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

Comparing libev/ev.pod (file contents):
Revision 1.27 by root, Wed Nov 14 05:02:07 2007 UTC vs.
Revision 1.36 by root, Sat Nov 24 07:14:26 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
		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
80	=item ev_set_allocator (void (cb)(void *ptr, long size))	121	=item ev_set_allocator (void (cb)(void *ptr, long size))
81		122
82	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
83	realloc C function, the semantics are identical). It is used to allocate	124	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	125	and free memory (no surprises here). If it returns zero when memory
…		…
86	destructive action. The default is your system realloc function.	127	destructive action. The default is your system realloc function.
87		128
88	You could override this function in high-availability programs to, say,	129	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,	130	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.	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);
91		152
92	=item ev_set_syserr_cb (void (cb)(const char msg));	153	=item ev_set_syserr_cb (void (cb)(const char msg));
93		154
94	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
95	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
…		…
97	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
98	matter what, when it returns. That is, libev will generally retry the	159	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	160	requested operation, or, if the condition doesn't go away, do bad stuff
100	(such as abort).	161	(such as abort).
101		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);
		174
102	=back	175	=back
103		176
104	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	177	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
105		178
106	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
…		…
119	=item struct ev_loop *ev_default_loop (unsigned int flags)	192	=item struct ev_loop *ev_default_loop (unsigned int flags)
120		193
121	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
122	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
123	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
124	flags).	197	flags. If that is troubling you, check C<ev_backend ()> afterwards).
125		198
126	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
127	function.	200	function.
128		201
129	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
130	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>).
131		204
132	It supports the following flags:	205	The following flags are supported:
133		206
134	=over 4	207	=over 4
135		208
136	=item C<EVFLAG_AUTO>	209	=item C<EVFLAG_AUTO>
137		210
…		…
145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
146	override the flags completely if it is found in the environment. This is	219	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	220	useful to try out specific backends to test their performance, or to work
148	around bugs.	221	around bugs.
149		222
150	=item C<EVMETHOD_SELECT> (portable select backend)	223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		224
		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.
		230
152	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	231	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
153		232
154	=item C<EVMETHOD_EPOLL> (linux 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).
155		237
156	=item C<EVMETHOD_KQUEUE> (some bsds only)	238	=item C<EVBACKEND_EPOLL> (value 4, Linux)
157		239
158	=item C<EVMETHOD_DEVPOLL> (solaris 8 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).
159		244
160	=item C<EVMETHOD_PORT> (solaris 10 only)	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
161		290
162	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
163	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
164	specified, any backend will do.	293	specified, most compiled-in backend will be tried, usually in reverse
		294	order of their flag values :)
165		295
166	=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);
167		311
168	=item struct ev_loop *ev_loop_new (unsigned int flags)	312	=item struct ev_loop *ev_loop_new (unsigned int flags)
169		313
170	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
171	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
172	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
173	undefined behaviour (or a failed assertion if assertions are enabled).	317	undefined behaviour (or a failed assertion if assertions are enabled).
174		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
175	=item ev_default_destroy ()	325	=item ev_default_destroy ()
176		326
177	Destroys the default loop again (frees all memory and kernel state	327	Destroys the default loop again (frees all memory and kernel state
178	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
179	any way whatsoever, although you cannot rely on this :).	329	any way whatsoever, although you cannot rely on this :).
…		…
188	This function reinitialises the kernel state for backends that have	338	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	339	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	340	after forking, in either the parent or child process (or both, but that
191	again makes little sense).	341	again makes little sense).
192		342
193	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
194	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
195	have to call it.	345	fork+exec, you don't have to call it.
196		346
197	The function itself is quite fast and it's usually not a problem to call	347	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	348	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>:	349	quite nicely into a call to C<pthread_atfork>:
200		350
201	pthread_atfork (0, 0, ev_default_fork);	351	pthread_atfork (0, 0, ev_default_fork);
202		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.
		356
203	=item ev_loop_fork (loop)	357	=item ev_loop_fork (loop)
204		358
205	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
206	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
207	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.
208		362
209	=item unsigned int ev_method (loop)	363	=item unsigned int ev_backend (loop)
210		364
211	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
212	use.	366	use.
213		367
214	=item ev_tstamp ev_now (loop)	368	=item ev_tstamp ev_now (loop)
215		369
216	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
217	got events and started processing them. This timestamp does not change	371	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	372	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	373	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).	374	event occuring (or more correctly, libev finding out about it).
221		375
222	=item ev_loop (loop, int flags)	376	=item ev_loop (loop, int flags)
223		377
224	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
225	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
226	events.	380	events.
227		381
228	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
229	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.
230		390
231	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
232	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
233	case there are no events and will return after one iteration of the loop.	393	case there are no events and will return after one iteration of the loop.
234		394
235	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
236	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
237	your process until at least one new event arrives, and will return after	397	your process until at least one new event arrives, and will return after
238	one iteration of the loop.	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.
239		402
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:	403	Here are the gory details of what C<ev_loop> does:
245		404
246	1. If there are no active watchers (reference count is zero), return.	405	* If there are no active watchers (reference count is zero), return.
247	2. Queue and immediately call all prepare watchers.	406	- Queue prepare watchers and then call all outstanding watchers.
248	3. If we have been forked, recreate the kernel state.	407	- If we have been forked, recreate the kernel state.
249	4. Update the kernel state with all outstanding changes.	408	- Update the kernel state with all outstanding changes.
250	5. Update the "event loop time".	409	- Update the "event loop time".
251	6. Calculate for how long to block.	410	- Calculate for how long to block.
252	7. Block the process, waiting for events.	411	- Block the process, waiting for any events.
		412	- Queue all outstanding I/O (fd) events.
253	8. Update the "event loop time" and do time jump handling.	413	- Update the "event loop time" and do time jump handling.
254	9. Queue all outstanding timers.	414	- Queue all outstanding timers.
255	10. Queue all outstanding periodics.	415	- Queue all outstanding periodics.
256	11. If no events are pending now, queue all idle watchers.	416	- If no events are pending now, queue all idle watchers.
257	12. Queue all check watchers.	417	- Queue all check watchers.
258	13. Call all queued watchers in reverse order (i.e. check watchers first).	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.
259	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	421	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
260	was used, return, otherwise continue with step #1.	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!
261		431
262	=item ev_unloop (loop, how)	432	=item ev_unloop (loop, how)
263		433
264	Can be used to make a call to C<ev_loop> return early (but only after it	434	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	435	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	449	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	450	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	451	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>.	452	libraries. Just remember to I<unref after start> and I<ref before stop>.
283		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);
		466
284	=back	467	=back
285		468
286	=head1 ANATOMY OF A WATCHER	469	=head1 ANATOMY OF A WATCHER
287		470
288	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
…		…
322	*) >>), 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
323	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	506	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
324		507
325	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
326	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
327	reinitialise it or call its set method.	510	reinitialise it or call its C<set> macro.
328
329	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
331	callback for it has not been called yet) you can use the C<ev_is_pending
332	(watcher *)> macro.
333		511
334	Each and every callback receives the event loop pointer as first, the	512	Each and every callback receives the event loop pointer as first, the
335	registered watcher structure as second, and a bitset of received events as	513	registered watcher structure as second, and a bitset of received events as
336	third argument.	514	third argument.
337		515
…		…
394	with the error from read() or write(). This will not work in multithreaded	572	with the error from read() or write(). This will not work in multithreaded
395	programs, though, so beware.	573	programs, though, so beware.
396		574
397	=back	575	=back
398		576
		577	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS
		578
		579	In the following description, C<TYPE> stands for the watcher type,
		580	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		581
		582	=over 4
		583
		584	=item C<ev_init> (ev_TYPE *watcher, callback)
		585
		586	This macro initialises the generic portion of a watcher. The contents
		587	of the watcher object can be arbitrary (so C<malloc> will do). Only
		588	the generic parts of the watcher are initialised, you I<need> to call
		589	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		590	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		591	which rolls both calls into one.
		592
		593	You can reinitialise a watcher at any time as long as it has been stopped
		594	(or never started) and there are no pending events outstanding.
		595
		596	The callbakc is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,
		597	int revents)>.
		598
		599	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		600
		601	This macro initialises the type-specific parts of a watcher. You need to
		602	call C<ev_init> at least once before you call this macro, but you can
		603	call C<ev_TYPE_set> any number of times. You must not, however, call this
		604	macro on a watcher that is active (it can be pending, however, which is a
		605	difference to the C<ev_init> macro).
		606
		607	Although some watcher types do not have type-specific arguments
		608	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		609
		610	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		611
		612	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		613	calls into a single call. This is the most convinient method to initialise
		614	a watcher. The same limitations apply, of course.
		615
		616	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)
		617
		618	Starts (activates) the given watcher. Only active watchers will receive
		619	events. If the watcher is already active nothing will happen.
		620
		621	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
		622
		623	Stops the given watcher again (if active) and clears the pending
		624	status. It is possible that stopped watchers are pending (for example,
		625	non-repeating timers are being stopped when they become pending), but
		626	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		627	you want to free or reuse the memory used by the watcher it is therefore a
		628	good idea to always call its C<ev_TYPE_stop> function.
		629
		630	=item bool ev_is_active (ev_TYPE *watcher)
		631
		632	Returns a true value iff the watcher is active (i.e. it has been started
		633	and not yet been stopped). As long as a watcher is active you must not modify
		634	it.
		635
		636	=item bool ev_is_pending (ev_TYPE *watcher)
		637
		638	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		639	events but its callback has not yet been invoked). As long as a watcher
		640	is pending (but not active) you must not call an init function on it (but
		641	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		642	libev (e.g. you cnanot C<free ()> it).
		643
		644	=item callback = ev_cb (ev_TYPE *watcher)
		645
		646	Returns the callback currently set on the watcher.
		647
		648	=item ev_cb_set (ev_TYPE *watcher, callback)
		649
		650	Change the callback. You can change the callback at virtually any time
		651	(modulo threads).
		652
		653	=back
		654
		655
399	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	656	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
400		657
401	Each watcher has, by default, a member C<void *data> that you can change	658	Each watcher has, by default, a member C<void *data> that you can change
402	and read at any time, libev will completely ignore it. This can be used	659	and read at any time, libev will completely ignore it. This can be used
403	to associate arbitrary data with your watcher. If you need more data and	660	to associate arbitrary data with your watcher. If you need more data and
…		…
429	=head1 WATCHER TYPES	686	=head1 WATCHER TYPES
430		687
431	This section describes each watcher in detail, but will not repeat	688	This section describes each watcher in detail, but will not repeat
432	information given in the last section.	689	information given in the last section.
433		690
		691
434	=head2 C<ev_io> - is this file descriptor readable or writable	692	=head2 C<ev_io> - is this file descriptor readable or writable
435		693
436	I/O watchers check whether a file descriptor is readable or writable	694	I/O watchers check whether a file descriptor is readable or writable
437	in each iteration of the event loop (This behaviour is called	695	in each iteration of the event loop (This behaviour is called
438	level-triggering because you keep receiving events as long as the	696	level-triggering because you keep receiving events as long as the
…		…
449	descriptors correctly if you register interest in two or more fds pointing	707	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	708	to the same underlying file/socket etc. description (that is, they share
451	the same underlying "file open").	709	the same underlying "file open").
452		710
453	If you must do this, then force the use of a known-to-be-good backend	711	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	712	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
455	EVMETHOD_POLL).	713	C<EVBACKEND_POLL>).
456		714
457	=over 4	715	=over 4
458		716
459	=item ev_io_init (ev_io *, callback, int fd, int events)	717	=item ev_io_init (ev_io *, callback, int fd, int events)
460		718
…		…
462		720
463	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	721	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 \|	722	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|
465	EV_WRITE> to receive the given events.	723	EV_WRITE> to receive the given events.
466		724
		725	Please note that most of the more scalable backend mechanisms (for example
		726	epoll and solaris ports) can result in spurious readyness notifications
		727	for file descriptors, so you practically need to use non-blocking I/O (and
		728	treat callback invocation as hint only), or retest separately with a safe
		729	interface before doing I/O (XLib can do this), or force the use of either
		730	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this
		731	problem. Also note that it is quite easy to have your callback invoked
		732	when the readyness condition is no longer valid even when employing
		733	typical ways of handling events, so its a good idea to use non-blocking
		734	I/O unconditionally.
		735
467	=back	736	=back
		737
		738	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
		739	readable, but only once. Since it is likely line-buffered, you could
		740	attempt to read a whole line in the callback:
		741
		742	static void
		743	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		744	{
		745	ev_io_stop (loop, w);
		746	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		747	}
		748
		749	...
		750	struct ev_loop *loop = ev_default_init (0);
		751	struct ev_io stdin_readable;
		752	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		753	ev_io_start (loop, &stdin_readable);
		754	ev_loop (loop, 0);
		755
468		756
469	=head2 C<ev_timer> - relative and optionally recurring timeouts	757	=head2 C<ev_timer> - relative and optionally recurring timeouts
470		758
471	Timer watchers are simple relative timers that generate an event after a	759	Timer watchers are simple relative timers that generate an event after a
472	given time, and optionally repeating in regular intervals after that.	760	given time, and optionally repeating in regular intervals after that.
473		761
474	The timers are based on real time, that is, if you register an event that	762	The timers are based on real time, that is, if you register an event that
475	times out after an hour and you reset your system clock to last years	763	times out after an hour and you reset your system clock to last years
476	time, it will still time out after (roughly) and hour. "Roughly" because	764	time, it will still time out after (roughly) and hour. "Roughly" because
477	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	765	detecting time jumps is hard, and some inaccuracies are unavoidable (the
478	monotonic clock option helps a lot here).	766	monotonic clock option helps a lot here).
479		767
480	The relative timeouts are calculated relative to the C<ev_now ()>	768	The relative timeouts are calculated relative to the C<ev_now ()>
481	time. This is usually the right thing as this timestamp refers to the time	769	time. This is usually the right thing as this timestamp refers to the time
482	of the event triggering whatever timeout you are modifying/starting. If	770	of the event triggering whatever timeout you are modifying/starting. If
483	you suspect event processing to be delayed and you need to base the timeout	771	you suspect event processing to be delayed and you I<need> to base the timeout
484	on the current time, use something like this to adjust for this:	772	on the current time, use something like this to adjust for this:
485		773
486	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	774	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		775
		776	The callback is guarenteed to be invoked only when its timeout has passed,
		777	but if multiple timers become ready during the same loop iteration then
		778	order of execution is undefined.
487		779
488	=over 4	780	=over 4
489		781
490	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	782	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
491		783
…		…
521	state where you do not expect data to travel on the socket, you can stop	813	state where you do not expect data to travel on the socket, you can stop
522	the timer, and again will automatically restart it if need be.	814	the timer, and again will automatically restart it if need be.
523		815
524	=back	816	=back
525		817
		818	Example: create a timer that fires after 60 seconds.
		819
		820	static void
		821	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		822	{
		823	.. one minute over, w is actually stopped right here
		824	}
		825
		826	struct ev_timer mytimer;
		827	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		828	ev_timer_start (loop, &mytimer);
		829
		830	Example: create a timeout timer that times out after 10 seconds of
		831	inactivity.
		832
		833	static void
		834	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		835	{
		836	.. ten seconds without any activity
		837	}
		838
		839	struct ev_timer mytimer;
		840	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		841	ev_timer_again (&mytimer); /* start timer */
		842	ev_loop (loop, 0);
		843
		844	// and in some piece of code that gets executed on any "activity":
		845	// reset the timeout to start ticking again at 10 seconds
		846	ev_timer_again (&mytimer);
		847
		848
526	=head2 C<ev_periodic> - to cron or not to cron	849	=head2 C<ev_periodic> - to cron or not to cron
527		850
528	Periodic watchers are also timers of a kind, but they are very versatile	851	Periodic watchers are also timers of a kind, but they are very versatile
529	(and unfortunately a bit complex).	852	(and unfortunately a bit complex).
530		853
…		…
538	again).	861	again).
539		862
540	They can also be used to implement vastly more complex timers, such as	863	They can also be used to implement vastly more complex timers, such as
541	triggering an event on eahc midnight, local time.	864	triggering an event on eahc midnight, local time.
542		865
		866	As with timers, the callback is guarenteed to be invoked only when the
		867	time (C<at>) has been passed, but if multiple periodic timers become ready
		868	during the same loop iteration then order of execution is undefined.
		869
543	=over 4	870	=over 4
544		871
545	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	872	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
546		873
547	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	874	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
548		875
549	Lots of arguments, lets sort it out... There are basically three modes of	876	Lots of arguments, lets sort it out... There are basically three modes of
550	operation, and we will explain them from simplest to complex:	877	operation, and we will explain them from simplest to complex:
551
552		878
553	=over 4	879	=over 4
554		880
555	=item * absolute timer (interval = reschedule_cb = 0)	881	=item * absolute timer (interval = reschedule_cb = 0)
556		882
…		…
621	when you changed some parameters or the reschedule callback would return	947	when you changed some parameters or the reschedule callback would return
622	a different time than the last time it was called (e.g. in a crond like	948	a different time than the last time it was called (e.g. in a crond like
623	program when the crontabs have changed).	949	program when the crontabs have changed).
624		950
625	=back	951	=back
		952
		953	Example: call a callback every hour, or, more precisely, whenever the
		954	system clock is divisible by 3600. The callback invocation times have
		955	potentially a lot of jittering, but good long-term stability.
		956
		957	static void
		958	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		959	{
		960	... its now a full hour (UTC, or TAI or whatever your clock follows)
		961	}
		962
		963	struct ev_periodic hourly_tick;
		964	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		965	ev_periodic_start (loop, &hourly_tick);
		966
		967	Example: the same as above, but use a reschedule callback to do it:
		968
		969	#include <math.h>
		970
		971	static ev_tstamp
		972	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		973	{
		974	return fmod (now, 3600.) + 3600.;
		975	}
		976
		977	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		978
		979	Example: call a callback every hour, starting now:
		980
		981	struct ev_periodic hourly_tick;
		982	ev_periodic_init (&hourly_tick, clock_cb,
		983	fmod (ev_now (loop), 3600.), 3600., 0);
		984	ev_periodic_start (loop, &hourly_tick);
		985
626		986
627	=head2 C<ev_signal> - signal me when a signal gets signalled	987	=head2 C<ev_signal> - signal me when a signal gets signalled
628		988
629	Signal watchers will trigger an event when the process receives a specific	989	Signal watchers will trigger an event when the process receives a specific
630	signal one or more times. Even though signals are very asynchronous, libev	990	signal one or more times. Even though signals are very asynchronous, libev
…		…
647	Configures the watcher to trigger on the given signal number (usually one	1007	Configures the watcher to trigger on the given signal number (usually one
648	of the C<SIGxxx> constants).	1008	of the C<SIGxxx> constants).
649		1009
650	=back	1010	=back
651		1011
		1012
652	=head2 C<ev_child> - wait for pid status changes	1013	=head2 C<ev_child> - wait for pid status changes
653		1014
654	Child watchers trigger when your process receives a SIGCHLD in response to	1015	Child watchers trigger when your process receives a SIGCHLD in response to
655	some child status changes (most typically when a child of yours dies).	1016	some child status changes (most typically when a child of yours dies).
656		1017
…		…
666	the status word (use the macros from C<sys/wait.h> and see your systems	1027	the status word (use the macros from C<sys/wait.h> and see your systems
667	C<waitpid> documentation). The C<rpid> member contains the pid of the	1028	C<waitpid> documentation). The C<rpid> member contains the pid of the
668	process causing the status change.	1029	process causing the status change.
669		1030
670	=back	1031	=back
		1032
		1033	Example: try to exit cleanly on SIGINT and SIGTERM.
		1034
		1035	static void
		1036	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1037	{
		1038	ev_unloop (loop, EVUNLOOP_ALL);
		1039	}
		1040
		1041	struct ev_signal signal_watcher;
		1042	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1043	ev_signal_start (loop, &sigint_cb);
		1044
671		1045
672	=head2 C<ev_idle> - when you've got nothing better to do	1046	=head2 C<ev_idle> - when you've got nothing better to do
673		1047
674	Idle watchers trigger events when there are no other events are pending	1048	Idle watchers trigger events when there are no other events are pending
675	(prepare, check and other idle watchers do not count). That is, as long	1049	(prepare, check and other idle watchers do not count). That is, as long
…		…
695	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1069	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
696	believe me.	1070	believe me.
697		1071
698	=back	1072	=back
699		1073
		1074	Example: dynamically allocate an C<ev_idle>, start it, and in the
		1075	callback, free it. Alos, use no error checking, as usual.
		1076
		1077	static void
		1078	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1079	{
		1080	free (w);
		1081	// now do something you wanted to do when the program has
		1082	// no longer asnything immediate to do.
		1083	}
		1084
		1085	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1086	ev_idle_init (idle_watcher, idle_cb);
		1087	ev_idle_start (loop, idle_cb);
		1088
		1089
700	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1090	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
701		1091
702	Prepare and check watchers are usually (but not always) used in tandem:	1092	Prepare and check watchers are usually (but not always) used in tandem:
703	prepare watchers get invoked before the process blocks and check watchers	1093	prepare watchers get invoked before the process blocks and check watchers
704	afterwards.	1094	afterwards.
705		1095
706	Their main purpose is to integrate other event mechanisms into libev. This	1096	Their main purpose is to integrate other event mechanisms into libev and
707	could be used, for example, to track variable changes, implement your own	1097	their use is somewhat advanced. This could be used, for example, to track
708	watchers, integrate net-snmp or a coroutine library and lots more.	1098	variable changes, implement your own watchers, integrate net-snmp or a
		1099	coroutine library and lots more.
709		1100
710	This is done by examining in each prepare call which file descriptors need	1101	This is done by examining in each prepare call which file descriptors need
711	to be watched by the other library, registering C<ev_io> watchers for	1102	to be watched by the other library, registering C<ev_io> watchers for
712	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1103	them and starting an C<ev_timer> watcher for any timeouts (many libraries
713	provide just this functionality). Then, in the check watcher you check for	1104	provide just this functionality). Then, in the check watcher you check for
…		…
735	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1126	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
736	macros, but using them is utterly, utterly and completely pointless.	1127	macros, but using them is utterly, utterly and completely pointless.
737		1128
738	=back	1129	=back
739		1130
		1131	Example: TODO.
		1132
		1133
		1134	=head2 C<ev_embed> - when one backend isn't enough
		1135
		1136	This is a rather advanced watcher type that lets you embed one event loop
		1137	into another (currently only C<ev_io> events are supported in the embedded
		1138	loop, other types of watchers might be handled in a delayed or incorrect
		1139	fashion and must not be used).
		1140
		1141	There are primarily two reasons you would want that: work around bugs and
		1142	prioritise I/O.
		1143
		1144	As an example for a bug workaround, the kqueue backend might only support
		1145	sockets on some platform, so it is unusable as generic backend, but you
		1146	still want to make use of it because you have many sockets and it scales
		1147	so nicely. In this case, you would create a kqueue-based loop and embed it
		1148	into your default loop (which might use e.g. poll). Overall operation will
		1149	be a bit slower because first libev has to poll and then call kevent, but
		1150	at least you can use both at what they are best.
		1151
		1152	As for prioritising I/O: rarely you have the case where some fds have
		1153	to be watched and handled very quickly (with low latency), and even
		1154	priorities and idle watchers might have too much overhead. In this case
		1155	you would put all the high priority stuff in one loop and all the rest in
		1156	a second one, and embed the second one in the first.
		1157
		1158	As long as the watcher is active, the callback will be invoked every time
		1159	there might be events pending in the embedded loop. The callback must then
		1160	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1161	their callbacks (you could also start an idle watcher to give the embedded
		1162	loop strictly lower priority for example). You can also set the callback
		1163	to C<0>, in which case the embed watcher will automatically execute the
		1164	embedded loop sweep.
		1165
		1166	As long as the watcher is started it will automatically handle events. The
		1167	callback will be invoked whenever some events have been handled. You can
		1168	set the callback to C<0> to avoid having to specify one if you are not
		1169	interested in that.
		1170
		1171	Also, there have not currently been made special provisions for forking:
		1172	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1173	but you will also have to stop and restart any C<ev_embed> watchers
		1174	yourself.
		1175
		1176	Unfortunately, not all backends are embeddable, only the ones returned by
		1177	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1178	portable one.
		1179
		1180	So when you want to use this feature you will always have to be prepared
		1181	that you cannot get an embeddable loop. The recommended way to get around
		1182	this is to have a separate variables for your embeddable loop, try to
		1183	create it, and if that fails, use the normal loop for everything:
		1184
		1185	struct ev_loop *loop_hi = ev_default_init (0);
		1186	struct ev_loop *loop_lo = 0;
		1187	struct ev_embed embed;
		1188
		1189	// see if there is a chance of getting one that works
		1190	// (remember that a flags value of 0 means autodetection)
		1191	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1192	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1193	: 0;
		1194
		1195	// if we got one, then embed it, otherwise default to loop_hi
		1196	if (loop_lo)
		1197	{
		1198	ev_embed_init (&embed, 0, loop_lo);
		1199	ev_embed_start (loop_hi, &embed);
		1200	}
		1201	else
		1202	loop_lo = loop_hi;
		1203
		1204	=over 4
		1205
		1206	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1207
		1208	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1209
		1210	Configures the watcher to embed the given loop, which must be
		1211	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1212	invoked automatically, otherwise it is the responsibility of the callback
		1213	to invoke it (it will continue to be called until the sweep has been done,
		1214	if you do not want thta, you need to temporarily stop the embed watcher).
		1215
		1216	=item ev_embed_sweep (loop, ev_embed *)
		1217
		1218	Make a single, non-blocking sweep over the embedded loop. This works
		1219	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1220	apropriate way for embedded loops.
		1221
		1222	=back
		1223
		1224
740	=head1 OTHER FUNCTIONS	1225	=head1 OTHER FUNCTIONS
741		1226
742	There are some other functions of possible interest. Described. Here. Now.	1227	There are some other functions of possible interest. Described. Here. Now.
743		1228
744	=over 4	1229	=over 4
…		…
773	/* stdin might have data for us, joy! */;	1258	/* stdin might have data for us, joy! */;
774	}	1259	}
775		1260
776	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1261	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
777		1262
778	=item ev_feed_event (loop, watcher, int events)	1263	=item ev_feed_event (ev_loop , watcher , int revents)
779		1264
780	Feeds the given event set into the event loop, as if the specified event	1265	Feeds the given event set into the event loop, as if the specified event
781	had happened for the specified watcher (which must be a pointer to an	1266	had happened for the specified watcher (which must be a pointer to an
782	initialised but not necessarily started event watcher).	1267	initialised but not necessarily started event watcher).
783		1268
784	=item ev_feed_fd_event (loop, int fd, int revents)	1269	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
785		1270
786	Feed an event on the given fd, as if a file descriptor backend detected	1271	Feed an event on the given fd, as if a file descriptor backend detected
787	the given events it.	1272	the given events it.
788		1273
789	=item ev_feed_signal_event (loop, int signum)	1274	=item ev_feed_signal_event (ev_loop *loop, int signum)
790		1275
791	Feed an event as if the given signal occured (loop must be the default loop!).	1276	Feed an event as if the given signal occured (C<loop> must be the default
		1277	loop!).
792		1278
793	=back	1279	=back
		1280
794		1281
795	=head1 LIBEVENT EMULATION	1282	=head1 LIBEVENT EMULATION
796		1283
797	Libev offers a compatibility emulation layer for libevent. It cannot	1284	Libev offers a compatibility emulation layer for libevent. It cannot
798	emulate the internals of libevent, so here are some usage hints:	1285	emulate the internals of libevent, so here are some usage hints:

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Comparing libev/ev.pod (file contents): Revision 1.27 by root, Wed Nov 14 05:02:07 2007 UTC vs. Revision 1.36 by root, Sat Nov 24 07:14:26 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.27 by root, Wed Nov 14 05:02:07 2007 UTC vs.
Revision 1.36 by root, Sat Nov 24 07:14:26 2007 UTC