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

Comparing libev/ev.pod (file contents):
Revision 1.5 by root, Mon Nov 12 08:11:57 2007 UTC vs.
Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC

…		…
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). It also is quite	30	loop mechanism itself (idle, prepare and check watchers). It also is quite
31	fast (see a L<http://libev.schmorp.de/bench.html\|benchmark> comparing it	31	fast (see this L<benchmark\|http://libev.schmorp.de/bench.html> comparing
32	to libevent).	32	it to libevent for example).
33		33
34	=head1 CONVENTIONS	34	=head1 CONVENTIONS
35		35
36	Libev is very configurable. In this manual the default configuration	36	Libev is very configurable. In this manual the default configuration
37	will be described, which supports multiple event loops. For more info	37	will be described, which supports multiple event loops. For more info
38	about various configuraiton options please have a look at the file	38	about various configuration options please have a look at the file
39	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
40	support for multiple event loops, then all functions taking an initial	40	support for multiple event loops, then all functions taking an initial
41	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 *>)
42	will not have this argument.	42	will not have this argument.
43		43
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	44	=head1 TIME REPRESENTATION
45		45
46	Libev represents time as a single floating point number, representing the	46	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	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	48	the beginning of 1970, details are complicated, don't ask). This type is
49	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
50	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.
51		58
52	=over 4	59	=over 4
53		60
54	=item ev_tstamp ev_time ()	61	=item ev_tstamp ev_time ()
55		62
56	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.
57		66
58	=item int ev_version_major ()	67	=item int ev_version_major ()
59		68
60	=item int ev_version_minor ()	69	=item int ev_version_minor ()
61		70
…		…
63	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
64	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
65	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
66	version of the library your program was compiled against.	75	version of the library your program was compiled against.
67		76
68	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,
69	as this indicates an incompatible change. Minor versions are usually	78	as this indicates an incompatible change. Minor versions are usually
70	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
71	not a problem.	80	not a problem.
72		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
73	=item ev_set_allocator (void (cb)(void *ptr, long size))	111	=item ev_set_allocator (void (cb)(void *ptr, long size))
74		112
75	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
76	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
77	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
78	might abort or take some potentially destructive action. The default is	116	needs to be allocated, the library might abort or take some potentially
79	your system realloc function.	117	destructive action. The default is your system realloc function.
80		118
81	You could override this function in high-availability programs to, say,	119	You could override this function in high-availability programs to, say,
82	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,
83	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);
84		142
85	=item ev_set_syserr_cb (void (cb)(const char msg));	143	=item ev_set_syserr_cb (void (cb)(const char msg));
86		144
87	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
88	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
89	indicating the system call or subsystem causing the problem. If this	147	indicating the system call or subsystem causing the problem. If this
90	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
91	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
92	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
93	(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);
94		164
95	=back	165	=back
96		166
97	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	167	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
98		168
99	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
100	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
101	events, and dynamically created loops which do not.	171	events, and dynamically created loops which do not.
102		172
103	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
104	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
105	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
106	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
107	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).
108		179
109	=over 4	180	=over 4
110		181
111	=item struct ev_loop *ev_default_loop (unsigned int flags)	182	=item struct ev_loop *ev_default_loop (unsigned int flags)
112		183
113	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
114	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
115	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
116	flags).	187	flags. If that is troubling you, check C<ev_backend ()> afterwards).
117		188
118	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
119	function.	190	function.
120		191
121	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
122	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>).
123		194
124	It supports the following flags:	195	The following flags are supported:
125		196
126	=over 4	197	=over 4
127		198
128	=item EVFLAG_AUTO	199	=item C<EVFLAG_AUTO>
129		200
130	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
131	thing, believe me).	202	thing, believe me).
132		203
133	=item EVFLAG_NOENV	204	=item C<EVFLAG_NOENV>
134		205
135	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
136	at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this	207	or setgid) then libev will I<not> look at the environment variable
137	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
138	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
139	bugs.	211	around bugs.
140		212
141	=item EVMETHOD_SELECT portable select backend	213	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
142		214
143	=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.
144		220
145	=item EVMETHOD_EPOLL linux only	221	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
146		222
147	=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).
148		227
149	=item EVMETHOD_DEVPOLL solaris 8 only	228	=item C<EVBACKEND_EPOLL> (value 4, Linux)
150		229
151	=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
152		280
153	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
154	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
155	specified, any backend will do.	283	specified, most compiled-in backend will be tried, usually in reverse
		284	order of their flag values :)
156		285
157	=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);
158		301
159	=item struct ev_loop *ev_loop_new (unsigned int flags)	302	=item struct ev_loop *ev_loop_new (unsigned int flags)
160		303
161	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
162	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
163	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
164	undefined behaviour (or a failed assertion if assertions are enabled).	307	undefined behaviour (or a failed assertion if assertions are enabled).
165		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
166	=item ev_default_destroy ()	315	=item ev_default_destroy ()
167		316
168	Destroys the default loop again (frees all memory and kernel state	317	Destroys the default loop again (frees all memory and kernel state
169	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
170	any way whatsoever, although you cnanot rely on this :).	319	any way whatsoever, although you cannot rely on this :).
171		320
172	=item ev_loop_destroy (loop)	321	=item ev_loop_destroy (loop)
173		322
174	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
175	earlier call to C<ev_loop_new>.	324	earlier call to C<ev_loop_new>.
…		…
179	This function reinitialises the kernel state for backends that have	328	This function reinitialises the kernel state for backends that have
180	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
181	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
182	again makes little sense).	331	again makes little sense).
183		332
184	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
185	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
186	have to call it.	335	fork+exec, you don't have to call it.
187		336
188	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
189	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
190	quite nicely into a call to C<pthread_atfork>:	339	quite nicely into a call to C<pthread_atfork>:
191		340
192	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.
193		346
194	=item ev_loop_fork (loop)	347	=item ev_loop_fork (loop)
195		348
196	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
197	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
198	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.
199		352
200	=item unsigned int ev_method (loop)	353	=item unsigned int ev_backend (loop)
201		354
202	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
203	use.	356	use.
204		357
205	=item ev_tstamp = ev_now (loop)	358	=item ev_tstamp ev_now (loop)
206		359
207	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
208	got events and started processing them. This timestamp does not change	361	received events and started processing them. This timestamp does not
209	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
210	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
211	occuring (or more correctly, the mainloop finding out about it).	364	event occuring (or more correctly, libev finding out about it).
212		365
213	=item ev_loop (loop, int flags)	366	=item ev_loop (loop, int flags)
214		367
215	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
216	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
217	events.	370	events.
218		371
219	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
220	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.
221		380
222	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
223	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
224	case there are no events.	383	case there are no events and will return after one iteration of the loop.
225		384
226	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
227	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
228	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.
229		392
230	This flags value could be used to implement alternative looping	393	Here are the gory details of what C<ev_loop> does:
231	constructs, but the C<prepare> and C<check> watchers provide a better and	394
232	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!
233		421
234	=item ev_unloop (loop, how)	422	=item ev_unloop (loop, how)
235		423
236	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
237	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
238	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.
239	calls return.
240		428
241	=item ev_ref (loop)	429	=item ev_ref (loop)
242		430
243	=item ev_unref (loop)	431	=item ev_unref (loop)
244		432
245	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
246	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
247	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
248	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
249	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
250	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
251	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
252	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
253	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);
254		456
255	=back	457	=back
256		458
257	=head1 ANATOMY OF A WATCHER	459	=head1 ANATOMY OF A WATCHER
258		460
259	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
260	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
261	become readable, you would create an ev_io watcher for that:	463	become readable, you would create an C<ev_io> watcher for that:
262		464
263	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)
264	{	466	{
265	ev_io_stop (w);	467	ev_io_stop (w);
266	ev_unloop (loop, EVUNLOOP_ALL);	468	ev_unloop (loop, EVUNLOOP_ALL);
…		…
293	*) >>), 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
294	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	496	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
295		497
296	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
297	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
298	reinitialise it or call its set method.	500	reinitialise it or call its set macro.
299		501
300	You cna check whether 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
301	(watcher *)> macro. To see whether an event is outstanding (but the	503	(watcher *)> macro. To see whether an event is outstanding (but the
302	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
303	(watcher *)> macro.	505	(watcher *)> macro.
304		506
305	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
306	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
307	third argument.	509	third argument.
308		510
309	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
310	(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
311	are:	513	are:
312		514
313	=over 4	515	=over 4
314		516
315	=item EV_READ	517	=item C<EV_READ>
316		518
317	=item EV_WRITE	519	=item C<EV_WRITE>
318		520
319	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
320	writable.	522	writable.
321		523
322	=item EV_TIMEOUT	524	=item C<EV_TIMEOUT>
323		525
324	The ev_timer watcher has timed out.	526	The C<ev_timer> watcher has timed out.
325		527
326	=item EV_PERIODIC	528	=item C<EV_PERIODIC>
327		529
328	The ev_periodic watcher has timed out.	530	The C<ev_periodic> watcher has timed out.
329		531
330	=item EV_SIGNAL	532	=item C<EV_SIGNAL>
331		533
332	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.
333		535
334	=item EV_CHILD	536	=item C<EV_CHILD>
335		537
336	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.
337		539
338	=item EV_IDLE	540	=item C<EV_IDLE>
339		541
340	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.
341		543
342	=item EV_PREPARE	544	=item C<EV_PREPARE>
343		545
344	=item EV_CHECK	546	=item C<EV_CHECK>
345		547
346	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
347	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
348	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
349	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
350	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
351	(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
352	C<ev_loop> from blocking).	554	C<ev_loop> from blocking).
353		555
354	=item EV_ERROR	556	=item C<EV_ERROR>
355		557
356	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
357	happen because the watcher could not be properly started because libev	559	happen because the watcher could not be properly started because libev
358	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
359	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
…		…
368	=back	570	=back
369		571
370	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	572	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
371		573
372	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
373	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
374	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
375	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
376	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
377	data:	579	data:
378		580
…		…
400	=head1 WATCHER TYPES	602	=head1 WATCHER TYPES
401		603
402	This section describes each watcher in detail, but will not repeat	604	This section describes each watcher in detail, but will not repeat
403	information given in the last section.	605	information given in the last section.
404		606
		607
405	=head2 struct ev_io - is my file descriptor readable or writable	608	=head2 C<ev_io> - is this file descriptor readable or writable
406		609
407	I/O watchers check whether a file descriptor is readable or writable	610	I/O watchers check whether a file descriptor is readable or writable
408	in each iteration of the event loop (This behaviour is called	611	in each iteration of the event loop (This behaviour is called
409	level-triggering because you keep receiving events as long as the	612	level-triggering because you keep receiving events as long as the
410	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
411	act on the event and neither want to receive future events).	614	act on the event and neither want to receive future events).
412		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
413	=over 4	631	=over 4
414		632
415	=item ev_io_init (ev_io *, callback, int fd, int events)	633	=item ev_io_init (ev_io *, callback, int fd, int events)
416		634
417	=item ev_io_set (ev_io *, int fd, int events)	635	=item ev_io_set (ev_io *, int fd, int events)
418		636
419	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
420	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 \|
421	EV_WRITE> to receive the given events.	639	EV_WRITE> to receive the given events.
422		640
423	=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.
424		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
425	=head2 struct ev_timer - relative and optionally recurring timeouts	673	=head2 C<ev_timer> - relative and optionally recurring timeouts
426		674
427	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
428	given time, and optionally repeating in regular intervals after that.	676	given time, and optionally repeating in regular intervals after that.
429		677
430	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
431	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
432	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
433	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	681	detecting time jumps is hard, and some inaccuracies are unavoidable (the
434	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.
435		695
436	=over 4	696	=over 4
437		697
438	=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)
439		699
…		…
445	later, again, and again, until stopped manually.	705	later, again, and again, until stopped manually.
446		706
447	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
448	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
449	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
450	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
451	timer will not fire more than once per event loop iteration.	711	timer will not fire more than once per event loop iteration.
452		712
453	=item ev_timer_again (loop)	713	=item ev_timer_again (loop)
454		714
455	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
…		…
462		722
463	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
464	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
465	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
466	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
467	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
468	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
469	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
470	the timer, and again will automatically restart it if need be.	730	the timer, and again will automatically restart it if need be.
471		731
472	=back	732	=back
473		733
		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
474	=head2 ev_periodic - to cron or not to cron it	765	=head2 C<ev_periodic> - to cron or not to cron
475		766
476	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
477	(and unfortunately a bit complex).	768	(and unfortunately a bit complex).
478		769
479	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)
480	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
481	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
482	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 ()
483	+ 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
484	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
485	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
486	again).	777	again).
487		778
488	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
489	triggering an event on eahc midnight, local time.	780	triggering an event on eahc midnight, local time.
490		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
491	=over 4	786	=over 4
492		787
493	=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)
494		789
495	=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)
496		791
497	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
498	operation, and we will explain them from simplest to complex:	793	operation, and we will explain them from simplest to complex:
499
500		794
501	=over 4	795	=over 4
502		796
503	=item * absolute timer (interval = reschedule_cb = 0)	797	=item * absolute timer (interval = reschedule_cb = 0)
504		798
…		…
518		812
519	ev_periodic_set (&periodic, 0., 3600., 0);	813	ev_periodic_set (&periodic, 0., 3600., 0);
520		814
521	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,
522	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
523	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
524	by 3600.	818	by 3600.
525		819
526	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
527	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
528	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.
529		823
530	=item * manual reschedule mode (reschedule_cb = callback)	824	=item * manual reschedule mode (reschedule_cb = callback)
531		825
532	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
533	ignored. Instead, each time the periodic watcher gets scheduled, the	827	ignored. Instead, each time the periodic watcher gets scheduled, the
534	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
535	current time as second argument.	829	current time as second argument.
536		830
537	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,
538	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,
539	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).
540		835
541	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,
542	ev_tstamp now)>, e.g.:	837	ev_tstamp now)>, e.g.:
543		838
544	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)
545	{	840	{
546	return now + 60.;	841	return now + 60.;
…		…
549	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
550	(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
551	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
552	might be called at other times, too.	847	might be called at other times, too.
553		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
554	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
555	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
556	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
557	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).
558		857
559	=back	858	=back
560		859
561	=item ev_periodic_again (loop, ev_periodic *)	860	=item ev_periodic_again (loop, ev_periodic *)
562		861
…		…
565	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
566	program when the crontabs have changed).	865	program when the crontabs have changed).
567		866
568	=back	867	=back
569		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
570	=head2 ev_signal - signal me when a signal gets signalled	903	=head2 C<ev_signal> - signal me when a signal gets signalled
571		904
572	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
573	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
574	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
575	normal event processing, like any other event.	908	normal event processing, like any other event.
576		909
577	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
578	first watcher gets started will libev actually register a signal watcher	911	first watcher gets started will libev actually register a signal watcher
579	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
580	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
581	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
582	SIG_DFL (regardless of what it was set to before).	915	SIG_DFL (regardless of what it was set to before).
…		…
590	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
591	of the C<SIGxxx> constants).	924	of the C<SIGxxx> constants).
592		925
593	=back	926	=back
594		927
595	=head2 ev_child - wait for pid status changes	928	=head2 C<ev_child> - wait for pid status changes
596		929
597	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
598	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).
599		932
600	=over 4	933	=over 4
…		…
604	=item ev_child_set (ev_child *, int pid)	937	=item ev_child_set (ev_child *, int pid)
605		938
606	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
607	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
608	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
609	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
610	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.
611		945
612	=back	946	=back
613		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
614	=head2 ev_idle - when you've got nothing better to do	961	=head2 C<ev_idle> - when you've got nothing better to do
615		962
616	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
617	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
618	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,
619	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 -
620	stopped, that is, or your process receives more events.	968	until stopped, that is, or your process receives more events and becomes
		969	busy.
621		970
622	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
623	active, the process will not block when waiting for new events.	972	active, the process will not block when waiting for new events.
624		973
625	Apart from keeping your process non-blocking (which is a useful	974	Apart from keeping your process non-blocking (which is a useful
…		…
635	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,
636	believe me.	985	believe me.
637		986
638	=back	987	=back
639		988
640	=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.
641		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
642	Prepare and check watchers usually (but not always) are used in	1007	Prepare and check watchers are usually (but not always) used in tandem:
643	tandom. Prepare watchers get invoked before the process blocks and check	1008	prepare watchers get invoked before the process blocks and check watchers
644	watchers afterwards.	1009	afterwards.
645		1010
646	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
647	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
648	watchers, integrate net-snmp or a coroutine library and lots more.	1013	watchers, integrate net-snmp or a coroutine library and lots more.
649		1014
650	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
651	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
652	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
653	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
654	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
655	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?).
656		1023
657	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
658	coroutines into libev programs, by yielding to other active coroutines	1025	coroutines into libev programs, by yielding to other active coroutines
659	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
660	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).
661		1032
662	=over 4	1033	=over 4
663		1034
664	=item ev_prepare_init (ev_prepare *, callback)	1035	=item ev_prepare_init (ev_prepare *, callback)
665		1036
666	=item ev_check_init (ev_check *, callback)	1037	=item ev_check_init (ev_check *, callback)
667		1038
668	Initialises and configures the prepare or check watcher - they have no	1039	Initialises and configures the prepare or check watcher - they have no
669	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>
670	macros, but using them is utterly, utterly pointless.	1041	macros, but using them is utterly, utterly and completely pointless.
671		1042
672	=back	1043	=back
		1044
		1045	Example: TODO.
		1046
673		1047
674	=head1 OTHER FUNCTIONS	1048	=head1 OTHER FUNCTIONS
675		1049
676	There are some other fucntions of possible interest. Described. Here. Now.	1050	There are some other functions of possible interest. Described. Here. Now.
677		1051
678	=over 4	1052	=over 4
679		1053
680	=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)
681		1055
682	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
683	callback on whichever event happens first and automatically stop both	1057	callback on whichever event happens first and automatically stop both
684	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
685	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
686	more watchers yourself.	1060	more watchers yourself.
687		1061
688	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
689	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
690	will be craeted and started.	1064	C<events> set will be craeted and started.
691		1065
692	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
693	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
694	= 0) will be started.	1068	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1069	dubious value.
695		1070
696	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
697	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
698	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>:
699		1075
700	static void stdin_ready (int revents, void *arg)	1076	static void stdin_ready (int revents, void *arg)
701	{	1077	{
702	if (revents & EV_TIMEOUT)	1078	if (revents & EV_TIMEOUT)
703	/* doh, nothing entered */	1079	/* doh, nothing entered */;
704	else if (revents & EV_READ)	1080	else if (revents & EV_READ)
705	/* stdin might have data for us, joy! */	1081	/* stdin might have data for us, joy! */;
706	}	1082	}
707		1083
708	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1084	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
709		1085
710	=item ev_feed_event (loop, watcher, int events)	1086	=item ev_feed_event (loop, watcher, int events)
711		1087
712	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
713	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
714	initialised but not necessarily active event watcher).	1090	initialised but not necessarily started event watcher).
715		1091
716	=item ev_feed_fd_event (loop, int fd, int revents)	1092	=item ev_feed_fd_event (loop, int fd, int revents)
717		1093
718	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.
719		1096
720	=item ev_feed_signal_event (loop, int signum)	1097	=item ev_feed_signal_event (loop, int signum)
721		1098
722	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!).
723		1100
724	=back	1101	=back
725		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
726	=head1 AUTHOR	1135	=head1 AUTHOR
727		1136
728	Marc Lehmann <libev@schmorp.de>.	1137	Marc Lehmann <libev@schmorp.de>.
729		1138

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing libev/ev.pod (file contents): Revision 1.5 by root, Mon Nov 12 08:11:57 2007 UTC vs. Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.5 by root, Mon Nov 12 08:11:57 2007 UTC vs.
Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC