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

Comparing libev/ev.pod (file contents):
Revision 1.30 by root, Fri Nov 23 04:36:03 2007 UTC vs.
Revision 1.44 by root, Sat Nov 24 16:57:30 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> (value 1, portable select backend)	223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		224
152	This is your standard select(2) backend. Not I<completely> standard, as	225	This is your standard select(2) backend. Not I<completely> standard, as
153	libev tries to roll its own fd_set with no limits on the number of fds,	226	libev tries to roll its own fd_set with no limits on the number of fds,
154	but if that fails, expect a fairly low limit on the number of fds when	227	but if that fails, expect a fairly low limit on the number of fds when
155	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	228	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
156	the fastest backend for a low number of fds.	229	the fastest backend for a low number of fds.
157		230
158	=item C<EVMETHOD_POLL> (value 2, poll backend, available everywhere except on windows)	231	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
159		232
160	And this is your standard poll(2) backend. It's more complicated than	233	And this is your standard poll(2) backend. It's more complicated than
161	select, but handles sparse fds better and has no artificial limit on the	234	select, but handles sparse fds better and has no artificial limit on the
162	number of fds you can use (except it will slow down considerably with a	235	number of fds you can use (except it will slow down considerably with a
163	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	236	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
164		237
165	=item C<EVMETHOD_EPOLL> (value 4, Linux)	238	=item C<EVBACKEND_EPOLL> (value 4, Linux)
166		239
167	For few fds, this backend is a bit little slower than poll and select,	240	For few fds, this backend is a bit little slower than poll and select,
168	but it scales phenomenally better. While poll and select usually scale like	241	but it scales phenomenally better. While poll and select usually scale like
169	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	242	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
170	either O(1) or O(active_fds).	243	either O(1) or O(active_fds).
…		…
173	result in some caching, there is still a syscall per such incident	246	result in some caching, there is still a syscall per such incident
174	(because the fd could point to a different file description now), so its	247	(because the fd could point to a different file description now), so its
175	best to avoid that. Also, dup()ed file descriptors might not work very	248	best to avoid that. Also, dup()ed file descriptors might not work very
176	well if you register events for both fds.	249	well if you register events for both fds.
177		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
178	=item C<EVMETHOD_KQUEUE> (value 8, most BSD clones)	255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
179		256
180	Kqueue deserves special mention, as at the time of this writing, it	257	Kqueue deserves special mention, as at the time of this writing, it
181	was broken on all BSDs except NetBSD (usually it doesn't work with	258	was broken on all BSDs except NetBSD (usually it doesn't work with
182	anything but sockets and pipes, except on Darwin, where of course its	259	anything but sockets and pipes, except on Darwin, where of course its
183	completely useless). For this reason its not being "autodetected" unless	260	completely useless). For this reason its not being "autodetected"
184	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).	261	unless you explicitly specify it explicitly in the flags (i.e. using
		262	C<EVBACKEND_KQUEUE>).
185		263
186	It scales in the same way as the epoll backend, but the interface to the	264	It scales in the same way as the epoll backend, but the interface to the
187	kernel is more efficient (which says nothing about its actual speed, of	265	kernel is more efficient (which says nothing about its actual speed, of
188	course). While starting and stopping an I/O watcher does not cause an	266	course). While starting and stopping an I/O watcher does not cause an
189	extra syscall as with epoll, it still adds up to four event changes per	267	extra syscall as with epoll, it still adds up to four event changes per
190	incident, so its best to avoid that.	268	incident, so its best to avoid that.
191		269
192	=item C<EVMETHOD_DEVPOLL> (value 16, Solaris 8)	270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
193		271
194	This is not implemented yet (and might never be).	272	This is not implemented yet (and might never be).
195		273
196	=item C<EVMETHOD_PORT> (value 32, Solaris 10)	274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
197		275
198	This uses the Solaris 10 port mechanism. As with everything on Solaris,	276	This uses the Solaris 10 port mechanism. As with everything on Solaris,
199	it's really slow, but it still scales very well (O(active_fds)).	277	it's really slow, but it still scales very well (O(active_fds)).
200		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
201	=item C<EVMETHOD_ALL>	283	=item C<EVBACKEND_ALL>
202		284
203	Try all backends (even potentially broken ones that wouldn't be tried	285	Try all backends (even potentially broken ones that wouldn't be tried
204	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	286	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
205	C<EVMETHOD_ALL & ~EVMETHOD_KQUEUE>.	287	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
206		288
207	=back	289	=back
208		290
209	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
210	backends will be tried (in the reverse order as given here). If none are	292	backends will be tried (in the reverse order as given here). If none are
211	specified, most compiled-in backend will be tried, usually in reverse	293	specified, most compiled-in backend will be tried, usually in reverse
212	order of their flag values :)	294	order of their flag values :)
213		295
		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);
		311
214	=item struct ev_loop *ev_loop_new (unsigned int flags)	312	=item struct ev_loop *ev_loop_new (unsigned int flags)
215		313
216	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
217	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
218	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
219	undefined behaviour (or a failed assertion if assertions are enabled).	317	undefined behaviour (or a failed assertion if assertions are enabled).
220		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
221	=item ev_default_destroy ()	325	=item ev_default_destroy ()
222		326
223	Destroys the default loop again (frees all memory and kernel state	327	Destroys the default loop again (frees all memory and kernel state
224	etc.). This stops all registered event watchers (by not touching them in	328	etc.). None of the active event watchers will be stopped in the normal
225	any way whatsoever, although you cannot rely on this :).	329	sense, so e.g. C<ev_is_active> might still return true. It is your
		330	responsibility to either stop all watchers cleanly yoursef I<before>
		331	calling this function, or cope with the fact afterwards (which is usually
		332	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		333	for example).
226		334
227	=item ev_loop_destroy (loop)	335	=item ev_loop_destroy (loop)
228		336
229	Like C<ev_default_destroy>, but destroys an event loop created by an	337	Like C<ev_default_destroy>, but destroys an event loop created by an
230	earlier call to C<ev_loop_new>.	338	earlier call to C<ev_loop_new>.
…		…
244	it just in case after a fork. To make this easy, the function will fit in	352	it just in case after a fork. To make this easy, the function will fit in
245	quite nicely into a call to C<pthread_atfork>:	353	quite nicely into a call to C<pthread_atfork>:
246		354
247	pthread_atfork (0, 0, ev_default_fork);	355	pthread_atfork (0, 0, ev_default_fork);
248		356
		357	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		358	without calling this function, so if you force one of those backends you
		359	do not need to care.
		360
249	=item ev_loop_fork (loop)	361	=item ev_loop_fork (loop)
250		362
251	Like C<ev_default_fork>, but acts on an event loop created by	363	Like C<ev_default_fork>, but acts on an event loop created by
252	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
253	after fork, and how you do this is entirely your own problem.	365	after fork, and how you do this is entirely your own problem.
254		366
255	=item unsigned int ev_method (loop)	367	=item unsigned int ev_backend (loop)
256		368
257	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
258	use.	370	use.
259		371
260	=item ev_tstamp ev_now (loop)	372	=item ev_tstamp ev_now (loop)
261		373
262	Returns the current "event loop time", which is the time the event loop	374	Returns the current "event loop time", which is the time the event loop
263	got events and started processing them. This timestamp does not change	375	received events and started processing them. This timestamp does not
264	as long as callbacks are being processed, and this is also the base time	376	change as long as callbacks are being processed, and this is also the base
265	used for relative timers. You can treat it as the timestamp of the event	377	time used for relative timers. You can treat it as the timestamp of the
266	occuring (or more correctly, the mainloop finding out about it).	378	event occuring (or more correctly, libev finding out about it).
267		379
268	=item ev_loop (loop, int flags)	380	=item ev_loop (loop, int flags)
269		381
270	Finally, this is it, the event handler. This function usually is called	382	Finally, this is it, the event handler. This function usually is called
271	after you initialised all your watchers and you want to start handling	383	after you initialised all your watchers and you want to start handling
272	events.	384	events.
273		385
274	If the flags argument is specified as 0, it will not return until either	386	If the flags argument is specified as C<0>, it will not return until
275	no event watchers are active anymore or C<ev_unloop> was called.	387	either no event watchers are active anymore or C<ev_unloop> was called.
		388
		389	Please note that an explicit C<ev_unloop> is usually better than
		390	relying on all watchers to be stopped when deciding when a program has
		391	finished (especially in interactive programs), but having a program that
		392	automatically loops as long as it has to and no longer by virtue of
		393	relying on its watchers stopping correctly is a thing of beauty.
276		394
277	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	395	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
278	those events and any outstanding ones, but will not block your process in	396	those events and any outstanding ones, but will not block your process in
279	case there are no events and will return after one iteration of the loop.	397	case there are no events and will return after one iteration of the loop.
280		398
281	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	399	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
282	neccessary) and will handle those and any outstanding ones. It will block	400	neccessary) and will handle those and any outstanding ones. It will block
283	your process until at least one new event arrives, and will return after	401	your process until at least one new event arrives, and will return after
284	one iteration of the loop.	402	one iteration of the loop. This is useful if you are waiting for some
		403	external event in conjunction with something not expressible using other
		404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		405	usually a better approach for this kind of thing.
285		406
286	This flags value could be used to implement alternative looping
287	constructs, but the C<prepare> and C<check> watchers provide a better and
288	more generic mechanism.
289
290	Here are the gory details of what ev_loop does:	407	Here are the gory details of what C<ev_loop> does:
291		408
292	1. If there are no active watchers (reference count is zero), return.	409	* If there are no active watchers (reference count is zero), return.
293	2. Queue and immediately call all prepare watchers.	410	- Queue prepare watchers and then call all outstanding watchers.
294	3. If we have been forked, recreate the kernel state.	411	- If we have been forked, recreate the kernel state.
295	4. Update the kernel state with all outstanding changes.	412	- Update the kernel state with all outstanding changes.
296	5. Update the "event loop time".	413	- Update the "event loop time".
297	6. Calculate for how long to block.	414	- Calculate for how long to block.
298	7. Block the process, waiting for events.	415	- Block the process, waiting for any events.
		416	- Queue all outstanding I/O (fd) events.
299	8. Update the "event loop time" and do time jump handling.	417	- Update the "event loop time" and do time jump handling.
300	9. Queue all outstanding timers.	418	- Queue all outstanding timers.
301	10. Queue all outstanding periodics.	419	- Queue all outstanding periodics.
302	11. If no events are pending now, queue all idle watchers.	420	- If no events are pending now, queue all idle watchers.
303	12. Queue all check watchers.	421	- Queue all check watchers.
304	13. Call all queued watchers in reverse order (i.e. check watchers first).	422	- Call all queued watchers in reverse order (i.e. check watchers first).
		423	Signals and child watchers are implemented as I/O watchers, and will
		424	be handled here by queueing them when their watcher gets executed.
305	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
306	was used, return, otherwise continue with step #1.	426	were used, return, otherwise continue with step *.
		427
		428	Example: queue some jobs and then loop until no events are outsanding
		429	anymore.
		430
		431	... queue jobs here, make sure they register event watchers as long
		432	... as they still have work to do (even an idle watcher will do..)
		433	ev_loop (my_loop, 0);
		434	... jobs done. yeah!
307		435
308	=item ev_unloop (loop, how)	436	=item ev_unloop (loop, how)
309		437
310	Can be used to make a call to C<ev_loop> return early (but only after it	438	Can be used to make a call to C<ev_loop> return early (but only after it
311	has processed all outstanding events). The C<how> argument must be either	439	has processed all outstanding events). The C<how> argument must be either
…		…
325	visible to the libev user and should not keep C<ev_loop> from exiting if	453	visible to the libev user and should not keep C<ev_loop> from exiting if
326	no event watchers registered by it are active. It is also an excellent	454	no event watchers registered by it are active. It is also an excellent
327	way to do this for generic recurring timers or from within third-party	455	way to do this for generic recurring timers or from within third-party
328	libraries. Just remember to I<unref after start> and I<ref before stop>.	456	libraries. Just remember to I<unref after start> and I<ref before stop>.
329		457
		458	Example: create a signal watcher, but keep it from keeping C<ev_loop>
		459	running when nothing else is active.
		460
		461	struct dv_signal exitsig;
		462	ev_signal_init (&exitsig, sig_cb, SIGINT);
		463	ev_signal_start (myloop, &exitsig);
		464	evf_unref (myloop);
		465
		466	Example: for some weird reason, unregister the above signal handler again.
		467
		468	ev_ref (myloop);
		469	ev_signal_stop (myloop, &exitsig);
		470
330	=back	471	=back
		472
331		473
332	=head1 ANATOMY OF A WATCHER	474	=head1 ANATOMY OF A WATCHER
333		475
334	A watcher is a structure that you create and register to record your	476	A watcher is a structure that you create and register to record your
335	interest in some event. For instance, if you want to wait for STDIN to	477	interest in some event. For instance, if you want to wait for STDIN to
…		…
368	*) >>), and you can stop watching for events at any time by calling the	510	*) >>), and you can stop watching for events at any time by calling the
369	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	511	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
370		512
371	As long as your watcher is active (has been started but not stopped) you	513	As long as your watcher is active (has been started but not stopped) you
372	must not touch the values stored in it. Most specifically you must never	514	must not touch the values stored in it. Most specifically you must never
373	reinitialise it or call its set method.	515	reinitialise it or call its C<set> macro.
374
375	You can check whether an event is active by calling the C<ev_is_active
376	(watcher *)> macro. To see whether an event is outstanding (but the
377	callback for it has not been called yet) you can use the C<ev_is_pending
378	(watcher *)> macro.
379		516
380	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
381	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
382	third argument.	519	third argument.
383		520
…		…
440	with the error from read() or write(). This will not work in multithreaded	577	with the error from read() or write(). This will not work in multithreaded
441	programs, though, so beware.	578	programs, though, so beware.
442		579
443	=back	580	=back
444		581
		582	=head2 GENERIC WATCHER FUNCTIONS
		583
		584	In the following description, C<TYPE> stands for the watcher type,
		585	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		586
		587	=over 4
		588
		589	=item C<ev_init> (ev_TYPE *watcher, callback)
		590
		591	This macro initialises the generic portion of a watcher. The contents
		592	of the watcher object can be arbitrary (so C<malloc> will do). Only
		593	the generic parts of the watcher are initialised, you I<need> to call
		594	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		595	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		596	which rolls both calls into one.
		597
		598	You can reinitialise a watcher at any time as long as it has been stopped
		599	(or never started) and there are no pending events outstanding.
		600
		601	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,
		602	int revents)>.
		603
		604	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		605
		606	This macro initialises the type-specific parts of a watcher. You need to
		607	call C<ev_init> at least once before you call this macro, but you can
		608	call C<ev_TYPE_set> any number of times. You must not, however, call this
		609	macro on a watcher that is active (it can be pending, however, which is a
		610	difference to the C<ev_init> macro).
		611
		612	Although some watcher types do not have type-specific arguments
		613	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		614
		615	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		616
		617	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		618	calls into a single call. This is the most convinient method to initialise
		619	a watcher. The same limitations apply, of course.
		620
		621	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)
		622
		623	Starts (activates) the given watcher. Only active watchers will receive
		624	events. If the watcher is already active nothing will happen.
		625
		626	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
		627
		628	Stops the given watcher again (if active) and clears the pending
		629	status. It is possible that stopped watchers are pending (for example,
		630	non-repeating timers are being stopped when they become pending), but
		631	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		632	you want to free or reuse the memory used by the watcher it is therefore a
		633	good idea to always call its C<ev_TYPE_stop> function.
		634
		635	=item bool ev_is_active (ev_TYPE *watcher)
		636
		637	Returns a true value iff the watcher is active (i.e. it has been started
		638	and not yet been stopped). As long as a watcher is active you must not modify
		639	it.
		640
		641	=item bool ev_is_pending (ev_TYPE *watcher)
		642
		643	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		644	events but its callback has not yet been invoked). As long as a watcher
		645	is pending (but not active) you must not call an init function on it (but
		646	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		647	libev (e.g. you cnanot C<free ()> it).
		648
		649	=item callback = ev_cb (ev_TYPE *watcher)
		650
		651	Returns the callback currently set on the watcher.
		652
		653	=item ev_cb_set (ev_TYPE *watcher, callback)
		654
		655	Change the callback. You can change the callback at virtually any time
		656	(modulo threads).
		657
		658	=back
		659
		660
445	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	661	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
446		662
447	Each watcher has, by default, a member C<void *data> that you can change	663	Each watcher has, by default, a member C<void *data> that you can change
448	and read at any time, libev will completely ignore it. This can be used	664	and read at any time, libev will completely ignore it. This can be used
449	to associate arbitrary data with your watcher. If you need more data and	665	to associate arbitrary data with your watcher. If you need more data and
…		…
475	=head1 WATCHER TYPES	691	=head1 WATCHER TYPES
476		692
477	This section describes each watcher in detail, but will not repeat	693	This section describes each watcher in detail, but will not repeat
478	information given in the last section.	694	information given in the last section.
479		695
		696
480	=head2 C<ev_io> - is this file descriptor readable or writable	697	=head2 C<ev_io> - is this file descriptor readable or writable?
481		698
482	I/O watchers check whether a file descriptor is readable or writable	699	I/O watchers check whether a file descriptor is readable or writable
483	in each iteration of the event loop (This behaviour is called	700	in each iteration of the event loop, or, more precisely, when reading
484	level-triggering because you keep receiving events as long as the	701	would not block the process and writing would at least be able to write
485	condition persists. Remember you can stop the watcher if you don't want to	702	some data. This behaviour is called level-triggering because you keep
486	act on the event and neither want to receive future events).	703	receiving events as long as the condition persists. Remember you can stop
		704	the watcher if you don't want to act on the event and neither want to
		705	receive future events.
487		706
488	In general you can register as many read and/or write event watchers per	707	In general you can register as many read and/or write event watchers per
489	fd as you want (as long as you don't confuse yourself). Setting all file	708	fd as you want (as long as you don't confuse yourself). Setting all file
490	descriptors to non-blocking mode is also usually a good idea (but not	709	descriptors to non-blocking mode is also usually a good idea (but not
491	required if you know what you are doing).	710	required if you know what you are doing).
492		711
493	You have to be careful with dup'ed file descriptors, though. Some backends	712	You have to be careful with dup'ed file descriptors, though. Some backends
494	(the linux epoll backend is a notable example) cannot handle dup'ed file	713	(the linux epoll backend is a notable example) cannot handle dup'ed file
495	descriptors correctly if you register interest in two or more fds pointing	714	descriptors correctly if you register interest in two or more fds pointing
496	to the same underlying file/socket etc. description (that is, they share	715	to the same underlying file/socket/etc. description (that is, they share
497	the same underlying "file open").	716	the same underlying "file open").
498		717
499	If you must do this, then force the use of a known-to-be-good backend	718	If you must do this, then force the use of a known-to-be-good backend
500	(at the time of this writing, this includes only EVMETHOD_SELECT and	719	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
501	EVMETHOD_POLL).	720	C<EVBACKEND_POLL>).
		721
		722	Another thing you have to watch out for is that it is quite easy to
		723	receive "spurious" readyness notifications, that is your callback might
		724	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		725	because there is no data. Not only are some backends known to create a
		726	lot of those (for example solaris ports), it is very easy to get into
		727	this situation even with a relatively standard program structure. Thus
		728	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		729	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		730
		731	If you cannot run the fd in non-blocking mode (for example you should not
		732	play around with an Xlib connection), then you have to seperately re-test
		733	wether a file descriptor is really ready with a known-to-be good interface
		734	such as poll (fortunately in our Xlib example, Xlib already does this on
		735	its own, so its quite safe to use).
502		736
503	=over 4	737	=over 4
504		738
505	=item ev_io_init (ev_io *, callback, int fd, int events)	739	=item ev_io_init (ev_io *, callback, int fd, int events)
506		740
507	=item ev_io_set (ev_io *, int fd, int events)	741	=item ev_io_set (ev_io *, int fd, int events)
508		742
509	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	743	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
510	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|	744	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
511	EV_WRITE> to receive the given events.	745	C<EV_READ \| EV_WRITE> to receive the given events.
512		746
513	=back	747	=back
514		748
		749	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
		750	readable, but only once. Since it is likely line-buffered, you could
		751	attempt to read a whole line in the callback:
		752
		753	static void
		754	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		755	{
		756	ev_io_stop (loop, w);
		757	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		758	}
		759
		760	...
		761	struct ev_loop *loop = ev_default_init (0);
		762	struct ev_io stdin_readable;
		763	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		764	ev_io_start (loop, &stdin_readable);
		765	ev_loop (loop, 0);
		766
		767
515	=head2 C<ev_timer> - relative and optionally recurring timeouts	768	=head2 C<ev_timer> - relative and optionally repeating timeouts
516		769
517	Timer watchers are simple relative timers that generate an event after a	770	Timer watchers are simple relative timers that generate an event after a
518	given time, and optionally repeating in regular intervals after that.	771	given time, and optionally repeating in regular intervals after that.
519		772
520	The timers are based on real time, that is, if you register an event that	773	The timers are based on real time, that is, if you register an event that
…		…
571	state where you do not expect data to travel on the socket, you can stop	824	state where you do not expect data to travel on the socket, you can stop
572	the timer, and again will automatically restart it if need be.	825	the timer, and again will automatically restart it if need be.
573		826
574	=back	827	=back
575		828
		829	Example: create a timer that fires after 60 seconds.
		830
		831	static void
		832	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		833	{
		834	.. one minute over, w is actually stopped right here
		835	}
		836
		837	struct ev_timer mytimer;
		838	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		839	ev_timer_start (loop, &mytimer);
		840
		841	Example: create a timeout timer that times out after 10 seconds of
		842	inactivity.
		843
		844	static void
		845	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		846	{
		847	.. ten seconds without any activity
		848	}
		849
		850	struct ev_timer mytimer;
		851	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		852	ev_timer_again (&mytimer); /* start timer */
		853	ev_loop (loop, 0);
		854
		855	// and in some piece of code that gets executed on any "activity":
		856	// reset the timeout to start ticking again at 10 seconds
		857	ev_timer_again (&mytimer);
		858
		859
576	=head2 C<ev_periodic> - to cron or not to cron	860	=head2 C<ev_periodic> - to cron or not to cron?
577		861
578	Periodic watchers are also timers of a kind, but they are very versatile	862	Periodic watchers are also timers of a kind, but they are very versatile
579	(and unfortunately a bit complex).	863	(and unfortunately a bit complex).
580		864
581	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	865	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
582	but on wallclock time (absolute time). You can tell a periodic watcher	866	but on wallclock time (absolute time). You can tell a periodic watcher
583	to trigger "at" some specific point in time. For example, if you tell a	867	to trigger "at" some specific point in time. For example, if you tell a
584	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	868	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
585	+ 10.>) and then reset your system clock to the last year, then it will	869	+ 10.>) and then reset your system clock to the last year, then it will
586	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	870	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
587	roughly 10 seconds later and of course not if you reset your system time	871	roughly 10 seconds later and of course not if you reset your system time
588	again).	872	again).
589		873
…		…
675	a different time than the last time it was called (e.g. in a crond like	959	a different time than the last time it was called (e.g. in a crond like
676	program when the crontabs have changed).	960	program when the crontabs have changed).
677		961
678	=back	962	=back
679		963
		964	Example: call a callback every hour, or, more precisely, whenever the
		965	system clock is divisible by 3600. The callback invocation times have
		966	potentially a lot of jittering, but good long-term stability.
		967
		968	static void
		969	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		970	{
		971	... its now a full hour (UTC, or TAI or whatever your clock follows)
		972	}
		973
		974	struct ev_periodic hourly_tick;
		975	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		976	ev_periodic_start (loop, &hourly_tick);
		977
		978	Example: the same as above, but use a reschedule callback to do it:
		979
		980	#include <math.h>
		981
		982	static ev_tstamp
		983	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		984	{
		985	return fmod (now, 3600.) + 3600.;
		986	}
		987
		988	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		989
		990	Example: call a callback every hour, starting now:
		991
		992	struct ev_periodic hourly_tick;
		993	ev_periodic_init (&hourly_tick, clock_cb,
		994	fmod (ev_now (loop), 3600.), 3600., 0);
		995	ev_periodic_start (loop, &hourly_tick);
		996
		997
680	=head2 C<ev_signal> - signal me when a signal gets signalled	998	=head2 C<ev_signal> - signal me when a signal gets signalled!
681		999
682	Signal watchers will trigger an event when the process receives a specific	1000	Signal watchers will trigger an event when the process receives a specific
683	signal one or more times. Even though signals are very asynchronous, libev	1001	signal one or more times. Even though signals are very asynchronous, libev
684	will try it's best to deliver signals synchronously, i.e. as part of the	1002	will try it's best to deliver signals synchronously, i.e. as part of the
685	normal event processing, like any other event.	1003	normal event processing, like any other event.
…		…
700	Configures the watcher to trigger on the given signal number (usually one	1018	Configures the watcher to trigger on the given signal number (usually one
701	of the C<SIGxxx> constants).	1019	of the C<SIGxxx> constants).
702		1020
703	=back	1021	=back
704		1022
		1023
705	=head2 C<ev_child> - wait for pid status changes	1024	=head2 C<ev_child> - watch out for process status changes
706		1025
707	Child watchers trigger when your process receives a SIGCHLD in response to	1026	Child watchers trigger when your process receives a SIGCHLD in response to
708	some child status changes (most typically when a child of yours dies).	1027	some child status changes (most typically when a child of yours dies).
709		1028
710	=over 4	1029	=over 4
…		…
720	C<waitpid> documentation). The C<rpid> member contains the pid of the	1039	C<waitpid> documentation). The C<rpid> member contains the pid of the
721	process causing the status change.	1040	process causing the status change.
722		1041
723	=back	1042	=back
724		1043
		1044	Example: try to exit cleanly on SIGINT and SIGTERM.
		1045
		1046	static void
		1047	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1048	{
		1049	ev_unloop (loop, EVUNLOOP_ALL);
		1050	}
		1051
		1052	struct ev_signal signal_watcher;
		1053	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1054	ev_signal_start (loop, &sigint_cb);
		1055
		1056
725	=head2 C<ev_idle> - when you've got nothing better to do	1057	=head2 C<ev_idle> - when you've got nothing better to do...
726		1058
727	Idle watchers trigger events when there are no other events are pending	1059	Idle watchers trigger events when there are no other events are pending
728	(prepare, check and other idle watchers do not count). That is, as long	1060	(prepare, check and other idle watchers do not count). That is, as long
729	as your process is busy handling sockets or timeouts (or even signals,	1061	as your process is busy handling sockets or timeouts (or even signals,
730	imagine) it will not be triggered. But when your process is idle all idle	1062	imagine) it will not be triggered. But when your process is idle all idle
…		…
748	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1080	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
749	believe me.	1081	believe me.
750		1082
751	=back	1083	=back
752		1084
		1085	Example: dynamically allocate an C<ev_idle>, start it, and in the
		1086	callback, free it. Alos, use no error checking, as usual.
		1087
		1088	static void
		1089	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1090	{
		1091	free (w);
		1092	// now do something you wanted to do when the program has
		1093	// no longer asnything immediate to do.
		1094	}
		1095
		1096	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1097	ev_idle_init (idle_watcher, idle_cb);
		1098	ev_idle_start (loop, idle_cb);
		1099
		1100
753	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1101	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
754		1102
755	Prepare and check watchers are usually (but not always) used in tandem:	1103	Prepare and check watchers are usually (but not always) used in tandem:
756	prepare watchers get invoked before the process blocks and check watchers	1104	prepare watchers get invoked before the process blocks and check watchers
757	afterwards.	1105	afterwards.
758		1106
759	Their main purpose is to integrate other event mechanisms into libev. This	1107	Their main purpose is to integrate other event mechanisms into libev and
760	could be used, for example, to track variable changes, implement your own	1108	their use is somewhat advanced. This could be used, for example, to track
761	watchers, integrate net-snmp or a coroutine library and lots more.	1109	variable changes, implement your own watchers, integrate net-snmp or a
		1110	coroutine library and lots more.
762		1111
763	This is done by examining in each prepare call which file descriptors need	1112	This is done by examining in each prepare call which file descriptors need
764	to be watched by the other library, registering C<ev_io> watchers for	1113	to be watched by the other library, registering C<ev_io> watchers for
765	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1114	them and starting an C<ev_timer> watcher for any timeouts (many libraries
766	provide just this functionality). Then, in the check watcher you check for	1115	provide just this functionality). Then, in the check watcher you check for
…		…
788	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1137	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
789	macros, but using them is utterly, utterly and completely pointless.	1138	macros, but using them is utterly, utterly and completely pointless.
790		1139
791	=back	1140	=back
792		1141
		1142	Example: TODO.
		1143
		1144
		1145	=head2 C<ev_embed> - when one backend isn't enough...
		1146
		1147	This is a rather advanced watcher type that lets you embed one event loop
		1148	into another (currently only C<ev_io> events are supported in the embedded
		1149	loop, other types of watchers might be handled in a delayed or incorrect
		1150	fashion and must not be used).
		1151
		1152	There are primarily two reasons you would want that: work around bugs and
		1153	prioritise I/O.
		1154
		1155	As an example for a bug workaround, the kqueue backend might only support
		1156	sockets on some platform, so it is unusable as generic backend, but you
		1157	still want to make use of it because you have many sockets and it scales
		1158	so nicely. In this case, you would create a kqueue-based loop and embed it
		1159	into your default loop (which might use e.g. poll). Overall operation will
		1160	be a bit slower because first libev has to poll and then call kevent, but
		1161	at least you can use both at what they are best.
		1162
		1163	As for prioritising I/O: rarely you have the case where some fds have
		1164	to be watched and handled very quickly (with low latency), and even
		1165	priorities and idle watchers might have too much overhead. In this case
		1166	you would put all the high priority stuff in one loop and all the rest in
		1167	a second one, and embed the second one in the first.
		1168
		1169	As long as the watcher is active, the callback will be invoked every time
		1170	there might be events pending in the embedded loop. The callback must then
		1171	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1172	their callbacks (you could also start an idle watcher to give the embedded
		1173	loop strictly lower priority for example). You can also set the callback
		1174	to C<0>, in which case the embed watcher will automatically execute the
		1175	embedded loop sweep.
		1176
		1177	As long as the watcher is started it will automatically handle events. The
		1178	callback will be invoked whenever some events have been handled. You can
		1179	set the callback to C<0> to avoid having to specify one if you are not
		1180	interested in that.
		1181
		1182	Also, there have not currently been made special provisions for forking:
		1183	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1184	but you will also have to stop and restart any C<ev_embed> watchers
		1185	yourself.
		1186
		1187	Unfortunately, not all backends are embeddable, only the ones returned by
		1188	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1189	portable one.
		1190
		1191	So when you want to use this feature you will always have to be prepared
		1192	that you cannot get an embeddable loop. The recommended way to get around
		1193	this is to have a separate variables for your embeddable loop, try to
		1194	create it, and if that fails, use the normal loop for everything:
		1195
		1196	struct ev_loop *loop_hi = ev_default_init (0);
		1197	struct ev_loop *loop_lo = 0;
		1198	struct ev_embed embed;
		1199
		1200	// see if there is a chance of getting one that works
		1201	// (remember that a flags value of 0 means autodetection)
		1202	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1203	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1204	: 0;
		1205
		1206	// if we got one, then embed it, otherwise default to loop_hi
		1207	if (loop_lo)
		1208	{
		1209	ev_embed_init (&embed, 0, loop_lo);
		1210	ev_embed_start (loop_hi, &embed);
		1211	}
		1212	else
		1213	loop_lo = loop_hi;
		1214
		1215	=over 4
		1216
		1217	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1218
		1219	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1220
		1221	Configures the watcher to embed the given loop, which must be
		1222	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1223	invoked automatically, otherwise it is the responsibility of the callback
		1224	to invoke it (it will continue to be called until the sweep has been done,
		1225	if you do not want thta, you need to temporarily stop the embed watcher).
		1226
		1227	=item ev_embed_sweep (loop, ev_embed *)
		1228
		1229	Make a single, non-blocking sweep over the embedded loop. This works
		1230	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1231	apropriate way for embedded loops.
		1232
		1233	=back
		1234
		1235
793	=head1 OTHER FUNCTIONS	1236	=head1 OTHER FUNCTIONS
794		1237
795	There are some other functions of possible interest. Described. Here. Now.	1238	There are some other functions of possible interest. Described. Here. Now.
796		1239
797	=over 4	1240	=over 4
…		…
826	/* stdin might have data for us, joy! */;	1269	/* stdin might have data for us, joy! */;
827	}	1270	}
828		1271
829	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1272	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
830		1273
831	=item ev_feed_event (loop, watcher, int events)	1274	=item ev_feed_event (ev_loop , watcher , int revents)
832		1275
833	Feeds the given event set into the event loop, as if the specified event	1276	Feeds the given event set into the event loop, as if the specified event
834	had happened for the specified watcher (which must be a pointer to an	1277	had happened for the specified watcher (which must be a pointer to an
835	initialised but not necessarily started event watcher).	1278	initialised but not necessarily started event watcher).
836		1279
837	=item ev_feed_fd_event (loop, int fd, int revents)	1280	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
838		1281
839	Feed an event on the given fd, as if a file descriptor backend detected	1282	Feed an event on the given fd, as if a file descriptor backend detected
840	the given events it.	1283	the given events it.
841		1284
842	=item ev_feed_signal_event (loop, int signum)	1285	=item ev_feed_signal_event (ev_loop *loop, int signum)
843		1286
844	Feed an event as if the given signal occured (loop must be the default loop!).	1287	Feed an event as if the given signal occured (C<loop> must be the default
		1288	loop!).
845		1289
846	=back	1290	=back
		1291
847		1292
848	=head1 LIBEVENT EMULATION	1293	=head1 LIBEVENT EMULATION
849		1294
850	Libev offers a compatibility emulation layer for libevent. It cannot	1295	Libev offers a compatibility emulation layer for libevent. It cannot
851	emulate the internals of libevent, so here are some usage hints:	1296	emulate the internals of libevent, so here are some usage hints:
…		…
872		1317
873	=back	1318	=back
874		1319
875	=head1 C++ SUPPORT	1320	=head1 C++ SUPPORT
876		1321
877	TBD.	1322	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1323	you to use some convinience methods to start/stop watchers and also change
		1324	the callback model to a model using method callbacks on objects.
		1325
		1326	To use it,
		1327
		1328	#include <ev++.h>
		1329
		1330	(it is not installed by default). This automatically includes F<ev.h>
		1331	and puts all of its definitions (many of them macros) into the global
		1332	namespace. All C++ specific things are put into the C<ev> namespace.
		1333
		1334	It should support all the same embedding options as F<ev.h>, most notably
		1335	C<EV_MULTIPLICITY>.
		1336
		1337	Here is a list of things available in the C<ev> namespace:
		1338
		1339	=over 4
		1340
		1341	=item C<ev::READ>, C<ev::WRITE> etc.
		1342
		1343	These are just enum values with the same values as the C<EV_READ> etc.
		1344	macros from F<ev.h>.
		1345
		1346	=item C<ev::tstamp>, C<ev::now>
		1347
		1348	Aliases to the same types/functions as with the C<ev_> prefix.
		1349
		1350	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1351
		1352	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1353	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1354	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1355	defines by many implementations.
		1356
		1357	All of those classes have these methods:
		1358
		1359	=over 4
		1360
		1361	=item ev::TYPE::TYPE (object , object::method )
		1362
		1363	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)
		1364
		1365	=item ev::TYPE::~TYPE
		1366
		1367	The constructor takes a pointer to an object and a method pointer to
		1368	the event handler callback to call in this class. The constructor calls
		1369	C<ev_init> for you, which means you have to call the C<set> method
		1370	before starting it. If you do not specify a loop then the constructor
		1371	automatically associates the default loop with this watcher.
		1372
		1373	The destructor automatically stops the watcher if it is active.
		1374
		1375	=item w->set (struct ev_loop *)
		1376
		1377	Associates a different C<struct ev_loop> with this watcher. You can only
		1378	do this when the watcher is inactive (and not pending either).
		1379
		1380	=item w->set ([args])
		1381
		1382	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1383	called at least once. Unlike the C counterpart, an active watcher gets
		1384	automatically stopped and restarted.
		1385
		1386	=item w->start ()
		1387
		1388	Starts the watcher. Note that there is no C<loop> argument as the
		1389	constructor already takes the loop.
		1390
		1391	=item w->stop ()
		1392
		1393	Stops the watcher if it is active. Again, no C<loop> argument.
		1394
		1395	=item w->again () C<ev::timer>, C<ev::periodic> only
		1396
		1397	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1398	C<ev_TYPE_again> function.
		1399
		1400	=item w->sweep () C<ev::embed> only
		1401
		1402	Invokes C<ev_embed_sweep>.
		1403
		1404	=back
		1405
		1406	=back
		1407
		1408	Example: Define a class with an IO and idle watcher, start one of them in
		1409	the constructor.
		1410
		1411	class myclass
		1412	{
		1413	ev_io io; void io_cb (ev::io &w, int revents);
		1414	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1415
		1416	myclass ();
		1417	}
		1418
		1419	myclass::myclass (int fd)
		1420	: io (this, &myclass::io_cb),
		1421	idle (this, &myclass::idle_cb)
		1422	{
		1423	io.start (fd, ev::READ);
		1424	}
		1425
		1426	=head1 EMBEDDING
		1427
		1428	Libev can (and often is) directly embedded into host
		1429	applications. Examples of applications that embed it include the Deliantra
		1430	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1431	and rxvt-unicode.
		1432
		1433	The goal is to enable you to just copy the neecssary files into your
		1434	source directory without having to change even a single line in them, so
		1435	you can easily upgrade by simply copying (or having a checked-out copy of
		1436	libev somewhere in your source tree).
		1437
		1438	=head2 FILESETS
		1439
		1440	Depending on what features you need you need to include one or more sets of files
		1441	in your app.
		1442
		1443	=head3 CORE EVENT LOOP
		1444
		1445	To include only the libev core (all the C<ev_*> functions), with manual
		1446	configuration (no autoconf):
		1447
		1448	#define EV_STANDALONE 1
		1449	#include "ev.c"
		1450
		1451	This will automatically include F<ev.h>, too, and should be done in a
		1452	single C source file only to provide the function implementations. To use
		1453	it, do the same for F<ev.h> in all files wishing to use this API (best
		1454	done by writing a wrapper around F<ev.h> that you can include instead and
		1455	where you can put other configuration options):
		1456
		1457	#define EV_STANDALONE 1
		1458	#include "ev.h"
		1459
		1460	Both header files and implementation files can be compiled with a C++
		1461	compiler (at least, thats a stated goal, and breakage will be treated
		1462	as a bug).
		1463
		1464	You need the following files in your source tree, or in a directory
		1465	in your include path (e.g. in libev/ when using -Ilibev):
		1466
		1467	ev.h
		1468	ev.c
		1469	ev_vars.h
		1470	ev_wrap.h
		1471
		1472	ev_win32.c required on win32 platforms only
		1473
		1474	ev_select.c only when select backend is enabled (which is by default)
		1475	ev_poll.c only when poll backend is enabled (disabled by default)
		1476	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1477	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1478	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1479
		1480	F<ev.c> includes the backend files directly when enabled, so you only need
		1481	to compile this single file.
		1482
		1483	=head3 LIBEVENT COMPATIBILITY API
		1484
		1485	To include the libevent compatibility API, also include:
		1486
		1487	#include "event.c"
		1488
		1489	in the file including F<ev.c>, and:
		1490
		1491	#include "event.h"
		1492
		1493	in the files that want to use the libevent API. This also includes F<ev.h>.
		1494
		1495	You need the following additional files for this:
		1496
		1497	event.h
		1498	event.c
		1499
		1500	=head3 AUTOCONF SUPPORT
		1501
		1502	Instead of using C<EV_STANDALONE=1> and providing your config in
		1503	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1504	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1505	include F<config.h> and configure itself accordingly.
		1506
		1507	For this of course you need the m4 file:
		1508
		1509	libev.m4
		1510
		1511	=head2 PREPROCESSOR SYMBOLS/MACROS
		1512
		1513	Libev can be configured via a variety of preprocessor symbols you have to define
		1514	before including any of its files. The default is not to build for multiplicity
		1515	and only include the select backend.
		1516
		1517	=over 4
		1518
		1519	=item EV_STANDALONE
		1520
		1521	Must always be C<1> if you do not use autoconf configuration, which
		1522	keeps libev from including F<config.h>, and it also defines dummy
		1523	implementations for some libevent functions (such as logging, which is not
		1524	supported). It will also not define any of the structs usually found in
		1525	F<event.h> that are not directly supported by the libev core alone.
		1526
		1527	=item EV_USE_MONOTONIC
		1528
		1529	If defined to be C<1>, libev will try to detect the availability of the
		1530	monotonic clock option at both compiletime and runtime. Otherwise no use
		1531	of the monotonic clock option will be attempted. If you enable this, you
		1532	usually have to link against librt or something similar. Enabling it when
		1533	the functionality isn't available is safe, though, althoguh you have
		1534	to make sure you link against any libraries where the C<clock_gettime>
		1535	function is hiding in (often F<-lrt>).
		1536
		1537	=item EV_USE_REALTIME
		1538
		1539	If defined to be C<1>, libev will try to detect the availability of the
		1540	realtime clock option at compiletime (and assume its availability at
		1541	runtime if successful). Otherwise no use of the realtime clock option will
		1542	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1543	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1544	in the description of C<EV_USE_MONOTONIC>, though.
		1545
		1546	=item EV_USE_SELECT
		1547
		1548	If undefined or defined to be C<1>, libev will compile in support for the
		1549	C<select>(2) backend. No attempt at autodetection will be done: if no
		1550	other method takes over, select will be it. Otherwise the select backend
		1551	will not be compiled in.
		1552
		1553	=item EV_SELECT_USE_FD_SET
		1554
		1555	If defined to C<1>, then the select backend will use the system C<fd_set>
		1556	structure. This is useful if libev doesn't compile due to a missing
		1557	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1558	exotic systems. This usually limits the range of file descriptors to some
		1559	low limit such as 1024 or might have other limitations (winsocket only
		1560	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1561	influence the size of the C<fd_set> used.
		1562
		1563	=item EV_SELECT_IS_WINSOCKET
		1564
		1565	When defined to C<1>, the select backend will assume that
		1566	select/socket/connect etc. don't understand file descriptors but
		1567	wants osf handles on win32 (this is the case when the select to
		1568	be used is the winsock select). This means that it will call
		1569	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1570	it is assumed that all these functions actually work on fds, even
		1571	on win32. Should not be defined on non-win32 platforms.
		1572
		1573	=item EV_USE_POLL
		1574
		1575	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1576	backend. Otherwise it will be enabled on non-win32 platforms. It
		1577	takes precedence over select.
		1578
		1579	=item EV_USE_EPOLL
		1580
		1581	If defined to be C<1>, libev will compile in support for the Linux
		1582	C<epoll>(7) backend. Its availability will be detected at runtime,
		1583	otherwise another method will be used as fallback. This is the
		1584	preferred backend for GNU/Linux systems.
		1585
		1586	=item EV_USE_KQUEUE
		1587
		1588	If defined to be C<1>, libev will compile in support for the BSD style
		1589	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		1590	otherwise another method will be used as fallback. This is the preferred
		1591	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		1592	supports some types of fds correctly (the only platform we found that
		1593	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		1594	not be used unless explicitly requested. The best way to use it is to find
		1595	out whether kqueue supports your type of fd properly and use an embedded
		1596	kqueue loop.
		1597
		1598	=item EV_USE_PORT
		1599
		1600	If defined to be C<1>, libev will compile in support for the Solaris
		1601	10 port style backend. Its availability will be detected at runtime,
		1602	otherwise another method will be used as fallback. This is the preferred
		1603	backend for Solaris 10 systems.
		1604
		1605	=item EV_USE_DEVPOLL
		1606
		1607	reserved for future expansion, works like the USE symbols above.
		1608
		1609	=item EV_H
		1610
		1611	The name of the F<ev.h> header file used to include it. The default if
		1612	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		1613	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		1614
		1615	=item EV_CONFIG_H
		1616
		1617	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		1618	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		1619	C<EV_H>, above.
		1620
		1621	=item EV_EVENT_H
		1622
		1623	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		1624	of how the F<event.h> header can be found.
		1625
		1626	=item EV_PROTOTYPES
		1627
		1628	If defined to be C<0>, then F<ev.h> will not define any function
		1629	prototypes, but still define all the structs and other symbols. This is
		1630	occasionally useful if you want to provide your own wrapper functions
		1631	around libev functions.
		1632
		1633	=item EV_MULTIPLICITY
		1634
		1635	If undefined or defined to C<1>, then all event-loop-specific functions
		1636	will have the C<struct ev_loop *> as first argument, and you can create
		1637	additional independent event loops. Otherwise there will be no support
		1638	for multiple event loops and there is no first event loop pointer
		1639	argument. Instead, all functions act on the single default loop.
		1640
		1641	=item EV_PERIODICS
		1642
		1643	If undefined or defined to be C<1>, then periodic timers are supported,
		1644	otherwise not. This saves a few kb of code.
		1645
		1646	=item EV_COMMON
		1647
		1648	By default, all watchers have a C<void *data> member. By redefining
		1649	this macro to a something else you can include more and other types of
		1650	members. You have to define it each time you include one of the files,
		1651	though, and it must be identical each time.
		1652
		1653	For example, the perl EV module uses something like this:
		1654
		1655	#define EV_COMMON \
		1656	SV self; / contains this struct */ \
		1657	SV cb_sv, fh /* note no trailing ";" */
		1658
		1659	=item EV_CB_DECLARE (type)
		1660
		1661	=item EV_CB_INVOKE (watcher, revents)
		1662
		1663	=item ev_set_cb (ev, cb)
		1664
		1665	Can be used to change the callback member declaration in each watcher,
		1666	and the way callbacks are invoked and set. Must expand to a struct member
		1667	definition and a statement, respectively. See the F<ev.v> header file for
		1668	their default definitions. One possible use for overriding these is to
		1669	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		1670	method calls instead of plain function calls in C++.
		1671
		1672	=head2 EXAMPLES
		1673
		1674	For a real-world example of a program the includes libev
		1675	verbatim, you can have a look at the EV perl module
		1676	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		1677	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		1678	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		1679	will be compiled. It is pretty complex because it provides its own header
		1680	file.
		1681
		1682	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		1683	that everybody includes and which overrides some autoconf choices:
		1684
		1685	#define EV_USE_POLL 0
		1686	#define EV_MULTIPLICITY 0
		1687	#define EV_PERIODICS 0
		1688	#define EV_CONFIG_H <config.h>
		1689
		1690	#include "ev++.h"
		1691
		1692	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		1693
		1694	#include "ev_cpp.h"
		1695	#include "ev.c"
878		1696
879	=head1 AUTHOR	1697	=head1 AUTHOR
880		1698
881	Marc Lehmann <libev@schmorp.de>.	1699	Marc Lehmann <libev@schmorp.de>.
882		1700

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Revision 1.44 by root, Sat Nov 24 16:57:30 2007 UTC