[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.1 by root, Mon Nov 12 07:58:13 2007 UTC vs.
Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC

…		…
8		8
9	=head1 DESCRIPTION	9	=head1 DESCRIPTION
10		10
11	Libev is an event loop: you register interest in certain events (such as a	11	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	12	file descriptor being readable or a timeout occuring), and it will manage
13	these event sources and provide your program events.	13	these event sources and provide your program with events.
14		14
15	To do this, it must take more or less complete control over your process	15	To do this, it must take more or less complete control over your process
16	(or thread) by executing the I<event loop> handler, and will then	16	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	17	communicate events via a callback mechanism.
18		18
…		…
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. This type is	46	Libev represents time as a single floating point number, representing the
		47	(fractional) number of seconds since the (POSIX) epoch (somewhere near
		48	the beginning of 1970, details are complicated, don't ask). This type is
45	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
46	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.
47		58
48	=over 4	59	=over 4
49		60
50	=item ev_tstamp ev_time ()	61	=item ev_tstamp ev_time ()
51		62
52	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.
53		66
54	=item int ev_version_major ()	67	=item int ev_version_major ()
55		68
56	=item int ev_version_minor ()	69	=item int ev_version_minor ()
57		70
…		…
59	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
60	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
61	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
62	version of the library your program was compiled against.	75	version of the library your program was compiled against.
63		76
64	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,
65	as this indicates an incompatible change. Minor versions are usually	78	as this indicates an incompatible change. Minor versions are usually
66	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
67	not a problem.	80	not a problem.
68		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
69	=item ev_set_allocator (void (cb)(void *ptr, long size))	111	=item ev_set_allocator (void (cb)(void *ptr, long size))
70		112
71	Sets the allocation function to use (the prototype is similar to the	113	Sets the allocation function to use (the prototype is similar to the
72	realloc function). It is used to allocate and free memory (no surprises	114	realloc C function, the semantics are identical). It is used to allocate
73	here). If it returns zero when memory needs to be allocated, the library	115	and free memory (no surprises here). If it returns zero when memory
74	might abort or take some potentially destructive action. The default is	116	needs to be allocated, the library might abort or take some potentially
75	your system realloc function.	117	destructive action. The default is your system realloc function.
76		118
77	You could override this function in high-availability programs to, say,	119	You could override this function in high-availability programs to, say,
78	free some memory if it cannot allocate memory, to use a special allocator,	120	free some memory if it cannot allocate memory, to use a special allocator,
79	or even to sleep a while and retry until some memory is available.	121	or even to sleep a while and retry until some memory is available.
		122
		123	Example: replace the libev allocator with one that waits a bit and then
		124	retries: better than mine).
		125
		126	static void *
		127	persistent_realloc (void *ptr, long size)
		128	{
		129	for (;;)
		130	{
		131	void *newptr = realloc (ptr, size);
		132
		133	if (newptr)
		134	return newptr;
		135
		136	sleep (60);
		137	}
		138	}
		139
		140	...
		141	ev_set_allocator (persistent_realloc);
80		142
81	=item ev_set_syserr_cb (void (cb)(const char msg));	143	=item ev_set_syserr_cb (void (cb)(const char msg));
82		144
83	Set the callback function to call on a retryable syscall error (such	145	Set the callback function to call on a retryable syscall error (such
84	as failed select, poll, epoll_wait). The message is a printable string	146	as failed select, poll, epoll_wait). The message is a printable string
85	indicating the system call or subsystem causing the problem. If this	147	indicating the system call or subsystem causing the problem. If this
86	callback is set, then libev will expect it to remedy the sitution, no	148	callback is set, then libev will expect it to remedy the sitution, no
87	matter what, when it returns. That is, libev will geenrally retry the	149	matter what, when it returns. That is, libev will generally retry the
88	requested operation, or, if the condition doesn't go away, do bad stuff	150	requested operation, or, if the condition doesn't go away, do bad stuff
89	(such as abort).	151	(such as abort).
		152
		153	Example: do the same thing as libev does internally:
		154
		155	static void
		156	fatal_error (const char *msg)
		157	{
		158	perror (msg);
		159	abort ();
		160	}
		161
		162	...
		163	ev_set_syserr_cb (fatal_error);
90		164
91	=back	165	=back
92		166
93	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	167	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
94		168
95	An event loop is described by a C<struct ev_loop *>. The library knows two	169	An event loop is described by a C<struct ev_loop *>. The library knows two
96	types of such loops, the I<default> loop, which supports signals and child	170	types of such loops, the I<default> loop, which supports signals and child
97	events, and dynamically created loops which do not.	171	events, and dynamically created loops which do not.
98		172
99	If you use threads, a common model is to run the default event loop	173	If you use threads, a common model is to run the default event loop
100	in your main thread (or in a separate thrad) and for each thread you	174	in your main thread (or in a separate thread) and for each thread you
101	create, you also create another event loop. Libev itself does no lockign	175	create, you also create another event loop. Libev itself does no locking
102	whatsoever, so if you mix calls to different event loops, make sure you	176	whatsoever, so if you mix calls to the same event loop in different
103	lock (this is usually a bad idea, though, even if done right).	177	threads, make sure you lock (this is usually a bad idea, though, even if
		178	done correctly, because it's hideous and inefficient).
104		179
105	=over 4	180	=over 4
106		181
107	=item struct ev_loop *ev_default_loop (unsigned int flags)	182	=item struct ev_loop *ev_default_loop (unsigned int flags)
108		183
109	This will initialise the default event loop if it hasn't been initialised	184	This will initialise the default event loop if it hasn't been initialised
110	yet and return it. If the default loop could not be initialised, returns	185	yet and return it. If the default loop could not be initialised, returns
111	false. If it already was initialised it simply returns it (and ignores the	186	false. If it already was initialised it simply returns it (and ignores the
112	flags).	187	flags. If that is troubling you, check C<ev_backend ()> afterwards).
113		188
114	If you don't know what event loop to use, use the one returned from this	189	If you don't know what event loop to use, use the one returned from this
115	function.	190	function.
116		191
117	The flags argument can be used to specify special behaviour or specific	192	The flags argument can be used to specify special behaviour or specific
118	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)	193	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
119		194
120	It supports the following flags:	195	The following flags are supported:
121		196
122	=over 4	197	=over 4
123		198
124	=item EVFLAG_AUTO	199	=item C<EVFLAG_AUTO>
125		200
126	The default flags value. Use this if you have no clue (its the right	201	The default flags value. Use this if you have no clue (it's the right
127	thing, believe me).	202	thing, believe me).
128		203
129	=item EVFLAG_NOENV	204	=item C<EVFLAG_NOENV>
130		205
131	If this flag bit is ored into the flag value then libev will I<not> look	206	If this flag bit is ored into the flag value (or the program runs setuid
132	at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this	207	or setgid) then libev will I<not> look at the environment variable
133	environment variable will override the flags completely. This is useful	208	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
		209	override the flags completely if it is found in the environment. This is
134	to try out specific backends to tets their performance, or to work around	210	useful to try out specific backends to test their performance, or to work
135	bugs.	211	around bugs.
136		212
137	=item EVMETHOD_SELECT portable select backend	213	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
138		214
139	=item EVMETHOD_POLL poll backend (everywhere except windows)	215	This is your standard select(2) backend. Not I<completely> standard, as
		216	libev tries to roll its own fd_set with no limits on the number of fds,
		217	but if that fails, expect a fairly low limit on the number of fds when
		218	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		219	the fastest backend for a low number of fds.
140		220
141	=item EVMETHOD_EPOLL linux only	221	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
142		222
143	=item EVMETHOD_KQUEUE some bsds only	223	And this is your standard poll(2) backend. It's more complicated than
		224	select, but handles sparse fds better and has no artificial limit on the
		225	number of fds you can use (except it will slow down considerably with a
		226	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
144		227
145	=item EVMETHOD_DEVPOLL solaris 8 only	228	=item C<EVBACKEND_EPOLL> (value 4, Linux)
146		229
147	=item EVMETHOD_PORT solaris 10 only	230	For few fds, this backend is a bit little slower than poll and select,
		231	but it scales phenomenally better. While poll and select usually scale like
		232	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		233	either O(1) or O(active_fds).
		234
		235	While stopping and starting an I/O watcher in the same iteration will
		236	result in some caching, there is still a syscall per such incident
		237	(because the fd could point to a different file description now), so its
		238	best to avoid that. Also, dup()ed file descriptors might not work very
		239	well if you register events for both fds.
		240
		241	Please note that epoll sometimes generates spurious notifications, so you
		242	need to use non-blocking I/O or other means to avoid blocking when no data
		243	(or space) is available.
		244
		245	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		246
		247	Kqueue deserves special mention, as at the time of this writing, it
		248	was broken on all BSDs except NetBSD (usually it doesn't work with
		249	anything but sockets and pipes, except on Darwin, where of course its
		250	completely useless). For this reason its not being "autodetected"
		251	unless you explicitly specify it explicitly in the flags (i.e. using
		252	C<EVBACKEND_KQUEUE>).
		253
		254	It scales in the same way as the epoll backend, but the interface to the
		255	kernel is more efficient (which says nothing about its actual speed, of
		256	course). While starting and stopping an I/O watcher does not cause an
		257	extra syscall as with epoll, it still adds up to four event changes per
		258	incident, so its best to avoid that.
		259
		260	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		261
		262	This is not implemented yet (and might never be).
		263
		264	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		265
		266	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		267	it's really slow, but it still scales very well (O(active_fds)).
		268
		269	Please note that solaris ports can result in a lot of spurious
		270	notifications, so you need to use non-blocking I/O or other means to avoid
		271	blocking when no data (or space) is available.
		272
		273	=item C<EVBACKEND_ALL>
		274
		275	Try all backends (even potentially broken ones that wouldn't be tried
		276	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		277	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		278
		279	=back
148		280
149	If one or more of these are ored into the flags value, then only these	281	If one or more of these are ored into the flags value, then only these
150	backends will be tried (in the reverse order as given here). If one are	282	backends will be tried (in the reverse order as given here). If none are
151	specified, any backend will do.	283	specified, most compiled-in backend will be tried, usually in reverse
		284	order of their flag values :)
152		285
153	=back	286	The most typical usage is like this:
		287
		288	if (!ev_default_loop (0))
		289	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		290
		291	Restrict libev to the select and poll backends, and do not allow
		292	environment settings to be taken into account:
		293
		294	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		295
		296	Use whatever libev has to offer, but make sure that kqueue is used if
		297	available (warning, breaks stuff, best use only with your own private
		298	event loop and only if you know the OS supports your types of fds):
		299
		300	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
154		301
155	=item struct ev_loop *ev_loop_new (unsigned int flags)	302	=item struct ev_loop *ev_loop_new (unsigned int flags)
156		303
157	Similar to C<ev_default_loop>, but always creates a new event loop that is	304	Similar to C<ev_default_loop>, but always creates a new event loop that is
158	always distinct from the default loop. Unlike the default loop, it cannot	305	always distinct from the default loop. Unlike the default loop, it cannot
159	handle signal and child watchers, and attempts to do so will be greeted by	306	handle signal and child watchers, and attempts to do so will be greeted by
160	undefined behaviour (or a failed assertion if assertions are enabled).	307	undefined behaviour (or a failed assertion if assertions are enabled).
161		308
		309	Example: try to create a event loop that uses epoll and nothing else.
		310
		311	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		312	if (!epoller)
		313	fatal ("no epoll found here, maybe it hides under your chair");
		314
162	=item ev_default_destroy ()	315	=item ev_default_destroy ()
163		316
164	Destroys the default loop again (frees all memory and kernel state	317	Destroys the default loop again (frees all memory and kernel state
165	etc.). This stops all registered event watchers (by not touching them in	318	etc.). This stops all registered event watchers (by not touching them in
166	any way whatsoever, although you cnanot rely on this :).	319	any way whatsoever, although you cannot rely on this :).
167		320
168	=item ev_loop_destroy (loop)	321	=item ev_loop_destroy (loop)
169		322
170	Like C<ev_default_destroy>, but destroys an event loop created by an	323	Like C<ev_default_destroy>, but destroys an event loop created by an
171	earlier call to C<ev_loop_new>.	324	earlier call to C<ev_loop_new>.
…		…
175	This function reinitialises the kernel state for backends that have	328	This function reinitialises the kernel state for backends that have
176	one. Despite the name, you can call it anytime, but it makes most sense	329	one. Despite the name, you can call it anytime, but it makes most sense
177	after forking, in either the parent or child process (or both, but that	330	after forking, in either the parent or child process (or both, but that
178	again makes little sense).	331	again makes little sense).
179		332
180	You I<must> call this function after forking if and only if you want to	333	You I<must> call this function in the child process after forking if and
181	use the event library in both processes. If you just fork+exec, you don't	334	only if you want to use the event library in both processes. If you just
182	have to call it.	335	fork+exec, you don't have to call it.
183		336
184	The function itself is quite fast and its usually not a problem to call	337	The function itself is quite fast and it's usually not a problem to call
185	it just in case after a fork. To make this easy, the function will fit in	338	it just in case after a fork. To make this easy, the function will fit in
186	quite nicely into a call to C<pthread_atfork>:	339	quite nicely into a call to C<pthread_atfork>:
187		340
188	pthread_atfork (0, 0, ev_default_fork);	341	pthread_atfork (0, 0, ev_default_fork);
		342
		343	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		344	without calling this function, so if you force one of those backends you
		345	do not need to care.
189		346
190	=item ev_loop_fork (loop)	347	=item ev_loop_fork (loop)
191		348
192	Like C<ev_default_fork>, but acts on an event loop created by	349	Like C<ev_default_fork>, but acts on an event loop created by
193	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	350	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
194	after fork, and how you do this is entirely your own problem.	351	after fork, and how you do this is entirely your own problem.
195		352
196	=item unsigned int ev_method (loop)	353	=item unsigned int ev_backend (loop)
197		354
198	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	355	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
199	use.	356	use.
200		357
201	=item ev_tstamp = ev_now (loop)	358	=item ev_tstamp ev_now (loop)
202		359
203	Returns the current "event loop time", which is the time the event loop	360	Returns the current "event loop time", which is the time the event loop
204	got events and started processing them. This timestamp does not change	361	received events and started processing them. This timestamp does not
205	as long as callbacks are being processed, and this is also the base time	362	change as long as callbacks are being processed, and this is also the base
206	used for relative timers. You can treat it as the timestamp of the event	363	time used for relative timers. You can treat it as the timestamp of the
207	occuring (or more correctly, the mainloop finding out about it).	364	event occuring (or more correctly, libev finding out about it).
208		365
209	=item ev_loop (loop, int flags)	366	=item ev_loop (loop, int flags)
210		367
211	Finally, this is it, the event handler. This function usually is called	368	Finally, this is it, the event handler. This function usually is called
212	after you initialised all your watchers and you want to start handling	369	after you initialised all your watchers and you want to start handling
213	events.	370	events.
214		371
215	If the flags argument is specified as 0, it will not return until either	372	If the flags argument is specified as C<0>, it will not return until
216	no event watchers are active anymore or C<ev_unloop> was called.	373	either no event watchers are active anymore or C<ev_unloop> was called.
		374
		375	Please note that an explicit C<ev_unloop> is usually better than
		376	relying on all watchers to be stopped when deciding when a program has
		377	finished (especially in interactive programs), but having a program that
		378	automatically loops as long as it has to and no longer by virtue of
		379	relying on its watchers stopping correctly is a thing of beauty.
217		380
218	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	381	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
219	those events and any outstanding ones, but will not block your process in	382	those events and any outstanding ones, but will not block your process in
220	case there are no events.	383	case there are no events and will return after one iteration of the loop.
221		384
222	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	385	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
223	neccessary) and will handle those and any outstanding ones. It will block	386	neccessary) and will handle those and any outstanding ones. It will block
224	your process until at least one new event arrives.	387	your process until at least one new event arrives, and will return after
		388	one iteration of the loop. This is useful if you are waiting for some
		389	external event in conjunction with something not expressible using other
		390	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		391	usually a better approach for this kind of thing.
225		392
226	This flags value could be used to implement alternative looping	393	Here are the gory details of what C<ev_loop> does:
227	constructs, but the C<prepare> and C<check> watchers provide a better and	394
228	more generic mechanism.	395	* If there are no active watchers (reference count is zero), return.
		396	- Queue prepare watchers and then call all outstanding watchers.
		397	- If we have been forked, recreate the kernel state.
		398	- Update the kernel state with all outstanding changes.
		399	- Update the "event loop time".
		400	- Calculate for how long to block.
		401	- Block the process, waiting for any events.
		402	- Queue all outstanding I/O (fd) events.
		403	- Update the "event loop time" and do time jump handling.
		404	- Queue all outstanding timers.
		405	- Queue all outstanding periodics.
		406	- If no events are pending now, queue all idle watchers.
		407	- Queue all check watchers.
		408	- Call all queued watchers in reverse order (i.e. check watchers first).
		409	Signals and child watchers are implemented as I/O watchers, and will
		410	be handled here by queueing them when their watcher gets executed.
		411	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		412	were used, return, otherwise continue with step *.
		413
		414	Example: queue some jobs and then loop until no events are outsanding
		415	anymore.
		416
		417	... queue jobs here, make sure they register event watchers as long
		418	... as they still have work to do (even an idle watcher will do..)
		419	ev_loop (my_loop, 0);
		420	... jobs done. yeah!
229		421
230	=item ev_unloop (loop, how)	422	=item ev_unloop (loop, how)
231		423
232	Can be used to make a call to C<ev_loop> return early. The C<how> argument	424	Can be used to make a call to C<ev_loop> return early (but only after it
		425	has processed all outstanding events). The C<how> argument must be either
233	must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop>	426	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
234	call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop>	427	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
235	calls return.
236		428
237	=item ev_ref (loop)	429	=item ev_ref (loop)
238		430
239	=item ev_unref (loop)	431	=item ev_unref (loop)
240		432
241	Ref/unref can be used to add or remove a refcount on the event loop: Every	433	Ref/unref can be used to add or remove a reference count on the event
242	watcher keeps one reference. If you have a long-runing watcher you never	434	loop: Every watcher keeps one reference, and as long as the reference
243	unregister that should not keep ev_loop from running, ev_unref() after	435	count is nonzero, C<ev_loop> will not return on its own. If you have
244	starting, and ev_ref() before stopping it. Libev itself uses this for	436	a watcher you never unregister that should not keep C<ev_loop> from
245	example for its internal signal pipe: It is not visible to you as a user	437	returning, ev_unref() after starting, and ev_ref() before stopping it. For
246	and should not keep C<ev_loop> from exiting if the work is done. It is	438	example, libev itself uses this for its internal signal pipe: It is not
247	also an excellent way to do this for generic recurring timers or from	439	visible to the libev user and should not keep C<ev_loop> from exiting if
248	within third-party libraries. Just remember to unref after start and ref	440	no event watchers registered by it are active. It is also an excellent
249	before stop.	441	way to do this for generic recurring timers or from within third-party
		442	libraries. Just remember to I<unref after start> and I<ref before stop>.
		443
		444	Example: create a signal watcher, but keep it from keeping C<ev_loop>
		445	running when nothing else is active.
		446
		447	struct dv_signal exitsig;
		448	ev_signal_init (&exitsig, sig_cb, SIGINT);
		449	ev_signal_start (myloop, &exitsig);
		450	evf_unref (myloop);
		451
		452	Example: for some weird reason, unregister the above signal handler again.
		453
		454	ev_ref (myloop);
		455	ev_signal_stop (myloop, &exitsig);
250		456
251	=back	457	=back
252		458
253	=head1 ANATOMY OF A WATCHER	459	=head1 ANATOMY OF A WATCHER
254		460
255	A watcher is a structure that you create and register to record your	461	A watcher is a structure that you create and register to record your
256	interest in some event. For instance, if you want to wait for STDIN to	462	interest in some event. For instance, if you want to wait for STDIN to
257	become readable, you would create an ev_io watcher for that:	463	become readable, you would create an C<ev_io> watcher for that:
258		464
259	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	465	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
260	{	466	{
261	ev_io_stop (w);	467	ev_io_stop (w);
262	ev_unloop (loop, EVUNLOOP_ALL);	468	ev_unloop (loop, EVUNLOOP_ALL);
…		…
289	*) >>), and you can stop watching for events at any time by calling the	495	*) >>), and you can stop watching for events at any time by calling the
290	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	496	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
291		497
292	As long as your watcher is active (has been started but not stopped) you	498	As long as your watcher is active (has been started but not stopped) you
293	must not touch the values stored in it. Most specifically you must never	499	must not touch the values stored in it. Most specifically you must never
294	reinitialise it or call its set method.	500	reinitialise it or call its set macro.
295		501
296	You cna check wether an event is active by calling the C<ev_is_active	502	You can check whether an event is active by calling the C<ev_is_active
297	(watcher *)> macro. To see wether an event is outstanding (but the	503	(watcher *)> macro. To see whether an event is outstanding (but the
298	callback for it has not been called yet) you cna use the C<ev_is_pending	504	callback for it has not been called yet) you can use the C<ev_is_pending
299	(watcher *)> macro.	505	(watcher *)> macro.
300		506
301	Each and every callback receives the event loop pointer as first, the	507	Each and every callback receives the event loop pointer as first, the
302	registered watcher structure as second, and a bitset of received events as	508	registered watcher structure as second, and a bitset of received events as
303	third argument.	509	third argument.
304		510
305	The rceeived events usually include a single bit per event type received	511	The received events usually include a single bit per event type received
306	(you can receive multiple events at the same time). The possible bit masks	512	(you can receive multiple events at the same time). The possible bit masks
307	are:	513	are:
308		514
309	=over 4	515	=over 4
310		516
311	=item EV_READ	517	=item C<EV_READ>
312		518
313	=item EV_WRITE	519	=item C<EV_WRITE>
314		520
315	The file descriptor in the ev_io watcher has become readable and/or	521	The file descriptor in the C<ev_io> watcher has become readable and/or
316	writable.	522	writable.
317		523
318	=item EV_TIMEOUT	524	=item C<EV_TIMEOUT>
319		525
320	The ev_timer watcher has timed out.	526	The C<ev_timer> watcher has timed out.
321		527
322	=item EV_PERIODIC	528	=item C<EV_PERIODIC>
323		529
324	The ev_periodic watcher has timed out.	530	The C<ev_periodic> watcher has timed out.
325		531
326	=item EV_SIGNAL	532	=item C<EV_SIGNAL>
327		533
328	The signal specified in the ev_signal watcher has been received by a thread.	534	The signal specified in the C<ev_signal> watcher has been received by a thread.
329		535
330	=item EV_CHILD	536	=item C<EV_CHILD>
331		537
332	The pid specified in the ev_child watcher has received a status change.	538	The pid specified in the C<ev_child> watcher has received a status change.
333		539
334	=item EV_IDLE	540	=item C<EV_IDLE>
335		541
336	The ev_idle watcher has determined that you have nothing better to do.	542	The C<ev_idle> watcher has determined that you have nothing better to do.
337		543
338	=item EV_PREPARE	544	=item C<EV_PREPARE>
339		545
340	=item EV_CHECK	546	=item C<EV_CHECK>
341		547
342	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	548	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
343	to gather new events, and all ev_check watchers are invoked just after	549	to gather new events, and all C<ev_check> watchers are invoked just after
344	C<ev_loop> has gathered them, but before it invokes any callbacks for any	550	C<ev_loop> has gathered them, but before it invokes any callbacks for any
345	received events. Callbacks of both watcher types can start and stop as	551	received events. Callbacks of both watcher types can start and stop as
346	many watchers as they want, and all of them will be taken into account	552	many watchers as they want, and all of them will be taken into account
347	(for example, a ev_prepare watcher might start an idle watcher to keep	553	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
348	C<ev_loop> from blocking).	554	C<ev_loop> from blocking).
349		555
350	=item EV_ERROR	556	=item C<EV_ERROR>
351		557
352	An unspecified error has occured, the watcher has been stopped. This might	558	An unspecified error has occured, the watcher has been stopped. This might
353	happen because the watcher could not be properly started because libev	559	happen because the watcher could not be properly started because libev
354	ran out of memory, a file descriptor was found to be closed or any other	560	ran out of memory, a file descriptor was found to be closed or any other
355	problem. You best act on it by reporting the problem and somehow coping	561	problem. You best act on it by reporting the problem and somehow coping
…		…
364	=back	570	=back
365		571
366	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	572	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
367		573
368	Each watcher has, by default, a member C<void *data> that you can change	574	Each watcher has, by default, a member C<void *data> that you can change
369	and read at any time, libev will completely ignore it. This cna be used	575	and read at any time, libev will completely ignore it. This can be used
370	to associate arbitrary data with your watcher. If you need more data and	576	to associate arbitrary data with your watcher. If you need more data and
371	don't want to allocate memory and store a pointer to it in that data	577	don't want to allocate memory and store a pointer to it in that data
372	member, you can also "subclass" the watcher type and provide your own	578	member, you can also "subclass" the watcher type and provide your own
373	data:	579	data:
374		580
…		…
396	=head1 WATCHER TYPES	602	=head1 WATCHER TYPES
397		603
398	This section describes each watcher in detail, but will not repeat	604	This section describes each watcher in detail, but will not repeat
399	information given in the last section.	605	information given in the last section.
400		606
		607
401	=head2 struct ev_io - is my file descriptor readable or writable	608	=head2 C<ev_io> - is this file descriptor readable or writable
402		609
403	I/O watchers check wether a file descriptor is readable or writable	610	I/O watchers check whether a file descriptor is readable or writable
404	in each iteration of the event loop (This behaviour is called	611	in each iteration of the event loop (This behaviour is called
405	level-triggering because you keep receiving events as long as the	612	level-triggering because you keep receiving events as long as the
406	condition persists. Remember you cna stop the watcher if you don't want to	613	condition persists. Remember you can stop the watcher if you don't want to
407	act on the event and neither want to receive future events).	614	act on the event and neither want to receive future events).
408		615
		616	In general you can register as many read and/or write event watchers per
		617	fd as you want (as long as you don't confuse yourself). Setting all file
		618	descriptors to non-blocking mode is also usually a good idea (but not
		619	required if you know what you are doing).
		620
		621	You have to be careful with dup'ed file descriptors, though. Some backends
		622	(the linux epoll backend is a notable example) cannot handle dup'ed file
		623	descriptors correctly if you register interest in two or more fds pointing
		624	to the same underlying file/socket etc. description (that is, they share
		625	the same underlying "file open").
		626
		627	If you must do this, then force the use of a known-to-be-good backend
		628	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
		629	C<EVBACKEND_POLL>).
		630
409	=over 4	631	=over 4
410		632
411	=item ev_io_init (ev_io *, callback, int fd, int events)	633	=item ev_io_init (ev_io *, callback, int fd, int events)
412		634
413	=item ev_io_set (ev_io *, int fd, int events)	635	=item ev_io_set (ev_io *, int fd, int events)
414		636
415	Configures an ev_io watcher. The fd is the file descriptor to rceeive	637	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive
416	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|	638	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|
417	EV_WRITE> to receive the given events.	639	EV_WRITE> to receive the given events.
418		640
419	=back	641	Please note that most of the more scalable backend mechanisms (for example
		642	epoll and solaris ports) can result in spurious readyness notifications
		643	for file descriptors, so you practically need to use non-blocking I/O (and
		644	treat callback invocation as hint only), or retest separately with a safe
		645	interface before doing I/O (XLib can do this), or force the use of either
		646	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this
		647	problem. Also note that it is quite easy to have your callback invoked
		648	when the readyness condition is no longer valid even when employing
		649	typical ways of handling events, so its a good idea to use non-blocking
		650	I/O unconditionally.
420		651
		652	=back
		653
		654	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
		655	readable, but only once. Since it is likely line-buffered, you could
		656	attempt to read a whole line in the callback:
		657
		658	static void
		659	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		660	{
		661	ev_io_stop (loop, w);
		662	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		663	}
		664
		665	...
		666	struct ev_loop *loop = ev_default_init (0);
		667	struct ev_io stdin_readable;
		668	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		669	ev_io_start (loop, &stdin_readable);
		670	ev_loop (loop, 0);
		671
		672
421	=head2 struct ev_timer - relative and optionally recurring timeouts	673	=head2 C<ev_timer> - relative and optionally recurring timeouts
422		674
423	Timer watchers are simple relative timers that generate an event after a	675	Timer watchers are simple relative timers that generate an event after a
424	given time, and optionally repeating in regular intervals after that.	676	given time, and optionally repeating in regular intervals after that.
425		677
426	The timers are based on real time, that is, if you register an event that	678	The timers are based on real time, that is, if you register an event that
427	times out after an hour and youreset your system clock to last years	679	times out after an hour and you reset your system clock to last years
428	time, it will still time out after (roughly) and hour. "Roughly" because	680	time, it will still time out after (roughly) and hour. "Roughly" because
429	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	681	detecting time jumps is hard, and some inaccuracies are unavoidable (the
430	monotonic clock option helps a lot here).	682	monotonic clock option helps a lot here).
		683
		684	The relative timeouts are calculated relative to the C<ev_now ()>
		685	time. This is usually the right thing as this timestamp refers to the time
		686	of the event triggering whatever timeout you are modifying/starting. If
		687	you suspect event processing to be delayed and you I<need> to base the timeout
		688	on the current time, use something like this to adjust for this:
		689
		690	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		691
		692	The callback is guarenteed to be invoked only when its timeout has passed,
		693	but if multiple timers become ready during the same loop iteration then
		694	order of execution is undefined.
431		695
432	=over 4	696	=over 4
433		697
434	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	698	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
435		699
…		…
441	later, again, and again, until stopped manually.	705	later, again, and again, until stopped manually.
442		706
443	The timer itself will do a best-effort at avoiding drift, that is, if you	707	The timer itself will do a best-effort at avoiding drift, that is, if you
444	configure a timer to trigger every 10 seconds, then it will trigger at	708	configure a timer to trigger every 10 seconds, then it will trigger at
445	exactly 10 second intervals. If, however, your program cannot keep up with	709	exactly 10 second intervals. If, however, your program cannot keep up with
446	the timer (ecause it takes longer than those 10 seconds to do stuff) the	710	the timer (because it takes longer than those 10 seconds to do stuff) the
447	timer will not fire more than once per event loop iteration.	711	timer will not fire more than once per event loop iteration.
448		712
449	=item ev_timer_again (loop)	713	=item ev_timer_again (loop)
450		714
451	This will act as if the timer timed out and restart it again if it is	715	This will act as if the timer timed out and restart it again if it is
…		…
458		722
459	This sounds a bit complicated, but here is a useful and typical	723	This sounds a bit complicated, but here is a useful and typical
460	example: Imagine you have a tcp connection and you want a so-called idle	724	example: Imagine you have a tcp connection and you want a so-called idle
461	timeout, that is, you want to be called when there have been, say, 60	725	timeout, that is, you want to be called when there have been, say, 60
462	seconds of inactivity on the socket. The easiest way to do this is to	726	seconds of inactivity on the socket. The easiest way to do this is to
463	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	727	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each
464	time you successfully read or write some data. If you go into an idle	728	time you successfully read or write some data. If you go into an idle
465	state where you do not expect data to travel on the socket, you can stop	729	state where you do not expect data to travel on the socket, you can stop
466	the timer, and again will automatically restart it if need be.	730	the timer, and again will automatically restart it if need be.
467		731
468	=back	732	=back
469		733
470	=head2 ev_periodic	734	Example: create a timer that fires after 60 seconds.
		735
		736	static void
		737	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		738	{
		739	.. one minute over, w is actually stopped right here
		740	}
		741
		742	struct ev_timer mytimer;
		743	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		744	ev_timer_start (loop, &mytimer);
		745
		746	Example: create a timeout timer that times out after 10 seconds of
		747	inactivity.
		748
		749	static void
		750	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		751	{
		752	.. ten seconds without any activity
		753	}
		754
		755	struct ev_timer mytimer;
		756	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		757	ev_timer_again (&mytimer); /* start timer */
		758	ev_loop (loop, 0);
		759
		760	// and in some piece of code that gets executed on any "activity":
		761	// reset the timeout to start ticking again at 10 seconds
		762	ev_timer_again (&mytimer);
		763
		764
		765	=head2 C<ev_periodic> - to cron or not to cron
471		766
472	Periodic watchers are also timers of a kind, but they are very versatile	767	Periodic watchers are also timers of a kind, but they are very versatile
473	(and unfortunately a bit complex).	768	(and unfortunately a bit complex).
474		769
475	Unlike ev_timer's, they are not based on real time (or relative time)	770	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
476	but on wallclock time (absolute time). You can tell a periodic watcher	771	but on wallclock time (absolute time). You can tell a periodic watcher
477	to trigger "at" some specific point in time. For example, if you tell a	772	to trigger "at" some specific point in time. For example, if you tell a
478	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	773	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
479	+ 10.>) and then reset your system clock to the last year, then it will	774	+ 10.>) and then reset your system clock to the last year, then it will
480	take a year to trigger the event (unlike an ev_timer, which would trigger	775	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
481	roughly 10 seconds later and of course not if you reset your system time	776	roughly 10 seconds later and of course not if you reset your system time
482	again).	777	again).
483		778
484	They can also be used to implement vastly more complex timers, such as	779	They can also be used to implement vastly more complex timers, such as
485	triggering an event on eahc midnight, local time.	780	triggering an event on eahc midnight, local time.
486		781
		782	As with timers, the callback is guarenteed to be invoked only when the
		783	time (C<at>) has been passed, but if multiple periodic timers become ready
		784	during the same loop iteration then order of execution is undefined.
		785
487	=over 4	786	=over 4
488		787
489	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	788	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
490		789
491	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	790	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
492		791
493	Lots of arguments, lets sort it out... There are basically three modes of	792	Lots of arguments, lets sort it out... There are basically three modes of
494	operation, and we will explain them from simplest to complex:	793	operation, and we will explain them from simplest to complex:
495
496		794
497	=over 4	795	=over 4
498		796
499	=item * absolute timer (interval = reschedule_cb = 0)	797	=item * absolute timer (interval = reschedule_cb = 0)
500		798
…		…
514		812
515	ev_periodic_set (&periodic, 0., 3600., 0);	813	ev_periodic_set (&periodic, 0., 3600., 0);
516		814
517	This doesn't mean there will always be 3600 seconds in between triggers,	815	This doesn't mean there will always be 3600 seconds in between triggers,
518	but only that the the callback will be called when the system time shows a	816	but only that the the callback will be called when the system time shows a
519	full hour (UTC), or more correct, when the system time is evenly divisible	817	full hour (UTC), or more correctly, when the system time is evenly divisible
520	by 3600.	818	by 3600.
521		819
522	Another way to think about it (for the mathematically inclined) is that	820	Another way to think about it (for the mathematically inclined) is that
523	ev_periodic will try to run the callback in this mode at the next possible	821	C<ev_periodic> will try to run the callback in this mode at the next possible
524	time where C<time = at (mod interval)>, regardless of any time jumps.	822	time where C<time = at (mod interval)>, regardless of any time jumps.
525		823
526	=item * manual reschedule mode (reschedule_cb = callback)	824	=item * manual reschedule mode (reschedule_cb = callback)
527		825
528	In this mode the values for C<interval> and C<at> are both being	826	In this mode the values for C<interval> and C<at> are both being
529	ignored. Instead, each time the periodic watcher gets scheduled, the	827	ignored. Instead, each time the periodic watcher gets scheduled, the
530	reschedule callback will be called with the watcher as first, and the	828	reschedule callback will be called with the watcher as first, and the
531	current time as second argument.	829	current time as second argument.
532		830
533	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	831	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
534	periodic watcher, ever, or make any event loop modificstions>. If you need	832	ever, or make any event loop modifications>. If you need to stop it,
535	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.	833	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		834	starting a prepare watcher).
536		835
537	Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	836	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
538	ev_tstamp now)>, e.g.:	837	ev_tstamp now)>, e.g.:
539		838
540	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	839	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
541	{	840	{
542	return now + 60.;	841	return now + 60.;
…		…
545	It must return the next time to trigger, based on the passed time value	844	It must return the next time to trigger, based on the passed time value
546	(that is, the lowest time value larger than to the second argument). It	845	(that is, the lowest time value larger than to the second argument). It
547	will usually be called just before the callback will be triggered, but	846	will usually be called just before the callback will be triggered, but
548	might be called at other times, too.	847	might be called at other times, too.
549		848
		849	NOTE: I<< This callback must always return a time that is later than the
		850	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		851
550	This can be used to create very complex timers, such as a timer that	852	This can be used to create very complex timers, such as a timer that
551	triggers on each midnight, local time. To do this, you would calculate the	853	triggers on each midnight, local time. To do this, you would calculate the
552	next midnight after C<now> and return the timestamp value for this. How you do this	854	next midnight after C<now> and return the timestamp value for this. How
553	is, again, up to you (but it is not trivial).	855	you do this is, again, up to you (but it is not trivial, which is the main
		856	reason I omitted it as an example).
554		857
555	=back	858	=back
556		859
557	=item ev_periodic_again (loop, ev_periodic *)	860	=item ev_periodic_again (loop, ev_periodic *)
558		861
…		…
561	a different time than the last time it was called (e.g. in a crond like	864	a different time than the last time it was called (e.g. in a crond like
562	program when the crontabs have changed).	865	program when the crontabs have changed).
563		866
564	=back	867	=back
565		868
		869	Example: call a callback every hour, or, more precisely, whenever the
		870	system clock is divisible by 3600. The callback invocation times have
		871	potentially a lot of jittering, but good long-term stability.
		872
		873	static void
		874	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		875	{
		876	... its now a full hour (UTC, or TAI or whatever your clock follows)
		877	}
		878
		879	struct ev_periodic hourly_tick;
		880	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		881	ev_periodic_start (loop, &hourly_tick);
		882
		883	Example: the same as above, but use a reschedule callback to do it:
		884
		885	#include <math.h>
		886
		887	static ev_tstamp
		888	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		889	{
		890	return fmod (now, 3600.) + 3600.;
		891	}
		892
		893	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		894
		895	Example: call a callback every hour, starting now:
		896
		897	struct ev_periodic hourly_tick;
		898	ev_periodic_init (&hourly_tick, clock_cb,
		899	fmod (ev_now (loop), 3600.), 3600., 0);
		900	ev_periodic_start (loop, &hourly_tick);
		901
		902
566	=head2 ev_signal - signal me when a signal gets signalled	903	=head2 C<ev_signal> - signal me when a signal gets signalled
567		904
568	Signal watchers will trigger an event when the process receives a specific	905	Signal watchers will trigger an event when the process receives a specific
569	signal one or more times. Even though signals are very asynchronous, libev	906	signal one or more times. Even though signals are very asynchronous, libev
570	will try its best to deliver signals synchronously, i.e. as part of the	907	will try it's best to deliver signals synchronously, i.e. as part of the
571	normal event processing, like any other event.	908	normal event processing, like any other event.
572		909
573	You cna configure as many watchers as you like per signal. Only when the	910	You can configure as many watchers as you like per signal. Only when the
574	first watcher gets started will libev actually register a signal watcher	911	first watcher gets started will libev actually register a signal watcher
575	with the kernel (thus it coexists with your own signal handlers as long	912	with the kernel (thus it coexists with your own signal handlers as long
576	as you don't register any with libev). Similarly, when the last signal	913	as you don't register any with libev). Similarly, when the last signal
577	watcher for a signal is stopped libev will reset the signal handler to	914	watcher for a signal is stopped libev will reset the signal handler to
578	SIG_DFL (regardless of what it was set to before).	915	SIG_DFL (regardless of what it was set to before).
…		…
586	Configures the watcher to trigger on the given signal number (usually one	923	Configures the watcher to trigger on the given signal number (usually one
587	of the C<SIGxxx> constants).	924	of the C<SIGxxx> constants).
588		925
589	=back	926	=back
590		927
591	=head2 ev_child - wait for pid status changes	928	=head2 C<ev_child> - wait for pid status changes
592		929
593	Child watchers trigger when your process receives a SIGCHLD in response to	930	Child watchers trigger when your process receives a SIGCHLD in response to
594	some child status changes (most typically when a child of yours dies).	931	some child status changes (most typically when a child of yours dies).
595		932
596	=over 4	933	=over 4
…		…
600	=item ev_child_set (ev_child *, int pid)	937	=item ev_child_set (ev_child *, int pid)
601		938
602	Configures the watcher to wait for status changes of process C<pid> (or	939	Configures the watcher to wait for status changes of process C<pid> (or
603	I<any> process if C<pid> is specified as C<0>). The callback can look	940	I<any> process if C<pid> is specified as C<0>). The callback can look
604	at the C<rstatus> member of the C<ev_child> watcher structure to see	941	at the C<rstatus> member of the C<ev_child> watcher structure to see
605	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	942	the status word (use the macros from C<sys/wait.h> and see your systems
606	contains the pid of the process causing the status change.	943	C<waitpid> documentation). The C<rpid> member contains the pid of the
		944	process causing the status change.
607		945
608	=back	946	=back
609		947
		948	Example: try to exit cleanly on SIGINT and SIGTERM.
		949
		950	static void
		951	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		952	{
		953	ev_unloop (loop, EVUNLOOP_ALL);
		954	}
		955
		956	struct ev_signal signal_watcher;
		957	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		958	ev_signal_start (loop, &sigint_cb);
		959
		960
610	=head2 ev_idle - when you've got nothing better to do	961	=head2 C<ev_idle> - when you've got nothing better to do
611		962
612	Idle watchers trigger events when there are no other I/O or timer (or	963	Idle watchers trigger events when there are no other events are pending
613	periodic) events pending. That is, as long as your process is busy	964	(prepare, check and other idle watchers do not count). That is, as long
614	handling sockets or timeouts it will not be called. But when your process	965	as your process is busy handling sockets or timeouts (or even signals,
615	is idle all idle watchers are being called again and again - until	966	imagine) it will not be triggered. But when your process is idle all idle
		967	watchers are being called again and again, once per event loop iteration -
616	stopped, that is, or your process receives more events.	968	until stopped, that is, or your process receives more events and becomes
		969	busy.
617		970
618	The most noteworthy effect is that as long as any idle watchers are	971	The most noteworthy effect is that as long as any idle watchers are
619	active, the process will not block when waiting for new events.	972	active, the process will not block when waiting for new events.
620		973
621	Apart from keeping your process non-blocking (which is a useful	974	Apart from keeping your process non-blocking (which is a useful
…		…
631	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	984	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
632	believe me.	985	believe me.
633		986
634	=back	987	=back
635		988
636	=head2 prepare and check - your hooks into the event loop	989	Example: dynamically allocate an C<ev_idle>, start it, and in the
		990	callback, free it. Alos, use no error checking, as usual.
637		991
		992	static void
		993	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		994	{
		995	free (w);
		996	// now do something you wanted to do when the program has
		997	// no longer asnything immediate to do.
		998	}
		999
		1000	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1001	ev_idle_init (idle_watcher, idle_cb);
		1002	ev_idle_start (loop, idle_cb);
		1003
		1004
		1005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
		1006
638	Prepare and check watchers usually (but not always) are used in	1007	Prepare and check watchers are usually (but not always) used in tandem:
639	tandom. Prepare watchers get invoked before the process blocks and check	1008	prepare watchers get invoked before the process blocks and check watchers
640	watchers afterwards.	1009	afterwards.
641		1010
642	Their main purpose is to integrate other event mechanisms into libev. This	1011	Their main purpose is to integrate other event mechanisms into libev. This
643	could be used, for example, to track variable changes, implement your own	1012	could be used, for example, to track variable changes, implement your own
644	watchers, integrate net-snmp or a coroutine library and lots more.	1013	watchers, integrate net-snmp or a coroutine library and lots more.
645		1014
646	This is done by examining in each prepare call which file descriptors need	1015	This is done by examining in each prepare call which file descriptors need
647	to be watched by the other library, registering ev_io watchers for them	1016	to be watched by the other library, registering C<ev_io> watchers for
648	and starting an ev_timer watcher for any timeouts (many libraries provide	1017	them and starting an C<ev_timer> watcher for any timeouts (many libraries
649	just this functionality). Then, in the check watcher you check for any	1018	provide just this functionality). Then, in the check watcher you check for
650	events that occured (by making your callbacks set soem flags for example)	1019	any events that occured (by checking the pending status of all watchers
651	and call back into the library.	1020	and stopping them) and call back into the library. The I/O and timer
		1021	callbacks will never actually be called (but must be valid nevertheless,
		1022	because you never know, you know?).
652		1023
653	As another example, the perl Coro module uses these hooks to integrate	1024	As another example, the Perl Coro module uses these hooks to integrate
654	coroutines into libev programs, by yielding to other active coroutines	1025	coroutines into libev programs, by yielding to other active coroutines
655	during each prepare and only letting the process block if no coroutines	1026	during each prepare and only letting the process block if no coroutines
656	are ready to run.	1027	are ready to run (it's actually more complicated: it only runs coroutines
		1028	with priority higher than or equal to the event loop and one coroutine
		1029	of lower priority, but only once, using idle watchers to keep the event
		1030	loop from blocking if lower-priority coroutines are active, thus mapping
		1031	low-priority coroutines to idle/background tasks).
657		1032
658	=over 4	1033	=over 4
659		1034
660	=item ev_prepare_init (ev_prepare *, callback)	1035	=item ev_prepare_init (ev_prepare *, callback)
661		1036
662	=item ev_check_init (ev_check *, callback)	1037	=item ev_check_init (ev_check *, callback)
663		1038
664	Initialises and configures the prepare or check watcher - they have no	1039	Initialises and configures the prepare or check watcher - they have no
665	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1040	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
666	macros, but using them is utterly, utterly pointless.	1041	macros, but using them is utterly, utterly and completely pointless.
667		1042
668	=back	1043	=back
		1044
		1045	Example: TODO.
		1046
669		1047
670	=head1 OTHER FUNCTIONS	1048	=head1 OTHER FUNCTIONS
671		1049
672	There are some other fucntions of possible interest. Described. Here. Now.	1050	There are some other functions of possible interest. Described. Here. Now.
673		1051
674	=over 4	1052	=over 4
675		1053
676	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1054	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
677		1055
678	This function combines a simple timer and an I/O watcher, calls your	1056	This function combines a simple timer and an I/O watcher, calls your
679	callback on whichever event happens first and automatically stop both	1057	callback on whichever event happens first and automatically stop both
680	watchers. This is useful if you want to wait for a single event on an fd	1058	watchers. This is useful if you want to wait for a single event on an fd
681	or timeout without havign to allocate/configure/start/stop/free one or	1059	or timeout without having to allocate/configure/start/stop/free one or
682	more watchers yourself.	1060	more watchers yourself.
683		1061
684	If C<fd> is less than 0, then no I/O watcher will be started and events is	1062	If C<fd> is less than 0, then no I/O watcher will be started and events
685	ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set	1063	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
686	will be craeted and started.	1064	C<events> set will be craeted and started.
687		1065
688	If C<timeout> is less than 0, then no timeout watcher will be	1066	If C<timeout> is less than 0, then no timeout watcher will be
689	started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat	1067	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
690	= 0) will be started.	1068	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1069	dubious value.
691		1070
692	The callback has the type C<void (cb)(int revents, void arg)> and	1071	The callback has the type C<void (cb)(int revents, void arg)> and gets
693	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1072	passed an C<revents> set like normal event callbacks (a combination of
694	EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>:	1073	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1074	value passed to C<ev_once>:
695		1075
696	static void stdin_ready (int revents, void *arg)	1076	static void stdin_ready (int revents, void *arg)
697	{	1077	{
698	if (revents & EV_TIMEOUT)	1078	if (revents & EV_TIMEOUT)
699	/* doh, nothing entered */	1079	/* doh, nothing entered */;
700	else if (revents & EV_READ)	1080	else if (revents & EV_READ)
701	/* stdin might have data for us, joy! */	1081	/* stdin might have data for us, joy! */;
702	}	1082	}
703		1083
704	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1084	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
705		1085
706	=item ev_feed_event (loop, watcher, int events)	1086	=item ev_feed_event (loop, watcher, int events)
707		1087
708	Feeds the given event set into the event loop, as if the specified event	1088	Feeds the given event set into the event loop, as if the specified event
709	has happened for the specified watcher (which must be a pointer to an	1089	had happened for the specified watcher (which must be a pointer to an
710	initialised but not necessarily active event watcher).	1090	initialised but not necessarily started event watcher).
711		1091
712	=item ev_feed_fd_event (loop, int fd, int revents)	1092	=item ev_feed_fd_event (loop, int fd, int revents)
713		1093
714	Feed an event on the given fd, as if a file descriptor backend detected it.	1094	Feed an event on the given fd, as if a file descriptor backend detected
		1095	the given events it.
715		1096
716	=item ev_feed_signal_event (loop, int signum)	1097	=item ev_feed_signal_event (loop, int signum)
717		1098
718	Feed an event as if the given signal occured (loop must be the default loop!).	1099	Feed an event as if the given signal occured (loop must be the default loop!).
719		1100
720	=back	1101	=back
721		1102
		1103
		1104	=head1 LIBEVENT EMULATION
		1105
		1106	Libev offers a compatibility emulation layer for libevent. It cannot
		1107	emulate the internals of libevent, so here are some usage hints:
		1108
		1109	=over 4
		1110
		1111	=item * Use it by including <event.h>, as usual.
		1112
		1113	=item * The following members are fully supported: ev_base, ev_callback,
		1114	ev_arg, ev_fd, ev_res, ev_events.
		1115
		1116	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1117	maintained by libev, it does not work exactly the same way as in libevent (consider
		1118	it a private API).
		1119
		1120	=item * Priorities are not currently supported. Initialising priorities
		1121	will fail and all watchers will have the same priority, even though there
		1122	is an ev_pri field.
		1123
		1124	=item * Other members are not supported.
		1125
		1126	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1127	to use the libev header file and library.
		1128
		1129	=back
		1130
		1131	=head1 C++ SUPPORT
		1132
		1133	TBD.
		1134
722	=head1 AUTHOR	1135	=head1 AUTHOR
723		1136
724	Marc Lehmann <libev@schmorp.de>.	1137	Marc Lehmann <libev@schmorp.de>.
725		1138

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Comparing libev/ev.pod (file contents): Revision 1.1 by root, Mon Nov 12 07:58:13 2007 UTC vs. Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC

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Revision 1.1 by root, Mon Nov 12 07:58:13 2007 UTC vs.
Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC