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

Comparing libev/ev.pod (file contents):
Revision 1.28 by root, Sat Nov 17 02:00:49 2007 UTC vs.
Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC

…		…
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
51		53
52	=head1 GLOBAL FUNCTIONS	54	=head1 GLOBAL FUNCTIONS
53		55
54	These functions can be called anytime, even before initialising the	56	These functions can be called anytime, even before initialising the
55	library in any way.	57	library in any way.
…		…
75	Usually, it's a good idea to terminate if the major versions mismatch,	77	Usually, it's a good idea to terminate if the major versions mismatch,
76	as this indicates an incompatible change. Minor versions are usually	78	as this indicates an incompatible change. Minor versions are usually
77	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
78	not a problem.	80	not a problem.
79		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
80	=item ev_set_allocator (void (cb)(void *ptr, long size))	111	=item ev_set_allocator (void (cb)(void *ptr, long size))
81		112
82	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
83	realloc C function, the semantics are identical). It is used to allocate	114	realloc C function, the semantics are identical). It is used to allocate
84	and free memory (no surprises here). If it returns zero when memory	115	and free memory (no surprises here). If it returns zero when memory
…		…
86	destructive action. The default is your system realloc function.	117	destructive action. The default is your system realloc function.
87		118
88	You could override this function in high-availability programs to, say,	119	You could override this function in high-availability programs to, say,
89	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,
90	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);
91		142
92	=item ev_set_syserr_cb (void (cb)(const char msg));	143	=item ev_set_syserr_cb (void (cb)(const char msg));
93		144
94	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
95	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
…		…
97	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
98	matter what, when it returns. That is, libev will generally retry the	149	matter what, when it returns. That is, libev will generally retry the
99	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
100	(such as abort).	151	(such as abort).
101		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);
		164
102	=back	165	=back
103		166
104	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	167	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
105		168
106	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
…		…
119	=item struct ev_loop *ev_default_loop (unsigned int flags)	182	=item struct ev_loop *ev_default_loop (unsigned int flags)
120		183
121	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
122	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
123	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
124	flags).	187	flags. If that is troubling you, check C<ev_backend ()> afterwards).
125		188
126	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
127	function.	190	function.
128		191
129	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
130	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>).
131		194
132	It supports the following flags:	195	The following flags are supported:
133		196
134	=over 4	197	=over 4
135		198
136	=item C<EVFLAG_AUTO>	199	=item C<EVFLAG_AUTO>
137		200
…		…
145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	208	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
146	override the flags completely if it is found in the environment. This is	209	override the flags completely if it is found in the environment. This is
147	useful to try out specific backends to test their performance, or to work	210	useful to try out specific backends to test their performance, or to work
148	around bugs.	211	around bugs.
149		212
150	=item C<EVMETHOD_SELECT> (portable select backend)	213	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		214
		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.
		220
152	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	221	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
153		222
154	=item C<EVMETHOD_EPOLL> (linux 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).
155		227
156	=item C<EVMETHOD_KQUEUE> (some bsds only)	228	=item C<EVBACKEND_EPOLL> (value 4, Linux)
157		229
158	=item C<EVMETHOD_DEVPOLL> (solaris 8 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).
159		234
160	=item C<EVMETHOD_PORT> (solaris 10 only)	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
161		280
162	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
163	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
164	specified, any backend will do.	283	specified, most compiled-in backend will be tried, usually in reverse
		284	order of their flag values :)
165		285
166	=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);
167		301
168	=item struct ev_loop *ev_loop_new (unsigned int flags)	302	=item struct ev_loop *ev_loop_new (unsigned int flags)
169		303
170	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
171	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
172	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
173	undefined behaviour (or a failed assertion if assertions are enabled).	307	undefined behaviour (or a failed assertion if assertions are enabled).
174		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
175	=item ev_default_destroy ()	315	=item ev_default_destroy ()
176		316
177	Destroys the default loop again (frees all memory and kernel state	317	Destroys the default loop again (frees all memory and kernel state
178	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
179	any way whatsoever, although you cannot rely on this :).	319	any way whatsoever, although you cannot rely on this :).
…		…
188	This function reinitialises the kernel state for backends that have	328	This function reinitialises the kernel state for backends that have
189	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
190	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
191	again makes little sense).	331	again makes little sense).
192		332
193	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
194	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
195	have to call it.	335	fork+exec, you don't have to call it.
196		336
197	The function itself is quite fast and it's usually not a problem to call	337	The function itself is quite fast and it's usually not a problem to call
198	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
199	quite nicely into a call to C<pthread_atfork>:	339	quite nicely into a call to C<pthread_atfork>:
200		340
201	pthread_atfork (0, 0, ev_default_fork);	341	pthread_atfork (0, 0, ev_default_fork);
202		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.
		346
203	=item ev_loop_fork (loop)	347	=item ev_loop_fork (loop)
204		348
205	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
206	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
207	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.
208		352
209	=item unsigned int ev_method (loop)	353	=item unsigned int ev_backend (loop)
210		354
211	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
212	use.	356	use.
213		357
214	=item ev_tstamp ev_now (loop)	358	=item ev_tstamp ev_now (loop)
215		359
216	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
217	got events and started processing them. This timestamp does not change	361	received events and started processing them. This timestamp does not
218	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
219	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
220	occuring (or more correctly, the mainloop finding out about it).	364	event occuring (or more correctly, libev finding out about it).
221		365
222	=item ev_loop (loop, int flags)	366	=item ev_loop (loop, int flags)
223		367
224	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
225	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
226	events.	370	events.
227		371
228	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
229	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.
230		380
231	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
232	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
233	case there are no events and will return after one iteration of the loop.	383	case there are no events and will return after one iteration of the loop.
234		384
235	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
236	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
237	your process until at least one new event arrives, and will return after	387	your process until at least one new event arrives, and will return after
238	one iteration of the loop.	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.
239		392
240	This flags value could be used to implement alternative looping
241	constructs, but the C<prepare> and C<check> watchers provide a better and
242	more generic mechanism.
243
244	Here are the gory details of what ev_loop does:	393	Here are the gory details of what C<ev_loop> does:
245		394
246	1. If there are no active watchers (reference count is zero), return.	395	* If there are no active watchers (reference count is zero), return.
247	2. Queue and immediately call all prepare watchers.	396	- Queue prepare watchers and then call all outstanding watchers.
248	3. If we have been forked, recreate the kernel state.	397	- If we have been forked, recreate the kernel state.
249	4. Update the kernel state with all outstanding changes.	398	- Update the kernel state with all outstanding changes.
250	5. Update the "event loop time".	399	- Update the "event loop time".
251	6. Calculate for how long to block.	400	- Calculate for how long to block.
252	7. Block the process, waiting for events.	401	- Block the process, waiting for any events.
		402	- Queue all outstanding I/O (fd) events.
253	8. Update the "event loop time" and do time jump handling.	403	- Update the "event loop time" and do time jump handling.
254	9. Queue all outstanding timers.	404	- Queue all outstanding timers.
255	10. Queue all outstanding periodics.	405	- Queue all outstanding periodics.
256	11. If no events are pending now, queue all idle watchers.	406	- If no events are pending now, queue all idle watchers.
257	12. Queue all check watchers.	407	- Queue all check watchers.
258	13. Call all queued watchers in reverse order (i.e. check watchers first).	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.
259	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	411	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
260	was used, return, otherwise continue with step #1.	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!
261		421
262	=item ev_unloop (loop, how)	422	=item ev_unloop (loop, how)
263		423
264	Can be used to make a call to C<ev_loop> return early (but only after it	424	Can be used to make a call to C<ev_loop> return early (but only after it
265	has processed all outstanding events). The C<how> argument must be either	425	has processed all outstanding events). The C<how> argument must be either
…		…
279	visible to the libev user and should not keep C<ev_loop> from exiting if	439	visible to the libev user and should not keep C<ev_loop> from exiting if
280	no event watchers registered by it are active. It is also an excellent	440	no event watchers registered by it are active. It is also an excellent
281	way to do this for generic recurring timers or from within third-party	441	way to do this for generic recurring timers or from within third-party
282	libraries. Just remember to I<unref after start> and I<ref before stop>.	442	libraries. Just remember to I<unref after start> and I<ref before stop>.
283		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);
		456
284	=back	457	=back
285		458
286	=head1 ANATOMY OF A WATCHER	459	=head1 ANATOMY OF A WATCHER
287		460
288	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
…		…
322	*) >>), 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
323	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	496	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
324		497
325	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
326	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
327	reinitialise it or call its set method.	500	reinitialise it or call its set macro.
328		501
329	You can 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
330	(watcher *)> macro. To see whether an event is outstanding (but the	503	(watcher *)> macro. To see whether an event is outstanding (but the
331	callback for it has not been called yet) you can use the C<ev_is_pending	504	callback for it has not been called yet) you can use the C<ev_is_pending
332	(watcher *)> macro.	505	(watcher *)> macro.
…		…
429	=head1 WATCHER TYPES	602	=head1 WATCHER TYPES
430		603
431	This section describes each watcher in detail, but will not repeat	604	This section describes each watcher in detail, but will not repeat
432	information given in the last section.	605	information given in the last section.
433		606
		607
434	=head2 C<ev_io> - is this file descriptor readable or writable	608	=head2 C<ev_io> - is this file descriptor readable or writable
435		609
436	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
437	in each iteration of the event loop (This behaviour is called	611	in each iteration of the event loop (This behaviour is called
438	level-triggering because you keep receiving events as long as the	612	level-triggering because you keep receiving events as long as the
…		…
449	descriptors correctly if you register interest in two or more fds pointing	623	descriptors correctly if you register interest in two or more fds pointing
450	to the same underlying file/socket etc. description (that is, they share	624	to the same underlying file/socket etc. description (that is, they share
451	the same underlying "file open").	625	the same underlying "file open").
452		626
453	If you must do this, then force the use of a known-to-be-good backend	627	If you must do this, then force the use of a known-to-be-good backend
454	(at the time of this writing, this includes only EVMETHOD_SELECT and	628	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
455	EVMETHOD_POLL).	629	C<EVBACKEND_POLL>).
456		630
457	=over 4	631	=over 4
458		632
459	=item ev_io_init (ev_io *, callback, int fd, int events)	633	=item ev_io_init (ev_io *, callback, int fd, int events)
460		634
…		…
462		636
463	Configures an C<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
464	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 \|
465	EV_WRITE> to receive the given events.	639	EV_WRITE> to receive the given events.
466		640
		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.
		651
467	=back	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
468		672
469	=head2 C<ev_timer> - relative and optionally recurring timeouts	673	=head2 C<ev_timer> - relative and optionally recurring timeouts
470		674
471	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
472	given time, and optionally repeating in regular intervals after that.	676	given time, and optionally repeating in regular intervals after that.
…		…
525	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
526	the timer, and again will automatically restart it if need be.	730	the timer, and again will automatically restart it if need be.
527		731
528	=back	732	=back
529		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
530	=head2 C<ev_periodic> - to cron or not to cron	765	=head2 C<ev_periodic> - to cron or not to cron
531		766
532	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
533	(and unfortunately a bit complex).	768	(and unfortunately a bit complex).
534		769
…		…
629	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
630	program when the crontabs have changed).	865	program when the crontabs have changed).
631		866
632	=back	867	=back
633		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
634	=head2 C<ev_signal> - signal me when a signal gets signalled	903	=head2 C<ev_signal> - signal me when a signal gets signalled
635		904
636	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
637	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
638	will try it's 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
…		…
673	the status word (use the macros from C<sys/wait.h> and see your systems	942	the status word (use the macros from C<sys/wait.h> and see your systems
674	C<waitpid> documentation). The C<rpid> member contains the pid of the	943	C<waitpid> documentation). The C<rpid> member contains the pid of the
675	process causing the status change.	944	process causing the status change.
676		945
677	=back	946	=back
		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
678		960
679	=head2 C<ev_idle> - when you've got nothing better to do	961	=head2 C<ev_idle> - when you've got nothing better to do
680		962
681	Idle watchers trigger events when there are no other events are pending	963	Idle watchers trigger events when there are no other events are pending
682	(prepare, check and other idle watchers do not count). That is, as long	964	(prepare, check and other idle watchers do not count). That is, as long
…		…
701	Initialises and configures the idle watcher - it has no parameters of any	983	Initialises and configures the idle watcher - it has no parameters of any
702	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,
703	believe me.	985	believe me.
704		986
705	=back	987	=back
		988
		989	Example: dynamically allocate an C<ev_idle>, start it, and in the
		990	callback, free it. Alos, use no error checking, as usual.
		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
706		1004
707	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
708		1006
709	Prepare and check watchers are usually (but not always) used in tandem:	1007	Prepare and check watchers are usually (but not always) used in tandem:
710	prepare watchers get invoked before the process blocks and check watchers	1008	prepare watchers get invoked before the process blocks and check watchers
…		…
742	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>
743	macros, but using them is utterly, utterly and completely pointless.	1041	macros, but using them is utterly, utterly and completely pointless.
744		1042
745	=back	1043	=back
746		1044
		1045	Example: TODO.
		1046
		1047
747	=head1 OTHER FUNCTIONS	1048	=head1 OTHER FUNCTIONS
748		1049
749	There are some other functions of possible interest. Described. Here. Now.	1050	There are some other functions of possible interest. Described. Here. Now.
750		1051
751	=over 4	1052	=over 4
…		…
797		1098
798	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!).
799		1100
800	=back	1101	=back
801		1102
		1103
802	=head1 LIBEVENT EMULATION	1104	=head1 LIBEVENT EMULATION
803		1105
804	Libev offers a compatibility emulation layer for libevent. It cannot	1106	Libev offers a compatibility emulation layer for libevent. It cannot
805	emulate the internals of libevent, so here are some usage hints:	1107	emulate the internals of libevent, so here are some usage hints:
806		1108

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Comparing libev/ev.pod (file contents): Revision 1.28 by root, Sat Nov 17 02:00:49 2007 UTC vs. Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.28 by root, Sat Nov 17 02:00:49 2007 UTC vs.
Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC