keep the event
1405	loop from blocking if lower-priority coroutines are active, thus mapping	2143	loop from blocking if lower-priority coroutines are active, thus mapping
1406	low-priority coroutines to idle/background tasks).	2144	low-priority coroutines to idle/background tasks).
1407		2145
		2146	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		2147	priority, to ensure that they are being run before any other watchers
		2148	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2149
		2150	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
		2151	activate ("feed") events into libev. While libev fully supports this, they
		2152	might get executed before other C<ev_check> watchers did their job. As
		2153	C<ev_check> watchers are often used to embed other (non-libev) event
		2154	loops those other event loops might be in an unusable state until their
		2155	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		2156	others).
		2157
		2158	=head3 Watcher-Specific Functions and Data Members
		2159
1408	=over 4	2160	=over 4
1409		2161
1410	=item ev_prepare_init (ev_prepare *, callback)	2162	=item ev_prepare_init (ev_prepare *, callback)
1411		2163
1412	=item ev_check_init (ev_check *, callback)	2164	=item ev_check_init (ev_check *, callback)
1413		2165
1414	Initialises and configures the prepare or check watcher - they have no	2166	Initialises and configures the prepare or check watcher - they have no
1415	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2167	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1416	macros, but using them is utterly, utterly and completely pointless.	2168	macros, but using them is utterly, utterly, utterly and completely
		2169	pointless.
1417		2170
1418	=back	2171	=back
1419		2172
1420	Example: To include a library such as adns, you would add IO watchers	2173	=head3 Examples
1421	and a timeout watcher in a prepare handler, as required by libadns, and	2174
		2175	There are a number of principal ways to embed other event loops or modules
		2176	into libev. Here are some ideas on how to include libadns into libev
		2177	(there is a Perl module named C<EV::ADNS> that does this, which you could
		2178	use as a working example. Another Perl module named C<EV::Glib> embeds a
		2179	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		2180	Glib event loop).
		2181
		2182	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1422	in a check watcher, destroy them and call into libadns. What follows is	2183	and in a check watcher, destroy them and call into libadns. What follows
1423	pseudo-code only of course:	2184	is pseudo-code only of course. This requires you to either use a low
		2185	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		2186	the callbacks for the IO/timeout watchers might not have been called yet.
1424		2187
1425	static ev_io iow [nfd];	2188	static ev_io iow [nfd];
1426	static ev_timer tw;	2189	static ev_timer tw;
1427		2190
1428	static void	2191	static void
1429	io_cb (ev_loop *loop, ev_io *w, int revents)	2192	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1430	{	2193	{
1431	// set the relevant poll flags
1432	// could also call adns_processreadable etc. here
1433	struct pollfd *fd = (struct pollfd *)w->data;
1434	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1435	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1436	}	2194	}
1437		2195
1438	// create io watchers for each fd and a timer before blocking	2196	// create io watchers for each fd and a timer before blocking
1439	static void	2197	static void
1440	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2198	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1441	{	2199	{
1442	int timeout = 3600000;truct pollfd fds [nfd];	2200	int timeout = 3600000;
		2201	struct pollfd fds [nfd];
1443	// actual code will need to loop here and realloc etc.	2202	// actual code will need to loop here and realloc etc.
1444	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1445		2204
1446	/* the callback is illegal, but won't be called as we stop during check */	2205	/* the callback is illegal, but won't be called as we stop during check */
1447	ev_timer_init (&tw, 0, timeout * 1e-3);	2206	ev_timer_init (&tw, 0, timeout * 1e-3);
1448	ev_timer_start (loop, &tw);	2207	ev_timer_start (loop, &tw);
1449		2208
1450	// create on ev_io per pollfd	2209	// create one ev_io per pollfd
1451	for (int i = 0; i < nfd; ++i)	2210	for (int i = 0; i < nfd; ++i)
1452	{	2211	{
1453	ev_io_init (iow + i, io_cb, fds [i].fd,	2212	ev_io_init (iow + i, io_cb, fds [i].fd,
1454	((fds [i].events & POLLIN ? EV_READ : 0)	2213	((fds [i].events & POLLIN ? EV_READ : 0)
1455	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2214	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1456		2215
1457	fds [i].revents = 0;	2216	fds [i].revents = 0;
1458	iow [i].data = fds + i;
1459	ev_io_start (loop, iow + i);	2217	ev_io_start (loop, iow + i);
1460	}	2218	}
1461	}	2219	}
1462		2220
1463	// stop all watchers after blocking	2221	// stop all watchers after blocking
1464	static void	2222	static void
1465	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2223	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1466	{	2224	{
1467	ev_timer_stop (loop, &tw);	2225	ev_timer_stop (loop, &tw);
1468		2226
1469	for (int i = 0; i < nfd; ++i)	2227	for (int i = 0; i < nfd; ++i)
		2228	{
		2229	// set the relevant poll flags
		2230	// could also call adns_processreadable etc. here
		2231	struct pollfd *fd = fds + i;
		2232	int revents = ev_clear_pending (iow + i);
		2233	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2234	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2235
		2236	// now stop the watcher
1470	ev_io_stop (loop, iow + i);	2237	ev_io_stop (loop, iow + i);
		2238	}
1471		2239
1472	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2240	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1473	}	2241	}
		2242
		2243	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2244	in the prepare watcher and would dispose of the check watcher.
		2245
		2246	Method 3: If the module to be embedded supports explicit event
		2247	notification (libadns does), you can also make use of the actual watcher
		2248	callbacks, and only destroy/create the watchers in the prepare watcher.
		2249
		2250	static void
		2251	timer_cb (EV_P_ ev_timer *w, int revents)
		2252	{
		2253	adns_state ads = (adns_state)w->data;
		2254	update_now (EV_A);
		2255
		2256	adns_processtimeouts (ads, &tv_now);
		2257	}
		2258
		2259	static void
		2260	io_cb (EV_P_ ev_io *w, int revents)
		2261	{
		2262	adns_state ads = (adns_state)w->data;
		2263	update_now (EV_A);
		2264
		2265	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2266	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2267	}
		2268
		2269	// do not ever call adns_afterpoll
		2270
		2271	Method 4: Do not use a prepare or check watcher because the module you
		2272	want to embed is not flexible enough to support it. Instead, you can
		2273	override their poll function. The drawback with this solution is that the
		2274	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
		2275	this approach, effectively embedding EV as a client into the horrible
		2276	libglib event loop.
		2277
		2278	static gint
		2279	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2280	{
		2281	int got_events = 0;
		2282
		2283	for (n = 0; n < nfds; ++n)
		2284	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2285
		2286	if (timeout >= 0)
		2287	// create/start timer
		2288
		2289	// poll
		2290	ev_loop (EV_A_ 0);
		2291
		2292	// stop timer again
		2293	if (timeout >= 0)
		2294	ev_timer_stop (EV_A_ &to);
		2295
		2296	// stop io watchers again - their callbacks should have set
		2297	for (n = 0; n < nfds; ++n)
		2298	ev_io_stop (EV_A_ iow [n]);
		2299
		2300	return got_events;
		2301	}
1474		2302
1475		2303
1476	=head2 C<ev_embed> - when one backend isn't enough...	2304	=head2 C<ev_embed> - when one backend isn't enough...
1477		2305
1478	This is a rather advanced watcher type that lets you embed one event loop	2306	This is a rather advanced watcher type that lets you embed one event loop
…		…
1484	prioritise I/O.	2312	prioritise I/O.
1485		2313
1486	As an example for a bug workaround, the kqueue backend might only support	2314	As an example for a bug workaround, the kqueue backend might only support
1487	sockets on some platform, so it is unusable as generic backend, but you	2315	sockets on some platform, so it is unusable as generic backend, but you
1488	still want to make use of it because you have many sockets and it scales	2316	still want to make use of it because you have many sockets and it scales
1489	so nicely. In this case, you would create a kqueue-based loop and embed it	2317	so nicely. In this case, you would create a kqueue-based loop and embed
1490	into your default loop (which might use e.g. poll). Overall operation will	2318	it into your default loop (which might use e.g. poll). Overall operation
1491	be a bit slower because first libev has to poll and then call kevent, but	2319	will be a bit slower because first libev has to call C<poll> and then
1492	at least you can use both at what they are best.	2320	C<kevent>, but at least you can use both mechanisms for what they are
		2321	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1493		2322
1494	As for prioritising I/O: rarely you have the case where some fds have	2323	As for prioritising I/O: under rare circumstances you have the case where
1495	to be watched and handled very quickly (with low latency), and even	2324	some fds have to be watched and handled very quickly (with low latency),
1496	priorities and idle watchers might have too much overhead. In this case	2325	and even priorities and idle watchers might have too much overhead. In
1497	you would put all the high priority stuff in one loop and all the rest in	2326	this case you would put all the high priority stuff in one loop and all
1498	a second one, and embed the second one in the first.	2327	the rest in a second one, and embed the second one in the first.
1499		2328
1500	As long as the watcher is active, the callback will be invoked every time	2329	As long as the watcher is active, the callback will be invoked every time
1501	there might be events pending in the embedded loop. The callback must then	2330	there might be events pending in the embedded loop. The callback must then
1502	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1503	their callbacks (you could also start an idle watcher to give the embedded	2332	their callbacks (you could also start an idle watcher to give the embedded
…		…
1511	interested in that.	2340	interested in that.
1512		2341
1513	Also, there have not currently been made special provisions for forking:	2342	Also, there have not currently been made special provisions for forking:
1514	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1515	but you will also have to stop and restart any C<ev_embed> watchers	2344	but you will also have to stop and restart any C<ev_embed> watchers
1516	yourself.	2345	yourself - but you can use a fork watcher to handle this automatically,
		2346	and future versions of libev might do just that.
1517		2347
1518	Unfortunately, not all backends are embeddable, only the ones returned by	2348	Unfortunately, not all backends are embeddable: only the ones returned by
1519	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1520	portable one.	2350	portable one.
1521		2351
1522	So when you want to use this feature you will always have to be prepared	2352	So when you want to use this feature you will always have to be prepared
1523	that you cannot get an embeddable loop. The recommended way to get around	2353	that you cannot get an embeddable loop. The recommended way to get around
1524	this is to have a separate variables for your embeddable loop, try to	2354	this is to have a separate variables for your embeddable loop, try to
1525	create it, and if that fails, use the normal loop for everything:	2355	create it, and if that fails, use the normal loop for everything.
1526		2356
1527	struct ev_loop *loop_hi = ev_default_init (0);	2357	=head3 C<ev_embed> and fork
1528	struct ev_loop *loop_lo = 0;
1529	struct ev_embed embed;
1530
1531	// see if there is a chance of getting one that works
1532	// (remember that a flags value of 0 means autodetection)
1533	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1534	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1535	: 0;
1536		2358
1537	// if we got one, then embed it, otherwise default to loop_hi	2359	While the C<ev_embed> watcher is running, forks in the embedding loop will
1538	if (loop_lo)	2360	automatically be applied to the embedded loop as well, so no special
1539	{	2361	fork handling is required in that case. When the watcher is not running,
1540	ev_embed_init (&embed, 0, loop_lo);	2362	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1541	ev_embed_start (loop_hi, &embed);	2363	as applicable.
1542	}	2364
1543	else	2365	=head3 Watcher-Specific Functions and Data Members
1544	loop_lo = loop_hi;
1545		2366
1546	=over 4	2367	=over 4
1547		2368
1548	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2369	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1549		2370
…		…
1551		2372
1552	Configures the watcher to embed the given loop, which must be	2373	Configures the watcher to embed the given loop, which must be
1553	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2374	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1554	invoked automatically, otherwise it is the responsibility of the callback	2375	invoked automatically, otherwise it is the responsibility of the callback
1555	to invoke it (it will continue to be called until the sweep has been done,	2376	to invoke it (it will continue to be called until the sweep has been done,
1556	if you do not want thta, you need to temporarily stop the embed watcher).	2377	if you do not want that, you need to temporarily stop the embed watcher).
1557		2378
1558	=item ev_embed_sweep (loop, ev_embed *)	2379	=item ev_embed_sweep (loop, ev_embed *)
1559		2380
1560	Make a single, non-blocking sweep over the embedded loop. This works	2381	Make a single, non-blocking sweep over the embedded loop. This works
1561	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2382	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1562	apropriate way for embedded loops.	2383	appropriate way for embedded loops.
1563		2384
1564	=item struct ev_loop *loop [read-only]	2385	=item struct ev_loop *other [read-only]
1565		2386
1566	The embedded event loop.	2387	The embedded event loop.
1567		2388
1568	=back	2389	=back
		2390
		2391	=head3 Examples
		2392
		2393	Example: Try to get an embeddable event loop and embed it into the default
		2394	event loop. If that is not possible, use the default loop. The default
		2395	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2396	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2397	used).
		2398
		2399	struct ev_loop *loop_hi = ev_default_init (0);
		2400	struct ev_loop *loop_lo = 0;
		2401	ev_embed embed;
		2402
		2403	// see if there is a chance of getting one that works
		2404	// (remember that a flags value of 0 means autodetection)
		2405	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2406	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2407	: 0;
		2408
		2409	// if we got one, then embed it, otherwise default to loop_hi
		2410	if (loop_lo)
		2411	{
		2412	ev_embed_init (&embed, 0, loop_lo);
		2413	ev_embed_start (loop_hi, &embed);
		2414	}
		2415	else
		2416	loop_lo = loop_hi;
		2417
		2418	Example: Check if kqueue is available but not recommended and create
		2419	a kqueue backend for use with sockets (which usually work with any
		2420	kqueue implementation). Store the kqueue/socket-only event loop in
		2421	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2422
		2423	struct ev_loop *loop = ev_default_init (0);
		2424	struct ev_loop *loop_socket = 0;
		2425	ev_embed embed;
		2426
		2427	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2428	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2429	{
		2430	ev_embed_init (&embed, 0, loop_socket);
		2431	ev_embed_start (loop, &embed);
		2432	}
		2433
		2434	if (!loop_socket)
		2435	loop_socket = loop;
		2436
		2437	// now use loop_socket for all sockets, and loop for everything else
1569		2438
1570		2439
1571	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2440	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1572		2441
1573	Fork watchers are called when a C<fork ()> was detected (usually because	2442	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1576	event loop blocks next and before C<ev_check> watchers are being called,	2445	event loop blocks next and before C<ev_check> watchers are being called,
1577	and only in the child after the fork. If whoever good citizen calling	2446	and only in the child after the fork. If whoever good citizen calling
1578	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1579	handlers will be invoked, too, of course.	2448	handlers will be invoked, too, of course.
1580		2449
		2450	=head3 Watcher-Specific Functions and Data Members
		2451
1581	=over 4	2452	=over 4
1582		2453
1583	=item ev_fork_init (ev_signal *, callback)	2454	=item ev_fork_init (ev_signal *, callback)
1584		2455
1585	Initialises and configures the fork watcher - it has no parameters of any	2456	Initialises and configures the fork watcher - it has no parameters of any
…		…
1587	believe me.	2458	believe me.
1588		2459
1589	=back	2460	=back
1590		2461
1591		2462
		2463	=head2 C<ev_async> - how to wake up another event loop
		2464
		2465	In general, you cannot use an C<ev_loop> from multiple threads or other
		2466	asynchronous sources such as signal handlers (as opposed to multiple event
		2467	loops - those are of course safe to use in different threads).
		2468
		2469	Sometimes, however, you need to wake up another event loop you do not
		2470	control, for example because it belongs to another thread. This is what
		2471	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2472	can signal it by calling C<ev_async_send>, which is thread- and signal
		2473	safe.
		2474
		2475	This functionality is very similar to C<ev_signal> watchers, as signals,
		2476	too, are asynchronous in nature, and signals, too, will be compressed
		2477	(i.e. the number of callback invocations may be less than the number of
		2478	C<ev_async_sent> calls).
		2479
		2480	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2481	just the default loop.
		2482
		2483	=head3 Queueing
		2484
		2485	C<ev_async> does not support queueing of data in any way. The reason
		2486	is that the author does not know of a simple (or any) algorithm for a
		2487	multiple-writer-single-reader queue that works in all cases and doesn't
		2488	need elaborate support such as pthreads.
		2489
		2490	That means that if you want to queue data, you have to provide your own
		2491	queue. But at least I can tell you how to implement locking around your
		2492	queue:
		2493
		2494	=over 4
		2495
		2496	=item queueing from a signal handler context
		2497
		2498	To implement race-free queueing, you simply add to the queue in the signal
		2499	handler but you block the signal handler in the watcher callback. Here is
		2500	an example that does that for some fictitious SIGUSR1 handler:
		2501
		2502	static ev_async mysig;
		2503
		2504	static void
		2505	sigusr1_handler (void)
		2506	{
		2507	sometype data;
		2508
		2509	// no locking etc.
		2510	queue_put (data);
		2511	ev_async_send (EV_DEFAULT_ &mysig);
		2512	}
		2513
		2514	static void
		2515	mysig_cb (EV_P_ ev_async *w, int revents)
		2516	{
		2517	sometype data;
		2518	sigset_t block, prev;
		2519
		2520	sigemptyset (&block);
		2521	sigaddset (&block, SIGUSR1);
		2522	sigprocmask (SIG_BLOCK, &block, &prev);
		2523
		2524	while (queue_get (&data))
		2525	process (data);
		2526
		2527	if (sigismember (&prev, SIGUSR1)
		2528	sigprocmask (SIG_UNBLOCK, &block, 0);
		2529	}
		2530
		2531	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2532	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2533	either...).
		2534
		2535	=item queueing from a thread context
		2536
		2537	The strategy for threads is different, as you cannot (easily) block
		2538	threads but you can easily preempt them, so to queue safely you need to
		2539	employ a traditional mutex lock, such as in this pthread example:
		2540
		2541	static ev_async mysig;
		2542	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2543
		2544	static void
		2545	otherthread (void)
		2546	{
		2547	// only need to lock the actual queueing operation
		2548	pthread_mutex_lock (&mymutex);
		2549	queue_put (data);
		2550	pthread_mutex_unlock (&mymutex);
		2551
		2552	ev_async_send (EV_DEFAULT_ &mysig);
		2553	}
		2554
		2555	static void
		2556	mysig_cb (EV_P_ ev_async *w, int revents)
		2557	{
		2558	pthread_mutex_lock (&mymutex);
		2559
		2560	while (queue_get (&data))
		2561	process (data);
		2562
		2563	pthread_mutex_unlock (&mymutex);
		2564	}
		2565
		2566	=back
		2567
		2568
		2569	=head3 Watcher-Specific Functions and Data Members
		2570
		2571	=over 4
		2572
		2573	=item ev_async_init (ev_async *, callback)
		2574
		2575	Initialises and configures the async watcher - it has no parameters of any
		2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2577	trust me.
		2578
		2579	=item ev_async_send (loop, ev_async *)
		2580
		2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2583	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2585	section below on what exactly this means).
		2586
		2587	This call incurs the overhead of a system call only once per loop iteration,
		2588	so while the overhead might be noticeable, it doesn't apply to repeated
		2589	calls to C<ev_async_send>.
		2590
		2591	=item bool = ev_async_pending (ev_async *)
		2592
		2593	Returns a non-zero value when C<ev_async_send> has been called on the
		2594	watcher but the event has not yet been processed (or even noted) by the
		2595	event loop.
		2596
		2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2598	the loop iterates next and checks for the watcher to have become active,
		2599	it will reset the flag again. C<ev_async_pending> can be used to very
		2600	quickly check whether invoking the loop might be a good idea.
		2601
		2602	Not that this does I<not> check whether the watcher itself is pending, only
		2603	whether it has been requested to make this watcher pending.
		2604
		2605	=back
		2606
		2607
1592	=head1 OTHER FUNCTIONS	2608	=head1 OTHER FUNCTIONS
1593		2609
1594	There are some other functions of possible interest. Described. Here. Now.	2610	There are some other functions of possible interest. Described. Here. Now.
1595		2611
1596	=over 4	2612	=over 4
1597		2613
1598	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2614	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1599		2615
1600	This function combines a simple timer and an I/O watcher, calls your	2616	This function combines a simple timer and an I/O watcher, calls your
1601	callback on whichever event happens first and automatically stop both	2617	callback on whichever event happens first and automatically stops both
1602	watchers. This is useful if you want to wait for a single event on an fd	2618	watchers. This is useful if you want to wait for a single event on an fd
1603	or timeout without having to allocate/configure/start/stop/free one or	2619	or timeout without having to allocate/configure/start/stop/free one or
1604	more watchers yourself.	2620	more watchers yourself.
1605		2621
1606	If C<fd> is less than 0, then no I/O watcher will be started and events	2622	If C<fd> is less than 0, then no I/O watcher will be started and the
1607	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2623	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1608	C<events> set will be craeted and started.	2624	the given C<fd> and C<events> set will be created and started.
1609		2625
1610	If C<timeout> is less than 0, then no timeout watcher will be	2626	If C<timeout> is less than 0, then no timeout watcher will be
1611	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1612	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2628	repeat = 0) will be started. C<0> is a valid timeout.
1613	dubious value.
1614		2629
1615	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1616	passed an C<revents> set like normal event callbacks (a combination of	2631	passed an C<revents> set like normal event callbacks (a combination of
1617	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1618	value passed to C<ev_once>:	2633	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2634	a timeout and an io event at the same time - you probably should give io
		2635	events precedence.
1619		2636
		2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2638
1620	static void stdin_ready (int revents, void *arg)	2639	static void stdin_ready (int revents, void *arg)
1621	{	2640	{
1622	if (revents & EV_TIMEOUT)
1623	/* doh, nothing entered */;
1624	else if (revents & EV_READ)	2641	if (revents & EV_READ)
1625	/* stdin might have data for us, joy! */;	2642	/* stdin might have data for us, joy! */;
		2643	else if (revents & EV_TIMEOUT)
		2644	/* doh, nothing entered */;
1626	}	2645	}
1627		2646
1628	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1629		2648
1630	=item ev_feed_event (ev_loop *, watcher *, int revents)	2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
1631		2650
1632	Feeds the given event set into the event loop, as if the specified event	2651	Feeds the given event set into the event loop, as if the specified event
1633	had happened for the specified watcher (which must be a pointer to an	2652	had happened for the specified watcher (which must be a pointer to an
1634	initialised but not necessarily started event watcher).	2653	initialised but not necessarily started event watcher).
1635		2654
1636	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
1637		2656
1638	Feed an event on the given fd, as if a file descriptor backend detected	2657	Feed an event on the given fd, as if a file descriptor backend detected
1639	the given events it.	2658	the given events it.
1640		2659
1641	=item ev_feed_signal_event (ev_loop *loop, int signum)	2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
1642		2661
1643	Feed an event as if the given signal occured (C<loop> must be the default	2662	Feed an event as if the given signal occurred (C<loop> must be the default
1644	loop!).	2663	loop!).
1645		2664
1646	=back	2665	=back
1647		2666
1648		2667
…		…
1664		2683
1665	=item * Priorities are not currently supported. Initialising priorities	2684	=item * Priorities are not currently supported. Initialising priorities
1666	will fail and all watchers will have the same priority, even though there	2685	will fail and all watchers will have the same priority, even though there
1667	is an ev_pri field.	2686	is an ev_pri field.
1668		2687
		2688	=item * In libevent, the last base created gets the signals, in libev, the
		2689	first base created (== the default loop) gets the signals.
		2690
1669	=item * Other members are not supported.	2691	=item * Other members are not supported.
1670		2692
1671	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2693	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1672	to use the libev header file and library.	2694	to use the libev header file and library.
1673		2695
1674	=back	2696	=back
1675		2697
1676	=head1 C++ SUPPORT	2698	=head1 C++ SUPPORT
1677		2699
1678	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2700	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1679	you to use some convinience methods to start/stop watchers and also change	2701	you to use some convenience methods to start/stop watchers and also change
1680	the callback model to a model using method callbacks on objects.	2702	the callback model to a model using method callbacks on objects.
1681		2703
1682	To use it,	2704	To use it,
1683		2705
1684	#include <ev++.h>	2706	#include <ev++.h>
1685		2707
1686	(it is not installed by default). This automatically includes F<ev.h>	2708	This automatically includes F<ev.h> and puts all of its definitions (many
1687	and puts all of its definitions (many of them macros) into the global	2709	of them macros) into the global namespace. All C++ specific things are
1688	namespace. All C++ specific things are put into the C<ev> namespace.	2710	put into the C<ev> namespace. It should support all the same embedding
		2711	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1689		2712
1690	It should support all the same embedding options as F<ev.h>, most notably	2713	Care has been taken to keep the overhead low. The only data member the C++
1691	C<EV_MULTIPLICITY>.	2714	classes add (compared to plain C-style watchers) is the event loop pointer
		2715	that the watcher is associated with (or no additional members at all if
		2716	you disable C<EV_MULTIPLICITY> when embedding libev).
		2717
		2718	Currently, functions, and static and non-static member functions can be
		2719	used as callbacks. Other types should be easy to add as long as they only
		2720	need one additional pointer for context. If you need support for other
		2721	types of functors please contact the author (preferably after implementing
		2722	it).
1692		2723
1693	Here is a list of things available in the C<ev> namespace:	2724	Here is a list of things available in the C<ev> namespace:
1694		2725
1695	=over 4	2726	=over 4
1696		2727
…		…
1712		2743
1713	All of those classes have these methods:	2744	All of those classes have these methods:
1714		2745
1715	=over 4	2746	=over 4
1716		2747
1717	=item ev::TYPE::TYPE (object *, object::method *)	2748	=item ev::TYPE::TYPE ()
1718		2749
1719	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2750	=item ev::TYPE::TYPE (struct ev_loop *)
1720		2751
1721	=item ev::TYPE::~TYPE	2752	=item ev::TYPE::~TYPE
1722		2753
1723	The constructor takes a pointer to an object and a method pointer to	2754	The constructor (optionally) takes an event loop to associate the watcher
1724	the event handler callback to call in this class. The constructor calls	2755	with. If it is omitted, it will use C<EV_DEFAULT>.
1725	C<ev_init> for you, which means you have to call the C<set> method	2756
1726	before starting it. If you do not specify a loop then the constructor	2757	The constructor calls C<ev_init> for you, which means you have to call the
1727	automatically associates the default loop with this watcher.	2758	C<set> method before starting it.
		2759
		2760	It will not set a callback, however: You have to call the templated C<set>
		2761	method to set a callback before you can start the watcher.
		2762
		2763	(The reason why you have to use a method is a limitation in C++ which does
		2764	not allow explicit template arguments for constructors).
1728		2765
1729	The destructor automatically stops the watcher if it is active.	2766	The destructor automatically stops the watcher if it is active.
		2767
		2768	=item w->set<class, &class::method> (object *)
		2769
		2770	This method sets the callback method to call. The method has to have a
		2771	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2772	first argument and the C<revents> as second. The object must be given as
		2773	parameter and is stored in the C<data> member of the watcher.
		2774
		2775	This method synthesizes efficient thunking code to call your method from
		2776	the C callback that libev requires. If your compiler can inline your
		2777	callback (i.e. it is visible to it at the place of the C<set> call and
		2778	your compiler is good :), then the method will be fully inlined into the
		2779	thunking function, making it as fast as a direct C callback.
		2780
		2781	Example: simple class declaration and watcher initialisation
		2782
		2783	struct myclass
		2784	{
		2785	void io_cb (ev::io &w, int revents) { }
		2786	}
		2787
		2788	myclass obj;
		2789	ev::io iow;
		2790	iow.set <myclass, &myclass::io_cb> (&obj);
		2791
		2792	=item w->set<function> (void *data = 0)
		2793
		2794	Also sets a callback, but uses a static method or plain function as
		2795	callback. The optional C<data> argument will be stored in the watcher's
		2796	C<data> member and is free for you to use.
		2797
		2798	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2799
		2800	See the method-C<set> above for more details.
		2801
		2802	Example: Use a plain function as callback.
		2803
		2804	static void io_cb (ev::io &w, int revents) { }
		2805	iow.set <io_cb> ();
1730		2806
1731	=item w->set (struct ev_loop *)	2807	=item w->set (struct ev_loop *)
1732		2808
1733	Associates a different C<struct ev_loop> with this watcher. You can only	2809	Associates a different C<struct ev_loop> with this watcher. You can only
1734	do this when the watcher is inactive (and not pending either).	2810	do this when the watcher is inactive (and not pending either).
1735		2811
1736	=item w->set ([args])	2812	=item w->set ([arguments])
1737		2813
1738	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2814	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1739	called at least once. Unlike the C counterpart, an active watcher gets	2815	called at least once. Unlike the C counterpart, an active watcher gets
1740	automatically stopped and restarted.	2816	automatically stopped and restarted when reconfiguring it with this
		2817	method.
1741		2818
1742	=item w->start ()	2819	=item w->start ()
1743		2820
1744	Starts the watcher. Note that there is no C<loop> argument as the	2821	Starts the watcher. Note that there is no C<loop> argument, as the
1745	constructor already takes the loop.	2822	constructor already stores the event loop.
1746		2823
1747	=item w->stop ()	2824	=item w->stop ()
1748		2825
1749	Stops the watcher if it is active. Again, no C<loop> argument.	2826	Stops the watcher if it is active. Again, no C<loop> argument.
1750		2827
1751	=item w->again () C<ev::timer>, C<ev::periodic> only	2828	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1752		2829
1753	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2830	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1754	C<ev_TYPE_again> function.	2831	C<ev_TYPE_again> function.
1755		2832
1756	=item w->sweep () C<ev::embed> only	2833	=item w->sweep () (C<ev::embed> only)
1757		2834
1758	Invokes C<ev_embed_sweep>.	2835	Invokes C<ev_embed_sweep>.
1759		2836
1760	=item w->update () C<ev::stat> only	2837	=item w->update () (C<ev::stat> only)
1761		2838
1762	Invokes C<ev_stat_stat>.	2839	Invokes C<ev_stat_stat>.
1763		2840
1764	=back	2841	=back
1765		2842
1766	=back	2843	=back
1767		2844
1768	Example: Define a class with an IO and idle watcher, start one of them in	2845	Example: Define a class with an IO and idle watcher, start one of them in
1769	the constructor.	2846	the constructor.
1770		2847
1771	class myclass	2848	class myclass
1772	{	2849	{
1773	ev_io io; void io_cb (ev::io &w, int revents);	2850	ev::io io ; void io_cb (ev::io &w, int revents);
1774	ev_idle idle void idle_cb (ev::idle &w, int revents);	2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);
1775		2852
1776	myclass ();	2853	myclass (int fd)
1777	}	2854	{
		2855	io .set <myclass, &myclass::io_cb > (this);
		2856	idle.set <myclass, &myclass::idle_cb> (this);
1778		2857
1779	myclass::myclass (int fd)
1780	: io (this, &myclass::io_cb),
1781	idle (this, &myclass::idle_cb)
1782	{
1783	io.start (fd, ev::READ);	2858	io.start (fd, ev::READ);
		2859	}
1784	}	2860	};
		2861
		2862
		2863	=head1 OTHER LANGUAGE BINDINGS
		2864
		2865	Libev does not offer other language bindings itself, but bindings for a
		2866	number of languages exist in the form of third-party packages. If you know
		2867	any interesting language binding in addition to the ones listed here, drop
		2868	me a note.
		2869
		2870	=over 4
		2871
		2872	=item Perl
		2873
		2874	The EV module implements the full libev API and is actually used to test
		2875	libev. EV is developed together with libev. Apart from the EV core module,
		2876	there are additional modules that implement libev-compatible interfaces
		2877	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2878	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2879	and C<EV::Glib>).
		2880
		2881	It can be found and installed via CPAN, its homepage is at
		2882	L<http://software.schmorp.de/pkg/EV>.
		2883
		2884	=item Python
		2885
		2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2887	seems to be quite complete and well-documented. Note, however, that the
		2888	patch they require for libev is outright dangerous as it breaks the ABI
		2889	for everybody else, and therefore, should never be applied in an installed
		2890	libev (if python requires an incompatible ABI then it needs to embed
		2891	libev).
		2892
		2893	=item Ruby
		2894
		2895	Tony Arcieri has written a ruby extension that offers access to a subset
		2896	of the libev API and adds file handle abstractions, asynchronous DNS and
		2897	more on top of it. It can be found via gem servers. Its homepage is at
		2898	L<http://rev.rubyforge.org/>.
		2899
		2900	=item D
		2901
		2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2904
		2905	=back
1785		2906
1786		2907
1787	=head1 MACRO MAGIC	2908	=head1 MACRO MAGIC
1788		2909
1789	Libev can be compiled with a variety of options, the most fundemantal is	2910	Libev can be compiled with a variety of options, the most fundamental
1790	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2911	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1791	callbacks have an initial C<struct ev_loop *> argument.	2912	functions and callbacks have an initial C<struct ev_loop *> argument.
1792		2913
1793	To make it easier to write programs that cope with either variant, the	2914	To make it easier to write programs that cope with either variant, the
1794	following macros are defined:	2915	following macros are defined:
1795		2916
1796	=over 4	2917	=over 4
…		…
1799		2920
1800	This provides the loop I<argument> for functions, if one is required ("ev	2921	This provides the loop I<argument> for functions, if one is required ("ev
1801	loop argument"). The C<EV_A> form is used when this is the sole argument,	2922	loop argument"). The C<EV_A> form is used when this is the sole argument,
1802	C<EV_A_> is used when other arguments are following. Example:	2923	C<EV_A_> is used when other arguments are following. Example:
1803		2924
1804	ev_unref (EV_A);	2925	ev_unref (EV_A);
1805	ev_timer_add (EV_A_ watcher);	2926	ev_timer_add (EV_A_ watcher);
1806	ev_loop (EV_A_ 0);	2927	ev_loop (EV_A_ 0);
1807		2928
1808	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2929	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1809	which is often provided by the following macro.	2930	which is often provided by the following macro.
1810		2931
1811	=item C<EV_P>, C<EV_P_>	2932	=item C<EV_P>, C<EV_P_>
1812		2933
1813	This provides the loop I<parameter> for functions, if one is required ("ev	2934	This provides the loop I<parameter> for functions, if one is required ("ev
1814	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2935	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1815	C<EV_P_> is used when other parameters are following. Example:	2936	C<EV_P_> is used when other parameters are following. Example:
1816		2937
1817	// this is how ev_unref is being declared	2938	// this is how ev_unref is being declared
1818	static void ev_unref (EV_P);	2939	static void ev_unref (EV_P);
1819		2940
1820	// this is how you can declare your typical callback	2941	// this is how you can declare your typical callback
1821	static void cb (EV_P_ ev_timer *w, int revents)	2942	static void cb (EV_P_ ev_timer *w, int revents)
1822		2943
1823	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2944	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1824	suitable for use with C<EV_A>.	2945	suitable for use with C<EV_A>.
1825		2946
1826	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2947	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1827		2948
1828	Similar to the other two macros, this gives you the value of the default	2949	Similar to the other two macros, this gives you the value of the default
1829	loop, if multiple loops are supported ("ev loop default").	2950	loop, if multiple loops are supported ("ev loop default").
1830		2951
		2952	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2953
		2954	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2955	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2956	is undefined when the default loop has not been initialised by a previous
		2957	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2958
		2959	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2960	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
		2961
1831	=back	2962	=back
1832		2963
1833	Example: Declare and initialise a check watcher, working regardless of	2964	Example: Declare and initialise a check watcher, utilising the above
1834	wether multiple loops are supported or not.	2965	macros so it will work regardless of whether multiple loops are supported
		2966	or not.
1835		2967
1836	static void	2968	static void
1837	check_cb (EV_P_ ev_timer *w, int revents)	2969	check_cb (EV_P_ ev_timer *w, int revents)
1838	{	2970	{
1839	ev_check_stop (EV_A_ w);	2971	ev_check_stop (EV_A_ w);
1840	}	2972	}
1841		2973
1842	ev_check check;	2974	ev_check check;
1843	ev_check_init (&check, check_cb);	2975	ev_check_init (&check, check_cb);
1844	ev_check_start (EV_DEFAULT_ &check);	2976	ev_check_start (EV_DEFAULT_ &check);
1845	ev_loop (EV_DEFAULT_ 0);	2977	ev_loop (EV_DEFAULT_ 0);
1846
1847		2978
1848	=head1 EMBEDDING	2979	=head1 EMBEDDING
1849		2980
1850	Libev can (and often is) directly embedded into host	2981	Libev can (and often is) directly embedded into host
1851	applications. Examples of applications that embed it include the Deliantra	2982	applications. Examples of applications that embed it include the Deliantra
1852	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2983	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1853	and rxvt-unicode.	2984	and rxvt-unicode.
1854		2985
1855	The goal is to enable you to just copy the neecssary files into your	2986	The goal is to enable you to just copy the necessary files into your
1856	source directory without having to change even a single line in them, so	2987	source directory without having to change even a single line in them, so
1857	you can easily upgrade by simply copying (or having a checked-out copy of	2988	you can easily upgrade by simply copying (or having a checked-out copy of
1858	libev somewhere in your source tree).	2989	libev somewhere in your source tree).
1859		2990
1860	=head2 FILESETS	2991	=head2 FILESETS
1861		2992
1862	Depending on what features you need you need to include one or more sets of files	2993	Depending on what features you need you need to include one or more sets of files
1863	in your app.	2994	in your application.
1864		2995
1865	=head3 CORE EVENT LOOP	2996	=head3 CORE EVENT LOOP
1866		2997
1867	To include only the libev core (all the C<ev_*> functions), with manual	2998	To include only the libev core (all the C<ev_*> functions), with manual
1868	configuration (no autoconf):	2999	configuration (no autoconf):
1869		3000
1870	#define EV_STANDALONE 1	3001	#define EV_STANDALONE 1
1871	#include "ev.c"	3002	#include "ev.c"
1872		3003
1873	This will automatically include F<ev.h>, too, and should be done in a	3004	This will automatically include F<ev.h>, too, and should be done in a
1874	single C source file only to provide the function implementations. To use	3005	single C source file only to provide the function implementations. To use
1875	it, do the same for F<ev.h> in all files wishing to use this API (best	3006	it, do the same for F<ev.h> in all files wishing to use this API (best
1876	done by writing a wrapper around F<ev.h> that you can include instead and	3007	done by writing a wrapper around F<ev.h> that you can include instead and
1877	where you can put other configuration options):	3008	where you can put other configuration options):
1878		3009
1879	#define EV_STANDALONE 1	3010	#define EV_STANDALONE 1
1880	#include "ev.h"	3011	#include "ev.h"
1881		3012
1882	Both header files and implementation files can be compiled with a C++	3013	Both header files and implementation files can be compiled with a C++
1883	compiler (at least, thats a stated goal, and breakage will be treated	3014	compiler (at least, thats a stated goal, and breakage will be treated
1884	as a bug).	3015	as a bug).
1885		3016
1886	You need the following files in your source tree, or in a directory	3017	You need the following files in your source tree, or in a directory
1887	in your include path (e.g. in libev/ when using -Ilibev):	3018	in your include path (e.g. in libev/ when using -Ilibev):
1888		3019
1889	ev.h	3020	ev.h
1890	ev.c	3021	ev.c
1891	ev_vars.h	3022	ev_vars.h
1892	ev_wrap.h	3023	ev_wrap.h
1893		3024
1894	ev_win32.c required on win32 platforms only	3025	ev_win32.c required on win32 platforms only
1895		3026
1896	ev_select.c only when select backend is enabled (which is by default)	3027	ev_select.c only when select backend is enabled (which is enabled by default)
1897	ev_poll.c only when poll backend is enabled (disabled by default)	3028	ev_poll.c only when poll backend is enabled (disabled by default)
1898	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3029	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1899	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3030	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1900	ev_port.c only when the solaris port backend is enabled (disabled by default)	3031	ev_port.c only when the solaris port backend is enabled (disabled by default)
1901		3032
1902	F<ev.c> includes the backend files directly when enabled, so you only need	3033	F<ev.c> includes the backend files directly when enabled, so you only need
1903	to compile this single file.	3034	to compile this single file.
1904		3035
1905	=head3 LIBEVENT COMPATIBILITY API	3036	=head3 LIBEVENT COMPATIBILITY API
1906		3037
1907	To include the libevent compatibility API, also include:	3038	To include the libevent compatibility API, also include:
1908		3039
1909	#include "event.c"	3040	#include "event.c"
1910		3041
1911	in the file including F<ev.c>, and:	3042	in the file including F<ev.c>, and:
1912		3043
1913	#include "event.h"	3044	#include "event.h"
1914		3045
1915	in the files that want to use the libevent API. This also includes F<ev.h>.	3046	in the files that want to use the libevent API. This also includes F<ev.h>.
1916		3047
1917	You need the following additional files for this:	3048	You need the following additional files for this:
1918		3049
1919	event.h	3050	event.h
1920	event.c	3051	event.c
1921		3052
1922	=head3 AUTOCONF SUPPORT	3053	=head3 AUTOCONF SUPPORT
1923		3054
1924	Instead of using C<EV_STANDALONE=1> and providing your config in	3055	Instead of using C<EV_STANDALONE=1> and providing your configuration in
1925	whatever way you want, you can also C<m4_include([libev.m4])> in your	3056	whatever way you want, you can also C<m4_include([libev.m4])> in your
1926	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3057	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1927	include F<config.h> and configure itself accordingly.	3058	include F<config.h> and configure itself accordingly.
1928		3059
1929	For this of course you need the m4 file:	3060	For this of course you need the m4 file:
1930		3061
1931	libev.m4	3062	libev.m4
1932		3063
1933	=head2 PREPROCESSOR SYMBOLS/MACROS	3064	=head2 PREPROCESSOR SYMBOLS/MACROS
1934		3065
1935	Libev can be configured via a variety of preprocessor symbols you have to define	3066	Libev can be configured via a variety of preprocessor symbols you have to
1936	before including any of its files. The default is not to build for multiplicity	3067	define before including any of its files. The default in the absence of
1937	and only include the select backend.	3068	autoconf is documented for every option.
1938		3069
1939	=over 4	3070	=over 4
1940		3071
1941	=item EV_STANDALONE	3072	=item EV_STANDALONE
1942		3073
…		…
1947	F<event.h> that are not directly supported by the libev core alone.	3078	F<event.h> that are not directly supported by the libev core alone.
1948		3079
1949	=item EV_USE_MONOTONIC	3080	=item EV_USE_MONOTONIC
1950		3081
1951	If defined to be C<1>, libev will try to detect the availability of the	3082	If defined to be C<1>, libev will try to detect the availability of the
1952	monotonic clock option at both compiletime and runtime. Otherwise no use	3083	monotonic clock option at both compile time and runtime. Otherwise no use
1953	of the monotonic clock option will be attempted. If you enable this, you	3084	of the monotonic clock option will be attempted. If you enable this, you
1954	usually have to link against librt or something similar. Enabling it when	3085	usually have to link against librt or something similar. Enabling it when
1955	the functionality isn't available is safe, though, althoguh you have	3086	the functionality isn't available is safe, though, although you have
1956	to make sure you link against any libraries where the C<clock_gettime>	3087	to make sure you link against any libraries where the C<clock_gettime>
1957	function is hiding in (often F<-lrt>).	3088	function is hiding in (often F<-lrt>).
1958		3089
1959	=item EV_USE_REALTIME	3090	=item EV_USE_REALTIME
1960		3091
1961	If defined to be C<1>, libev will try to detect the availability of the	3092	If defined to be C<1>, libev will try to detect the availability of the
1962	realtime clock option at compiletime (and assume its availability at	3093	real-time clock option at compile time (and assume its availability at
1963	runtime if successful). Otherwise no use of the realtime clock option will	3094	runtime if successful). Otherwise no use of the real-time clock option will
1964	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1965	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1966	in the description of C<EV_USE_MONOTONIC>, though.	3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		3098
		3099	=item EV_USE_NANOSLEEP
		3100
		3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		3102	and will use it for delays. Otherwise it will use C<select ()>.
		3103
		3104	=item EV_USE_EVENTFD
		3105
		3106	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3107	available and will probe for kernel support at runtime. This will improve
		3108	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3109	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3110	2.7 or newer, otherwise disabled.
1967		3111
1968	=item EV_USE_SELECT	3112	=item EV_USE_SELECT
1969		3113
1970	If undefined or defined to be C<1>, libev will compile in support for the	3114	If undefined or defined to be C<1>, libev will compile in support for the
1971	C<select>(2) backend. No attempt at autodetection will be done: if no	3115	C<select>(2) backend. No attempt at auto-detection will be done: if no
1972	other method takes over, select will be it. Otherwise the select backend	3116	other method takes over, select will be it. Otherwise the select backend
1973	will not be compiled in.	3117	will not be compiled in.
1974		3118
1975	=item EV_SELECT_USE_FD_SET	3119	=item EV_SELECT_USE_FD_SET
1976		3120
1977	If defined to C<1>, then the select backend will use the system C<fd_set>	3121	If defined to C<1>, then the select backend will use the system C<fd_set>
1978	structure. This is useful if libev doesn't compile due to a missing	3122	structure. This is useful if libev doesn't compile due to a missing
1979	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
1980	exotic systems. This usually limits the range of file descriptors to some	3124	exotic systems. This usually limits the range of file descriptors to some
1981	low limit such as 1024 or might have other limitations (winsocket only	3125	low limit such as 1024 or might have other limitations (winsocket only
1982	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
1983	influence the size of the C<fd_set> used.	3127	influence the size of the C<fd_set> used.
1984		3128
…		…
1990	be used is the winsock select). This means that it will call	3134	be used is the winsock select). This means that it will call
1991	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1992	it is assumed that all these functions actually work on fds, even	3136	it is assumed that all these functions actually work on fds, even
1993	on win32. Should not be defined on non-win32 platforms.	3137	on win32. Should not be defined on non-win32 platforms.
1994		3138
		3139	=item EV_FD_TO_WIN32_HANDLE
		3140
		3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3142	file descriptors to socket handles. When not defining this symbol (the
		3143	default), then libev will call C<_get_osfhandle>, which is usually
		3144	correct. In some cases, programs use their own file descriptor management,
		3145	in which case they can provide this function to map fds to socket handles.
		3146
1995	=item EV_USE_POLL	3147	=item EV_USE_POLL
1996		3148
1997	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1998	backend. Otherwise it will be enabled on non-win32 platforms. It	3150	backend. Otherwise it will be enabled on non-win32 platforms. It
1999	takes precedence over select.	3151	takes precedence over select.
2000		3152
2001	=item EV_USE_EPOLL	3153	=item EV_USE_EPOLL
2002		3154
2003	If defined to be C<1>, libev will compile in support for the Linux	3155	If defined to be C<1>, libev will compile in support for the Linux
2004	C<epoll>(7) backend. Its availability will be detected at runtime,	3156	C<epoll>(7) backend. Its availability will be detected at runtime,
2005	otherwise another method will be used as fallback. This is the	3157	otherwise another method will be used as fallback. This is the preferred
2006	preferred backend for GNU/Linux systems.	3158	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3159	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2007		3160
2008	=item EV_USE_KQUEUE	3161	=item EV_USE_KQUEUE
2009		3162
2010	If defined to be C<1>, libev will compile in support for the BSD style	3163	If defined to be C<1>, libev will compile in support for the BSD style
2011	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3164	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2024	otherwise another method will be used as fallback. This is the preferred	3177	otherwise another method will be used as fallback. This is the preferred
2025	backend for Solaris 10 systems.	3178	backend for Solaris 10 systems.
2026		3179
2027	=item EV_USE_DEVPOLL	3180	=item EV_USE_DEVPOLL
2028		3181
2029	reserved for future expansion, works like the USE symbols above.	3182	Reserved for future expansion, works like the USE symbols above.
2030		3183
2031	=item EV_USE_INOTIFY	3184	=item EV_USE_INOTIFY
2032		3185
2033	If defined to be C<1>, libev will compile in support for the Linux inotify	3186	If defined to be C<1>, libev will compile in support for the Linux inotify
2034	interface to speed up C<ev_stat> watchers. Its actual availability will	3187	interface to speed up C<ev_stat> watchers. Its actual availability will
2035	be detected at runtime.	3188	be detected at runtime. If undefined, it will be enabled if the headers
		3189	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3190
		3191	=item EV_ATOMIC_T
		3192
		3193	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3194	access is atomic with respect to other threads or signal contexts. No such
		3195	type is easily found in the C language, so you can provide your own type
		3196	that you know is safe for your purposes. It is used both for signal handler "locking"
		3197	as well as for signal and thread safety in C<ev_async> watchers.
		3198
		3199	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3200	(from F<signal.h>), which is usually good enough on most platforms.
2036		3201
2037	=item EV_H	3202	=item EV_H
2038		3203
2039	The name of the F<ev.h> header file used to include it. The default if	3204	The name of the F<ev.h> header file used to include it. The default if
2040	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3205	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2041	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3206	used to virtually rename the F<ev.h> header file in case of conflicts.
2042		3207
2043	=item EV_CONFIG_H	3208	=item EV_CONFIG_H
2044		3209
2045	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3210	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2046	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3211	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2047	C<EV_H>, above.	3212	C<EV_H>, above.
2048		3213
2049	=item EV_EVENT_H	3214	=item EV_EVENT_H
2050		3215
2051	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3216	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2052	of how the F<event.h> header can be found.	3217	of how the F<event.h> header can be found, the default is C<"event.h">.
2053		3218
2054	=item EV_PROTOTYPES	3219	=item EV_PROTOTYPES
2055		3220
2056	If defined to be C<0>, then F<ev.h> will not define any function	3221	If defined to be C<0>, then F<ev.h> will not define any function
2057	prototypes, but still define all the structs and other symbols. This is	3222	prototypes, but still define all the structs and other symbols. This is
…		…
2064	will have the C<struct ev_loop *> as first argument, and you can create	3229	will have the C<struct ev_loop *> as first argument, and you can create
2065	additional independent event loops. Otherwise there will be no support	3230	additional independent event loops. Otherwise there will be no support
2066	for multiple event loops and there is no first event loop pointer	3231	for multiple event loops and there is no first event loop pointer
2067	argument. Instead, all functions act on the single default loop.	3232	argument. Instead, all functions act on the single default loop.
2068		3233
		3234	=item EV_MINPRI
		3235
		3236	=item EV_MAXPRI
		3237
		3238	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		3239	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		3240	provide for more priorities by overriding those symbols (usually defined
		3241	to be C<-2> and C<2>, respectively).
		3242
		3243	When doing priority-based operations, libev usually has to linearly search
		3244	all the priorities, so having many of them (hundreds) uses a lot of space
		3245	and time, so using the defaults of five priorities (-2 .. +2) is usually
		3246	fine.
		3247
		3248	If your embedding application does not need any priorities, defining these
		3249	both to C<0> will save some memory and CPU.
		3250
2069	=item EV_PERIODIC_ENABLE	3251	=item EV_PERIODIC_ENABLE
2070		3252
2071	If undefined or defined to be C<1>, then periodic timers are supported. If	3253	If undefined or defined to be C<1>, then periodic timers are supported. If
2072	defined to be C<0>, then they are not. Disabling them saves a few kB of	3254	defined to be C<0>, then they are not. Disabling them saves a few kB of
2073	code.	3255	code.
2074		3256
		3257	=item EV_IDLE_ENABLE
		3258
		3259	If undefined or defined to be C<1>, then idle watchers are supported. If
		3260	defined to be C<0>, then they are not. Disabling them saves a few kB of
		3261	code.
		3262
2075	=item EV_EMBED_ENABLE	3263	=item EV_EMBED_ENABLE
2076		3264
2077	If undefined or defined to be C<1>, then embed watchers are supported. If	3265	If undefined or defined to be C<1>, then embed watchers are supported. If
2078	defined to be C<0>, then they are not.	3266	defined to be C<0>, then they are not. Embed watchers rely on most other
		3267	watcher types, which therefore must not be disabled.
2079		3268
2080	=item EV_STAT_ENABLE	3269	=item EV_STAT_ENABLE
2081		3270
2082	If undefined or defined to be C<1>, then stat watchers are supported. If	3271	If undefined or defined to be C<1>, then stat watchers are supported. If
2083	defined to be C<0>, then they are not.	3272	defined to be C<0>, then they are not.
…		…
2085	=item EV_FORK_ENABLE	3274	=item EV_FORK_ENABLE
2086		3275
2087	If undefined or defined to be C<1>, then fork watchers are supported. If	3276	If undefined or defined to be C<1>, then fork watchers are supported. If
2088	defined to be C<0>, then they are not.	3277	defined to be C<0>, then they are not.
2089		3278
		3279	=item EV_ASYNC_ENABLE
		3280
		3281	If undefined or defined to be C<1>, then async watchers are supported. If
		3282	defined to be C<0>, then they are not.
		3283
2090	=item EV_MINIMAL	3284	=item EV_MINIMAL
2091		3285
2092	If you need to shave off some kilobytes of code at the expense of some	3286	If you need to shave off some kilobytes of code at the expense of some
2093	speed, define this symbol to C<1>. Currently only used for gcc to override	3287	speed, define this symbol to C<1>. Currently this is used to override some
2094	some inlining decisions, saves roughly 30% codesize of amd64.	3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3289	much smaller 2-heap for timer management over the default 4-heap.
2095		3290
2096	=item EV_PID_HASHSIZE	3291	=item EV_PID_HASHSIZE
2097		3292
2098	C<ev_child> watchers use a small hash table to distribute workload by	3293	C<ev_child> watchers use a small hash table to distribute workload by
2099	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2100	than enough. If you need to manage thousands of children you might want to	3295	than enough. If you need to manage thousands of children you might want to
2101	increase this value (I<must> be a power of two).	3296	increase this value (I<must> be a power of two).
2102		3297
2103	=item EV_INOTIFY_HASHSIZE	3298	=item EV_INOTIFY_HASHSIZE
2104		3299
2105	C<ev_staz> watchers use a small hash table to distribute workload by	3300	C<ev_stat> watchers use a small hash table to distribute workload by
2106	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3301	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2107	usually more than enough. If you need to manage thousands of C<ev_stat>	3302	usually more than enough. If you need to manage thousands of C<ev_stat>
2108	watchers you might want to increase this value (I<must> be a power of	3303	watchers you might want to increase this value (I<must> be a power of
2109	two).	3304	two).
2110		3305
		3306	=item EV_USE_4HEAP
		3307
		3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3311	faster performance with many (thousands) of watchers.
		3312
		3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3314	(disabled).
		3315
		3316	=item EV_HEAP_CACHE_AT
		3317
		3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3322	but avoids random read accesses on heap changes. This improves performance
		3323	noticeably with many (hundreds) of watchers.
		3324
		3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3326	(disabled).
		3327
		3328	=item EV_VERIFY
		3329
		3330	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3331	be done: If set to C<0>, no internal verification code will be compiled
		3332	in. If set to C<1>, then verification code will be compiled in, but not
		3333	called. If set to C<2>, then the internal verification code will be
		3334	called once per loop, which can slow down libev. If set to C<3>, then the
		3335	verification code will be called very frequently, which will slow down
		3336	libev considerably.
		3337
		3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3339	C<0>.
		3340
2111	=item EV_COMMON	3341	=item EV_COMMON
2112		3342
2113	By default, all watchers have a C<void *data> member. By redefining	3343	By default, all watchers have a C<void *data> member. By redefining
2114	this macro to a something else you can include more and other types of	3344	this macro to a something else you can include more and other types of
2115	members. You have to define it each time you include one of the files,	3345	members. You have to define it each time you include one of the files,
2116	though, and it must be identical each time.	3346	though, and it must be identical each time.
2117		3347
2118	For example, the perl EV module uses something like this:	3348	For example, the perl EV module uses something like this:
2119		3349
2120	#define EV_COMMON \	3350	#define EV_COMMON \
2121	SV *self; /* contains this struct */ \	3351	SV *self; /* contains this struct */ \
2122	SV *cb_sv, *fh /* note no trailing ";" */	3352	SV *cb_sv, *fh /* note no trailing ";" */
2123		3353
2124	=item EV_CB_DECLARE (type)	3354	=item EV_CB_DECLARE (type)
2125		3355
2126	=item EV_CB_INVOKE (watcher, revents)	3356	=item EV_CB_INVOKE (watcher, revents)
2127		3357
2128	=item ev_set_cb (ev, cb)	3358	=item ev_set_cb (ev, cb)
2129		3359
2130	Can be used to change the callback member declaration in each watcher,	3360	Can be used to change the callback member declaration in each watcher,
2131	and the way callbacks are invoked and set. Must expand to a struct member	3361	and the way callbacks are invoked and set. Must expand to a struct member
2132	definition and a statement, respectively. See the F<ev.v> header file for	3362	definition and a statement, respectively. See the F<ev.h> header file for
2133	their default definitions. One possible use for overriding these is to	3363	their default definitions. One possible use for overriding these is to
2134	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3364	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2135	method calls instead of plain function calls in C++.	3365	method calls instead of plain function calls in C++.
		3366
		3367	=back
		3368
		3369	=head2 EXPORTED API SYMBOLS
		3370
		3371	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3372	exported symbols, you can use the provided F<Symbol.*> files which list
		3373	all public symbols, one per line:
		3374
		3375	Symbols.ev for libev proper
		3376	Symbols.event for the libevent emulation
		3377
		3378	This can also be used to rename all public symbols to avoid clashes with
		3379	multiple versions of libev linked together (which is obviously bad in
		3380	itself, but sometimes it is inconvenient to avoid this).
		3381
		3382	A sed command like this will create wrapper C<#define>'s that you need to
		3383	include before including F<ev.h>:
		3384
		3385	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3386
		3387	This would create a file F<wrap.h> which essentially looks like this:
		3388
		3389	#define ev_backend myprefix_ev_backend
		3390	#define ev_check_start myprefix_ev_check_start
		3391	#define ev_check_stop myprefix_ev_check_stop
		3392	...
2136		3393
2137	=head2 EXAMPLES	3394	=head2 EXAMPLES
2138		3395
2139	For a real-world example of a program the includes libev	3396	For a real-world example of a program the includes libev
2140	verbatim, you can have a look at the EV perl module	3397	verbatim, you can have a look at the EV perl module
…		…
2143	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	3400	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2144	will be compiled. It is pretty complex because it provides its own header	3401	will be compiled. It is pretty complex because it provides its own header
2145	file.	3402	file.
2146		3403
2147	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3404	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2148	that everybody includes and which overrides some autoconf choices:	3405	that everybody includes and which overrides some configure choices:
2149		3406
		3407	#define EV_MINIMAL 1
2150	#define EV_USE_POLL 0	3408	#define EV_USE_POLL 0
2151	#define EV_MULTIPLICITY 0	3409	#define EV_MULTIPLICITY 0
2152	#define EV_PERIODICS 0	3410	#define EV_PERIODIC_ENABLE 0
		3411	#define EV_STAT_ENABLE 0
		3412	#define EV_FORK_ENABLE 0
2153	#define EV_CONFIG_H <config.h>	3413	#define EV_CONFIG_H <config.h>
		3414	#define EV_MINPRI 0
		3415	#define EV_MAXPRI 0
2154		3416
2155	#include "ev++.h"	3417	#include "ev++.h"
2156		3418
2157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2158		3420
2159	#include "ev_cpp.h"	3421	#include "ev_cpp.h"
2160	#include "ev.c"	3422	#include "ev.c"
2161		3423
		3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2162		3425
		3426	=head2 THREADS AND COROUTINES
		3427
		3428	=head3 THREADS
		3429
		3430	All libev functions are reentrant and thread-safe unless explicitly
		3431	documented otherwise, but libev implements no locking itself. This means
		3432	that you can use as many loops as you want in parallel, as long as there
		3433	are no concurrent calls into any libev function with the same loop
		3434	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3435	of course): libev guarantees that different event loops share no data
		3436	structures that need any locking.
		3437
		3438	Or to put it differently: calls with different loop parameters can be done
		3439	concurrently from multiple threads, calls with the same loop parameter
		3440	must be done serially (but can be done from different threads, as long as
		3441	only one thread ever is inside a call at any point in time, e.g. by using
		3442	a mutex per loop).
		3443
		3444	Specifically to support threads (and signal handlers), libev implements
		3445	so-called C<ev_async> watchers, which allow some limited form of
		3446	concurrency on the same event loop, namely waking it up "from the
		3447	outside".
		3448
		3449	If you want to know which design (one loop, locking, or multiple loops
		3450	without or something else still) is best for your problem, then I cannot
		3451	help you, but here is some generic advice:
		3452
		3453	=over 4
		3454
		3455	=item * most applications have a main thread: use the default libev loop
		3456	in that thread, or create a separate thread running only the default loop.
		3457
		3458	This helps integrating other libraries or software modules that use libev
		3459	themselves and don't care/know about threading.
		3460
		3461	=item * one loop per thread is usually a good model.
		3462
		3463	Doing this is almost never wrong, sometimes a better-performance model
		3464	exists, but it is always a good start.
		3465
		3466	=item * other models exist, such as the leader/follower pattern, where one
		3467	loop is handed through multiple threads in a kind of round-robin fashion.
		3468
		3469	Choosing a model is hard - look around, learn, know that usually you can do
		3470	better than you currently do :-)
		3471
		3472	=item * often you need to talk to some other thread which blocks in the
		3473	event loop.
		3474
		3475	C<ev_async> watchers can be used to wake them up from other threads safely
		3476	(or from signal contexts...).
		3477
		3478	An example use would be to communicate signals or other events that only
		3479	work in the default loop by registering the signal watcher with the
		3480	default loop and triggering an C<ev_async> watcher from the default loop
		3481	watcher callback into the event loop interested in the signal.
		3482
		3483	=back
		3484
		3485	=head3 COROUTINES
		3486
		3487	Libev is very accommodating to coroutines ("cooperative threads"):
		3488	libev fully supports nesting calls to its functions from different
		3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3490	different coroutines, and switch freely between both coroutines running the
		3491	loop, as long as you don't confuse yourself). The only exception is that
		3492	you must not do this from C<ev_periodic> reschedule callbacks.
		3493
		3494	Care has been taken to ensure that libev does not keep local state inside
		3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3496	they do not clal any callbacks.
		3497
		3498	=head2 COMPILER WARNINGS
		3499
		3500	Depending on your compiler and compiler settings, you might get no or a
		3501	lot of warnings when compiling libev code. Some people are apparently
		3502	scared by this.
		3503
		3504	However, these are unavoidable for many reasons. For one, each compiler
		3505	has different warnings, and each user has different tastes regarding
		3506	warning options. "Warn-free" code therefore cannot be a goal except when
		3507	targeting a specific compiler and compiler-version.
		3508
		3509	Another reason is that some compiler warnings require elaborate
		3510	workarounds, or other changes to the code that make it less clear and less
		3511	maintainable.
		3512
		3513	And of course, some compiler warnings are just plain stupid, or simply
		3514	wrong (because they don't actually warn about the condition their message
		3515	seems to warn about). For example, certain older gcc versions had some
		3516	warnings that resulted an extreme number of false positives. These have
		3517	been fixed, but some people still insist on making code warn-free with
		3518	such buggy versions.
		3519
		3520	While libev is written to generate as few warnings as possible,
		3521	"warn-free" code is not a goal, and it is recommended not to build libev
		3522	with any compiler warnings enabled unless you are prepared to cope with
		3523	them (e.g. by ignoring them). Remember that warnings are just that:
		3524	warnings, not errors, or proof of bugs.
		3525
		3526
		3527	=head2 VALGRIND
		3528
		3529	Valgrind has a special section here because it is a popular tool that is
		3530	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3531
		3532	If you think you found a bug (memory leak, uninitialised data access etc.)
		3533	in libev, then check twice: If valgrind reports something like:
		3534
		3535	==2274== definitely lost: 0 bytes in 0 blocks.
		3536	==2274== possibly lost: 0 bytes in 0 blocks.
		3537	==2274== still reachable: 256 bytes in 1 blocks.
		3538
		3539	Then there is no memory leak, just as memory accounted to global variables
		3540	is not a memleak - the memory is still being refernced, and didn't leak.
		3541
		3542	Similarly, under some circumstances, valgrind might report kernel bugs
		3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3544	although an acceptable workaround has been found here), or it might be
		3545	confused.
		3546
		3547	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3548	make it into some kind of religion.
		3549
		3550	If you are unsure about something, feel free to contact the mailing list
		3551	with the full valgrind report and an explanation on why you think this
		3552	is a bug in libev (best check the archives, too :). However, don't be
		3553	annoyed when you get a brisk "this is no bug" answer and take the chance
		3554	of learning how to interpret valgrind properly.
		3555
		3556	If you need, for some reason, empty reports from valgrind for your project
		3557	I suggest using suppression lists.
		3558
		3559
		3560	=head1 PORTABILITY NOTES
		3561
		3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3563
		3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3565	requires, and its I/O model is fundamentally incompatible with the POSIX
		3566	model. Libev still offers limited functionality on this platform in
		3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3568	descriptors. This only applies when using Win32 natively, not when using
		3569	e.g. cygwin.
		3570
		3571	Lifting these limitations would basically require the full
		3572	re-implementation of the I/O system. If you are into these kinds of
		3573	things, then note that glib does exactly that for you in a very portable
		3574	way (note also that glib is the slowest event library known to man).
		3575
		3576	There is no supported compilation method available on windows except
		3577	embedding it into other applications.
		3578
		3579	Not a libev limitation but worth mentioning: windows apparently doesn't
		3580	accept large writes: instead of resulting in a partial write, windows will
		3581	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3582	so make sure you only write small amounts into your sockets (less than a
		3583	megabyte seems safe, but this apparently depends on the amount of memory
		3584	available).
		3585
		3586	Due to the many, low, and arbitrary limits on the win32 platform and
		3587	the abysmal performance of winsockets, using a large number of sockets
		3588	is not recommended (and not reasonable). If your program needs to use
		3589	more than a hundred or so sockets, then likely it needs to use a totally
		3590	different implementation for windows, as libev offers the POSIX readiness
		3591	notification model, which cannot be implemented efficiently on windows
		3592	(Microsoft monopoly games).
		3593
		3594	A typical way to use libev under windows is to embed it (see the embedding
		3595	section for details) and use the following F<evwrap.h> header file instead
		3596	of F<ev.h>:
		3597
		3598	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3599	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3600
		3601	#include "ev.h"
		3602
		3603	And compile the following F<evwrap.c> file into your project (make sure
		3604	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3605
		3606	#include "evwrap.h"
		3607	#include "ev.c"
		3608
		3609	=over 4
		3610
		3611	=item The winsocket select function
		3612
		3613	The winsocket C<select> function doesn't follow POSIX in that it
		3614	requires socket I<handles> and not socket I<file descriptors> (it is
		3615	also extremely buggy). This makes select very inefficient, and also
		3616	requires a mapping from file descriptors to socket handles (the Microsoft
		3617	C runtime provides the function C<_open_osfhandle> for this). See the
		3618	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3619	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3620
		3621	The configuration for a "naked" win32 using the Microsoft runtime
		3622	libraries and raw winsocket select is:
		3623
		3624	#define EV_USE_SELECT 1
		3625	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3626
		3627	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3628	complexity in the O(n²) range when using win32.
		3629
		3630	=item Limited number of file descriptors
		3631
		3632	Windows has numerous arbitrary (and low) limits on things.
		3633
		3634	Early versions of winsocket's select only supported waiting for a maximum
		3635	of C<64> handles (probably owning to the fact that all windows kernels
		3636	can only wait for C<64> things at the same time internally; Microsoft
		3637	recommends spawning a chain of threads and wait for 63 handles and the
		3638	previous thread in each. Great).
		3639
		3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3641	to some high number (e.g. C<2048>) before compiling the winsocket select
		3642	call (which might be in libev or elsewhere, for example, perl does its own
		3643	select emulation on windows).
		3644
		3645	Another limit is the number of file descriptors in the Microsoft runtime
		3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3647	or something like this inside Microsoft). You can increase this by calling
		3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3649	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3650	libraries.
		3651
		3652	This might get you to about C<512> or C<2048> sockets (depending on
		3653	windows version and/or the phase of the moon). To get more, you need to
		3654	wrap all I/O functions and provide your own fd management, but the cost of
		3655	calling select (O(n²)) will likely make this unworkable.
		3656
		3657	=back
		3658
		3659	=head2 PORTABILITY REQUIREMENTS
		3660
		3661	In addition to a working ISO-C implementation and of course the
		3662	backend-specific APIs, libev relies on a few additional extensions:
		3663
		3664	=over 4
		3665
		3666	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3667	calling conventions regardless of C<ev_watcher_type *>.
		3668
		3669	Libev assumes not only that all watcher pointers have the same internal
		3670	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3671	assumes that the same (machine) code can be used to call any watcher
		3672	callback: The watcher callbacks have different type signatures, but libev
		3673	calls them using an C<ev_watcher *> internally.
		3674
		3675	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3676
		3677	The type C<sig_atomic_t volatile> (or whatever is defined as
		3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3679	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3680	believed to be sufficiently portable.
		3681
		3682	=item C<sigprocmask> must work in a threaded environment
		3683
		3684	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3685	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3686	pthread implementations will either allow C<sigprocmask> in the "main
		3687	thread" or will block signals process-wide, both behaviours would
		3688	be compatible with libev. Interaction between C<sigprocmask> and
		3689	C<pthread_sigmask> could complicate things, however.
		3690
		3691	The most portable way to handle signals is to block signals in all threads
		3692	except the initial one, and run the default loop in the initial thread as
		3693	well.
		3694
		3695	=item C<long> must be large enough for common memory allocation sizes
		3696
		3697	To improve portability and simplify its API, libev uses C<long> internally
		3698	instead of C<size_t> when allocating its data structures. On non-POSIX
		3699	systems (Microsoft...) this might be unexpectedly low, but is still at
		3700	least 31 bits everywhere, which is enough for hundreds of millions of
		3701	watchers.
		3702
		3703	=item C<double> must hold a time value in seconds with enough accuracy
		3704
		3705	The type C<double> is used to represent timestamps. It is required to
		3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3707	enough for at least into the year 4000. This requirement is fulfilled by
		3708	implementations implementing IEEE 754 (basically all existing ones).
		3709
		3710	=back
		3711
		3712	If you know of other additional requirements drop me a note.
		3713
		3714
2163	=head1 COMPLEXITIES	3715	=head1 ALGORITHMIC COMPLEXITIES
2164		3716
2165	In this section the complexities of (many of) the algorithms used inside	3717	In this section the complexities of (many of) the algorithms used inside
2166	libev will be explained. For complexity discussions about backends see the	3718	libev will be documented. For complexity discussions about backends see
2167	documentation for C<ev_default_init>.	3719	the documentation for C<ev_default_init>.
		3720
		3721	All of the following are about amortised time: If an array needs to be
		3722	extended, libev needs to realloc and move the whole array, but this
		3723	happens asymptotically rarer with higher number of elements, so O(1) might
		3724	mean that libev does a lengthy realloc operation in rare cases, but on
		3725	average it is much faster and asymptotically approaches constant time.
2168		3726
2169	=over 4	3727	=over 4
2170		3728
2171	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3729	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2172		3730
		3731	This means that, when you have a watcher that triggers in one hour and
		3732	there are 100 watchers that would trigger before that, then inserting will
		3733	have to skip roughly seven (C<ld 100>) of these watchers.
		3734
2173	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3735	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2174		3736
		3737	That means that changing a timer costs less than removing/adding them,
		3738	as only the relative motion in the event queue has to be paid for.
		3739
2175	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3740	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2176		3741
		3742	These just add the watcher into an array or at the head of a list.
		3743
2177	=item Stopping check/prepare/idle watchers: O(1)	3744	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2178		3745
2179	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3746	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2180		3747
		3748	These watchers are stored in lists, so they need to be walked to find the
		3749	correct watcher to remove. The lists are usually short (you don't usually
		3750	have many watchers waiting for the same fd or signal: one is typical, two
		3751	is rare).
		3752
2181	=item Finding the next timer per loop iteration: O(1)	3753	=item Finding the next timer in each loop iteration: O(1)
		3754
		3755	By virtue of using a binary or 4-heap, the next timer is always found at a
		3756	fixed position in the storage array.
2182		3757
2183	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3758	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2184		3759
2185	=item Activating one watcher: O(1)	3760	A change means an I/O watcher gets started or stopped, which requires
		3761	libev to recalculate its status (and possibly tell the kernel, depending
		3762	on backend and whether C<ev_io_set> was used).
		3763
		3764	=item Activating one watcher (putting it into the pending state): O(1)
		3765
		3766	=item Priority handling: O(number_of_priorities)
		3767
		3768	Priorities are implemented by allocating some space for each
		3769	priority. When doing priority-based operations, libev usually has to
		3770	linearly search all the priorities, but starting/stopping and activating
		3771	watchers becomes O(1) with respect to priority handling.
		3772
		3773	=item Sending an ev_async: O(1)
		3774
		3775	=item Processing ev_async_send: O(number_of_async_watchers)
		3776
		3777	=item Processing signals: O(max_signal_number)
		3778
		3779	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3780	calls in the current loop iteration. Checking for async and signal events
		3781	involves iterating over all running async watchers or all signal numbers.
2186		3782
2187	=back	3783	=back
2188		3784
2189		3785
2190	=head1 AUTHOR	3786	=head1 AUTHOR

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