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

Comparing libev/ev.pod (file contents):
Revision 1.3 by root, Mon Nov 12 08:03:31 2007 UTC vs.
Revision 1.35 by root, Fri Nov 23 19:35:09 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, representing the	46	Libev represents time as a single floating point number, representing the
45	(fractional) number of seconds since the (POSIX) epoch (somewhere near	47	(fractional) number of seconds since the (POSIX) epoch (somewhere near
46	the beginning of 1970, details are complicated, don't ask). This type is	48	the beginning of 1970, details are complicated, don't ask). This type is
47	called C<ev_tstamp>, which is what you should use too. It usually aliases	49	called C<ev_tstamp>, which is what you should use too. It usually aliases
48	to the double type in C.	50	to the C<double> type in C, and when you need to do any calculations on
		51	it, you should treat it as such.
		52
		53
		54	=head1 GLOBAL FUNCTIONS
		55
		56	These functions can be called anytime, even before initialising the
		57	library in any way.
49		58
50	=over 4	59	=over 4
51		60
52	=item ev_tstamp ev_time ()	61	=item ev_tstamp ev_time ()
53		62
54	Returns the current time as libev would use it.	63	Returns the current time as libev would use it. Please note that the
		64	C<ev_now> function is usually faster and also often returns the timestamp
		65	you actually want to know.
55		66
56	=item int ev_version_major ()	67	=item int ev_version_major ()
57		68
58	=item int ev_version_minor ()	69	=item int ev_version_minor ()
59		70
…		…
61	you linked against by calling the functions C<ev_version_major> and	72	you linked against by calling the functions C<ev_version_major> and
62	C<ev_version_minor>. If you want, you can compare against the global	73	C<ev_version_minor>. If you want, you can compare against the global
63	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	74	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
64	version of the library your program was compiled against.	75	version of the library your program was compiled against.
65		76
66	Usually, its a good idea to terminate if the major versions mismatch,	77	Usually, it's a good idea to terminate if the major versions mismatch,
67	as this indicates an incompatible change. Minor versions are usually	78	as this indicates an incompatible change. Minor versions are usually
68	compatible to older versions, so a larger minor version alone is usually	79	compatible to older versions, so a larger minor version alone is usually
69	not a problem.	80	not a problem.
70		81
		82	Example: make sure we haven't accidentally been linked against the wrong
		83	version:
		84
		85	assert (("libev version mismatch",
		86	ev_version_major () == EV_VERSION_MAJOR
		87	&& ev_version_minor () >= EV_VERSION_MINOR));
		88
		89	=item unsigned int ev_supported_backends ()
		90
		91	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		92	value) compiled into this binary of libev (independent of their
		93	availability on the system you are running on). See C<ev_default_loop> for
		94	a description of the set values.
		95
		96	Example: make sure we have the epoll method, because yeah this is cool and
		97	a must have and can we have a torrent of it please!!!11
		98
		99	assert (("sorry, no epoll, no sex",
		100	ev_supported_backends () & EVBACKEND_EPOLL));
		101
		102	=item unsigned int ev_recommended_backends ()
		103
		104	Return the set of all backends compiled into this binary of libev and also
		105	recommended for this platform. This set is often smaller than the one
		106	returned by C<ev_supported_backends>, as for example kqueue is broken on
		107	most BSDs and will not be autodetected unless you explicitly request it
		108	(assuming you know what you are doing). This is the set of backends that
		109	libev will probe for if you specify no backends explicitly.
		110
		111	=item unsigned int ev_embeddable_backends ()
		112
		113	Returns the set of backends that are embeddable in other event loops. This
		114	is the theoretical, all-platform, value. To find which backends
		115	might be supported on the current system, you would need to look at
		116	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		117	recommended ones.
		118
		119	See the description of C<ev_embed> watchers for more info.
		120
71	=item ev_set_allocator (void (cb)(void *ptr, long size))	121	=item ev_set_allocator (void (cb)(void *ptr, long size))
72		122
73	Sets the allocation function to use (the prototype is similar to the	123	Sets the allocation function to use (the prototype is similar to the
74	realloc function). It is used to allocate and free memory (no surprises	124	realloc C function, the semantics are identical). It is used to allocate
75	here). If it returns zero when memory needs to be allocated, the library	125	and free memory (no surprises here). If it returns zero when memory
76	might abort or take some potentially destructive action. The default is	126	needs to be allocated, the library might abort or take some potentially
77	your system realloc function.	127	destructive action. The default is your system realloc function.
78		128
79	You could override this function in high-availability programs to, say,	129	You could override this function in high-availability programs to, say,
80	free some memory if it cannot allocate memory, to use a special allocator,	130	free some memory if it cannot allocate memory, to use a special allocator,
81	or even to sleep a while and retry until some memory is available.	131	or even to sleep a while and retry until some memory is available.
		132
		133	Example: replace the libev allocator with one that waits a bit and then
		134	retries: better than mine).
		135
		136	static void *
		137	persistent_realloc (void *ptr, long size)
		138	{
		139	for (;;)
		140	{
		141	void *newptr = realloc (ptr, size);
		142
		143	if (newptr)
		144	return newptr;
		145
		146	sleep (60);
		147	}
		148	}
		149
		150	...
		151	ev_set_allocator (persistent_realloc);
82		152
83	=item ev_set_syserr_cb (void (cb)(const char msg));	153	=item ev_set_syserr_cb (void (cb)(const char msg));
84		154
85	Set the callback function to call on a retryable syscall error (such	155	Set the callback function to call on a retryable syscall error (such
86	as failed select, poll, epoll_wait). The message is a printable string	156	as failed select, poll, epoll_wait). The message is a printable string
87	indicating the system call or subsystem causing the problem. If this	157	indicating the system call or subsystem causing the problem. If this
88	callback is set, then libev will expect it to remedy the sitution, no	158	callback is set, then libev will expect it to remedy the sitution, no
89	matter what, when it returns. That is, libev will geenrally retry the	159	matter what, when it returns. That is, libev will generally retry the
90	requested operation, or, if the condition doesn't go away, do bad stuff	160	requested operation, or, if the condition doesn't go away, do bad stuff
91	(such as abort).	161	(such as abort).
		162
		163	Example: do the same thing as libev does internally:
		164
		165	static void
		166	fatal_error (const char *msg)
		167	{
		168	perror (msg);
		169	abort ();
		170	}
		171
		172	...
		173	ev_set_syserr_cb (fatal_error);
92		174
93	=back	175	=back
94		176
95	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	177	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
96		178
97	An event loop is described by a C<struct ev_loop *>. The library knows two	179	An event loop is described by a C<struct ev_loop *>. The library knows two
98	types of such loops, the I<default> loop, which supports signals and child	180	types of such loops, the I<default> loop, which supports signals and child
99	events, and dynamically created loops which do not.	181	events, and dynamically created loops which do not.
100		182
101	If you use threads, a common model is to run the default event loop	183	If you use threads, a common model is to run the default event loop
102	in your main thread (or in a separate thrad) and for each thread you	184	in your main thread (or in a separate thread) and for each thread you
103	create, you also create another event loop. Libev itself does no lockign	185	create, you also create another event loop. Libev itself does no locking
104	whatsoever, so if you mix calls to different event loops, make sure you	186	whatsoever, so if you mix calls to the same event loop in different
105	lock (this is usually a bad idea, though, even if done right).	187	threads, make sure you lock (this is usually a bad idea, though, even if
		188	done correctly, because it's hideous and inefficient).
106		189
107	=over 4	190	=over 4
108		191
109	=item struct ev_loop *ev_default_loop (unsigned int flags)	192	=item struct ev_loop *ev_default_loop (unsigned int flags)
110		193
111	This will initialise the default event loop if it hasn't been initialised	194	This will initialise the default event loop if it hasn't been initialised
112	yet and return it. If the default loop could not be initialised, returns	195	yet and return it. If the default loop could not be initialised, returns
113	false. If it already was initialised it simply returns it (and ignores the	196	false. If it already was initialised it simply returns it (and ignores the
114	flags).	197	flags. If that is troubling you, check C<ev_backend ()> afterwards).
115		198
116	If you don't know what event loop to use, use the one returned from this	199	If you don't know what event loop to use, use the one returned from this
117	function.	200	function.
118		201
119	The flags argument can be used to specify special behaviour or specific	202	The flags argument can be used to specify special behaviour or specific
120	backends to use, and is usually specified as 0 (or EVFLAG_AUTO)	203	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
121		204
122	It supports the following flags:	205	The following flags are supported:
123		206
124	=over 4	207	=over 4
125		208
126	=item EVFLAG_AUTO	209	=item C<EVFLAG_AUTO>
127		210
128	The default flags value. Use this if you have no clue (its the right	211	The default flags value. Use this if you have no clue (it's the right
129	thing, believe me).	212	thing, believe me).
130		213
131	=item EVFLAG_NOENV	214	=item C<EVFLAG_NOENV>
132		215
133	If this flag bit is ored into the flag value then libev will I<not> look	216	If this flag bit is ored into the flag value (or the program runs setuid
134	at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this	217	or setgid) then libev will I<not> look at the environment variable
135	environment variable will override the flags completely. This is useful	218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
		219	override the flags completely if it is found in the environment. This is
136	to try out specific backends to tets their performance, or to work around	220	useful to try out specific backends to test their performance, or to work
137	bugs.	221	around bugs.
138		222
139	=item EVMETHOD_SELECT portable select backend	223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
140		224
141	=item EVMETHOD_POLL poll backend (everywhere except windows)	225	This is your standard select(2) backend. Not I<completely> standard, as
		226	libev tries to roll its own fd_set with no limits on the number of fds,
		227	but if that fails, expect a fairly low limit on the number of fds when
		228	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		229	the fastest backend for a low number of fds.
142		230
143	=item EVMETHOD_EPOLL linux only	231	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
144		232
145	=item EVMETHOD_KQUEUE some bsds only	233	And this is your standard poll(2) backend. It's more complicated than
		234	select, but handles sparse fds better and has no artificial limit on the
		235	number of fds you can use (except it will slow down considerably with a
		236	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
146		237
147	=item EVMETHOD_DEVPOLL solaris 8 only	238	=item C<EVBACKEND_EPOLL> (value 4, Linux)
148		239
149	=item EVMETHOD_PORT solaris 10 only	240	For few fds, this backend is a bit little slower than poll and select,
		241	but it scales phenomenally better. While poll and select usually scale like
		242	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		243	either O(1) or O(active_fds).
		244
		245	While stopping and starting an I/O watcher in the same iteration will
		246	result in some caching, there is still a syscall per such incident
		247	(because the fd could point to a different file description now), so its
		248	best to avoid that. Also, dup()ed file descriptors might not work very
		249	well if you register events for both fds.
		250
		251	Please note that epoll sometimes generates spurious notifications, so you
		252	need to use non-blocking I/O or other means to avoid blocking when no data
		253	(or space) is available.
		254
		255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		256
		257	Kqueue deserves special mention, as at the time of this writing, it
		258	was broken on all BSDs except NetBSD (usually it doesn't work with
		259	anything but sockets and pipes, except on Darwin, where of course its
		260	completely useless). For this reason its not being "autodetected"
		261	unless you explicitly specify it explicitly in the flags (i.e. using
		262	C<EVBACKEND_KQUEUE>).
		263
		264	It scales in the same way as the epoll backend, but the interface to the
		265	kernel is more efficient (which says nothing about its actual speed, of
		266	course). While starting and stopping an I/O watcher does not cause an
		267	extra syscall as with epoll, it still adds up to four event changes per
		268	incident, so its best to avoid that.
		269
		270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		271
		272	This is not implemented yet (and might never be).
		273
		274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		275
		276	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		277	it's really slow, but it still scales very well (O(active_fds)).
		278
		279	Please note that solaris ports can result in a lot of spurious
		280	notifications, so you need to use non-blocking I/O or other means to avoid
		281	blocking when no data (or space) is available.
		282
		283	=item C<EVBACKEND_ALL>
		284
		285	Try all backends (even potentially broken ones that wouldn't be tried
		286	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		287	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		288
		289	=back
150		290
151	If one or more of these are ored into the flags value, then only these	291	If one or more of these are ored into the flags value, then only these
152	backends will be tried (in the reverse order as given here). If one are	292	backends will be tried (in the reverse order as given here). If none are
153	specified, any backend will do.	293	specified, most compiled-in backend will be tried, usually in reverse
		294	order of their flag values :)
154		295
155	=back	296	The most typical usage is like this:
		297
		298	if (!ev_default_loop (0))
		299	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		300
		301	Restrict libev to the select and poll backends, and do not allow
		302	environment settings to be taken into account:
		303
		304	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		305
		306	Use whatever libev has to offer, but make sure that kqueue is used if
		307	available (warning, breaks stuff, best use only with your own private
		308	event loop and only if you know the OS supports your types of fds):
		309
		310	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
156		311
157	=item struct ev_loop *ev_loop_new (unsigned int flags)	312	=item struct ev_loop *ev_loop_new (unsigned int flags)
158		313
159	Similar to C<ev_default_loop>, but always creates a new event loop that is	314	Similar to C<ev_default_loop>, but always creates a new event loop that is
160	always distinct from the default loop. Unlike the default loop, it cannot	315	always distinct from the default loop. Unlike the default loop, it cannot
161	handle signal and child watchers, and attempts to do so will be greeted by	316	handle signal and child watchers, and attempts to do so will be greeted by
162	undefined behaviour (or a failed assertion if assertions are enabled).	317	undefined behaviour (or a failed assertion if assertions are enabled).
163		318
		319	Example: try to create a event loop that uses epoll and nothing else.
		320
		321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		322	if (!epoller)
		323	fatal ("no epoll found here, maybe it hides under your chair");
		324
164	=item ev_default_destroy ()	325	=item ev_default_destroy ()
165		326
166	Destroys the default loop again (frees all memory and kernel state	327	Destroys the default loop again (frees all memory and kernel state
167	etc.). This stops all registered event watchers (by not touching them in	328	etc.). This stops all registered event watchers (by not touching them in
168	any way whatsoever, although you cnanot rely on this :).	329	any way whatsoever, although you cannot rely on this :).
169		330
170	=item ev_loop_destroy (loop)	331	=item ev_loop_destroy (loop)
171		332
172	Like C<ev_default_destroy>, but destroys an event loop created by an	333	Like C<ev_default_destroy>, but destroys an event loop created by an
173	earlier call to C<ev_loop_new>.	334	earlier call to C<ev_loop_new>.
…		…
177	This function reinitialises the kernel state for backends that have	338	This function reinitialises the kernel state for backends that have
178	one. Despite the name, you can call it anytime, but it makes most sense	339	one. Despite the name, you can call it anytime, but it makes most sense
179	after forking, in either the parent or child process (or both, but that	340	after forking, in either the parent or child process (or both, but that
180	again makes little sense).	341	again makes little sense).
181		342
182	You I<must> call this function after forking if and only if you want to	343	You I<must> call this function in the child process after forking if and
183	use the event library in both processes. If you just fork+exec, you don't	344	only if you want to use the event library in both processes. If you just
184	have to call it.	345	fork+exec, you don't have to call it.
185		346
186	The function itself is quite fast and its usually not a problem to call	347	The function itself is quite fast and it's usually not a problem to call
187	it just in case after a fork. To make this easy, the function will fit in	348	it just in case after a fork. To make this easy, the function will fit in
188	quite nicely into a call to C<pthread_atfork>:	349	quite nicely into a call to C<pthread_atfork>:
189		350
190	pthread_atfork (0, 0, ev_default_fork);	351	pthread_atfork (0, 0, ev_default_fork);
		352
		353	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		354	without calling this function, so if you force one of those backends you
		355	do not need to care.
191		356
192	=item ev_loop_fork (loop)	357	=item ev_loop_fork (loop)
193		358
194	Like C<ev_default_fork>, but acts on an event loop created by	359	Like C<ev_default_fork>, but acts on an event loop created by
195	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	360	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
196	after fork, and how you do this is entirely your own problem.	361	after fork, and how you do this is entirely your own problem.
197		362
198	=item unsigned int ev_method (loop)	363	=item unsigned int ev_backend (loop)
199		364
200	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	365	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
201	use.	366	use.
202		367
203	=item ev_tstamp = ev_now (loop)	368	=item ev_tstamp ev_now (loop)
204		369
205	Returns the current "event loop time", which is the time the event loop	370	Returns the current "event loop time", which is the time the event loop
206	got events and started processing them. This timestamp does not change	371	received events and started processing them. This timestamp does not
207	as long as callbacks are being processed, and this is also the base time	372	change as long as callbacks are being processed, and this is also the base
208	used for relative timers. You can treat it as the timestamp of the event	373	time used for relative timers. You can treat it as the timestamp of the
209	occuring (or more correctly, the mainloop finding out about it).	374	event occuring (or more correctly, libev finding out about it).
210		375
211	=item ev_loop (loop, int flags)	376	=item ev_loop (loop, int flags)
212		377
213	Finally, this is it, the event handler. This function usually is called	378	Finally, this is it, the event handler. This function usually is called
214	after you initialised all your watchers and you want to start handling	379	after you initialised all your watchers and you want to start handling
215	events.	380	events.
216		381
217	If the flags argument is specified as 0, it will not return until either	382	If the flags argument is specified as C<0>, it will not return until
218	no event watchers are active anymore or C<ev_unloop> was called.	383	either no event watchers are active anymore or C<ev_unloop> was called.
		384
		385	Please note that an explicit C<ev_unloop> is usually better than
		386	relying on all watchers to be stopped when deciding when a program has
		387	finished (especially in interactive programs), but having a program that
		388	automatically loops as long as it has to and no longer by virtue of
		389	relying on its watchers stopping correctly is a thing of beauty.
219		390
220	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	391	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
221	those events and any outstanding ones, but will not block your process in	392	those events and any outstanding ones, but will not block your process in
222	case there are no events.	393	case there are no events and will return after one iteration of the loop.
223		394
224	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	395	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
225	neccessary) and will handle those and any outstanding ones. It will block	396	neccessary) and will handle those and any outstanding ones. It will block
226	your process until at least one new event arrives.	397	your process until at least one new event arrives, and will return after
		398	one iteration of the loop. This is useful if you are waiting for some
		399	external event in conjunction with something not expressible using other
		400	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		401	usually a better approach for this kind of thing.
227		402
228	This flags value could be used to implement alternative looping	403	Here are the gory details of what C<ev_loop> does:
229	constructs, but the C<prepare> and C<check> watchers provide a better and	404
230	more generic mechanism.	405	* If there are no active watchers (reference count is zero), return.
		406	- Queue prepare watchers and then call all outstanding watchers.
		407	- If we have been forked, recreate the kernel state.
		408	- Update the kernel state with all outstanding changes.
		409	- Update the "event loop time".
		410	- Calculate for how long to block.
		411	- Block the process, waiting for any events.
		412	- Queue all outstanding I/O (fd) events.
		413	- Update the "event loop time" and do time jump handling.
		414	- Queue all outstanding timers.
		415	- Queue all outstanding periodics.
		416	- If no events are pending now, queue all idle watchers.
		417	- Queue all check watchers.
		418	- Call all queued watchers in reverse order (i.e. check watchers first).
		419	Signals and child watchers are implemented as I/O watchers, and will
		420	be handled here by queueing them when their watcher gets executed.
		421	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		422	were used, return, otherwise continue with step *.
		423
		424	Example: queue some jobs and then loop until no events are outsanding
		425	anymore.
		426
		427	... queue jobs here, make sure they register event watchers as long
		428	... as they still have work to do (even an idle watcher will do..)
		429	ev_loop (my_loop, 0);
		430	... jobs done. yeah!
231		431
232	=item ev_unloop (loop, how)	432	=item ev_unloop (loop, how)
233		433
234	Can be used to make a call to C<ev_loop> return early. The C<how> argument	434	Can be used to make a call to C<ev_loop> return early (but only after it
		435	has processed all outstanding events). The C<how> argument must be either
235	must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop>	436	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
236	call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop>	437	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
237	calls return.
238		438
239	=item ev_ref (loop)	439	=item ev_ref (loop)
240		440
241	=item ev_unref (loop)	441	=item ev_unref (loop)
242		442
243	Ref/unref can be used to add or remove a refcount on the event loop: Every	443	Ref/unref can be used to add or remove a reference count on the event
244	watcher keeps one reference. If you have a long-runing watcher you never	444	loop: Every watcher keeps one reference, and as long as the reference
245	unregister that should not keep ev_loop from running, ev_unref() after	445	count is nonzero, C<ev_loop> will not return on its own. If you have
246	starting, and ev_ref() before stopping it. Libev itself uses this for	446	a watcher you never unregister that should not keep C<ev_loop> from
247	example for its internal signal pipe: It is not visible to you as a user	447	returning, ev_unref() after starting, and ev_ref() before stopping it. For
248	and should not keep C<ev_loop> from exiting if the work is done. It is	448	example, libev itself uses this for its internal signal pipe: It is not
249	also an excellent way to do this for generic recurring timers or from	449	visible to the libev user and should not keep C<ev_loop> from exiting if
250	within third-party libraries. Just remember to unref after start and ref	450	no event watchers registered by it are active. It is also an excellent
251	before stop.	451	way to do this for generic recurring timers or from within third-party
		452	libraries. Just remember to I<unref after start> and I<ref before stop>.
		453
		454	Example: create a signal watcher, but keep it from keeping C<ev_loop>
		455	running when nothing else is active.
		456
		457	struct dv_signal exitsig;
		458	ev_signal_init (&exitsig, sig_cb, SIGINT);
		459	ev_signal_start (myloop, &exitsig);
		460	evf_unref (myloop);
		461
		462	Example: for some weird reason, unregister the above signal handler again.
		463
		464	ev_ref (myloop);
		465	ev_signal_stop (myloop, &exitsig);
252		466
253	=back	467	=back
254		468
255	=head1 ANATOMY OF A WATCHER	469	=head1 ANATOMY OF A WATCHER
256		470
257	A watcher is a structure that you create and register to record your	471	A watcher is a structure that you create and register to record your
258	interest in some event. For instance, if you want to wait for STDIN to	472	interest in some event. For instance, if you want to wait for STDIN to
259	become readable, you would create an ev_io watcher for that:	473	become readable, you would create an C<ev_io> watcher for that:
260		474
261	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	475	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)
262	{	476	{
263	ev_io_stop (w);	477	ev_io_stop (w);
264	ev_unloop (loop, EVUNLOOP_ALL);	478	ev_unloop (loop, EVUNLOOP_ALL);
…		…
291	*) >>), and you can stop watching for events at any time by calling the	505	*) >>), and you can stop watching for events at any time by calling the
292	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	506	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
293		507
294	As long as your watcher is active (has been started but not stopped) you	508	As long as your watcher is active (has been started but not stopped) you
295	must not touch the values stored in it. Most specifically you must never	509	must not touch the values stored in it. Most specifically you must never
296	reinitialise it or call its set method.	510	reinitialise it or call its set macro.
297		511
298	You cna check wether an event is active by calling the C<ev_is_active	512	You can check whether an event is active by calling the C<ev_is_active
299	(watcher *)> macro. To see wether an event is outstanding (but the	513	(watcher *)> macro. To see whether an event is outstanding (but the
300	callback for it has not been called yet) you cna use the C<ev_is_pending	514	callback for it has not been called yet) you can use the C<ev_is_pending
301	(watcher *)> macro.	515	(watcher *)> macro.
302		516
303	Each and every callback receives the event loop pointer as first, the	517	Each and every callback receives the event loop pointer as first, the
304	registered watcher structure as second, and a bitset of received events as	518	registered watcher structure as second, and a bitset of received events as
305	third argument.	519	third argument.
306		520
307	The rceeived events usually include a single bit per event type received	521	The received events usually include a single bit per event type received
308	(you can receive multiple events at the same time). The possible bit masks	522	(you can receive multiple events at the same time). The possible bit masks
309	are:	523	are:
310		524
311	=over 4	525	=over 4
312		526
313	=item EV_READ	527	=item C<EV_READ>
314		528
315	=item EV_WRITE	529	=item C<EV_WRITE>
316		530
317	The file descriptor in the ev_io watcher has become readable and/or	531	The file descriptor in the C<ev_io> watcher has become readable and/or
318	writable.	532	writable.
319		533
320	=item EV_TIMEOUT	534	=item C<EV_TIMEOUT>
321		535
322	The ev_timer watcher has timed out.	536	The C<ev_timer> watcher has timed out.
323		537
324	=item EV_PERIODIC	538	=item C<EV_PERIODIC>
325		539
326	The ev_periodic watcher has timed out.	540	The C<ev_periodic> watcher has timed out.
327		541
328	=item EV_SIGNAL	542	=item C<EV_SIGNAL>
329		543
330	The signal specified in the ev_signal watcher has been received by a thread.	544	The signal specified in the C<ev_signal> watcher has been received by a thread.
331		545
332	=item EV_CHILD	546	=item C<EV_CHILD>
333		547
334	The pid specified in the ev_child watcher has received a status change.	548	The pid specified in the C<ev_child> watcher has received a status change.
335		549
336	=item EV_IDLE	550	=item C<EV_IDLE>
337		551
338	The ev_idle watcher has determined that you have nothing better to do.	552	The C<ev_idle> watcher has determined that you have nothing better to do.
339		553
340	=item EV_PREPARE	554	=item C<EV_PREPARE>
341		555
342	=item EV_CHECK	556	=item C<EV_CHECK>
343		557
344	All ev_prepare watchers are invoked just I<before> C<ev_loop> starts	558	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
345	to gather new events, and all ev_check watchers are invoked just after	559	to gather new events, and all C<ev_check> watchers are invoked just after
346	C<ev_loop> has gathered them, but before it invokes any callbacks for any	560	C<ev_loop> has gathered them, but before it invokes any callbacks for any
347	received events. Callbacks of both watcher types can start and stop as	561	received events. Callbacks of both watcher types can start and stop as
348	many watchers as they want, and all of them will be taken into account	562	many watchers as they want, and all of them will be taken into account
349	(for example, a ev_prepare watcher might start an idle watcher to keep	563	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
350	C<ev_loop> from blocking).	564	C<ev_loop> from blocking).
351		565
352	=item EV_ERROR	566	=item C<EV_ERROR>
353		567
354	An unspecified error has occured, the watcher has been stopped. This might	568	An unspecified error has occured, the watcher has been stopped. This might
355	happen because the watcher could not be properly started because libev	569	happen because the watcher could not be properly started because libev
356	ran out of memory, a file descriptor was found to be closed or any other	570	ran out of memory, a file descriptor was found to be closed or any other
357	problem. You best act on it by reporting the problem and somehow coping	571	problem. You best act on it by reporting the problem and somehow coping
…		…
366	=back	580	=back
367		581
368	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	582	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
369		583
370	Each watcher has, by default, a member C<void *data> that you can change	584	Each watcher has, by default, a member C<void *data> that you can change
371	and read at any time, libev will completely ignore it. This cna be used	585	and read at any time, libev will completely ignore it. This can be used
372	to associate arbitrary data with your watcher. If you need more data and	586	to associate arbitrary data with your watcher. If you need more data and
373	don't want to allocate memory and store a pointer to it in that data	587	don't want to allocate memory and store a pointer to it in that data
374	member, you can also "subclass" the watcher type and provide your own	588	member, you can also "subclass" the watcher type and provide your own
375	data:	589	data:
376		590
…		…
398	=head1 WATCHER TYPES	612	=head1 WATCHER TYPES
399		613
400	This section describes each watcher in detail, but will not repeat	614	This section describes each watcher in detail, but will not repeat
401	information given in the last section.	615	information given in the last section.
402		616
		617
403	=head2 struct ev_io - is my file descriptor readable or writable	618	=head2 C<ev_io> - is this file descriptor readable or writable
404		619
405	I/O watchers check wether a file descriptor is readable or writable	620	I/O watchers check whether a file descriptor is readable or writable
406	in each iteration of the event loop (This behaviour is called	621	in each iteration of the event loop (This behaviour is called
407	level-triggering because you keep receiving events as long as the	622	level-triggering because you keep receiving events as long as the
408	condition persists. Remember you cna stop the watcher if you don't want to	623	condition persists. Remember you can stop the watcher if you don't want to
409	act on the event and neither want to receive future events).	624	act on the event and neither want to receive future events).
410		625
		626	In general you can register as many read and/or write event watchers per
		627	fd as you want (as long as you don't confuse yourself). Setting all file
		628	descriptors to non-blocking mode is also usually a good idea (but not
		629	required if you know what you are doing).
		630
		631	You have to be careful with dup'ed file descriptors, though. Some backends
		632	(the linux epoll backend is a notable example) cannot handle dup'ed file
		633	descriptors correctly if you register interest in two or more fds pointing
		634	to the same underlying file/socket etc. description (that is, they share
		635	the same underlying "file open").
		636
		637	If you must do this, then force the use of a known-to-be-good backend
		638	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
		639	C<EVBACKEND_POLL>).
		640
411	=over 4	641	=over 4
412		642
413	=item ev_io_init (ev_io *, callback, int fd, int events)	643	=item ev_io_init (ev_io *, callback, int fd, int events)
414		644
415	=item ev_io_set (ev_io *, int fd, int events)	645	=item ev_io_set (ev_io *, int fd, int events)
416		646
417	Configures an ev_io watcher. The fd is the file descriptor to rceeive	647	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive
418	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|	648	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|
419	EV_WRITE> to receive the given events.	649	EV_WRITE> to receive the given events.
420		650
421	=back	651	Please note that most of the more scalable backend mechanisms (for example
		652	epoll and solaris ports) can result in spurious readyness notifications
		653	for file descriptors, so you practically need to use non-blocking I/O (and
		654	treat callback invocation as hint only), or retest separately with a safe
		655	interface before doing I/O (XLib can do this), or force the use of either
		656	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this
		657	problem. Also note that it is quite easy to have your callback invoked
		658	when the readyness condition is no longer valid even when employing
		659	typical ways of handling events, so its a good idea to use non-blocking
		660	I/O unconditionally.
422		661
		662	=back
		663
		664	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
		665	readable, but only once. Since it is likely line-buffered, you could
		666	attempt to read a whole line in the callback:
		667
		668	static void
		669	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		670	{
		671	ev_io_stop (loop, w);
		672	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		673	}
		674
		675	...
		676	struct ev_loop *loop = ev_default_init (0);
		677	struct ev_io stdin_readable;
		678	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		679	ev_io_start (loop, &stdin_readable);
		680	ev_loop (loop, 0);
		681
		682
423	=head2 struct ev_timer - relative and optionally recurring timeouts	683	=head2 C<ev_timer> - relative and optionally recurring timeouts
424		684
425	Timer watchers are simple relative timers that generate an event after a	685	Timer watchers are simple relative timers that generate an event after a
426	given time, and optionally repeating in regular intervals after that.	686	given time, and optionally repeating in regular intervals after that.
427		687
428	The timers are based on real time, that is, if you register an event that	688	The timers are based on real time, that is, if you register an event that
429	times out after an hour and youreset your system clock to last years	689	times out after an hour and you reset your system clock to last years
430	time, it will still time out after (roughly) and hour. "Roughly" because	690	time, it will still time out after (roughly) and hour. "Roughly" because
431	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	691	detecting time jumps is hard, and some inaccuracies are unavoidable (the
432	monotonic clock option helps a lot here).	692	monotonic clock option helps a lot here).
		693
		694	The relative timeouts are calculated relative to the C<ev_now ()>
		695	time. This is usually the right thing as this timestamp refers to the time
		696	of the event triggering whatever timeout you are modifying/starting. If
		697	you suspect event processing to be delayed and you I<need> to base the timeout
		698	on the current time, use something like this to adjust for this:
		699
		700	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		701
		702	The callback is guarenteed to be invoked only when its timeout has passed,
		703	but if multiple timers become ready during the same loop iteration then
		704	order of execution is undefined.
433		705
434	=over 4	706	=over 4
435		707
436	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	708	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
437		709
…		…
443	later, again, and again, until stopped manually.	715	later, again, and again, until stopped manually.
444		716
445	The timer itself will do a best-effort at avoiding drift, that is, if you	717	The timer itself will do a best-effort at avoiding drift, that is, if you
446	configure a timer to trigger every 10 seconds, then it will trigger at	718	configure a timer to trigger every 10 seconds, then it will trigger at
447	exactly 10 second intervals. If, however, your program cannot keep up with	719	exactly 10 second intervals. If, however, your program cannot keep up with
448	the timer (ecause it takes longer than those 10 seconds to do stuff) the	720	the timer (because it takes longer than those 10 seconds to do stuff) the
449	timer will not fire more than once per event loop iteration.	721	timer will not fire more than once per event loop iteration.
450		722
451	=item ev_timer_again (loop)	723	=item ev_timer_again (loop)
452		724
453	This will act as if the timer timed out and restart it again if it is	725	This will act as if the timer timed out and restart it again if it is
…		…
460		732
461	This sounds a bit complicated, but here is a useful and typical	733	This sounds a bit complicated, but here is a useful and typical
462	example: Imagine you have a tcp connection and you want a so-called idle	734	example: Imagine you have a tcp connection and you want a so-called idle
463	timeout, that is, you want to be called when there have been, say, 60	735	timeout, that is, you want to be called when there have been, say, 60
464	seconds of inactivity on the socket. The easiest way to do this is to	736	seconds of inactivity on the socket. The easiest way to do this is to
465	configure an ev_timer with after=repeat=60 and calling ev_timer_again each	737	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each
466	time you successfully read or write some data. If you go into an idle	738	time you successfully read or write some data. If you go into an idle
467	state where you do not expect data to travel on the socket, you can stop	739	state where you do not expect data to travel on the socket, you can stop
468	the timer, and again will automatically restart it if need be.	740	the timer, and again will automatically restart it if need be.
469		741
470	=back	742	=back
471		743
		744	Example: create a timer that fires after 60 seconds.
		745
		746	static void
		747	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		748	{
		749	.. one minute over, w is actually stopped right here
		750	}
		751
		752	struct ev_timer mytimer;
		753	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		754	ev_timer_start (loop, &mytimer);
		755
		756	Example: create a timeout timer that times out after 10 seconds of
		757	inactivity.
		758
		759	static void
		760	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		761	{
		762	.. ten seconds without any activity
		763	}
		764
		765	struct ev_timer mytimer;
		766	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		767	ev_timer_again (&mytimer); /* start timer */
		768	ev_loop (loop, 0);
		769
		770	// and in some piece of code that gets executed on any "activity":
		771	// reset the timeout to start ticking again at 10 seconds
		772	ev_timer_again (&mytimer);
		773
		774
472	=head2 ev_periodic - to cron or not to cron it	775	=head2 C<ev_periodic> - to cron or not to cron
473		776
474	Periodic watchers are also timers of a kind, but they are very versatile	777	Periodic watchers are also timers of a kind, but they are very versatile
475	(and unfortunately a bit complex).	778	(and unfortunately a bit complex).
476		779
477	Unlike ev_timer's, they are not based on real time (or relative time)	780	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
478	but on wallclock time (absolute time). You can tell a periodic watcher	781	but on wallclock time (absolute time). You can tell a periodic watcher
479	to trigger "at" some specific point in time. For example, if you tell a	782	to trigger "at" some specific point in time. For example, if you tell a
480	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	783	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
481	+ 10.>) and then reset your system clock to the last year, then it will	784	+ 10.>) and then reset your system clock to the last year, then it will
482	take a year to trigger the event (unlike an ev_timer, which would trigger	785	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
483	roughly 10 seconds later and of course not if you reset your system time	786	roughly 10 seconds later and of course not if you reset your system time
484	again).	787	again).
485		788
486	They can also be used to implement vastly more complex timers, such as	789	They can also be used to implement vastly more complex timers, such as
487	triggering an event on eahc midnight, local time.	790	triggering an event on eahc midnight, local time.
488		791
		792	As with timers, the callback is guarenteed to be invoked only when the
		793	time (C<at>) has been passed, but if multiple periodic timers become ready
		794	during the same loop iteration then order of execution is undefined.
		795
489	=over 4	796	=over 4
490		797
491	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	798	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
492		799
493	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	800	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
494		801
495	Lots of arguments, lets sort it out... There are basically three modes of	802	Lots of arguments, lets sort it out... There are basically three modes of
496	operation, and we will explain them from simplest to complex:	803	operation, and we will explain them from simplest to complex:
497
498		804
499	=over 4	805	=over 4
500		806
501	=item * absolute timer (interval = reschedule_cb = 0)	807	=item * absolute timer (interval = reschedule_cb = 0)
502		808
…		…
516		822
517	ev_periodic_set (&periodic, 0., 3600., 0);	823	ev_periodic_set (&periodic, 0., 3600., 0);
518		824
519	This doesn't mean there will always be 3600 seconds in between triggers,	825	This doesn't mean there will always be 3600 seconds in between triggers,
520	but only that the the callback will be called when the system time shows a	826	but only that the the callback will be called when the system time shows a
521	full hour (UTC), or more correct, when the system time is evenly divisible	827	full hour (UTC), or more correctly, when the system time is evenly divisible
522	by 3600.	828	by 3600.
523		829
524	Another way to think about it (for the mathematically inclined) is that	830	Another way to think about it (for the mathematically inclined) is that
525	ev_periodic will try to run the callback in this mode at the next possible	831	C<ev_periodic> will try to run the callback in this mode at the next possible
526	time where C<time = at (mod interval)>, regardless of any time jumps.	832	time where C<time = at (mod interval)>, regardless of any time jumps.
527		833
528	=item * manual reschedule mode (reschedule_cb = callback)	834	=item * manual reschedule mode (reschedule_cb = callback)
529		835
530	In this mode the values for C<interval> and C<at> are both being	836	In this mode the values for C<interval> and C<at> are both being
531	ignored. Instead, each time the periodic watcher gets scheduled, the	837	ignored. Instead, each time the periodic watcher gets scheduled, the
532	reschedule callback will be called with the watcher as first, and the	838	reschedule callback will be called with the watcher as first, and the
533	current time as second argument.	839	current time as second argument.
534		840
535	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	841	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
536	periodic watcher, ever, or make any event loop modificstions>. If you need	842	ever, or make any event loop modifications>. If you need to stop it,
537	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.	843	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		844	starting a prepare watcher).
538		845
539	Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	846	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
540	ev_tstamp now)>, e.g.:	847	ev_tstamp now)>, e.g.:
541		848
542	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	849	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
543	{	850	{
544	return now + 60.;	851	return now + 60.;
…		…
547	It must return the next time to trigger, based on the passed time value	854	It must return the next time to trigger, based on the passed time value
548	(that is, the lowest time value larger than to the second argument). It	855	(that is, the lowest time value larger than to the second argument). It
549	will usually be called just before the callback will be triggered, but	856	will usually be called just before the callback will be triggered, but
550	might be called at other times, too.	857	might be called at other times, too.
551		858
		859	NOTE: I<< This callback must always return a time that is later than the
		860	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		861
552	This can be used to create very complex timers, such as a timer that	862	This can be used to create very complex timers, such as a timer that
553	triggers on each midnight, local time. To do this, you would calculate the	863	triggers on each midnight, local time. To do this, you would calculate the
554	next midnight after C<now> and return the timestamp value for this. How you do this	864	next midnight after C<now> and return the timestamp value for this. How
555	is, again, up to you (but it is not trivial).	865	you do this is, again, up to you (but it is not trivial, which is the main
		866	reason I omitted it as an example).
556		867
557	=back	868	=back
558		869
559	=item ev_periodic_again (loop, ev_periodic *)	870	=item ev_periodic_again (loop, ev_periodic *)
560		871
…		…
563	a different time than the last time it was called (e.g. in a crond like	874	a different time than the last time it was called (e.g. in a crond like
564	program when the crontabs have changed).	875	program when the crontabs have changed).
565		876
566	=back	877	=back
567		878
		879	Example: call a callback every hour, or, more precisely, whenever the
		880	system clock is divisible by 3600. The callback invocation times have
		881	potentially a lot of jittering, but good long-term stability.
		882
		883	static void
		884	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		885	{
		886	... its now a full hour (UTC, or TAI or whatever your clock follows)
		887	}
		888
		889	struct ev_periodic hourly_tick;
		890	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		891	ev_periodic_start (loop, &hourly_tick);
		892
		893	Example: the same as above, but use a reschedule callback to do it:
		894
		895	#include <math.h>
		896
		897	static ev_tstamp
		898	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		899	{
		900	return fmod (now, 3600.) + 3600.;
		901	}
		902
		903	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		904
		905	Example: call a callback every hour, starting now:
		906
		907	struct ev_periodic hourly_tick;
		908	ev_periodic_init (&hourly_tick, clock_cb,
		909	fmod (ev_now (loop), 3600.), 3600., 0);
		910	ev_periodic_start (loop, &hourly_tick);
		911
		912
568	=head2 ev_signal - signal me when a signal gets signalled	913	=head2 C<ev_signal> - signal me when a signal gets signalled
569		914
570	Signal watchers will trigger an event when the process receives a specific	915	Signal watchers will trigger an event when the process receives a specific
571	signal one or more times. Even though signals are very asynchronous, libev	916	signal one or more times. Even though signals are very asynchronous, libev
572	will try its best to deliver signals synchronously, i.e. as part of the	917	will try it's best to deliver signals synchronously, i.e. as part of the
573	normal event processing, like any other event.	918	normal event processing, like any other event.
574		919
575	You cna configure as many watchers as you like per signal. Only when the	920	You can configure as many watchers as you like per signal. Only when the
576	first watcher gets started will libev actually register a signal watcher	921	first watcher gets started will libev actually register a signal watcher
577	with the kernel (thus it coexists with your own signal handlers as long	922	with the kernel (thus it coexists with your own signal handlers as long
578	as you don't register any with libev). Similarly, when the last signal	923	as you don't register any with libev). Similarly, when the last signal
579	watcher for a signal is stopped libev will reset the signal handler to	924	watcher for a signal is stopped libev will reset the signal handler to
580	SIG_DFL (regardless of what it was set to before).	925	SIG_DFL (regardless of what it was set to before).
…		…
588	Configures the watcher to trigger on the given signal number (usually one	933	Configures the watcher to trigger on the given signal number (usually one
589	of the C<SIGxxx> constants).	934	of the C<SIGxxx> constants).
590		935
591	=back	936	=back
592		937
		938
593	=head2 ev_child - wait for pid status changes	939	=head2 C<ev_child> - wait for pid status changes
594		940
595	Child watchers trigger when your process receives a SIGCHLD in response to	941	Child watchers trigger when your process receives a SIGCHLD in response to
596	some child status changes (most typically when a child of yours dies).	942	some child status changes (most typically when a child of yours dies).
597		943
598	=over 4	944	=over 4
…		…
602	=item ev_child_set (ev_child *, int pid)	948	=item ev_child_set (ev_child *, int pid)
603		949
604	Configures the watcher to wait for status changes of process C<pid> (or	950	Configures the watcher to wait for status changes of process C<pid> (or
605	I<any> process if C<pid> is specified as C<0>). The callback can look	951	I<any> process if C<pid> is specified as C<0>). The callback can look
606	at the C<rstatus> member of the C<ev_child> watcher structure to see	952	at the C<rstatus> member of the C<ev_child> watcher structure to see
607	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	953	the status word (use the macros from C<sys/wait.h> and see your systems
608	contains the pid of the process causing the status change.	954	C<waitpid> documentation). The C<rpid> member contains the pid of the
		955	process causing the status change.
609		956
610	=back	957	=back
611		958
		959	Example: try to exit cleanly on SIGINT and SIGTERM.
		960
		961	static void
		962	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		963	{
		964	ev_unloop (loop, EVUNLOOP_ALL);
		965	}
		966
		967	struct ev_signal signal_watcher;
		968	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		969	ev_signal_start (loop, &sigint_cb);
		970
		971
612	=head2 ev_idle - when you've got nothing better to do	972	=head2 C<ev_idle> - when you've got nothing better to do
613		973
614	Idle watchers trigger events when there are no other I/O or timer (or	974	Idle watchers trigger events when there are no other events are pending
615	periodic) events pending. That is, as long as your process is busy	975	(prepare, check and other idle watchers do not count). That is, as long
616	handling sockets or timeouts it will not be called. But when your process	976	as your process is busy handling sockets or timeouts (or even signals,
617	is idle all idle watchers are being called again and again - until	977	imagine) it will not be triggered. But when your process is idle all idle
		978	watchers are being called again and again, once per event loop iteration -
618	stopped, that is, or your process receives more events.	979	until stopped, that is, or your process receives more events and becomes
		980	busy.
619		981
620	The most noteworthy effect is that as long as any idle watchers are	982	The most noteworthy effect is that as long as any idle watchers are
621	active, the process will not block when waiting for new events.	983	active, the process will not block when waiting for new events.
622		984
623	Apart from keeping your process non-blocking (which is a useful	985	Apart from keeping your process non-blocking (which is a useful
…		…
633	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	995	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
634	believe me.	996	believe me.
635		997
636	=back	998	=back
637		999
638	=head2 prepare and check - your hooks into the event loop	1000	Example: dynamically allocate an C<ev_idle>, start it, and in the
		1001	callback, free it. Alos, use no error checking, as usual.
639		1002
		1003	static void
		1004	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1005	{
		1006	free (w);
		1007	// now do something you wanted to do when the program has
		1008	// no longer asnything immediate to do.
		1009	}
		1010
		1011	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1012	ev_idle_init (idle_watcher, idle_cb);
		1013	ev_idle_start (loop, idle_cb);
		1014
		1015
		1016	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
		1017
640	Prepare and check watchers usually (but not always) are used in	1018	Prepare and check watchers are usually (but not always) used in tandem:
641	tandom. Prepare watchers get invoked before the process blocks and check	1019	prepare watchers get invoked before the process blocks and check watchers
642	watchers afterwards.	1020	afterwards.
643		1021
644	Their main purpose is to integrate other event mechanisms into libev. This	1022	Their main purpose is to integrate other event mechanisms into libev and
645	could be used, for example, to track variable changes, implement your own	1023	their use is somewhat advanced. This could be used, for example, to track
646	watchers, integrate net-snmp or a coroutine library and lots more.	1024	variable changes, implement your own watchers, integrate net-snmp or a
		1025	coroutine library and lots more.
647		1026
648	This is done by examining in each prepare call which file descriptors need	1027	This is done by examining in each prepare call which file descriptors need
649	to be watched by the other library, registering ev_io watchers for them	1028	to be watched by the other library, registering C<ev_io> watchers for
650	and starting an ev_timer watcher for any timeouts (many libraries provide	1029	them and starting an C<ev_timer> watcher for any timeouts (many libraries
651	just this functionality). Then, in the check watcher you check for any	1030	provide just this functionality). Then, in the check watcher you check for
652	events that occured (by making your callbacks set soem flags for example)	1031	any events that occured (by checking the pending status of all watchers
653	and call back into the library.	1032	and stopping them) and call back into the library. The I/O and timer
		1033	callbacks will never actually be called (but must be valid nevertheless,
		1034	because you never know, you know?).
654		1035
655	As another example, the perl Coro module uses these hooks to integrate	1036	As another example, the Perl Coro module uses these hooks to integrate
656	coroutines into libev programs, by yielding to other active coroutines	1037	coroutines into libev programs, by yielding to other active coroutines
657	during each prepare and only letting the process block if no coroutines	1038	during each prepare and only letting the process block if no coroutines
658	are ready to run.	1039	are ready to run (it's actually more complicated: it only runs coroutines
		1040	with priority higher than or equal to the event loop and one coroutine
		1041	of lower priority, but only once, using idle watchers to keep the event
		1042	loop from blocking if lower-priority coroutines are active, thus mapping
		1043	low-priority coroutines to idle/background tasks).
659		1044
660	=over 4	1045	=over 4
661		1046
662	=item ev_prepare_init (ev_prepare *, callback)	1047	=item ev_prepare_init (ev_prepare *, callback)
663		1048
664	=item ev_check_init (ev_check *, callback)	1049	=item ev_check_init (ev_check *, callback)
665		1050
666	Initialises and configures the prepare or check watcher - they have no	1051	Initialises and configures the prepare or check watcher - they have no
667	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1052	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
668	macros, but using them is utterly, utterly pointless.	1053	macros, but using them is utterly, utterly and completely pointless.
669		1054
670	=back	1055	=back
		1056
		1057	Example: TODO.
		1058
		1059
		1060	=head2 C<ev_embed> - when one backend isn't enough
		1061
		1062	This is a rather advanced watcher type that lets you embed one event loop
		1063	into another.
		1064
		1065	There are primarily two reasons you would want that: work around bugs and
		1066	prioritise I/O.
		1067
		1068	As an example for a bug workaround, the kqueue backend might only support
		1069	sockets on some platform, so it is unusable as generic backend, but you
		1070	still want to make use of it because you have many sockets and it scales
		1071	so nicely. In this case, you would create a kqueue-based loop and embed it
		1072	into your default loop (which might use e.g. poll). Overall operation will
		1073	be a bit slower because first libev has to poll and then call kevent, but
		1074	at least you can use both at what they are best.
		1075
		1076	As for prioritising I/O: rarely you have the case where some fds have
		1077	to be watched and handled very quickly (with low latency), and even
		1078	priorities and idle watchers might have too much overhead. In this case
		1079	you would put all the high priority stuff in one loop and all the rest in
		1080	a second one, and embed the second one in the first.
		1081
		1082	As long as the watcher is started it will automatically handle events. The
		1083	callback will be invoked whenever some events have been handled. You can
		1084	set the callback to C<0> to avoid having to specify one if you are not
		1085	interested in that.
		1086
		1087	Also, there have not currently been made special provisions for forking:
		1088	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1089	but you will also have to stop and restart any C<ev_embed> watchers
		1090	yourself.
		1091
		1092	Unfortunately, not all backends are embeddable, only the ones returned by
		1093	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1094	portable one.
		1095
		1096	So when you want to use this feature you will always have to be prepared
		1097	that you cannot get an embeddable loop. The recommended way to get around
		1098	this is to have a separate variables for your embeddable loop, try to
		1099	create it, and if that fails, use the normal loop for everything:
		1100
		1101	struct ev_loop *loop_hi = ev_default_init (0);
		1102	struct ev_loop *loop_lo = 0;
		1103	struct ev_embed embed;
		1104
		1105	// see if there is a chance of getting one that works
		1106	// (remember that a flags value of 0 means autodetection)
		1107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1109	: 0;
		1110
		1111	// if we got one, then embed it, otherwise default to loop_hi
		1112	if (loop_lo)
		1113	{
		1114	ev_embed_init (&embed, 0, loop_lo);
		1115	ev_embed_start (loop_hi, &embed);
		1116	}
		1117	else
		1118	loop_lo = loop_hi;
		1119
		1120	=over 4
		1121
		1122	=item ev_embed_init (ev_embed , callback, struct ev_loop loop)
		1123
		1124	=item ev_embed_set (ev_embed , callback, struct ev_loop loop)
		1125
		1126	Configures the watcher to embed the given loop, which must be embeddable.
		1127
		1128	=back
		1129
671		1130
672	=head1 OTHER FUNCTIONS	1131	=head1 OTHER FUNCTIONS
673		1132
674	There are some other fucntions of possible interest. Described. Here. Now.	1133	There are some other functions of possible interest. Described. Here. Now.
675		1134
676	=over 4	1135	=over 4
677		1136
678	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	1137	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
679		1138
680	This function combines a simple timer and an I/O watcher, calls your	1139	This function combines a simple timer and an I/O watcher, calls your
681	callback on whichever event happens first and automatically stop both	1140	callback on whichever event happens first and automatically stop both
682	watchers. This is useful if you want to wait for a single event on an fd	1141	watchers. This is useful if you want to wait for a single event on an fd
683	or timeout without havign to allocate/configure/start/stop/free one or	1142	or timeout without having to allocate/configure/start/stop/free one or
684	more watchers yourself.	1143	more watchers yourself.
685		1144
686	If C<fd> is less than 0, then no I/O watcher will be started and events is	1145	If C<fd> is less than 0, then no I/O watcher will be started and events
687	ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set	1146	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
688	will be craeted and started.	1147	C<events> set will be craeted and started.
689		1148
690	If C<timeout> is less than 0, then no timeout watcher will be	1149	If C<timeout> is less than 0, then no timeout watcher will be
691	started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat	1150	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
692	= 0) will be started.	1151	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		1152	dubious value.
693		1153
694	The callback has the type C<void (cb)(int revents, void arg)> and	1154	The callback has the type C<void (cb)(int revents, void arg)> and gets
695	gets passed an events set (normally a combination of EV_ERROR, EV_READ,	1155	passed an C<revents> set like normal event callbacks (a combination of
696	EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>:	1156	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		1157	value passed to C<ev_once>:
697		1158
698	static void stdin_ready (int revents, void *arg)	1159	static void stdin_ready (int revents, void *arg)
699	{	1160	{
700	if (revents & EV_TIMEOUT)	1161	if (revents & EV_TIMEOUT)
701	/* doh, nothing entered */	1162	/* doh, nothing entered */;
702	else if (revents & EV_READ)	1163	else if (revents & EV_READ)
703	/* stdin might have data for us, joy! */	1164	/* stdin might have data for us, joy! */;
704	}	1165	}
705		1166
706	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	1167	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
707		1168
708	=item ev_feed_event (loop, watcher, int events)	1169	=item ev_feed_event (loop, watcher, int events)
709		1170
710	Feeds the given event set into the event loop, as if the specified event	1171	Feeds the given event set into the event loop, as if the specified event
711	has happened for the specified watcher (which must be a pointer to an	1172	had happened for the specified watcher (which must be a pointer to an
712	initialised but not necessarily active event watcher).	1173	initialised but not necessarily started event watcher).
713		1174
714	=item ev_feed_fd_event (loop, int fd, int revents)	1175	=item ev_feed_fd_event (loop, int fd, int revents)
715		1176
716	Feed an event on the given fd, as if a file descriptor backend detected it.	1177	Feed an event on the given fd, as if a file descriptor backend detected
		1178	the given events it.
717		1179
718	=item ev_feed_signal_event (loop, int signum)	1180	=item ev_feed_signal_event (loop, int signum)
719		1181
720	Feed an event as if the given signal occured (loop must be the default loop!).	1182	Feed an event as if the given signal occured (loop must be the default loop!).
721		1183
722	=back	1184	=back
723		1185
		1186
		1187	=head1 LIBEVENT EMULATION
		1188
		1189	Libev offers a compatibility emulation layer for libevent. It cannot
		1190	emulate the internals of libevent, so here are some usage hints:
		1191
		1192	=over 4
		1193
		1194	=item * Use it by including <event.h>, as usual.
		1195
		1196	=item * The following members are fully supported: ev_base, ev_callback,
		1197	ev_arg, ev_fd, ev_res, ev_events.
		1198
		1199	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		1200	maintained by libev, it does not work exactly the same way as in libevent (consider
		1201	it a private API).
		1202
		1203	=item * Priorities are not currently supported. Initialising priorities
		1204	will fail and all watchers will have the same priority, even though there
		1205	is an ev_pri field.
		1206
		1207	=item * Other members are not supported.
		1208
		1209	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		1210	to use the libev header file and library.
		1211
		1212	=back
		1213
		1214	=head1 C++ SUPPORT
		1215
		1216	TBD.
		1217
724	=head1 AUTHOR	1218	=head1 AUTHOR
725		1219
726	Marc Lehmann <libev@schmorp.de>.	1220	Marc Lehmann <libev@schmorp.de>.
727		1221

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Revision 1.3 by root, Mon Nov 12 08:03:31 2007 UTC vs.
Revision 1.35 by root, Fri Nov 23 19:35:09 2007 UTC