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Revision 1.4 by root, Mon Nov 12 08:11:01 2007 UTC vs.
Revision 1.46 by root, Mon Nov 26 10:20:43 2007 UTC

…		…
25		25
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	26	Libev supports select, poll, the linux-specific epoll and the bsd-specific
27	kqueue mechanisms for file descriptor events, relative timers, absolute	27	kqueue mechanisms for file descriptor events, relative timers, absolute
28	timers with customised rescheduling, signal events, process status change	28	timers with customised rescheduling, signal events, process status change
29	events (related to SIGCHLD), and event watchers dealing with the event	29	events (related to SIGCHLD), and event watchers dealing with the event
30	loop mechanism itself (idle, prepare and check watchers).	30	loop mechanism itself (idle, prepare and check watchers). It also is quite
		31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing
		32	it to libevent for example).
31		33
32	=head1 CONVENTIONS	34	=head1 CONVENTIONS
33		35
34	Libev is very configurable. In this manual the default configuration	36	Libev is very configurable. In this manual the default configuration
35	will be described, which supports multiple event loops. For more info	37	will be described, which supports multiple event loops. For more info
36	about various configuraiton options please have a look at the file	38	about various configuration options please have a look at the file
37	F<README.embed> in the libev distribution. If libev was configured without	39	F<README.embed> in the libev distribution. If libev was configured without
38	support for multiple event loops, then all functions taking an initial	40	support for multiple event loops, then all functions taking an initial
39	argument of name C<loop> (which is always of type C<struct ev_loop *>)	41	argument of name C<loop> (which is always of type C<struct ev_loop *>)
40	will not have this argument.	42	will not have this argument.
41		43
42	=head1 TIME AND OTHER GLOBAL FUNCTIONS	44	=head1 TIME REPRESENTATION
43		45
44	Libev represents time as a single floating point number, representing the	46	Libev represents time as a single floating point number, representing the
45	(fractional) number of seconds since the (POSIX) epoch (somewhere near	47	(fractional) number of seconds since the (POSIX) epoch (somewhere near
46	the beginning of 1970, details are complicated, don't ask). This type is	48	the beginning of 1970, details are complicated, don't ask). This type is
47	called C<ev_tstamp>, which is what you should use too. It usually aliases	49	called C<ev_tstamp>, which is what you should use too. It usually aliases
48	to the double type in C.	50	to the C<double> type in C, and when you need to do any calculations on
		51	it, you should treat it as such.
		52
		53
		54	=head1 GLOBAL FUNCTIONS
		55
		56	These functions can be called anytime, even before initialising the
		57	library in any way.
49		58
50	=over 4	59	=over 4
51		60
52	=item ev_tstamp ev_time ()	61	=item ev_tstamp ev_time ()
53		62
54	Returns the current time as libev would use it.	63	Returns the current time as libev would use it. Please note that the
		64	C<ev_now> function is usually faster and also often returns the timestamp
		65	you actually want to know.
55		66
56	=item int ev_version_major ()	67	=item int ev_version_major ()
57		68
58	=item int ev_version_minor ()	69	=item int ev_version_minor ()
59		70
…		…
61	you linked against by calling the functions C<ev_version_major> and	72	you linked against by calling the functions C<ev_version_major> and
62	C<ev_version_minor>. If you want, you can compare against the global	73	C<ev_version_minor>. If you want, you can compare against the global
63	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	74	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
64	version of the library your program was compiled against.	75	version of the library your program was compiled against.
65		76
66	Usually, its a good idea to terminate if the major versions mismatch,	77	Usually, it's a good idea to terminate if the major versions mismatch,
67	as this indicates an incompatible change. Minor versions are usually	78	as this indicates an incompatible change. Minor versions are usually
68	compatible to older versions, so a larger minor version alone is usually	79	compatible to older versions, so a larger minor version alone is usually
69	not a problem.	80	not a problem.
70		81
		82	Example: make sure we haven't accidentally been linked against the wrong
		83	version:
		84
		85	assert (("libev version mismatch",
		86	ev_version_major () == EV_VERSION_MAJOR
		87	&& ev_version_minor () >= EV_VERSION_MINOR));
		88
		89	=item unsigned int ev_supported_backends ()
		90
		91	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		92	value) compiled into this binary of libev (independent of their
		93	availability on the system you are running on). See C<ev_default_loop> for
		94	a description of the set values.
		95
		96	Example: make sure we have the epoll method, because yeah this is cool and
		97	a must have and can we have a torrent of it please!!!11
		98
		99	assert (("sorry, no epoll, no sex",
		100	ev_supported_backends () & EVBACKEND_EPOLL));
		101
		102	=item unsigned int ev_recommended_backends ()
		103
		104	Return the set of all backends compiled into this binary of libev and also
		105	recommended for this platform. This set is often smaller than the one
		106	returned by C<ev_supported_backends>, as for example kqueue is broken on
		107	most BSDs and will not be autodetected unless you explicitly request it
		108	(assuming you know what you are doing). This is the set of backends that
		109	libev will probe for if you specify no backends explicitly.
		110
		111	=item unsigned int ev_embeddable_backends ()
		112
		113	Returns the set of backends that are embeddable in other event loops. This
		114	is the theoretical, all-platform, value. To find which backends
		115	might be supported on the current system, you would need to look at
		116	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		117	recommended ones.
		118
		119	See the description of C<ev_embed> watchers for more info.
		120
71	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
72		122
73	Sets the allocation function to use (the prototype is similar to the	123	Sets the allocation function to use (the prototype is similar to the
74	realloc function). It is used to allocate and free memory (no surprises	124	realloc C function, the semantics are identical). It is used to allocate
75	here). If it returns zero when memory needs to be allocated, the library	125	and free memory (no surprises here). If it returns zero when memory
76	might abort or take some potentially destructive action. The default is	126	needs to be allocated, the library might abort or take some potentially
77	your system realloc function.	127	destructive action. The default is your system realloc function.
78		128
79	You could override this function in high-availability programs to, say,	129	You could override this function in high-availability programs to, say,
80	free some memory if it cannot allocate memory, to use a special allocator,	130	free some memory if it cannot allocate memory, to use a special allocator,
81	or even to sleep a while and retry until some memory is available.	131	or even to sleep a while and retry until some memory is available.
		132
		133	Example: replace the libev allocator with one that waits a bit and then
		134	retries: better than mine).
		135
		136	static void *
		137	persistent_realloc (void *ptr, long size)
		138	{
		139	for (;;)
		140	{
		141	void *newptr = realloc (ptr, size);
		142
		143	if (newptr)
		144	return newptr;
		145
		146	sleep (60);
		147	}
		148	}
		149
		150	...
		151	ev_set_allocator (persistent_realloc);
82		152
83	=item ev_set_syserr_cb (void (*cb)(const char *msg));	153	=item ev_set_syserr_cb (void (*cb)(const char *msg));
84		154
85	Set the callback function to call on a retryable syscall error (such	155	Set the callback function to call on a retryable syscall error (such
86	as failed select, poll, epoll_wait). The message is a printable string	156	as failed select, poll, epoll_wait). The message is a printable string
87	indicating the system call or subsystem causing the problem. If this	157	indicating the system call or subsystem causing the problem. If this
88	callback is set, then libev will expect it to remedy the sitution, no	158	callback is set, then libev will expect it to remedy the sitution, no
89	matter what, when it returns. That is, libev will geenrally retry the	159	matter what, when it returns. That is, libev will generally retry the
90	requested operation, or, if the condition doesn't go away, do bad stuff	160	requested operation, or, if the condition doesn't go away, do bad stuff
91	(such as abort).	161	(such as abort).
		162
		163	Example: do the same thing as libev does internally:
		164
		165	static void
		166	fatal_error (const char *msg)
		167	{
		168	perror (msg);
		169	abort ();
		170	}
		171
		172	...
		173	ev_set_syserr_cb (fatal_error);
92		174
93	=back	175	=back
94		176
95	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	177	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
96		178
97	An event loop is described by a C<struct ev_loop *>. The library knows two	179	An event loop is described by a C<struct ev_loop *>. The library knows two
98	types of such loops, the I<default> loop, which supports signals and child	180	types of such loops, the I<default> loop, which supports signals and child
99	events, and dynamically created loops which do not.	181	events, and dynamically created loops which do not.
100		182
101	If you use threads, a common model is to run the default event loop	183	If you use threads, a common model is to run the default event loop
102	in your main thread (or in a separate thrad) and for each thread you	184	in your main thread (or in a separate thread) and for each thread you
103	create, you also create another event loop. Libev itself does no lockign	185	create, you also create another event loop. Libev itself does no locking
104	whatsoever, so if you mix calls to different event loops, make sure you	186	whatsoever, so if you mix calls to the same event loop in different
105	lock (this is usually a bad idea, though, even if done right).	187	threads, make sure you lock (this is usually a bad idea, though, even if
		188	done correctly, because it's hideous and inefficient).
106		189
107	=over 4	190	=over 4
108		191
109	=item struct ev_loop *ev_default_loop (unsigned int flags)	192	=item struct ev_loop *ev_default_loop (unsigned int flags)
110		193
111	This will initialise the default event loop if it hasn't been initialised	194	This will initialise the default event loop if it hasn't been initialised
112	yet and return it. If the default loop could not be initialised, returns	195	yet and return it. If the default loop could not be initialised, returns
113	false. If it already was initialised it simply returns it (and ignores the	196	false. If it already was initialised it simply returns it (and ignores the
114	flags).	197	flags. If that is troubling you, check C<ev_backend ()> afterwards).
115		198
116	If you don't know what event loop to use, use the one returned from this	199	If you don't know what event loop to use, use the one returned from this
117	function.	200	function.
118		201
119	The flags argument can be used to specify special behaviour or specific	202	The flags argument can be used to specify special behaviour or specific
120	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)	203	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
121		204
122	It supports the following flags:	205	The following flags are supported:
123		206
124	=over 4	207	=over 4
125		208
126	=item EVFLAG_AUTO	209	=item C<EVFLAG_AUTO>
127		210
128	The default flags value. Use this if you have no clue (its the right	211	The default flags value. Use this if you have no clue (it's the right
129	thing, believe me).	212	thing, believe me).
130		213
131	=item EVFLAG_NOENV	214	=item C<EVFLAG_NOENV>
132		215
133	If this flag bit is ored into the flag value then libev will I<not> look	216	If this flag bit is ored into the flag value (or the program runs setuid
134	at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this	217	or setgid) then libev will I<not> look at the environment variable
135	environment variable will override the flags completely. This is useful	218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
		219	override the flags completely if it is found in the environment. This is
136	to try out specific backends to tets their performance, or to work around	220	useful to try out specific backends to test their performance, or to work
137	bugs.	221	around bugs.
138		222
139	=item EVMETHOD_SELECT portable select backend	223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
140		224
141	=item EVMETHOD_POLL poll backend (everywhere except windows)	225	This is your standard select(2) backend. Not I<completely> standard, as
		226	libev tries to roll its own fd_set with no limits on the number of fds,
		227	but if that fails, expect a fairly low limit on the number of fds when
		228	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		229	the fastest backend for a low number of fds.
142		230
143	=item EVMETHOD_EPOLL linux only	231	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
144		232
145	=item EVMETHOD_KQUEUE some bsds only	233	And this is your standard poll(2) backend. It's more complicated than
		234	select, but handles sparse fds better and has no artificial limit on the
		235	number of fds you can use (except it will slow down considerably with a
		236	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
146		237
147	=item EVMETHOD_DEVPOLL solaris 8 only	238	=item C<EVBACKEND_EPOLL> (value 4, Linux)
148		239
149	=item EVMETHOD_PORT solaris 10 only	240	For few fds, this backend is a bit little slower than poll and select,
		241	but it scales phenomenally better. While poll and select usually scale like
		242	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		243	either O(1) or O(active_fds).
		244
		245	While stopping and starting an I/O watcher in the same iteration will
		246	result in some caching, there is still a syscall per such incident
		247	(because the fd could point to a different file description now), so its
		248	best to avoid that. Also, dup()ed file descriptors might not work very
		249	well if you register events for both fds.
		250
		251	Please note that epoll sometimes generates spurious notifications, so you
		252	need to use non-blocking I/O or other means to avoid blocking when no data
		253	(or space) is available.
		254
		255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		256
		257	Kqueue deserves special mention, as at the time of this writing, it
		258	was broken on all BSDs except NetBSD (usually it doesn't work with
		259	anything but sockets and pipes, except on Darwin, where of course its
		260	completely useless). For this reason its not being "autodetected"
		261	unless you explicitly specify it explicitly in the flags (i.e. using
		262	C<EVBACKEND_KQUEUE>).
		263
		264	It scales in the same way as the epoll backend, but the interface to the
		265	kernel is more efficient (which says nothing about its actual speed, of
		266	course). While starting and stopping an I/O watcher does not cause an
		267	extra syscall as with epoll, it still adds up to four event changes per
		268	incident, so its best to avoid that.
		269
		270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		271
		272	This is not implemented yet (and might never be).
		273
		274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		275
		276	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		277	it's really slow, but it still scales very well (O(active_fds)).
		278
		279	Please note that solaris ports can result in a lot of spurious
		280	notifications, so you need to use non-blocking I/O or other means to avoid
		281	blocking when no data (or space) is available.
		282
		283	=item C<EVBACKEND_ALL>
		284
		285	Try all backends (even potentially broken ones that wouldn't be tried
		286	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		287	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		288
		289	=back
150		290
151	If one or more of these are ored into the flags value, then only these	291	If one or more of these are ored into the flags value, then only these
152	backends will be tried (in the reverse order as given here). If one are	292	backends will be tried (in the reverse order as given here). If none are
153	specified, any backend will do.	293	specified, most compiled-in backend will be tried, usually in reverse
		294	order of their flag values :)
154		295
155	=back	296	The most typical usage is like this:
		297
		298	if (!ev_default_loop (0))
		299	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		300
		301	Restrict libev to the select and poll backends, and do not allow
		302	environment settings to be taken into account:
		303
		304	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		305
		306	Use whatever libev has to offer, but make sure that kqueue is used if
		307	available (warning, breaks stuff, best use only with your own private
		308	event loop and only if you know the OS supports your types of fds):
		309
		310	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
156		311
157	=item struct ev_loop *ev_loop_new (unsigned int flags)	312	=item struct ev_loop *ev_loop_new (unsigned int flags)
158		313
159	Similar to C<ev_default_loop>, but always creates a new event loop that is	314	Similar to C<ev_default_loop>, but always creates a new event loop that is
160	always distinct from the default loop. Unlike the default loop, it cannot	315	always distinct from the default loop. Unlike the default loop, it cannot
161	handle signal and child watchers, and attempts to do so will be greeted by	316	handle signal and child watchers, and attempts to do so will be greeted by
162	undefined behaviour (or a failed assertion if assertions are enabled).	317	undefined behaviour (or a failed assertion if assertions are enabled).
163		318
		319	Example: try to create a event loop that uses epoll and nothing else.
		320
		321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		322	if (!epoller)
		323	fatal ("no epoll found here, maybe it hides under your chair");
		324
164	=item ev_default_destroy ()	325	=item ev_default_destroy ()
165		326
166	Destroys the default loop again (frees all memory and kernel state	327	Destroys the default loop again (frees all memory and kernel state
167	etc.). This stops all registered event watchers (by not touching them in	328	etc.). None of the active event watchers will be stopped in the normal
168	any way whatsoever, although you cnanot rely on this :).	329	sense, so e.g. C<ev_is_active> might still return true. It is your
		330	responsibility to either stop all watchers cleanly yoursef I<before>
		331	calling this function, or cope with the fact afterwards (which is usually
		332	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		333	for example).
169		334
170	=item ev_loop_destroy (loop)	335	=item ev_loop_destroy (loop)
171		336
172	Like C<ev_default_destroy>, but destroys an event loop created by an	337	Like C<ev_default_destroy>, but destroys an event loop created by an
173	earlier call to C<ev_loop_new>.	338	earlier call to C<ev_loop_new>.
…		…
177	This function reinitialises the kernel state for backends that have	342	This function reinitialises the kernel state for backends that have
178	one. Despite the name, you can call it anytime, but it makes most sense	343	one. Despite the name, you can call it anytime, but it makes most sense
179	after forking, in either the parent or child process (or both, but that	344	after forking, in either the parent or child process (or both, but that
180	again makes little sense).	345	again makes little sense).
181		346
182	You I<must> call this function after forking if and only if you want to	347	You I<must> call this function in the child process after forking if and
183	use the event library in both processes. If you just fork+exec, you don't	348	only if you want to use the event library in both processes. If you just
184	have to call it.	349	fork+exec, you don't have to call it.
185		350
186	The function itself is quite fast and its usually not a problem to call	351	The function itself is quite fast and it's usually not a problem to call
187	it just in case after a fork. To make this easy, the function will fit in	352	it just in case after a fork. To make this easy, the function will fit in
188	quite nicely into a call to C<pthread_atfork>:	353	quite nicely into a call to C<pthread_atfork>:
189		354
190	pthread_atfork (0, 0, ev_default_fork);	355	pthread_atfork (0, 0, ev_default_fork);
		356
		357	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		358	without calling this function, so if you force one of those backends you
		359	do not need to care.
191		360
192	=item ev_loop_fork (loop)	361	=item ev_loop_fork (loop)
193		362
194	Like C<ev_default_fork>, but acts on an event loop created by	363	Like C<ev_default_fork>, but acts on an event loop created by
195	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
196	after fork, and how you do this is entirely your own problem.	365	after fork, and how you do this is entirely your own problem.
197		366
198	=item unsigned int ev_method (loop)	367	=item unsigned int ev_backend (loop)
199		368
200	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
201	use.	370	use.
202		371
203	=item ev_tstamp = ev_now (loop)	372	=item ev_tstamp ev_now (loop)
204		373
205	Returns the current "event loop time", which is the time the event loop	374	Returns the current "event loop time", which is the time the event loop
206	got events and started processing them. This timestamp does not change	375	received events and started processing them. This timestamp does not
207	as long as callbacks are being processed, and this is also the base time	376	change as long as callbacks are being processed, and this is also the base
208	used for relative timers. You can treat it as the timestamp of the event	377	time used for relative timers. You can treat it as the timestamp of the
209	occuring (or more correctly, the mainloop finding out about it).	378	event occuring (or more correctly, libev finding out about it).
210		379
211	=item ev_loop (loop, int flags)	380	=item ev_loop (loop, int flags)
212		381
213	Finally, this is it, the event handler. This function usually is called	382	Finally, this is it, the event handler. This function usually is called
214	after you initialised all your watchers and you want to start handling	383	after you initialised all your watchers and you want to start handling
215	events.	384	events.
216		385
217	If the flags argument is specified as 0, it will not return until either	386	If the flags argument is specified as C<0>, it will not return until
218	no event watchers are active anymore or C<ev_unloop> was called.	387	either no event watchers are active anymore or C<ev_unloop> was called.
		388
		389	Please note that an explicit C<ev_unloop> is usually better than
		390	relying on all watchers to be stopped when deciding when a program has
		391	finished (especially in interactive programs), but having a program that
		392	automatically loops as long as it has to and no longer by virtue of
		393	relying on its watchers stopping correctly is a thing of beauty.
219		394
220	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	395	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
221	those events and any outstanding ones, but will not block your process in	396	those events and any outstanding ones, but will not block your process in
222	case there are no events.	397	case there are no events and will return after one iteration of the loop.
223		398
224	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	399	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
225	neccessary) and will handle those and any outstanding ones. It will block	400	neccessary) and will handle those and any outstanding ones. It will block
226	your process until at least one new event arrives.	401	your process until at least one new event arrives, and will return after
		402	one iteration of the loop. This is useful if you are waiting for some
		403	external event in conjunction with something not expressible using other
		404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		405	usually a better approach for this kind of thing.
227		406
228	This flags value could be used to implement alternative looping	407	Here are the gory details of what C<ev_loop> does:
229	constructs, but the C<prepare> and C<check> watchers provide a better and	408
230	more generic mechanism.	409	* If there are no active watchers (reference count is zero), return.
		410	- Queue prepare watchers and then call all outstanding watchers.
		411	- If we have been forked, recreate the kernel state.
		412	- Update the kernel state with all outstanding changes.
		413	- Update the "event loop time".
		414	- Calculate for how long to block.
		415	- Block the process, waiting for any events.
		416	- Queue all outstanding I/O (fd) events.
		417	- Update the "event loop time" and do time jump handling.
		418	- Queue all outstanding timers.
		419	- Queue all outstanding periodics.
		420	- If no events are pending now, queue all idle watchers.
		421	- Queue all check watchers.
		422	- Call all queued watchers in reverse order (i.e. check watchers first).
		423	Signals and child watchers are implemented as I/O watchers, and will
		424	be handled here by queueing them when their watcher gets executed.
		425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		426	were used, return, otherwise continue with step *.
		427
		428	Example: queue some jobs and then loop until no events are outsanding
		429	anymore.
		430
		431	... queue jobs here, make sure they register event watchers as long
		432	... as they still have work to do (even an idle watcher will do..)
		433	ev_loop (my_loop, 0);
		434	... jobs done. yeah!
231		435
232	=item ev_unloop (loop, how)	436	=item ev_unloop (loop, how)
233		437
234	Can be used to make a call to C<ev_loop> return early. The C<how> argument	438	Can be used to make a call to C<ev_loop> return early (but only after it
		439	has processed all outstanding events). The C<how> argument must be either
235	must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop>	440	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
236	call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop>	441	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
237	calls return.
238		442
239	=item ev_ref (loop)	443	=item ev_ref (loop)
240		444
241	=item ev_unref (loop)	445	=item ev_unref (loop)
242		446
243	Ref/unref can be used to add or remove a refcount on the event loop: Every	447	Ref/unref can be used to add or remove a reference count on the event
244	watcher keeps one reference. If you have a long-runing watcher you never	448	loop: Every watcher keeps one reference, and as long as the reference
245	unregister that should not keep ev_loop from running, ev_unref() after	449	count is nonzero, C<ev_loop> will not return on its own. If you have
246	starting, and ev_ref() before stopping it. Libev itself uses this for	450	a watcher you never unregister that should not keep C<ev_loop> from
247	example for its internal signal pipe: It is not visible to you as a user	451	returning, ev_unref() after starting, and ev_ref() before stopping it. For
248	and should not keep C<ev_loop> from exiting if the work is done. It is	452	example, libev itself uses this for its internal signal pipe: It is not
249	also an excellent way to do this for generic recurring timers or from	453	visible to the libev user and should not keep C<ev_loop> from exiting if
250	within third-party libraries. Just remember to unref after start and ref	454	no event watchers registered by it are active. It is also an excellent
251	before stop.	455	way to do this for generic recurring timers or from within third-party
		456	libraries. Just remember to I<unref after start> and I<ref before stop>.
252		457
		458	Example: create a signal watcher, but keep it from keeping C<ev_loop>
		459	running when nothing else is active.
		460
		461	struct dv_signal exitsig;
		462	ev_signal_init (&exitsig, sig_cb, SIGINT);
		463	ev_signal_start (myloop, &exitsig);
		464	evf_unref (myloop);
		465
		466	Example: for some weird reason, unregister the above signal handler again.
		467
		468	ev_ref (myloop);
		469	ev_signal_stop (myloop, &exitsig);
		470
253	=back	471	=back
		472
254		473
255	=head1 ANATOMY OF A WATCHER	474	=head1 ANATOMY OF A WATCHER
256		475
257	A watcher is a structure that you create and register to record your	476	A watcher is a structure that you create and register to record your
258	interest in some event. For instance, if you want to wait for STDIN to	477	interest in some event. For instance, if you want to wait for STDIN to
259	become readable, you would create an ev_io watcher for that:	478	become readable, you would create an C<ev_io> watcher for that:
260		479
261	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	480	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
262	{	481	{
263	ev_io_stop (w);	482	ev_io_stop (w);
264	ev_unloop (loop, EVUNLOOP_ALL);	483	ev_unloop (loop, EVUNLOOP_ALL);
…		…
291	*) >>), and you can stop watching for events at any time by calling the	510	*) >>), and you can stop watching for events at any time by calling the
292	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	511	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
293		512
294	As long as your watcher is active (has been started but not stopped) you	513	As long as your watcher is active (has been started but not stopped) you
295	must not touch the values stored in it. Most specifically you must never	514	must not touch the values stored in it. Most specifically you must never
296	reinitialise it or call its set method.	515	reinitialise it or call its C<set> macro.
297
298	You cna check whether an event is active by calling the C<ev_is_active
299	(watcher *)> macro. To see whether an event is outstanding (but the
300	callback for it has not been called yet) you cna use the C<ev_is_pending
301	(watcher *)> macro.
302		516
303	Each and every callback receives the event loop pointer as first, the	517	Each and every callback receives the event loop pointer as first, the
304	registered watcher structure as second, and a bitset of received events as	518	registered watcher structure as second, and a bitset of received events as
305	third argument.	519	third argument.
306		520
307	The rceeived events usually include a single bit per event type received	521	The received events usually include a single bit per event type received
308	(you can receive multiple events at the same time). The possible bit masks	522	(you can receive multiple events at the same time). The possible bit masks
309	are:	523	are:
310		524
311	=over 4	525	=over 4
312		526
313	=item EV_READ	527	=item C<EV_READ>
314		528
315	=item EV_WRITE	529	=item C<EV_WRITE>
316		530
317	The file descriptor in the ev_io watcher has become readable and/or	531	The file descriptor in the C<ev_io> watcher has become readable and/or
318	writable.	532	writable.
319		533
320	=item EV_TIMEOUT	534	=item C<EV_TIMEOUT>
321		535
322	The ev_timer watcher has timed out.	536	The C<ev_timer> watcher has timed out.
323		537
324	=item EV_PERIODIC	538	=item C<EV_PERIODIC>
325		539
326	The ev_periodic watcher has timed out.	540	The C<ev_periodic> watcher has timed out.
327		541
328	=item EV_SIGNAL	542	=item C<EV_SIGNAL>
329		543
330	The signal specified in the ev_signal watcher has been received by a thread.	544	The signal specified in the C<ev_signal> watcher has been received by a thread.
331		545
332	=item EV_CHILD	546	=item C<EV_CHILD>
333		547
334	The pid specified in the ev_child watcher has received a status change.	548	The pid specified in the C<ev_child> watcher has received a status change.
335		549
336	=item EV_IDLE	550	=item C<EV_IDLE>
337		551
338	The ev_idle watcher has determined that you have nothing better to do.	552	The C<ev_idle> watcher has determined that you have nothing better to do.
339		553
340	=item EV_PREPARE	554	=item C<EV_PREPARE>
341		555
342	=item EV_CHECK	556	=item C<EV_CHECK>
343		557
344	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	558	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
345	to gather new events, and all ev_check watchers are invoked just after	559	to gather new events, and all C<ev_check> watchers are invoked just after
346	C<ev_loop> has gathered them, but before it invokes any callbacks for any	560	C<ev_loop> has gathered them, but before it invokes any callbacks for any
347	received events. Callbacks of both watcher types can start and stop as	561	received events. Callbacks of both watcher types can start and stop as
348	many watchers as they want, and all of them will be taken into account	562	many watchers as they want, and all of them will be taken into account
349	(for example, a ev_prepare watcher might start an idle watcher to keep	563	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
350	C<ev_loop> from blocking).	564	C<ev_loop> from blocking).
351		565
352	=item EV_ERROR	566	=item C<EV_ERROR>
353		567
354	An unspecified error has occured, the watcher has been stopped. This might	568	An unspecified error has occured, the watcher has been stopped. This might
355	happen because the watcher could not be properly started because libev	569	happen because the watcher could not be properly started because libev
356	ran out of memory, a file descriptor was found to be closed or any other	570	ran out of memory, a file descriptor was found to be closed or any other
357	problem. You best act on it by reporting the problem and somehow coping	571	problem. You best act on it by reporting the problem and somehow coping
…		…
363	with the error from read() or write(). This will not work in multithreaded	577	with the error from read() or write(). This will not work in multithreaded
364	programs, though, so beware.	578	programs, though, so beware.
365		579
366	=back	580	=back
367		581
		582	=head2 GENERIC WATCHER FUNCTIONS
		583
		584	In the following description, C<TYPE> stands for the watcher type,
		585	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		586
		587	=over 4
		588
		589	=item C<ev_init> (ev_TYPE *watcher, callback)
		590
		591	This macro initialises the generic portion of a watcher. The contents
		592	of the watcher object can be arbitrary (so C<malloc> will do). Only
		593	the generic parts of the watcher are initialised, you I<need> to call
		594	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		595	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		596	which rolls both calls into one.
		597
		598	You can reinitialise a watcher at any time as long as it has been stopped
		599	(or never started) and there are no pending events outstanding.
		600
		601	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		602	int revents)>.
		603
		604	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		605
		606	This macro initialises the type-specific parts of a watcher. You need to
		607	call C<ev_init> at least once before you call this macro, but you can
		608	call C<ev_TYPE_set> any number of times. You must not, however, call this
		609	macro on a watcher that is active (it can be pending, however, which is a
		610	difference to the C<ev_init> macro).
		611
		612	Although some watcher types do not have type-specific arguments
		613	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		614
		615	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		616
		617	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		618	calls into a single call. This is the most convinient method to initialise
		619	a watcher. The same limitations apply, of course.
		620
		621	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		622
		623	Starts (activates) the given watcher. Only active watchers will receive
		624	events. If the watcher is already active nothing will happen.
		625
		626	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		627
		628	Stops the given watcher again (if active) and clears the pending
		629	status. It is possible that stopped watchers are pending (for example,
		630	non-repeating timers are being stopped when they become pending), but
		631	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		632	you want to free or reuse the memory used by the watcher it is therefore a
		633	good idea to always call its C<ev_TYPE_stop> function.
		634
		635	=item bool ev_is_active (ev_TYPE *watcher)
		636
		637	Returns a true value iff the watcher is active (i.e. it has been started
		638	and not yet been stopped). As long as a watcher is active you must not modify
		639	it.
		640
		641	=item bool ev_is_pending (ev_TYPE *watcher)
		642
		643	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		644	events but its callback has not yet been invoked). As long as a watcher
		645	is pending (but not active) you must not call an init function on it (but
		646	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		647	libev (e.g. you cnanot C<free ()> it).
		648
		649	=item callback = ev_cb (ev_TYPE *watcher)
		650
		651	Returns the callback currently set on the watcher.
		652
		653	=item ev_cb_set (ev_TYPE *watcher, callback)
		654
		655	Change the callback. You can change the callback at virtually any time
		656	(modulo threads).
		657
		658	=back
		659
		660
368	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	661	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
369		662
370	Each watcher has, by default, a member C<void *data> that you can change	663	Each watcher has, by default, a member C<void *data> that you can change
371	and read at any time, libev will completely ignore it. This cna be used	664	and read at any time, libev will completely ignore it. This can be used
372	to associate arbitrary data with your watcher. If you need more data and	665	to associate arbitrary data with your watcher. If you need more data and
373	don't want to allocate memory and store a pointer to it in that data	666	don't want to allocate memory and store a pointer to it in that data
374	member, you can also "subclass" the watcher type and provide your own	667	member, you can also "subclass" the watcher type and provide your own
375	data:	668	data:
376		669
…		…
398	=head1 WATCHER TYPES	691	=head1 WATCHER TYPES
399		692
400	This section describes each watcher in detail, but will not repeat	693	This section describes each watcher in detail, but will not repeat
401	information given in the last section.	694	information given in the last section.
402		695
		696
403	=head2 struct ev_io - is my file descriptor readable or writable	697	=head2 C<ev_io> - is this file descriptor readable or writable?
404		698
405	I/O watchers check whether a file descriptor is readable or writable	699	I/O watchers check whether a file descriptor is readable or writable
406	in each iteration of the event loop (This behaviour is called	700	in each iteration of the event loop, or, more precisely, when reading
407	level-triggering because you keep receiving events as long as the	701	would not block the process and writing would at least be able to write
408	condition persists. Remember you cna stop the watcher if you don't want to	702	some data. This behaviour is called level-triggering because you keep
409	act on the event and neither want to receive future events).	703	receiving events as long as the condition persists. Remember you can stop
		704	the watcher if you don't want to act on the event and neither want to
		705	receive future events.
		706
		707	In general you can register as many read and/or write event watchers per
		708	fd as you want (as long as you don't confuse yourself). Setting all file
		709	descriptors to non-blocking mode is also usually a good idea (but not
		710	required if you know what you are doing).
		711
		712	You have to be careful with dup'ed file descriptors, though. Some backends
		713	(the linux epoll backend is a notable example) cannot handle dup'ed file
		714	descriptors correctly if you register interest in two or more fds pointing
		715	to the same underlying file/socket/etc. description (that is, they share
		716	the same underlying "file open").
		717
		718	If you must do this, then force the use of a known-to-be-good backend
		719	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
		720	C<EVBACKEND_POLL>).
		721
		722	Another thing you have to watch out for is that it is quite easy to
		723	receive "spurious" readyness notifications, that is your callback might
		724	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		725	because there is no data. Not only are some backends known to create a
		726	lot of those (for example solaris ports), it is very easy to get into
		727	this situation even with a relatively standard program structure. Thus
		728	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		729	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		730
		731	If you cannot run the fd in non-blocking mode (for example you should not
		732	play around with an Xlib connection), then you have to seperately re-test
		733	wether a file descriptor is really ready with a known-to-be good interface
		734	such as poll (fortunately in our Xlib example, Xlib already does this on
		735	its own, so its quite safe to use).
410		736
411	=over 4	737	=over 4
412		738
413	=item ev_io_init (ev_io *, callback, int fd, int events)	739	=item ev_io_init (ev_io *, callback, int fd, int events)
414		740
415	=item ev_io_set (ev_io *, int fd, int events)	741	=item ev_io_set (ev_io *, int fd, int events)
416		742
417	Configures an ev_io watcher. The fd is the file descriptor to rceeive	743	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
418	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	744	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
419	EV_WRITE> to receive the given events.	745	C<EV_READ | EV_WRITE> to receive the given events.
420		746
421	=back	747	=back
422		748
		749	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
		750	readable, but only once. Since it is likely line-buffered, you could
		751	attempt to read a whole line in the callback:
		752
		753	static void
		754	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		755	{
		756	ev_io_stop (loop, w);
		757	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		758	}
		759
		760	...
		761	struct ev_loop *loop = ev_default_init (0);
		762	struct ev_io stdin_readable;
		763	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		764	ev_io_start (loop, &stdin_readable);
		765	ev_loop (loop, 0);
		766
		767
423	=head2 struct ev_timer - relative and optionally recurring timeouts	768	=head2 C<ev_timer> - relative and optionally repeating timeouts
424		769
425	Timer watchers are simple relative timers that generate an event after a	770	Timer watchers are simple relative timers that generate an event after a
426	given time, and optionally repeating in regular intervals after that.	771	given time, and optionally repeating in regular intervals after that.
427		772
428	The timers are based on real time, that is, if you register an event that	773	The timers are based on real time, that is, if you register an event that
429	times out after an hour and youreset your system clock to last years	774	times out after an hour and you reset your system clock to last years
430	time, it will still time out after (roughly) and hour. "Roughly" because	775	time, it will still time out after (roughly) and hour. "Roughly" because
431	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	776	detecting time jumps is hard, and some inaccuracies are unavoidable (the
432	monotonic clock option helps a lot here).	777	monotonic clock option helps a lot here).
		778
		779	The relative timeouts are calculated relative to the C<ev_now ()>
		780	time. This is usually the right thing as this timestamp refers to the time
		781	of the event triggering whatever timeout you are modifying/starting. If
		782	you suspect event processing to be delayed and you I<need> to base the timeout
		783	on the current time, use something like this to adjust for this:
		784
		785	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		786
		787	The callback is guarenteed to be invoked only when its timeout has passed,
		788	but if multiple timers become ready during the same loop iteration then
		789	order of execution is undefined.
433		790
434	=over 4	791	=over 4
435		792
436	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	793	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
437		794
…		…
443	later, again, and again, until stopped manually.	800	later, again, and again, until stopped manually.
444		801
445	The timer itself will do a best-effort at avoiding drift, that is, if you	802	The timer itself will do a best-effort at avoiding drift, that is, if you
446	configure a timer to trigger every 10 seconds, then it will trigger at	803	configure a timer to trigger every 10 seconds, then it will trigger at
447	exactly 10 second intervals. If, however, your program cannot keep up with	804	exactly 10 second intervals. If, however, your program cannot keep up with
448	the timer (ecause it takes longer than those 10 seconds to do stuff) the	805	the timer (because it takes longer than those 10 seconds to do stuff) the
449	timer will not fire more than once per event loop iteration.	806	timer will not fire more than once per event loop iteration.
450		807
451	=item ev_timer_again (loop)	808	=item ev_timer_again (loop)
452		809
453	This will act as if the timer timed out and restart it again if it is	810	This will act as if the timer timed out and restart it again if it is
…		…
460		817
461	This sounds a bit complicated, but here is a useful and typical	818	This sounds a bit complicated, but here is a useful and typical
462	example: Imagine you have a tcp connection and you want a so-called idle	819	example: Imagine you have a tcp connection and you want a so-called idle
463	timeout, that is, you want to be called when there have been, say, 60	820	timeout, that is, you want to be called when there have been, say, 60
464	seconds of inactivity on the socket. The easiest way to do this is to	821	seconds of inactivity on the socket. The easiest way to do this is to
465	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	822	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each
466	time you successfully read or write some data. If you go into an idle	823	time you successfully read or write some data. If you go into an idle
467	state where you do not expect data to travel on the socket, you can stop	824	state where you do not expect data to travel on the socket, you can stop
468	the timer, and again will automatically restart it if need be.	825	the timer, and again will automatically restart it if need be.
469		826
470	=back	827	=back
471		828
		829	Example: create a timer that fires after 60 seconds.
		830
		831	static void
		832	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		833	{
		834	.. one minute over, w is actually stopped right here
		835	}
		836
		837	struct ev_timer mytimer;
		838	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		839	ev_timer_start (loop, &mytimer);
		840
		841	Example: create a timeout timer that times out after 10 seconds of
		842	inactivity.
		843
		844	static void
		845	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		846	{
		847	.. ten seconds without any activity
		848	}
		849
		850	struct ev_timer mytimer;
		851	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		852	ev_timer_again (&mytimer); /* start timer */
		853	ev_loop (loop, 0);
		854
		855	// and in some piece of code that gets executed on any "activity":
		856	// reset the timeout to start ticking again at 10 seconds
		857	ev_timer_again (&mytimer);
		858
		859
472	=head2 ev_periodic - to cron or not to cron it	860	=head2 C<ev_periodic> - to cron or not to cron?
473		861
474	Periodic watchers are also timers of a kind, but they are very versatile	862	Periodic watchers are also timers of a kind, but they are very versatile
475	(and unfortunately a bit complex).	863	(and unfortunately a bit complex).
476		864
477	Unlike ev_timer's, they are not based on real time (or relative time)	865	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
478	but on wallclock time (absolute time). You can tell a periodic watcher	866	but on wallclock time (absolute time). You can tell a periodic watcher
479	to trigger "at" some specific point in time. For example, if you tell a	867	to trigger "at" some specific point in time. For example, if you tell a
480	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	868	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
481	+ 10.>) and then reset your system clock to the last year, then it will	869	+ 10.>) and then reset your system clock to the last year, then it will
482	take a year to trigger the event (unlike an ev_timer, which would trigger	870	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
483	roughly 10 seconds later and of course not if you reset your system time	871	roughly 10 seconds later and of course not if you reset your system time
484	again).	872	again).
485		873
486	They can also be used to implement vastly more complex timers, such as	874	They can also be used to implement vastly more complex timers, such as
487	triggering an event on eahc midnight, local time.	875	triggering an event on eahc midnight, local time.
488		876
		877	As with timers, the callback is guarenteed to be invoked only when the
		878	time (C<at>) has been passed, but if multiple periodic timers become ready
		879	during the same loop iteration then order of execution is undefined.
		880
489	=over 4	881	=over 4
490		882
491	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	883	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
492		884
493	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	885	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
494		886
495	Lots of arguments, lets sort it out... There are basically three modes of	887	Lots of arguments, lets sort it out... There are basically three modes of
496	operation, and we will explain them from simplest to complex:	888	operation, and we will explain them from simplest to complex:
497
498		889
499	=over 4	890	=over 4
500		891
501	=item * absolute timer (interval = reschedule_cb = 0)	892	=item * absolute timer (interval = reschedule_cb = 0)
502		893
…		…
516		907
517	ev_periodic_set (&periodic, 0., 3600., 0);	908	ev_periodic_set (&periodic, 0., 3600., 0);
518		909
519	This doesn't mean there will always be 3600 seconds in between triggers,	910	This doesn't mean there will always be 3600 seconds in between triggers,
520	but only that the the callback will be called when the system time shows a	911	but only that the the callback will be called when the system time shows a
521	full hour (UTC), or more correct, when the system time is evenly divisible	912	full hour (UTC), or more correctly, when the system time is evenly divisible
522	by 3600.	913	by 3600.
523		914
524	Another way to think about it (for the mathematically inclined) is that	915	Another way to think about it (for the mathematically inclined) is that
525	ev_periodic will try to run the callback in this mode at the next possible	916	C<ev_periodic> will try to run the callback in this mode at the next possible
526	time where C<time = at (mod interval)>, regardless of any time jumps.	917	time where C<time = at (mod interval)>, regardless of any time jumps.
527		918
528	=item * manual reschedule mode (reschedule_cb = callback)	919	=item * manual reschedule mode (reschedule_cb = callback)
529		920
530	In this mode the values for C<interval> and C<at> are both being	921	In this mode the values for C<interval> and C<at> are both being
531	ignored. Instead, each time the periodic watcher gets scheduled, the	922	ignored. Instead, each time the periodic watcher gets scheduled, the
532	reschedule callback will be called with the watcher as first, and the	923	reschedule callback will be called with the watcher as first, and the
533	current time as second argument.	924	current time as second argument.
534		925
535	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	926	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
536	periodic watcher, ever, or make any event loop modificstions>. If you need	927	ever, or make any event loop modifications>. If you need to stop it,
537	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.	928	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		929	starting a prepare watcher).
538		930
539	Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	931	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
540	ev_tstamp now)>, e.g.:	932	ev_tstamp now)>, e.g.:
541		933
542	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	934	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
543	{	935	{
544	return now + 60.;	936	return now + 60.;
…		…
547	It must return the next time to trigger, based on the passed time value	939	It must return the next time to trigger, based on the passed time value
548	(that is, the lowest time value larger than to the second argument). It	940	(that is, the lowest time value larger than to the second argument). It
549	will usually be called just before the callback will be triggered, but	941	will usually be called just before the callback will be triggered, but
550	might be called at other times, too.	942	might be called at other times, too.
551		943
		944	NOTE: I<< This callback must always return a time that is later than the
		945	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		946
552	This can be used to create very complex timers, such as a timer that	947	This can be used to create very complex timers, such as a timer that
553	triggers on each midnight, local time. To do this, you would calculate the	948	triggers on each midnight, local time. To do this, you would calculate the
554	next midnight after C<now> and return the timestamp value for this. How you do this	949	next midnight after C<now> and return the timestamp value for this. How
555	is, again, up to you (but it is not trivial).	950	you do this is, again, up to you (but it is not trivial, which is the main
		951	reason I omitted it as an example).
556		952
557	=back	953	=back
558		954
559	=item ev_periodic_again (loop, ev_periodic *)	955	=item ev_periodic_again (loop, ev_periodic *)
560		956
…		…
563	a different time than the last time it was called (e.g. in a crond like	959	a different time than the last time it was called (e.g. in a crond like
564	program when the crontabs have changed).	960	program when the crontabs have changed).
565		961
566	=back	962	=back
567		963
		964	Example: call a callback every hour, or, more precisely, whenever the
		965	system clock is divisible by 3600. The callback invocation times have
		966	potentially a lot of jittering, but good long-term stability.
		967
		968	static void
		969	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		970	{
		971	... its now a full hour (UTC, or TAI or whatever your clock follows)
		972	}
		973
		974	struct ev_periodic hourly_tick;
		975	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		976	ev_periodic_start (loop, &hourly_tick);
		977
		978	Example: the same as above, but use a reschedule callback to do it:
		979
		980	#include <math.h>
		981
		982	static ev_tstamp
		983	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		984	{
		985	return fmod (now, 3600.) + 3600.;
		986	}
		987
		988	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		989
		990	Example: call a callback every hour, starting now:
		991
		992	struct ev_periodic hourly_tick;
		993	ev_periodic_init (&hourly_tick, clock_cb,
		994	fmod (ev_now (loop), 3600.), 3600., 0);
		995	ev_periodic_start (loop, &hourly_tick);
		996
		997
568	=head2 ev_signal - signal me when a signal gets signalled	998	=head2 C<ev_signal> - signal me when a signal gets signalled!
569		999
570	Signal watchers will trigger an event when the process receives a specific	1000	Signal watchers will trigger an event when the process receives a specific
571	signal one or more times. Even though signals are very asynchronous, libev	1001	signal one or more times. Even though signals are very asynchronous, libev
572	will try its best to deliver signals synchronously, i.e. as part of the	1002	will try it's best to deliver signals synchronously, i.e. as part of the
573	normal event processing, like any other event.	1003	normal event processing, like any other event.
574		1004
575	You cna configure as many watchers as you like per signal. Only when the	1005	You can configure as many watchers as you like per signal. Only when the
576	first watcher gets started will libev actually register a signal watcher	1006	first watcher gets started will libev actually register a signal watcher
577	with the kernel (thus it coexists with your own signal handlers as long	1007	with the kernel (thus it coexists with your own signal handlers as long
578	as you don't register any with libev). Similarly, when the last signal	1008	as you don't register any with libev). Similarly, when the last signal
579	watcher for a signal is stopped libev will reset the signal handler to	1009	watcher for a signal is stopped libev will reset the signal handler to
580	SIG_DFL (regardless of what it was set to before).	1010	SIG_DFL (regardless of what it was set to before).
…		…
588	Configures the watcher to trigger on the given signal number (usually one	1018	Configures the watcher to trigger on the given signal number (usually one
589	of the C<SIGxxx> constants).	1019	of the C<SIGxxx> constants).
590		1020
591	=back	1021	=back
592		1022
		1023
593	=head2 ev_child - wait for pid status changes	1024	=head2 C<ev_child> - watch out for process status changes
594		1025
595	Child watchers trigger when your process receives a SIGCHLD in response to	1026	Child watchers trigger when your process receives a SIGCHLD in response to
596	some child status changes (most typically when a child of yours dies).	1027	some child status changes (most typically when a child of yours dies).
597		1028
598	=over 4	1029	=over 4
…		…
602	=item ev_child_set (ev_child *, int pid)	1033	=item ev_child_set (ev_child *, int pid)
603		1034
604	Configures the watcher to wait for status changes of process C<pid> (or	1035	Configures the watcher to wait for status changes of process C<pid> (or
605	I<any> process if C<pid> is specified as C<0>). The callback can look	1036	I<any> process if C<pid> is specified as C<0>). The callback can look
606	at the C<rstatus> member of the C<ev_child> watcher structure to see	1037	at the C<rstatus> member of the C<ev_child> watcher structure to see
607	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	1038	the status word (use the macros from C<sys/wait.h> and see your systems
608	contains the pid of the process causing the status change.	1039	C<waitpid> documentation). The C<rpid> member contains the pid of the
		1040	process causing the status change.
609		1041
610	=back	1042	=back
611		1043
		1044	Example: try to exit cleanly on SIGINT and SIGTERM.
		1045
		1046	static void
		1047	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1048	{
		1049	ev_unloop (loop, EVUNLOOP_ALL);
		1050	}
		1051
		1052	struct ev_signal signal_watcher;
		1053	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1054	ev_signal_start (loop, &sigint_cb);
		1055
		1056
612	=head2 ev_idle - when you've got nothing better to do	1057	=head2 C<ev_idle> - when you've got nothing better to do...
613		1058
614	Idle watchers trigger events when there are no other I/O or timer (or	1059	Idle watchers trigger events when there are no other events are pending
615	periodic) events pending. That is, as long as your process is busy	1060	(prepare, check and other idle watchers do not count). That is, as long
616	handling sockets or timeouts it will not be called. But when your process	1061	as your process is busy handling sockets or timeouts (or even signals,
617	is idle all idle watchers are being called again and again - until	1062	imagine) it will not be triggered. But when your process is idle all idle
		1063	watchers are being called again and again, once per event loop iteration -
618	stopped, that is, or your process receives more events.	1064	until stopped, that is, or your process receives more events and becomes
		1065	busy.
619		1066
620	The most noteworthy effect is that as long as any idle watchers are	1067	The most noteworthy effect is that as long as any idle watchers are
621	active, the process will not block when waiting for new events.	1068	active, the process will not block when waiting for new events.
622		1069
623	Apart from keeping your process non-blocking (which is a useful	1070	Apart from keeping your process non-blocking (which is a useful
…		…
633	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1080	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
634	believe me.	1081	believe me.
635		1082
636	=back	1083	=back
637		1084
638	=head2 prepare and check - your hooks into the event loop	1085	Example: dynamically allocate an C<ev_idle>, start it, and in the
		1086	callback, free it. Alos, use no error checking, as usual.
639		1087
		1088	static void
		1089	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1090	{
		1091	free (w);
		1092	// now do something you wanted to do when the program has
		1093	// no longer asnything immediate to do.
		1094	}
		1095
		1096	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1097	ev_idle_init (idle_watcher, idle_cb);
		1098	ev_idle_start (loop, idle_cb);
		1099
		1100
		1101	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
		1102
640	Prepare and check watchers usually (but not always) are used in	1103	Prepare and check watchers are usually (but not always) used in tandem:
641	tandom. Prepare watchers get invoked before the process blocks and check	1104	prepare watchers get invoked before the process blocks and check watchers
642	watchers afterwards.	1105	afterwards.
643		1106
		1107	You I<must not> call C<ev_loop> or similar functions that enter
		1108	the current event loop from either C<ev_prepare> or C<ev_check>
		1109	watchers. Other loops than the current one are fine, however. The
		1110	rationale behind this is that you do not need to check for recursion in
		1111	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1112	C<ev_check> so if you have one watcher of each kind they will always be
		1113	called in pairs bracketing the blocking call.
		1114
644	Their main purpose is to integrate other event mechanisms into libev. This	1115	Their main purpose is to integrate other event mechanisms into libev and
645	could be used, for example, to track variable changes, implement your own	1116	their use is somewhat advanced. This could be used, for example, to track
646	watchers, integrate net-snmp or a coroutine library and lots more.	1117	variable changes, implement your own watchers, integrate net-snmp or a
		1118	coroutine library and lots more. They are also occasionally useful if
		1119	you cache some data and want to flush it before blocking (for example,
		1120	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1121	watcher).
647		1122
648	This is done by examining in each prepare call which file descriptors need	1123	This is done by examining in each prepare call which file descriptors need
649	to be watched by the other library, registering ev_io watchers for them	1124	to be watched by the other library, registering C<ev_io> watchers for
650	and starting an ev_timer watcher for any timeouts (many libraries provide	1125	them and starting an C<ev_timer> watcher for any timeouts (many libraries
651	just this functionality). Then, in the check watcher you check for any	1126	provide just this functionality). Then, in the check watcher you check for
652	events that occured (by making your callbacks set soem flags for example)	1127	any events that occured (by checking the pending status of all watchers
653	and call back into the library.	1128	and stopping them) and call back into the library. The I/O and timer
		1129	callbacks will never actually be called (but must be valid nevertheless,
		1130	because you never know, you know?).
654		1131
655	As another example, the perl Coro module uses these hooks to integrate	1132	As another example, the Perl Coro module uses these hooks to integrate
656	coroutines into libev programs, by yielding to other active coroutines	1133	coroutines into libev programs, by yielding to other active coroutines
657	during each prepare and only letting the process block if no coroutines	1134	during each prepare and only letting the process block if no coroutines
658	are ready to run.	1135	are ready to run (it's actually more complicated: it only runs coroutines
		1136	with priority higher than or equal to the event loop and one coroutine
		1137	of lower priority, but only once, using idle watchers to keep the event
		1138	loop from blocking if lower-priority coroutines are active, thus mapping
		1139	low-priority coroutines to idle/background tasks).
659		1140
660	=over 4	1141	=over 4
661		1142
662	=item ev_prepare_init (ev_prepare *, callback)	1143	=item ev_prepare_init (ev_prepare *, callback)
663		1144
664	=item ev_check_init (ev_check *, callback)	1145	=item ev_check_init (ev_check *, callback)
665		1146
666	Initialises and configures the prepare or check watcher - they have no	1147	Initialises and configures the prepare or check watcher - they have no
667	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1148	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
668	macros, but using them is utterly, utterly pointless.	1149	macros, but using them is utterly, utterly and completely pointless.
669		1150
670	=back	1151	=back
		1152
		1153	Example: To include a library such as adns, you would add IO watchers
		1154	and a timeout watcher in a prepare handler, as required by libadns, and
		1155	in a check watcher, destroy them and call into libadns. What follows is
		1156	pseudo-code only of course:
		1157
		1158	static ev_io iow [nfd];
		1159	static ev_timer tw;
		1160
		1161	static void
		1162	io_cb (ev_loop *loop, ev_io *w, int revents)
		1163	{
		1164	// set the relevant poll flags
		1165	// could also call adns_processreadable etc. here
		1166	struct pollfd *fd = (struct pollfd *)w->data;
		1167	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1168	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1169	}
		1170
		1171	// create io watchers for each fd and a timer before blocking
		1172	static void
		1173	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1174	{
		1175	int timeout = 3600000;truct pollfd fds [nfd];
		1176	// actual code will need to loop here and realloc etc.
		1177	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1178
		1179	/* the callback is illegal, but won't be called as we stop during check */
		1180	ev_timer_init (&tw, 0, timeout * 1e-3);
		1181	ev_timer_start (loop, &tw);
		1182
		1183	// create on ev_io per pollfd
		1184	for (int i = 0; i < nfd; ++i)
		1185	{
		1186	ev_io_init (iow + i, io_cb, fds [i].fd,
		1187	((fds [i].events & POLLIN ? EV_READ : 0)
		1188	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1189
		1190	fds [i].revents = 0;
		1191	iow [i].data = fds + i;
		1192	ev_io_start (loop, iow + i);
		1193	}
		1194	}
		1195
		1196	// stop all watchers after blocking
		1197	static void
		1198	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1199	{
		1200	ev_timer_stop (loop, &tw);
		1201
		1202	for (int i = 0; i < nfd; ++i)
		1203	ev_io_stop (loop, iow + i);
		1204
		1205	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1206	}
		1207
		1208
		1209	=head2 C<ev_embed> - when one backend isn't enough...
		1210
		1211	This is a rather advanced watcher type that lets you embed one event loop
		1212	into another (currently only C<ev_io> events are supported in the embedded
		1213	loop, other types of watchers might be handled in a delayed or incorrect
		1214	fashion and must not be used).
		1215
		1216	There are primarily two reasons you would want that: work around bugs and
		1217	prioritise I/O.
		1218
		1219	As an example for a bug workaround, the kqueue backend might only support
		1220	sockets on some platform, so it is unusable as generic backend, but you
		1221	still want to make use of it because you have many sockets and it scales
		1222	so nicely. In this case, you would create a kqueue-based loop and embed it
		1223	into your default loop (which might use e.g. poll). Overall operation will
		1224	be a bit slower because first libev has to poll and then call kevent, but
		1225	at least you can use both at what they are best.
		1226
		1227	As for prioritising I/O: rarely you have the case where some fds have
		1228	to be watched and handled very quickly (with low latency), and even
		1229	priorities and idle watchers might have too much overhead. In this case
		1230	you would put all the high priority stuff in one loop and all the rest in
		1231	a second one, and embed the second one in the first.
		1232
		1233	As long as the watcher is active, the callback will be invoked every time
		1234	there might be events pending in the embedded loop. The callback must then
		1235	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1236	their callbacks (you could also start an idle watcher to give the embedded
		1237	loop strictly lower priority for example). You can also set the callback
		1238	to C<0>, in which case the embed watcher will automatically execute the
		1239	embedded loop sweep.
		1240
		1241	As long as the watcher is started it will automatically handle events. The
		1242	callback will be invoked whenever some events have been handled. You can
		1243	set the callback to C<0> to avoid having to specify one if you are not
		1244	interested in that.
		1245
		1246	Also, there have not currently been made special provisions for forking:
		1247	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1248	but you will also have to stop and restart any C<ev_embed> watchers
		1249	yourself.
		1250
		1251	Unfortunately, not all backends are embeddable, only the ones returned by
		1252	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1253	portable one.
		1254
		1255	So when you want to use this feature you will always have to be prepared
		1256	that you cannot get an embeddable loop. The recommended way to get around
		1257	this is to have a separate variables for your embeddable loop, try to
		1258	create it, and if that fails, use the normal loop for everything:
		1259
		1260	struct ev_loop *loop_hi = ev_default_init (0);
		1261	struct ev_loop *loop_lo = 0;
		1262	struct ev_embed embed;
		1263
		1264	// see if there is a chance of getting one that works
		1265	// (remember that a flags value of 0 means autodetection)
		1266	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1267	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1268	: 0;
		1269
		1270	// if we got one, then embed it, otherwise default to loop_hi
		1271	if (loop_lo)
		1272	{
		1273	ev_embed_init (&embed, 0, loop_lo);
		1274	ev_embed_start (loop_hi, &embed);
		1275	}
		1276	else
		1277	loop_lo = loop_hi;
		1278
		1279	=over 4
		1280
		1281	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1282
		1283	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1284
		1285	Configures the watcher to embed the given loop, which must be
		1286	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1287	invoked automatically, otherwise it is the responsibility of the callback
		1288	to invoke it (it will continue to be called until the sweep has been done,
		1289	if you do not want thta, you need to temporarily stop the embed watcher).
		1290
		1291	=item ev_embed_sweep (loop, ev_embed *)
		1292
		1293	Make a single, non-blocking sweep over the embedded loop. This works
		1294	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1295	apropriate way for embedded loops.
		1296
		1297	=back
		1298
671		1299
672	=head1 OTHER FUNCTIONS	1300	=head1 OTHER FUNCTIONS
673		1301
674	There are some other fucntions of possible interest. Described. Here. Now.	1302	There are some other functions of possible interest. Described. Here. Now.
675		1303
676	=over 4	1304	=over 4
677		1305
678	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1306	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
679		1307
680	This function combines a simple timer and an I/O watcher, calls your	1308	This function combines a simple timer and an I/O watcher, calls your
681	callback on whichever event happens first and automatically stop both	1309	callback on whichever event happens first and automatically stop both
682	watchers. This is useful if you want to wait for a single event on an fd	1310	watchers. This is useful if you want to wait for a single event on an fd
683	or timeout without havign to allocate/configure/start/stop/free one or	1311	or timeout without having to allocate/configure/start/stop/free one or
684	more watchers yourself.	1312	more watchers yourself.
685		1313
686	If C<fd> is less than 0, then no I/O watcher will be started and events is	1314	If C<fd> is less than 0, then no I/O watcher will be started and events
687	ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set	1315	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
688	will be craeted and started.	1316	C<events> set will be craeted and started.
689		1317
690	If C<timeout> is less than 0, then no timeout watcher will be	1318	If C<timeout> is less than 0, then no timeout watcher will be
691	started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat	1319	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
692	= 0) will be started.	1320	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1321	dubious value.
693		1322
694	The callback has the type C<void (*cb)(int revents, void *arg)> and	1323	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
695	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1324	passed an C<revents> set like normal event callbacks (a combination of
696	EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>:	1325	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1326	value passed to C<ev_once>:
697		1327
698	static void stdin_ready (int revents, void *arg)	1328	static void stdin_ready (int revents, void *arg)
699	{	1329	{
700	if (revents & EV_TIMEOUT)	1330	if (revents & EV_TIMEOUT)
701	/* doh, nothing entered */	1331	/* doh, nothing entered */;
702	else if (revents & EV_READ)	1332	else if (revents & EV_READ)
703	/* stdin might have data for us, joy! */	1333	/* stdin might have data for us, joy! */;
704	}	1334	}
705		1335
706	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1336	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
707		1337
708	=item ev_feed_event (loop, watcher, int events)	1338	=item ev_feed_event (ev_loop *, watcher *, int revents)
709		1339
710	Feeds the given event set into the event loop, as if the specified event	1340	Feeds the given event set into the event loop, as if the specified event
711	has happened for the specified watcher (which must be a pointer to an	1341	had happened for the specified watcher (which must be a pointer to an
712	initialised but not necessarily active event watcher).	1342	initialised but not necessarily started event watcher).
713		1343
714	=item ev_feed_fd_event (loop, int fd, int revents)	1344	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
715		1345
716	Feed an event on the given fd, as if a file descriptor backend detected it.	1346	Feed an event on the given fd, as if a file descriptor backend detected
		1347	the given events it.
717		1348
718	=item ev_feed_signal_event (loop, int signum)	1349	=item ev_feed_signal_event (ev_loop *loop, int signum)
719		1350
720	Feed an event as if the given signal occured (loop must be the default loop!).	1351	Feed an event as if the given signal occured (C<loop> must be the default
		1352	loop!).
721		1353
722	=back	1354	=back
		1355
		1356
		1357	=head1 LIBEVENT EMULATION
		1358
		1359	Libev offers a compatibility emulation layer for libevent. It cannot
		1360	emulate the internals of libevent, so here are some usage hints:
		1361
		1362	=over 4
		1363
		1364	=item * Use it by including <event.h>, as usual.
		1365
		1366	=item * The following members are fully supported: ev_base, ev_callback,
		1367	ev_arg, ev_fd, ev_res, ev_events.
		1368
		1369	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1370	maintained by libev, it does not work exactly the same way as in libevent (consider
		1371	it a private API).
		1372
		1373	=item * Priorities are not currently supported. Initialising priorities
		1374	will fail and all watchers will have the same priority, even though there
		1375	is an ev_pri field.
		1376
		1377	=item * Other members are not supported.
		1378
		1379	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1380	to use the libev header file and library.
		1381
		1382	=back
		1383
		1384	=head1 C++ SUPPORT
		1385
		1386	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1387	you to use some convinience methods to start/stop watchers and also change
		1388	the callback model to a model using method callbacks on objects.
		1389
		1390	To use it,
		1391
		1392	#include <ev++.h>
		1393
		1394	(it is not installed by default). This automatically includes F<ev.h>
		1395	and puts all of its definitions (many of them macros) into the global
		1396	namespace. All C++ specific things are put into the C<ev> namespace.
		1397
		1398	It should support all the same embedding options as F<ev.h>, most notably
		1399	C<EV_MULTIPLICITY>.
		1400
		1401	Here is a list of things available in the C<ev> namespace:
		1402
		1403	=over 4
		1404
		1405	=item C<ev::READ>, C<ev::WRITE> etc.
		1406
		1407	These are just enum values with the same values as the C<EV_READ> etc.
		1408	macros from F<ev.h>.
		1409
		1410	=item C<ev::tstamp>, C<ev::now>
		1411
		1412	Aliases to the same types/functions as with the C<ev_> prefix.
		1413
		1414	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1415
		1416	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1417	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1418	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1419	defines by many implementations.
		1420
		1421	All of those classes have these methods:
		1422
		1423	=over 4
		1424
		1425	=item ev::TYPE::TYPE (object *, object::method *)
		1426
		1427	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
		1428
		1429	=item ev::TYPE::~TYPE
		1430
		1431	The constructor takes a pointer to an object and a method pointer to
		1432	the event handler callback to call in this class. The constructor calls
		1433	C<ev_init> for you, which means you have to call the C<set> method
		1434	before starting it. If you do not specify a loop then the constructor
		1435	automatically associates the default loop with this watcher.
		1436
		1437	The destructor automatically stops the watcher if it is active.
		1438
		1439	=item w->set (struct ev_loop *)
		1440
		1441	Associates a different C<struct ev_loop> with this watcher. You can only
		1442	do this when the watcher is inactive (and not pending either).
		1443
		1444	=item w->set ([args])
		1445
		1446	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1447	called at least once. Unlike the C counterpart, an active watcher gets
		1448	automatically stopped and restarted.
		1449
		1450	=item w->start ()
		1451
		1452	Starts the watcher. Note that there is no C<loop> argument as the
		1453	constructor already takes the loop.
		1454
		1455	=item w->stop ()
		1456
		1457	Stops the watcher if it is active. Again, no C<loop> argument.
		1458
		1459	=item w->again () C<ev::timer>, C<ev::periodic> only
		1460
		1461	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1462	C<ev_TYPE_again> function.
		1463
		1464	=item w->sweep () C<ev::embed> only
		1465
		1466	Invokes C<ev_embed_sweep>.
		1467
		1468	=back
		1469
		1470	=back
		1471
		1472	Example: Define a class with an IO and idle watcher, start one of them in
		1473	the constructor.
		1474
		1475	class myclass
		1476	{
		1477	ev_io io; void io_cb (ev::io &w, int revents);
		1478	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1479
		1480	myclass ();
		1481	}
		1482
		1483	myclass::myclass (int fd)
		1484	: io (this, &myclass::io_cb),
		1485	idle (this, &myclass::idle_cb)
		1486	{
		1487	io.start (fd, ev::READ);
		1488	}
		1489
		1490	=head1 EMBEDDING
		1491
		1492	Libev can (and often is) directly embedded into host
		1493	applications. Examples of applications that embed it include the Deliantra
		1494	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1495	and rxvt-unicode.
		1496
		1497	The goal is to enable you to just copy the neecssary files into your
		1498	source directory without having to change even a single line in them, so
		1499	you can easily upgrade by simply copying (or having a checked-out copy of
		1500	libev somewhere in your source tree).
		1501
		1502	=head2 FILESETS
		1503
		1504	Depending on what features you need you need to include one or more sets of files
		1505	in your app.
		1506
		1507	=head3 CORE EVENT LOOP
		1508
		1509	To include only the libev core (all the C<ev_*> functions), with manual
		1510	configuration (no autoconf):
		1511
		1512	#define EV_STANDALONE 1
		1513	#include "ev.c"
		1514
		1515	This will automatically include F<ev.h>, too, and should be done in a
		1516	single C source file only to provide the function implementations. To use
		1517	it, do the same for F<ev.h> in all files wishing to use this API (best
		1518	done by writing a wrapper around F<ev.h> that you can include instead and
		1519	where you can put other configuration options):
		1520
		1521	#define EV_STANDALONE 1
		1522	#include "ev.h"
		1523
		1524	Both header files and implementation files can be compiled with a C++
		1525	compiler (at least, thats a stated goal, and breakage will be treated
		1526	as a bug).
		1527
		1528	You need the following files in your source tree, or in a directory
		1529	in your include path (e.g. in libev/ when using -Ilibev):
		1530
		1531	ev.h
		1532	ev.c
		1533	ev_vars.h
		1534	ev_wrap.h
		1535
		1536	ev_win32.c required on win32 platforms only
		1537
		1538	ev_select.c only when select backend is enabled (which is by default)
		1539	ev_poll.c only when poll backend is enabled (disabled by default)
		1540	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1541	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1542	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1543
		1544	F<ev.c> includes the backend files directly when enabled, so you only need
		1545	to compile this single file.
		1546
		1547	=head3 LIBEVENT COMPATIBILITY API
		1548
		1549	To include the libevent compatibility API, also include:
		1550
		1551	#include "event.c"
		1552
		1553	in the file including F<ev.c>, and:
		1554
		1555	#include "event.h"
		1556
		1557	in the files that want to use the libevent API. This also includes F<ev.h>.
		1558
		1559	You need the following additional files for this:
		1560
		1561	event.h
		1562	event.c
		1563
		1564	=head3 AUTOCONF SUPPORT
		1565
		1566	Instead of using C<EV_STANDALONE=1> and providing your config in
		1567	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1568	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1569	include F<config.h> and configure itself accordingly.
		1570
		1571	For this of course you need the m4 file:
		1572
		1573	libev.m4
		1574
		1575	=head2 PREPROCESSOR SYMBOLS/MACROS
		1576
		1577	Libev can be configured via a variety of preprocessor symbols you have to define
		1578	before including any of its files. The default is not to build for multiplicity
		1579	and only include the select backend.
		1580
		1581	=over 4
		1582
		1583	=item EV_STANDALONE
		1584
		1585	Must always be C<1> if you do not use autoconf configuration, which
		1586	keeps libev from including F<config.h>, and it also defines dummy
		1587	implementations for some libevent functions (such as logging, which is not
		1588	supported). It will also not define any of the structs usually found in
		1589	F<event.h> that are not directly supported by the libev core alone.
		1590
		1591	=item EV_USE_MONOTONIC
		1592
		1593	If defined to be C<1>, libev will try to detect the availability of the
		1594	monotonic clock option at both compiletime and runtime. Otherwise no use
		1595	of the monotonic clock option will be attempted. If you enable this, you
		1596	usually have to link against librt or something similar. Enabling it when
		1597	the functionality isn't available is safe, though, althoguh you have
		1598	to make sure you link against any libraries where the C<clock_gettime>
		1599	function is hiding in (often F<-lrt>).
		1600
		1601	=item EV_USE_REALTIME
		1602
		1603	If defined to be C<1>, libev will try to detect the availability of the
		1604	realtime clock option at compiletime (and assume its availability at
		1605	runtime if successful). Otherwise no use of the realtime clock option will
		1606	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1607	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1608	in the description of C<EV_USE_MONOTONIC>, though.
		1609
		1610	=item EV_USE_SELECT
		1611
		1612	If undefined or defined to be C<1>, libev will compile in support for the
		1613	C<select>(2) backend. No attempt at autodetection will be done: if no
		1614	other method takes over, select will be it. Otherwise the select backend
		1615	will not be compiled in.
		1616
		1617	=item EV_SELECT_USE_FD_SET
		1618
		1619	If defined to C<1>, then the select backend will use the system C<fd_set>
		1620	structure. This is useful if libev doesn't compile due to a missing
		1621	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1622	exotic systems. This usually limits the range of file descriptors to some
		1623	low limit such as 1024 or might have other limitations (winsocket only
		1624	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1625	influence the size of the C<fd_set> used.
		1626
		1627	=item EV_SELECT_IS_WINSOCKET
		1628
		1629	When defined to C<1>, the select backend will assume that
		1630	select/socket/connect etc. don't understand file descriptors but
		1631	wants osf handles on win32 (this is the case when the select to
		1632	be used is the winsock select). This means that it will call
		1633	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1634	it is assumed that all these functions actually work on fds, even
		1635	on win32. Should not be defined on non-win32 platforms.
		1636
		1637	=item EV_USE_POLL
		1638
		1639	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1640	backend. Otherwise it will be enabled on non-win32 platforms. It
		1641	takes precedence over select.
		1642
		1643	=item EV_USE_EPOLL
		1644
		1645	If defined to be C<1>, libev will compile in support for the Linux
		1646	C<epoll>(7) backend. Its availability will be detected at runtime,
		1647	otherwise another method will be used as fallback. This is the
		1648	preferred backend for GNU/Linux systems.
		1649
		1650	=item EV_USE_KQUEUE
		1651
		1652	If defined to be C<1>, libev will compile in support for the BSD style
		1653	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		1654	otherwise another method will be used as fallback. This is the preferred
		1655	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		1656	supports some types of fds correctly (the only platform we found that
		1657	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		1658	not be used unless explicitly requested. The best way to use it is to find
		1659	out whether kqueue supports your type of fd properly and use an embedded
		1660	kqueue loop.
		1661
		1662	=item EV_USE_PORT
		1663
		1664	If defined to be C<1>, libev will compile in support for the Solaris
		1665	10 port style backend. Its availability will be detected at runtime,
		1666	otherwise another method will be used as fallback. This is the preferred
		1667	backend for Solaris 10 systems.
		1668
		1669	=item EV_USE_DEVPOLL
		1670
		1671	reserved for future expansion, works like the USE symbols above.
		1672
		1673	=item EV_H
		1674
		1675	The name of the F<ev.h> header file used to include it. The default if
		1676	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		1677	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		1678
		1679	=item EV_CONFIG_H
		1680
		1681	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		1682	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		1683	C<EV_H>, above.
		1684
		1685	=item EV_EVENT_H
		1686
		1687	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		1688	of how the F<event.h> header can be found.
		1689
		1690	=item EV_PROTOTYPES
		1691
		1692	If defined to be C<0>, then F<ev.h> will not define any function
		1693	prototypes, but still define all the structs and other symbols. This is
		1694	occasionally useful if you want to provide your own wrapper functions
		1695	around libev functions.
		1696
		1697	=item EV_MULTIPLICITY
		1698
		1699	If undefined or defined to C<1>, then all event-loop-specific functions
		1700	will have the C<struct ev_loop *> as first argument, and you can create
		1701	additional independent event loops. Otherwise there will be no support
		1702	for multiple event loops and there is no first event loop pointer
		1703	argument. Instead, all functions act on the single default loop.
		1704
		1705	=item EV_PERIODICS
		1706
		1707	If undefined or defined to be C<1>, then periodic timers are supported,
		1708	otherwise not. This saves a few kb of code.
		1709
		1710	=item EV_COMMON
		1711
		1712	By default, all watchers have a C<void *data> member. By redefining
		1713	this macro to a something else you can include more and other types of
		1714	members. You have to define it each time you include one of the files,
		1715	though, and it must be identical each time.
		1716
		1717	For example, the perl EV module uses something like this:
		1718
		1719	#define EV_COMMON \
		1720	SV *self; /* contains this struct */ \
		1721	SV *cb_sv, *fh /* note no trailing ";" */
		1722
		1723	=item EV_CB_DECLARE (type)
		1724
		1725	=item EV_CB_INVOKE (watcher, revents)
		1726
		1727	=item ev_set_cb (ev, cb)
		1728
		1729	Can be used to change the callback member declaration in each watcher,
		1730	and the way callbacks are invoked and set. Must expand to a struct member
		1731	definition and a statement, respectively. See the F<ev.v> header file for
		1732	their default definitions. One possible use for overriding these is to
		1733	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		1734	method calls instead of plain function calls in C++.
		1735
		1736	=head2 EXAMPLES
		1737
		1738	For a real-world example of a program the includes libev
		1739	verbatim, you can have a look at the EV perl module
		1740	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		1741	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		1742	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		1743	will be compiled. It is pretty complex because it provides its own header
		1744	file.
		1745
		1746	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		1747	that everybody includes and which overrides some autoconf choices:
		1748
		1749	#define EV_USE_POLL 0
		1750	#define EV_MULTIPLICITY 0
		1751	#define EV_PERIODICS 0
		1752	#define EV_CONFIG_H <config.h>
		1753
		1754	#include "ev++.h"
		1755
		1756	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		1757
		1758	#include "ev_cpp.h"
		1759	#include "ev.c"
		1760
		1761
		1762	=head1 COMPLEXITIES
		1763
		1764	In this section the complexities of (many of) the algorithms used inside
		1765	libev will be explained. For complexity discussions about backends see the
		1766	documentation for C<ev_default_init>.
		1767
		1768	=over 4
		1769
		1770	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		1771
		1772	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		1773
		1774	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		1775
		1776	=item Stopping check/prepare/idle watchers: O(1)
		1777
		1778	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))
		1779
		1780	=item Finding the next timer per loop iteration: O(1)
		1781
		1782	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		1783
		1784	=item Activating one watcher: O(1)
		1785
		1786	=back
		1787
723		1788
724	=head1 AUTHOR	1789	=head1 AUTHOR
725		1790
726	Marc Lehmann <libev@schmorp.de>.	1791	Marc Lehmann <libev@schmorp.de>.
727		1792

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