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Comparing libev/ev.pod (file contents):
Revision 1.30 by root, Fri Nov 23 04:36:03 2007 UTC vs.
Revision 1.51 by root, Tue Nov 27 19:23:31 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.
51		52
52	=head1 GLOBAL FUNCTIONS	53	=head1 GLOBAL FUNCTIONS
53		54
54	These functions can be called anytime, even before initialising the	55	These functions can be called anytime, even before initialising the
55	library in any way.	56	library in any way.
…		…
75	Usually, it's a good idea to terminate if the major versions mismatch,	76	Usually, it's a good idea to terminate if the major versions mismatch,
76	as this indicates an incompatible change. Minor versions are usually	77	as this indicates an incompatible change. Minor versions are usually
77	compatible to older versions, so a larger minor version alone is usually	78	compatible to older versions, so a larger minor version alone is usually
78	not a problem.	79	not a problem.
79		80
		81	Example: make sure we haven't accidentally been linked against the wrong
		82	version:
		83
		84	assert (("libev version mismatch",
		85	ev_version_major () == EV_VERSION_MAJOR
		86	&& ev_version_minor () >= EV_VERSION_MINOR));
		87
		88	=item unsigned int ev_supported_backends ()
		89
		90	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		91	value) compiled into this binary of libev (independent of their
		92	availability on the system you are running on). See C<ev_default_loop> for
		93	a description of the set values.
		94
		95	Example: make sure we have the epoll method, because yeah this is cool and
		96	a must have and can we have a torrent of it please!!!11
		97
		98	assert (("sorry, no epoll, no sex",
		99	ev_supported_backends () & EVBACKEND_EPOLL));
		100
		101	=item unsigned int ev_recommended_backends ()
		102
		103	Return the set of all backends compiled into this binary of libev and also
		104	recommended for this platform. This set is often smaller than the one
		105	returned by C<ev_supported_backends>, as for example kqueue is broken on
		106	most BSDs and will not be autodetected unless you explicitly request it
		107	(assuming you know what you are doing). This is the set of backends that
		108	libev will probe for if you specify no backends explicitly.
		109
		110	=item unsigned int ev_embeddable_backends ()
		111
		112	Returns the set of backends that are embeddable in other event loops. This
		113	is the theoretical, all-platform, value. To find which backends
		114	might be supported on the current system, you would need to look at
		115	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		116	recommended ones.
		117
		118	See the description of C<ev_embed> watchers for more info.
		119
80	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	120	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
81		121
82	Sets the allocation function to use (the prototype is similar to the	122	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	123	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	124	and free memory (no surprises here). If it returns zero when memory
…		…
86	destructive action. The default is your system realloc function.	126	destructive action. The default is your system realloc function.
87		127
88	You could override this function in high-availability programs to, say,	128	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,	129	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.	130	or even to sleep a while and retry until some memory is available.
		131
		132	Example: replace the libev allocator with one that waits a bit and then
		133	retries: better than mine).
		134
		135	static void *
		136	persistent_realloc (void *ptr, long size)
		137	{
		138	for (;;)
		139	{
		140	void *newptr = realloc (ptr, size);
		141
		142	if (newptr)
		143	return newptr;
		144
		145	sleep (60);
		146	}
		147	}
		148
		149	...
		150	ev_set_allocator (persistent_realloc);
91		151
92	=item ev_set_syserr_cb (void (*cb)(const char *msg));	152	=item ev_set_syserr_cb (void (*cb)(const char *msg));
93		153
94	Set the callback function to call on a retryable syscall error (such	154	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	155	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	157	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	158	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	159	requested operation, or, if the condition doesn't go away, do bad stuff
100	(such as abort).	160	(such as abort).
101		161
		162	Example: do the same thing as libev does internally:
		163
		164	static void
		165	fatal_error (const char *msg)
		166	{
		167	perror (msg);
		168	abort ();
		169	}
		170
		171	...
		172	ev_set_syserr_cb (fatal_error);
		173
102	=back	174	=back
103		175
104	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	176	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
105		177
106	An event loop is described by a C<struct ev_loop *>. The library knows two	178	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)	191	=item struct ev_loop *ev_default_loop (unsigned int flags)
120		192
121	This will initialise the default event loop if it hasn't been initialised	193	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	194	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	195	false. If it already was initialised it simply returns it (and ignores the
124	flags).	196	flags. If that is troubling you, check C<ev_backend ()> afterwards).
125		197
126	If you don't know what event loop to use, use the one returned from this	198	If you don't know what event loop to use, use the one returned from this
127	function.	199	function.
128		200
129	The flags argument can be used to specify special behaviour or specific	201	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).	202	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
131		203
132	It supports the following flags:	204	The following flags are supported:
133		205
134	=over 4	206	=over 4
135		207
136	=item C<EVFLAG_AUTO>	208	=item C<EVFLAG_AUTO>
137		209
…		…
145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	217	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
146	override the flags completely if it is found in the environment. This is	218	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	219	useful to try out specific backends to test their performance, or to work
148	around bugs.	220	around bugs.
149		221
150	=item C<EVMETHOD_SELECT> (value 1, portable select backend)	222	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
151		223
152	This is your standard select(2) backend. Not I<completely> standard, as	224	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,	225	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	226	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	227	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.	228	the fastest backend for a low number of fds.
157		229
158	=item C<EVMETHOD_POLL> (value 2, poll backend, available everywhere except on windows)	230	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
159		231
160	And this is your standard poll(2) backend. It's more complicated than	232	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	233	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	234	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).	235	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
164		236
165	=item C<EVMETHOD_EPOLL> (value 4, Linux)	237	=item C<EVBACKEND_EPOLL> (value 4, Linux)
166		238
167	For few fds, this backend is a bit little slower than poll and select,	239	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	240	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	241	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).	242	either O(1) or O(active_fds).
…		…
173	result in some caching, there is still a syscall per such incident	245	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	246	(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	247	best to avoid that. Also, dup()ed file descriptors might not work very
176	well if you register events for both fds.	248	well if you register events for both fds.
177		249
		250	Please note that epoll sometimes generates spurious notifications, so you
		251	need to use non-blocking I/O or other means to avoid blocking when no data
		252	(or space) is available.
		253
178	=item C<EVMETHOD_KQUEUE> (value 8, most BSD clones)	254	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
179		255
180	Kqueue deserves special mention, as at the time of this writing, it	256	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	257	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	258	anything but sockets and pipes, except on Darwin, where of course its
183	completely useless). For this reason its not being "autodetected" unless	259	completely useless). For this reason its not being "autodetected"
184	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).	260	unless you explicitly specify it explicitly in the flags (i.e. using
		261	C<EVBACKEND_KQUEUE>).
185		262
186	It scales in the same way as the epoll backend, but the interface to the	263	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	264	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	265	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	266	extra syscall as with epoll, it still adds up to four event changes per
190	incident, so its best to avoid that.	267	incident, so its best to avoid that.
191		268
192	=item C<EVMETHOD_DEVPOLL> (value 16, Solaris 8)	269	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
193		270
194	This is not implemented yet (and might never be).	271	This is not implemented yet (and might never be).
195		272
196	=item C<EVMETHOD_PORT> (value 32, Solaris 10)	273	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
197		274
198	This uses the Solaris 10 port mechanism. As with everything on Solaris,	275	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)).	276	it's really slow, but it still scales very well (O(active_fds)).
200		277
		278	Please note that solaris ports can result in a lot of spurious
		279	notifications, so you need to use non-blocking I/O or other means to avoid
		280	blocking when no data (or space) is available.
		281
201	=item C<EVMETHOD_ALL>	282	=item C<EVBACKEND_ALL>
202		283
203	Try all backends (even potentially broken ones that wouldn't be tried	284	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	285	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
205	C<EVMETHOD_ALL & ~EVMETHOD_KQUEUE>.	286	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
206		287
207	=back	288	=back
208		289
209	If one or more of these are ored into the flags value, then only these	290	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	291	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	292	specified, most compiled-in backend will be tried, usually in reverse
212	order of their flag values :)	293	order of their flag values :)
213		294
		295	The most typical usage is like this:
		296
		297	if (!ev_default_loop (0))
		298	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		299
		300	Restrict libev to the select and poll backends, and do not allow
		301	environment settings to be taken into account:
		302
		303	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		304
		305	Use whatever libev has to offer, but make sure that kqueue is used if
		306	available (warning, breaks stuff, best use only with your own private
		307	event loop and only if you know the OS supports your types of fds):
		308
		309	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
		310
214	=item struct ev_loop *ev_loop_new (unsigned int flags)	311	=item struct ev_loop *ev_loop_new (unsigned int flags)
215		312
216	Similar to C<ev_default_loop>, but always creates a new event loop that is	313	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	314	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	315	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).	316	undefined behaviour (or a failed assertion if assertions are enabled).
220		317
		318	Example: try to create a event loop that uses epoll and nothing else.
		319
		320	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		321	if (!epoller)
		322	fatal ("no epoll found here, maybe it hides under your chair");
		323
221	=item ev_default_destroy ()	324	=item ev_default_destroy ()
222		325
223	Destroys the default loop again (frees all memory and kernel state	326	Destroys the default loop again (frees all memory and kernel state
224	etc.). This stops all registered event watchers (by not touching them in	327	etc.). None of the active event watchers will be stopped in the normal
225	any way whatsoever, although you cannot rely on this :).	328	sense, so e.g. C<ev_is_active> might still return true. It is your
		329	responsibility to either stop all watchers cleanly yoursef I<before>
		330	calling this function, or cope with the fact afterwards (which is usually
		331	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		332	for example).
226		333
227	=item ev_loop_destroy (loop)	334	=item ev_loop_destroy (loop)
228		335
229	Like C<ev_default_destroy>, but destroys an event loop created by an	336	Like C<ev_default_destroy>, but destroys an event loop created by an
230	earlier call to C<ev_loop_new>.	337	earlier call to C<ev_loop_new>.
…		…
244	it just in case after a fork. To make this easy, the function will fit in	351	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>:	352	quite nicely into a call to C<pthread_atfork>:
246		353
247	pthread_atfork (0, 0, ev_default_fork);	354	pthread_atfork (0, 0, ev_default_fork);
248		355
		356	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		357	without calling this function, so if you force one of those backends you
		358	do not need to care.
		359
249	=item ev_loop_fork (loop)	360	=item ev_loop_fork (loop)
250		361
251	Like C<ev_default_fork>, but acts on an event loop created by	362	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	363	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.	364	after fork, and how you do this is entirely your own problem.
254		365
255	=item unsigned int ev_method (loop)	366	=item unsigned int ev_backend (loop)
256		367
257	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	368	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
258	use.	369	use.
259		370
260	=item ev_tstamp ev_now (loop)	371	=item ev_tstamp ev_now (loop)
261		372
262	Returns the current "event loop time", which is the time the event loop	373	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	374	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	375	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	376	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).	377	event occuring (or more correctly, libev finding out about it).
267		378
268	=item ev_loop (loop, int flags)	379	=item ev_loop (loop, int flags)
269		380
270	Finally, this is it, the event handler. This function usually is called	381	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	382	after you initialised all your watchers and you want to start handling
272	events.	383	events.
273		384
274	If the flags argument is specified as 0, it will not return until either	385	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.	386	either no event watchers are active anymore or C<ev_unloop> was called.
		387
		388	Please note that an explicit C<ev_unloop> is usually better than
		389	relying on all watchers to be stopped when deciding when a program has
		390	finished (especially in interactive programs), but having a program that
		391	automatically loops as long as it has to and no longer by virtue of
		392	relying on its watchers stopping correctly is a thing of beauty.
276		393
277	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	394	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	395	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.	396	case there are no events and will return after one iteration of the loop.
280		397
281	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	398	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	399	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	400	your process until at least one new event arrives, and will return after
284	one iteration of the loop.	401	one iteration of the loop. This is useful if you are waiting for some
		402	external event in conjunction with something not expressible using other
		403	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		404	usually a better approach for this kind of thing.
285		405
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:	406	Here are the gory details of what C<ev_loop> does:
291		407
292	1. If there are no active watchers (reference count is zero), return.	408	* If there are no active watchers (reference count is zero), return.
293	2. Queue and immediately call all prepare watchers.	409	- Queue prepare watchers and then call all outstanding watchers.
294	3. If we have been forked, recreate the kernel state.	410	- If we have been forked, recreate the kernel state.
295	4. Update the kernel state with all outstanding changes.	411	- Update the kernel state with all outstanding changes.
296	5. Update the "event loop time".	412	- Update the "event loop time".
297	6. Calculate for how long to block.	413	- Calculate for how long to block.
298	7. Block the process, waiting for events.	414	- Block the process, waiting for any events.
		415	- Queue all outstanding I/O (fd) events.
299	8. Update the "event loop time" and do time jump handling.	416	- Update the "event loop time" and do time jump handling.
300	9. Queue all outstanding timers.	417	- Queue all outstanding timers.
301	10. Queue all outstanding periodics.	418	- Queue all outstanding periodics.
302	11. If no events are pending now, queue all idle watchers.	419	- If no events are pending now, queue all idle watchers.
303	12. Queue all check watchers.	420	- Queue all check watchers.
304	13. Call all queued watchers in reverse order (i.e. check watchers first).	421	- Call all queued watchers in reverse order (i.e. check watchers first).
		422	Signals and child watchers are implemented as I/O watchers, and will
		423	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	424	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
306	was used, return, otherwise continue with step #1.	425	were used, return, otherwise continue with step *.
		426
		427	Example: queue some jobs and then loop until no events are outsanding
		428	anymore.
		429
		430	... queue jobs here, make sure they register event watchers as long
		431	... as they still have work to do (even an idle watcher will do..)
		432	ev_loop (my_loop, 0);
		433	... jobs done. yeah!
307		434
308	=item ev_unloop (loop, how)	435	=item ev_unloop (loop, how)
309		436
310	Can be used to make a call to C<ev_loop> return early (but only after it	437	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	438	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	452	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	453	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	454	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>.	455	libraries. Just remember to I<unref after start> and I<ref before stop>.
329		456
		457	Example: create a signal watcher, but keep it from keeping C<ev_loop>
		458	running when nothing else is active.
		459
		460	struct dv_signal exitsig;
		461	ev_signal_init (&exitsig, sig_cb, SIGINT);
		462	ev_signal_start (myloop, &exitsig);
		463	evf_unref (myloop);
		464
		465	Example: for some weird reason, unregister the above signal handler again.
		466
		467	ev_ref (myloop);
		468	ev_signal_stop (myloop, &exitsig);
		469
330	=back	470	=back
		471
331		472
332	=head1 ANATOMY OF A WATCHER	473	=head1 ANATOMY OF A WATCHER
333		474
334	A watcher is a structure that you create and register to record your	475	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	476	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	509	*) >>), and you can stop watching for events at any time by calling the
369	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	510	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
370		511
371	As long as your watcher is active (has been started but not stopped) you	512	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	513	must not touch the values stored in it. Most specifically you must never
373	reinitialise it or call its set method.	514	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		515
380	Each and every callback receives the event loop pointer as first, the	516	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	517	registered watcher structure as second, and a bitset of received events as
382	third argument.	518	third argument.
383		519
…		…
407	The signal specified in the C<ev_signal> watcher has been received by a thread.	543	The signal specified in the C<ev_signal> watcher has been received by a thread.
408		544
409	=item C<EV_CHILD>	545	=item C<EV_CHILD>
410		546
411	The pid specified in the C<ev_child> watcher has received a status change.	547	The pid specified in the C<ev_child> watcher has received a status change.
		548
		549	=item C<EV_STAT>
		550
		551	The path specified in the C<ev_stat> watcher changed its attributes somehow.
412		552
413	=item C<EV_IDLE>	553	=item C<EV_IDLE>
414		554
415	The C<ev_idle> watcher has determined that you have nothing better to do.	555	The C<ev_idle> watcher has determined that you have nothing better to do.
416		556
…		…
424	received events. Callbacks of both watcher types can start and stop as	564	received events. Callbacks of both watcher types can start and stop as
425	many watchers as they want, and all of them will be taken into account	565	many watchers as they want, and all of them will be taken into account
426	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	566	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
427	C<ev_loop> from blocking).	567	C<ev_loop> from blocking).
428		568
		569	=item C<EV_EMBED>
		570
		571	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		572
		573	=item C<EV_FORK>
		574
		575	The event loop has been resumed in the child process after fork (see
		576	C<ev_fork>).
		577
429	=item C<EV_ERROR>	578	=item C<EV_ERROR>
430		579
431	An unspecified error has occured, the watcher has been stopped. This might	580	An unspecified error has occured, the watcher has been stopped. This might
432	happen because the watcher could not be properly started because libev	581	happen because the watcher could not be properly started because libev
433	ran out of memory, a file descriptor was found to be closed or any other	582	ran out of memory, a file descriptor was found to be closed or any other
…		…
439	your callbacks is well-written it can just attempt the operation and cope	588	your callbacks is well-written it can just attempt the operation and cope
440	with the error from read() or write(). This will not work in multithreaded	589	with the error from read() or write(). This will not work in multithreaded
441	programs, though, so beware.	590	programs, though, so beware.
442		591
443	=back	592	=back
		593
		594	=head2 GENERIC WATCHER FUNCTIONS
		595
		596	In the following description, C<TYPE> stands for the watcher type,
		597	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		598
		599	=over 4
		600
		601	=item C<ev_init> (ev_TYPE *watcher, callback)
		602
		603	This macro initialises the generic portion of a watcher. The contents
		604	of the watcher object can be arbitrary (so C<malloc> will do). Only
		605	the generic parts of the watcher are initialised, you I<need> to call
		606	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		607	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		608	which rolls both calls into one.
		609
		610	You can reinitialise a watcher at any time as long as it has been stopped
		611	(or never started) and there are no pending events outstanding.
		612
		613	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		614	int revents)>.
		615
		616	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		617
		618	This macro initialises the type-specific parts of a watcher. You need to
		619	call C<ev_init> at least once before you call this macro, but you can
		620	call C<ev_TYPE_set> any number of times. You must not, however, call this
		621	macro on a watcher that is active (it can be pending, however, which is a
		622	difference to the C<ev_init> macro).
		623
		624	Although some watcher types do not have type-specific arguments
		625	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		626
		627	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		628
		629	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		630	calls into a single call. This is the most convinient method to initialise
		631	a watcher. The same limitations apply, of course.
		632
		633	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		634
		635	Starts (activates) the given watcher. Only active watchers will receive
		636	events. If the watcher is already active nothing will happen.
		637
		638	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		639
		640	Stops the given watcher again (if active) and clears the pending
		641	status. It is possible that stopped watchers are pending (for example,
		642	non-repeating timers are being stopped when they become pending), but
		643	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		644	you want to free or reuse the memory used by the watcher it is therefore a
		645	good idea to always call its C<ev_TYPE_stop> function.
		646
		647	=item bool ev_is_active (ev_TYPE *watcher)
		648
		649	Returns a true value iff the watcher is active (i.e. it has been started
		650	and not yet been stopped). As long as a watcher is active you must not modify
		651	it.
		652
		653	=item bool ev_is_pending (ev_TYPE *watcher)
		654
		655	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		656	events but its callback has not yet been invoked). As long as a watcher
		657	is pending (but not active) you must not call an init function on it (but
		658	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		659	libev (e.g. you cnanot C<free ()> it).
		660
		661	=item callback = ev_cb (ev_TYPE *watcher)
		662
		663	Returns the callback currently set on the watcher.
		664
		665	=item ev_cb_set (ev_TYPE *watcher, callback)
		666
		667	Change the callback. You can change the callback at virtually any time
		668	(modulo threads).
		669
		670	=back
		671
444		672
445	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	673	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
446		674
447	Each watcher has, by default, a member C<void *data> that you can change	675	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	676	and read at any time, libev will completely ignore it. This can be used
…		…
473		701
474		702
475	=head1 WATCHER TYPES	703	=head1 WATCHER TYPES
476		704
477	This section describes each watcher in detail, but will not repeat	705	This section describes each watcher in detail, but will not repeat
478	information given in the last section.	706	information given in the last section. Any initialisation/set macros,
		707	functions and members specific to the watcher type are explained.
479		708
		709	Members are additionally marked with either I<[read-only]>, meaning that,
		710	while the watcher is active, you can look at the member and expect some
		711	sensible content, but you must not modify it (you can modify it while the
		712	watcher is stopped to your hearts content), or I<[read-write]>, which
		713	means you can expect it to have some sensible content while the watcher
		714	is active, but you can also modify it. Modifying it may not do something
		715	sensible or take immediate effect (or do anything at all), but libev will
		716	not crash or malfunction in any way.
		717
		718
480	=head2 C<ev_io> - is this file descriptor readable or writable	719	=head2 C<ev_io> - is this file descriptor readable or writable?
481		720
482	I/O watchers check whether a file descriptor is readable or writable	721	I/O watchers check whether a file descriptor is readable or writable
483	in each iteration of the event loop (This behaviour is called	722	in each iteration of the event loop, or, more precisely, when reading
484	level-triggering because you keep receiving events as long as the	723	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	724	some data. This behaviour is called level-triggering because you keep
486	act on the event and neither want to receive future events).	725	receiving events as long as the condition persists. Remember you can stop
		726	the watcher if you don't want to act on the event and neither want to
		727	receive future events.
487		728
488	In general you can register as many read and/or write event watchers per	729	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	730	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	731	descriptors to non-blocking mode is also usually a good idea (but not
491	required if you know what you are doing).	732	required if you know what you are doing).
492		733
493	You have to be careful with dup'ed file descriptors, though. Some backends	734	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	735	(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	736	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	737	to the same underlying file/socket/etc. description (that is, they share
497	the same underlying "file open").	738	the same underlying "file open").
498		739
499	If you must do this, then force the use of a known-to-be-good backend	740	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	741	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
501	EVMETHOD_POLL).	742	C<EVBACKEND_POLL>).
		743
		744	Another thing you have to watch out for is that it is quite easy to
		745	receive "spurious" readyness notifications, that is your callback might
		746	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		747	because there is no data. Not only are some backends known to create a
		748	lot of those (for example solaris ports), it is very easy to get into
		749	this situation even with a relatively standard program structure. Thus
		750	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		751	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		752
		753	If you cannot run the fd in non-blocking mode (for example you should not
		754	play around with an Xlib connection), then you have to seperately re-test
		755	wether a file descriptor is really ready with a known-to-be good interface
		756	such as poll (fortunately in our Xlib example, Xlib already does this on
		757	its own, so its quite safe to use).
502		758
503	=over 4	759	=over 4
504		760
505	=item ev_io_init (ev_io *, callback, int fd, int events)	761	=item ev_io_init (ev_io *, callback, int fd, int events)
506		762
507	=item ev_io_set (ev_io *, int fd, int events)	763	=item ev_io_set (ev_io *, int fd, int events)
508		764
509	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	765	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 |	766	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
511	EV_WRITE> to receive the given events.	767	C<EV_READ | EV_WRITE> to receive the given events.
512		768
513	=back	769	=item int fd [read-only]
514		770
		771	The file descriptor being watched.
		772
		773	=item int events [read-only]
		774
		775	The events being watched.
		776
		777	=back
		778
		779	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
		780	readable, but only once. Since it is likely line-buffered, you could
		781	attempt to read a whole line in the callback:
		782
		783	static void
		784	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		785	{
		786	ev_io_stop (loop, w);
		787	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		788	}
		789
		790	...
		791	struct ev_loop *loop = ev_default_init (0);
		792	struct ev_io stdin_readable;
		793	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		794	ev_io_start (loop, &stdin_readable);
		795	ev_loop (loop, 0);
		796
		797
515	=head2 C<ev_timer> - relative and optionally recurring timeouts	798	=head2 C<ev_timer> - relative and optionally repeating timeouts
516		799
517	Timer watchers are simple relative timers that generate an event after a	800	Timer watchers are simple relative timers that generate an event after a
518	given time, and optionally repeating in regular intervals after that.	801	given time, and optionally repeating in regular intervals after that.
519		802
520	The timers are based on real time, that is, if you register an event that	803	The timers are based on real time, that is, if you register an event that
…		…
561		844
562	If the timer is repeating, either start it if necessary (with the repeat	845	If the timer is repeating, either start it if necessary (with the repeat
563	value), or reset the running timer to the repeat value.	846	value), or reset the running timer to the repeat value.
564		847
565	This sounds a bit complicated, but here is a useful and typical	848	This sounds a bit complicated, but here is a useful and typical
566	example: Imagine you have a tcp connection and you want a so-called idle	849	example: Imagine you have a tcp connection and you want a so-called
567	timeout, that is, you want to be called when there have been, say, 60	850	idle timeout, that is, you want to be called when there have been,
568	seconds of inactivity on the socket. The easiest way to do this is to	851	say, 60 seconds of inactivity on the socket. The easiest way to do
569	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	852	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling
570	time you successfully read or write some data. If you go into an idle	853	C<ev_timer_again> each time you successfully read or write some data. If
571	state where you do not expect data to travel on the socket, you can stop	854	you go into an idle state where you do not expect data to travel on the
572	the timer, and again will automatically restart it if need be.	855	socket, you can stop the timer, and again will automatically restart it if
		856	need be.
573		857
574	=back	858	You can also ignore the C<after> value and C<ev_timer_start> altogether
		859	and only ever use the C<repeat> value:
575		860
		861	ev_timer_init (timer, callback, 0., 5.);
		862	ev_timer_again (loop, timer);
		863	...
		864	timer->again = 17.;
		865	ev_timer_again (loop, timer);
		866	...
		867	timer->again = 10.;
		868	ev_timer_again (loop, timer);
		869
		870	This is more efficient then stopping/starting the timer eahc time you want
		871	to modify its timeout value.
		872
		873	=item ev_tstamp repeat [read-write]
		874
		875	The current C<repeat> value. Will be used each time the watcher times out
		876	or C<ev_timer_again> is called and determines the next timeout (if any),
		877	which is also when any modifications are taken into account.
		878
		879	=back
		880
		881	Example: create a timer that fires after 60 seconds.
		882
		883	static void
		884	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		885	{
		886	.. one minute over, w is actually stopped right here
		887	}
		888
		889	struct ev_timer mytimer;
		890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		891	ev_timer_start (loop, &mytimer);
		892
		893	Example: create a timeout timer that times out after 10 seconds of
		894	inactivity.
		895
		896	static void
		897	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		898	{
		899	.. ten seconds without any activity
		900	}
		901
		902	struct ev_timer mytimer;
		903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		904	ev_timer_again (&mytimer); /* start timer */
		905	ev_loop (loop, 0);
		906
		907	// and in some piece of code that gets executed on any "activity":
		908	// reset the timeout to start ticking again at 10 seconds
		909	ev_timer_again (&mytimer);
		910
		911
576	=head2 C<ev_periodic> - to cron or not to cron	912	=head2 C<ev_periodic> - to cron or not to cron?
577		913
578	Periodic watchers are also timers of a kind, but they are very versatile	914	Periodic watchers are also timers of a kind, but they are very versatile
579	(and unfortunately a bit complex).	915	(and unfortunately a bit complex).
580		916
581	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	917	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	918	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	919	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 ()	920	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	921	+ 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	922	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	923	roughly 10 seconds later and of course not if you reset your system time
588	again).	924	again).
589		925
…		…
673	Simply stops and restarts the periodic watcher again. This is only useful	1009	Simply stops and restarts the periodic watcher again. This is only useful
674	when you changed some parameters or the reschedule callback would return	1010	when you changed some parameters or the reschedule callback would return
675	a different time than the last time it was called (e.g. in a crond like	1011	a different time than the last time it was called (e.g. in a crond like
676	program when the crontabs have changed).	1012	program when the crontabs have changed).
677		1013
678	=back	1014	=item ev_tstamp interval [read-write]
679		1015
		1016	The current interval value. Can be modified any time, but changes only
		1017	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1018	called.
		1019
		1020	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1021
		1022	The current reschedule callback, or C<0>, if this functionality is
		1023	switched off. Can be changed any time, but changes only take effect when
		1024	the periodic timer fires or C<ev_periodic_again> is being called.
		1025
		1026	=back
		1027
		1028	Example: call a callback every hour, or, more precisely, whenever the
		1029	system clock is divisible by 3600. The callback invocation times have
		1030	potentially a lot of jittering, but good long-term stability.
		1031
		1032	static void
		1033	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1034	{
		1035	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1036	}
		1037
		1038	struct ev_periodic hourly_tick;
		1039	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1040	ev_periodic_start (loop, &hourly_tick);
		1041
		1042	Example: the same as above, but use a reschedule callback to do it:
		1043
		1044	#include <math.h>
		1045
		1046	static ev_tstamp
		1047	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1048	{
		1049	return fmod (now, 3600.) + 3600.;
		1050	}
		1051
		1052	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1053
		1054	Example: call a callback every hour, starting now:
		1055
		1056	struct ev_periodic hourly_tick;
		1057	ev_periodic_init (&hourly_tick, clock_cb,
		1058	fmod (ev_now (loop), 3600.), 3600., 0);
		1059	ev_periodic_start (loop, &hourly_tick);
		1060
		1061
680	=head2 C<ev_signal> - signal me when a signal gets signalled	1062	=head2 C<ev_signal> - signal me when a signal gets signalled!
681		1063
682	Signal watchers will trigger an event when the process receives a specific	1064	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	1065	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	1066	will try it's best to deliver signals synchronously, i.e. as part of the
685	normal event processing, like any other event.	1067	normal event processing, like any other event.
…		…
698	=item ev_signal_set (ev_signal *, int signum)	1080	=item ev_signal_set (ev_signal *, int signum)
699		1081
700	Configures the watcher to trigger on the given signal number (usually one	1082	Configures the watcher to trigger on the given signal number (usually one
701	of the C<SIGxxx> constants).	1083	of the C<SIGxxx> constants).
702		1084
703	=back	1085	=item int signum [read-only]
704		1086
		1087	The signal the watcher watches out for.
		1088
		1089	=back
		1090
		1091
705	=head2 C<ev_child> - wait for pid status changes	1092	=head2 C<ev_child> - watch out for process status changes
706		1093
707	Child watchers trigger when your process receives a SIGCHLD in response to	1094	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).	1095	some child status changes (most typically when a child of yours dies).
709		1096
710	=over 4	1097	=over 4
…		…
718	at the C<rstatus> member of the C<ev_child> watcher structure to see	1105	at the C<rstatus> member of the C<ev_child> watcher structure to see
719	the status word (use the macros from C<sys/wait.h> and see your systems	1106	the status word (use the macros from C<sys/wait.h> and see your systems
720	C<waitpid> documentation). The C<rpid> member contains the pid of the	1107	C<waitpid> documentation). The C<rpid> member contains the pid of the
721	process causing the status change.	1108	process causing the status change.
722		1109
723	=back	1110	=item int pid [read-only]
724		1111
		1112	The process id this watcher watches out for, or C<0>, meaning any process id.
		1113
		1114	=item int rpid [read-write]
		1115
		1116	The process id that detected a status change.
		1117
		1118	=item int rstatus [read-write]
		1119
		1120	The process exit/trace status caused by C<rpid> (see your systems
		1121	C<waitpid> and C<sys/wait.h> documentation for details).
		1122
		1123	=back
		1124
		1125	Example: try to exit cleanly on SIGINT and SIGTERM.
		1126
		1127	static void
		1128	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1129	{
		1130	ev_unloop (loop, EVUNLOOP_ALL);
		1131	}
		1132
		1133	struct ev_signal signal_watcher;
		1134	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1135	ev_signal_start (loop, &sigint_cb);
		1136
		1137
		1138	=head2 C<ev_stat> - did the file attributes just change?
		1139
		1140	This watches a filesystem path for attribute changes. That is, it calls
		1141	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1142	compared to the last time, invoking the callback if it did.
		1143
		1144	The path does not need to exist: changing from "path exists" to "path does
		1145	not exist" is a status change like any other. The condition "path does
		1146	not exist" is signified by the C<st_nlink> field being zero (which is
		1147	otherwise always forced to be at least one) and all the other fields of
		1148	the stat buffer having unspecified contents.
		1149
		1150	Since there is no standard to do this, the portable implementation simply
		1151	calls C<stat (2)> regulalry on the path to see if it changed somehow. You
		1152	can specify a recommended polling interval for this case. If you specify
		1153	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1154	unspecified default> value will be used (which you can expect to be around
		1155	five seconds, although this might change dynamically). Libev will also
		1156	impose a minimum interval which is currently around C<0.1>, but thats
		1157	usually overkill.
		1158
		1159	This watcher type is not meant for massive numbers of stat watchers,
		1160	as even with OS-supported change notifications, this can be
		1161	resource-intensive.
		1162
		1163	At the time of this writing, no specific OS backends are implemented, but
		1164	if demand increases, at least a kqueue and inotify backend will be added.
		1165
		1166	=over 4
		1167
		1168	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1169
		1170	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1171
		1172	Configures the watcher to wait for status changes of the given
		1173	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1174	be detected and should normally be specified as C<0> to let libev choose
		1175	a suitable value. The memory pointed to by C<path> must point to the same
		1176	path for as long as the watcher is active.
		1177
		1178	The callback will be receive C<EV_STAT> when a change was detected,
		1179	relative to the attributes at the time the watcher was started (or the
		1180	last change was detected).
		1181
		1182	=item ev_stat_stat (ev_stat *)
		1183
		1184	Updates the stat buffer immediately with new values. If you change the
		1185	watched path in your callback, you could call this fucntion to avoid
		1186	detecting this change (while introducing a race condition). Can also be
		1187	useful simply to find out the new values.
		1188
		1189	=item ev_statdata attr [read-only]
		1190
		1191	The most-recently detected attributes of the file. Although the type is of
		1192	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1193	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1194	was some error while C<stat>ing the file.
		1195
		1196	=item ev_statdata prev [read-only]
		1197
		1198	The previous attributes of the file. The callback gets invoked whenever
		1199	C<prev> != C<attr>.
		1200
		1201	=item ev_tstamp interval [read-only]
		1202
		1203	The specified interval.
		1204
		1205	=item const char *path [read-only]
		1206
		1207	The filesystem path that is being watched.
		1208
		1209	=back
		1210
		1211	Example: Watch C</etc/passwd> for attribute changes.
		1212
		1213	static void
		1214	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1215	{
		1216	/* /etc/passwd changed in some way */
		1217	if (w->attr.st_nlink)
		1218	{
		1219	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1220	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1221	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1222	}
		1223	else
		1224	/* you shalt not abuse printf for puts */
		1225	puts ("wow, /etc/passwd is not there, expect problems. "
		1226	"if this is windows, they already arrived\n");
		1227	}
		1228
		1229	...
		1230	ev_stat passwd;
		1231
		1232	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1233	ev_stat_start (loop, &passwd);
		1234
		1235
725	=head2 C<ev_idle> - when you've got nothing better to do	1236	=head2 C<ev_idle> - when you've got nothing better to do...
726		1237
727	Idle watchers trigger events when there are no other events are pending	1238	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	1239	(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,	1240	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	1241	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,	1259	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
749	believe me.	1260	believe me.
750		1261
751	=back	1262	=back
752		1263
		1264	Example: dynamically allocate an C<ev_idle>, start it, and in the
		1265	callback, free it. Alos, use no error checking, as usual.
		1266
		1267	static void
		1268	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1269	{
		1270	free (w);
		1271	// now do something you wanted to do when the program has
		1272	// no longer asnything immediate to do.
		1273	}
		1274
		1275	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1276	ev_idle_init (idle_watcher, idle_cb);
		1277	ev_idle_start (loop, idle_cb);
		1278
		1279
753	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1280	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
754		1281
755	Prepare and check watchers are usually (but not always) used in tandem:	1282	Prepare and check watchers are usually (but not always) used in tandem:
756	prepare watchers get invoked before the process blocks and check watchers	1283	prepare watchers get invoked before the process blocks and check watchers
757	afterwards.	1284	afterwards.
758		1285
		1286	You I<must not> call C<ev_loop> or similar functions that enter
		1287	the current event loop from either C<ev_prepare> or C<ev_check>
		1288	watchers. Other loops than the current one are fine, however. The
		1289	rationale behind this is that you do not need to check for recursion in
		1290	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1291	C<ev_check> so if you have one watcher of each kind they will always be
		1292	called in pairs bracketing the blocking call.
		1293
759	Their main purpose is to integrate other event mechanisms into libev. This	1294	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	1295	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.	1296	variable changes, implement your own watchers, integrate net-snmp or a
		1297	coroutine library and lots more. They are also occasionally useful if
		1298	you cache some data and want to flush it before blocking (for example,
		1299	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1300	watcher).
762		1301
763	This is done by examining in each prepare call which file descriptors need	1302	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	1303	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	1304	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	1305	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>	1327	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.	1328	macros, but using them is utterly, utterly and completely pointless.
790		1329
791	=back	1330	=back
792		1331
		1332	Example: To include a library such as adns, you would add IO watchers
		1333	and a timeout watcher in a prepare handler, as required by libadns, and
		1334	in a check watcher, destroy them and call into libadns. What follows is
		1335	pseudo-code only of course:
		1336
		1337	static ev_io iow [nfd];
		1338	static ev_timer tw;
		1339
		1340	static void
		1341	io_cb (ev_loop *loop, ev_io *w, int revents)
		1342	{
		1343	// set the relevant poll flags
		1344	// could also call adns_processreadable etc. here
		1345	struct pollfd *fd = (struct pollfd *)w->data;
		1346	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1347	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1348	}
		1349
		1350	// create io watchers for each fd and a timer before blocking
		1351	static void
		1352	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1353	{
		1354	int timeout = 3600000;truct pollfd fds [nfd];
		1355	// actual code will need to loop here and realloc etc.
		1356	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1357
		1358	/* the callback is illegal, but won't be called as we stop during check */
		1359	ev_timer_init (&tw, 0, timeout * 1e-3);
		1360	ev_timer_start (loop, &tw);
		1361
		1362	// create on ev_io per pollfd
		1363	for (int i = 0; i < nfd; ++i)
		1364	{
		1365	ev_io_init (iow + i, io_cb, fds [i].fd,
		1366	((fds [i].events & POLLIN ? EV_READ : 0)
		1367	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1368
		1369	fds [i].revents = 0;
		1370	iow [i].data = fds + i;
		1371	ev_io_start (loop, iow + i);
		1372	}
		1373	}
		1374
		1375	// stop all watchers after blocking
		1376	static void
		1377	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1378	{
		1379	ev_timer_stop (loop, &tw);
		1380
		1381	for (int i = 0; i < nfd; ++i)
		1382	ev_io_stop (loop, iow + i);
		1383
		1384	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1385	}
		1386
		1387
		1388	=head2 C<ev_embed> - when one backend isn't enough...
		1389
		1390	This is a rather advanced watcher type that lets you embed one event loop
		1391	into another (currently only C<ev_io> events are supported in the embedded
		1392	loop, other types of watchers might be handled in a delayed or incorrect
		1393	fashion and must not be used).
		1394
		1395	There are primarily two reasons you would want that: work around bugs and
		1396	prioritise I/O.
		1397
		1398	As an example for a bug workaround, the kqueue backend might only support
		1399	sockets on some platform, so it is unusable as generic backend, but you
		1400	still want to make use of it because you have many sockets and it scales
		1401	so nicely. In this case, you would create a kqueue-based loop and embed it
		1402	into your default loop (which might use e.g. poll). Overall operation will
		1403	be a bit slower because first libev has to poll and then call kevent, but
		1404	at least you can use both at what they are best.
		1405
		1406	As for prioritising I/O: rarely you have the case where some fds have
		1407	to be watched and handled very quickly (with low latency), and even
		1408	priorities and idle watchers might have too much overhead. In this case
		1409	you would put all the high priority stuff in one loop and all the rest in
		1410	a second one, and embed the second one in the first.
		1411
		1412	As long as the watcher is active, the callback will be invoked every time
		1413	there might be events pending in the embedded loop. The callback must then
		1414	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1415	their callbacks (you could also start an idle watcher to give the embedded
		1416	loop strictly lower priority for example). You can also set the callback
		1417	to C<0>, in which case the embed watcher will automatically execute the
		1418	embedded loop sweep.
		1419
		1420	As long as the watcher is started it will automatically handle events. The
		1421	callback will be invoked whenever some events have been handled. You can
		1422	set the callback to C<0> to avoid having to specify one if you are not
		1423	interested in that.
		1424
		1425	Also, there have not currently been made special provisions for forking:
		1426	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1427	but you will also have to stop and restart any C<ev_embed> watchers
		1428	yourself.
		1429
		1430	Unfortunately, not all backends are embeddable, only the ones returned by
		1431	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1432	portable one.
		1433
		1434	So when you want to use this feature you will always have to be prepared
		1435	that you cannot get an embeddable loop. The recommended way to get around
		1436	this is to have a separate variables for your embeddable loop, try to
		1437	create it, and if that fails, use the normal loop for everything:
		1438
		1439	struct ev_loop *loop_hi = ev_default_init (0);
		1440	struct ev_loop *loop_lo = 0;
		1441	struct ev_embed embed;
		1442
		1443	// see if there is a chance of getting one that works
		1444	// (remember that a flags value of 0 means autodetection)
		1445	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1446	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1447	: 0;
		1448
		1449	// if we got one, then embed it, otherwise default to loop_hi
		1450	if (loop_lo)
		1451	{
		1452	ev_embed_init (&embed, 0, loop_lo);
		1453	ev_embed_start (loop_hi, &embed);
		1454	}
		1455	else
		1456	loop_lo = loop_hi;
		1457
		1458	=over 4
		1459
		1460	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1461
		1462	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1463
		1464	Configures the watcher to embed the given loop, which must be
		1465	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1466	invoked automatically, otherwise it is the responsibility of the callback
		1467	to invoke it (it will continue to be called until the sweep has been done,
		1468	if you do not want thta, you need to temporarily stop the embed watcher).
		1469
		1470	=item ev_embed_sweep (loop, ev_embed *)
		1471
		1472	Make a single, non-blocking sweep over the embedded loop. This works
		1473	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1474	apropriate way for embedded loops.
		1475
		1476	=item struct ev_loop *loop [read-only]
		1477
		1478	The embedded event loop.
		1479
		1480	=back
		1481
		1482
		1483	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1484
		1485	Fork watchers are called when a C<fork ()> was detected (usually because
		1486	whoever is a good citizen cared to tell libev about it by calling
		1487	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1488	event loop blocks next and before C<ev_check> watchers are being called,
		1489	and only in the child after the fork. If whoever good citizen calling
		1490	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1491	handlers will be invoked, too, of course.
		1492
		1493	=over 4
		1494
		1495	=item ev_fork_init (ev_signal *, callback)
		1496
		1497	Initialises and configures the fork watcher - it has no parameters of any
		1498	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1499	believe me.
		1500
		1501	=back
		1502
		1503
793	=head1 OTHER FUNCTIONS	1504	=head1 OTHER FUNCTIONS
794		1505
795	There are some other functions of possible interest. Described. Here. Now.	1506	There are some other functions of possible interest. Described. Here. Now.
796		1507
797	=over 4	1508	=over 4
…		…
826	/* stdin might have data for us, joy! */;	1537	/* stdin might have data for us, joy! */;
827	}	1538	}
828		1539
829	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1540	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
830		1541
831	=item ev_feed_event (loop, watcher, int events)	1542	=item ev_feed_event (ev_loop *, watcher *, int revents)
832		1543
833	Feeds the given event set into the event loop, as if the specified event	1544	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	1545	had happened for the specified watcher (which must be a pointer to an
835	initialised but not necessarily started event watcher).	1546	initialised but not necessarily started event watcher).
836		1547
837	=item ev_feed_fd_event (loop, int fd, int revents)	1548	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
838		1549
839	Feed an event on the given fd, as if a file descriptor backend detected	1550	Feed an event on the given fd, as if a file descriptor backend detected
840	the given events it.	1551	the given events it.
841		1552
842	=item ev_feed_signal_event (loop, int signum)	1553	=item ev_feed_signal_event (ev_loop *loop, int signum)
843		1554
844	Feed an event as if the given signal occured (loop must be the default loop!).	1555	Feed an event as if the given signal occured (C<loop> must be the default
		1556	loop!).
845		1557
846	=back	1558	=back
		1559
847		1560
848	=head1 LIBEVENT EMULATION	1561	=head1 LIBEVENT EMULATION
849		1562
850	Libev offers a compatibility emulation layer for libevent. It cannot	1563	Libev offers a compatibility emulation layer for libevent. It cannot
851	emulate the internals of libevent, so here are some usage hints:	1564	emulate the internals of libevent, so here are some usage hints:
…		…
872		1585
873	=back	1586	=back
874		1587
875	=head1 C++ SUPPORT	1588	=head1 C++ SUPPORT
876		1589
877	TBD.	1590	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1591	you to use some convinience methods to start/stop watchers and also change
		1592	the callback model to a model using method callbacks on objects.
		1593
		1594	To use it,
		1595
		1596	#include <ev++.h>
		1597
		1598	(it is not installed by default). This automatically includes F<ev.h>
		1599	and puts all of its definitions (many of them macros) into the global
		1600	namespace. All C++ specific things are put into the C<ev> namespace.
		1601
		1602	It should support all the same embedding options as F<ev.h>, most notably
		1603	C<EV_MULTIPLICITY>.
		1604
		1605	Here is a list of things available in the C<ev> namespace:
		1606
		1607	=over 4
		1608
		1609	=item C<ev::READ>, C<ev::WRITE> etc.
		1610
		1611	These are just enum values with the same values as the C<EV_READ> etc.
		1612	macros from F<ev.h>.
		1613
		1614	=item C<ev::tstamp>, C<ev::now>
		1615
		1616	Aliases to the same types/functions as with the C<ev_> prefix.
		1617
		1618	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1619
		1620	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1621	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1622	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1623	defines by many implementations.
		1624
		1625	All of those classes have these methods:
		1626
		1627	=over 4
		1628
		1629	=item ev::TYPE::TYPE (object *, object::method *)
		1630
		1631	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
		1632
		1633	=item ev::TYPE::~TYPE
		1634
		1635	The constructor takes a pointer to an object and a method pointer to
		1636	the event handler callback to call in this class. The constructor calls
		1637	C<ev_init> for you, which means you have to call the C<set> method
		1638	before starting it. If you do not specify a loop then the constructor
		1639	automatically associates the default loop with this watcher.
		1640
		1641	The destructor automatically stops the watcher if it is active.
		1642
		1643	=item w->set (struct ev_loop *)
		1644
		1645	Associates a different C<struct ev_loop> with this watcher. You can only
		1646	do this when the watcher is inactive (and not pending either).
		1647
		1648	=item w->set ([args])
		1649
		1650	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1651	called at least once. Unlike the C counterpart, an active watcher gets
		1652	automatically stopped and restarted.
		1653
		1654	=item w->start ()
		1655
		1656	Starts the watcher. Note that there is no C<loop> argument as the
		1657	constructor already takes the loop.
		1658
		1659	=item w->stop ()
		1660
		1661	Stops the watcher if it is active. Again, no C<loop> argument.
		1662
		1663	=item w->again () C<ev::timer>, C<ev::periodic> only
		1664
		1665	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1666	C<ev_TYPE_again> function.
		1667
		1668	=item w->sweep () C<ev::embed> only
		1669
		1670	Invokes C<ev_embed_sweep>.
		1671
		1672	=item w->update () C<ev::stat> only
		1673
		1674	Invokes C<ev_stat_stat>.
		1675
		1676	=back
		1677
		1678	=back
		1679
		1680	Example: Define a class with an IO and idle watcher, start one of them in
		1681	the constructor.
		1682
		1683	class myclass
		1684	{
		1685	ev_io io; void io_cb (ev::io &w, int revents);
		1686	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1687
		1688	myclass ();
		1689	}
		1690
		1691	myclass::myclass (int fd)
		1692	: io (this, &myclass::io_cb),
		1693	idle (this, &myclass::idle_cb)
		1694	{
		1695	io.start (fd, ev::READ);
		1696	}
		1697
		1698
		1699	=head1 MACRO MAGIC
		1700
		1701	Libev can be compiled with a variety of options, the most fundemantal is
		1702	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1703	callbacks have an initial C<struct ev_loop *> argument.
		1704
		1705	To make it easier to write programs that cope with either variant, the
		1706	following macros are defined:
		1707
		1708	=over 4
		1709
		1710	=item C<EV_A>, C<EV_A_>
		1711
		1712	This provides the loop I<argument> for functions, if one is required ("ev
		1713	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1714	C<EV_A_> is used when other arguments are following. Example:
		1715
		1716	ev_unref (EV_A);
		1717	ev_timer_add (EV_A_ watcher);
		1718	ev_loop (EV_A_ 0);
		1719
		1720	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1721	which is often provided by the following macro.
		1722
		1723	=item C<EV_P>, C<EV_P_>
		1724
		1725	This provides the loop I<parameter> for functions, if one is required ("ev
		1726	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1727	C<EV_P_> is used when other parameters are following. Example:
		1728
		1729	// this is how ev_unref is being declared
		1730	static void ev_unref (EV_P);
		1731
		1732	// this is how you can declare your typical callback
		1733	static void cb (EV_P_ ev_timer *w, int revents)
		1734
		1735	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1736	suitable for use with C<EV_A>.
		1737
		1738	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1739
		1740	Similar to the other two macros, this gives you the value of the default
		1741	loop, if multiple loops are supported ("ev loop default").
		1742
		1743	=back
		1744
		1745	Example: Declare and initialise a check watcher, working regardless of
		1746	wether multiple loops are supported or not.
		1747
		1748	static void
		1749	check_cb (EV_P_ ev_timer *w, int revents)
		1750	{
		1751	ev_check_stop (EV_A_ w);
		1752	}
		1753
		1754	ev_check check;
		1755	ev_check_init (&check, check_cb);
		1756	ev_check_start (EV_DEFAULT_ &check);
		1757	ev_loop (EV_DEFAULT_ 0);
		1758
		1759
		1760	=head1 EMBEDDING
		1761
		1762	Libev can (and often is) directly embedded into host
		1763	applications. Examples of applications that embed it include the Deliantra
		1764	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1765	and rxvt-unicode.
		1766
		1767	The goal is to enable you to just copy the neecssary files into your
		1768	source directory without having to change even a single line in them, so
		1769	you can easily upgrade by simply copying (or having a checked-out copy of
		1770	libev somewhere in your source tree).
		1771
		1772	=head2 FILESETS
		1773
		1774	Depending on what features you need you need to include one or more sets of files
		1775	in your app.
		1776
		1777	=head3 CORE EVENT LOOP
		1778
		1779	To include only the libev core (all the C<ev_*> functions), with manual
		1780	configuration (no autoconf):
		1781
		1782	#define EV_STANDALONE 1
		1783	#include "ev.c"
		1784
		1785	This will automatically include F<ev.h>, too, and should be done in a
		1786	single C source file only to provide the function implementations. To use
		1787	it, do the same for F<ev.h> in all files wishing to use this API (best
		1788	done by writing a wrapper around F<ev.h> that you can include instead and
		1789	where you can put other configuration options):
		1790
		1791	#define EV_STANDALONE 1
		1792	#include "ev.h"
		1793
		1794	Both header files and implementation files can be compiled with a C++
		1795	compiler (at least, thats a stated goal, and breakage will be treated
		1796	as a bug).
		1797
		1798	You need the following files in your source tree, or in a directory
		1799	in your include path (e.g. in libev/ when using -Ilibev):
		1800
		1801	ev.h
		1802	ev.c
		1803	ev_vars.h
		1804	ev_wrap.h
		1805
		1806	ev_win32.c required on win32 platforms only
		1807
		1808	ev_select.c only when select backend is enabled (which is by default)
		1809	ev_poll.c only when poll backend is enabled (disabled by default)
		1810	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1811	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1812	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1813
		1814	F<ev.c> includes the backend files directly when enabled, so you only need
		1815	to compile this single file.
		1816
		1817	=head3 LIBEVENT COMPATIBILITY API
		1818
		1819	To include the libevent compatibility API, also include:
		1820
		1821	#include "event.c"
		1822
		1823	in the file including F<ev.c>, and:
		1824
		1825	#include "event.h"
		1826
		1827	in the files that want to use the libevent API. This also includes F<ev.h>.
		1828
		1829	You need the following additional files for this:
		1830
		1831	event.h
		1832	event.c
		1833
		1834	=head3 AUTOCONF SUPPORT
		1835
		1836	Instead of using C<EV_STANDALONE=1> and providing your config in
		1837	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1838	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1839	include F<config.h> and configure itself accordingly.
		1840
		1841	For this of course you need the m4 file:
		1842
		1843	libev.m4
		1844
		1845	=head2 PREPROCESSOR SYMBOLS/MACROS
		1846
		1847	Libev can be configured via a variety of preprocessor symbols you have to define
		1848	before including any of its files. The default is not to build for multiplicity
		1849	and only include the select backend.
		1850
		1851	=over 4
		1852
		1853	=item EV_STANDALONE
		1854
		1855	Must always be C<1> if you do not use autoconf configuration, which
		1856	keeps libev from including F<config.h>, and it also defines dummy
		1857	implementations for some libevent functions (such as logging, which is not
		1858	supported). It will also not define any of the structs usually found in
		1859	F<event.h> that are not directly supported by the libev core alone.
		1860
		1861	=item EV_USE_MONOTONIC
		1862
		1863	If defined to be C<1>, libev will try to detect the availability of the
		1864	monotonic clock option at both compiletime and runtime. Otherwise no use
		1865	of the monotonic clock option will be attempted. If you enable this, you
		1866	usually have to link against librt or something similar. Enabling it when
		1867	the functionality isn't available is safe, though, althoguh you have
		1868	to make sure you link against any libraries where the C<clock_gettime>
		1869	function is hiding in (often F<-lrt>).
		1870
		1871	=item EV_USE_REALTIME
		1872
		1873	If defined to be C<1>, libev will try to detect the availability of the
		1874	realtime clock option at compiletime (and assume its availability at
		1875	runtime if successful). Otherwise no use of the realtime clock option will
		1876	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1877	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1878	in the description of C<EV_USE_MONOTONIC>, though.
		1879
		1880	=item EV_USE_SELECT
		1881
		1882	If undefined or defined to be C<1>, libev will compile in support for the
		1883	C<select>(2) backend. No attempt at autodetection will be done: if no
		1884	other method takes over, select will be it. Otherwise the select backend
		1885	will not be compiled in.
		1886
		1887	=item EV_SELECT_USE_FD_SET
		1888
		1889	If defined to C<1>, then the select backend will use the system C<fd_set>
		1890	structure. This is useful if libev doesn't compile due to a missing
		1891	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		1892	exotic systems. This usually limits the range of file descriptors to some
		1893	low limit such as 1024 or might have other limitations (winsocket only
		1894	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		1895	influence the size of the C<fd_set> used.
		1896
		1897	=item EV_SELECT_IS_WINSOCKET
		1898
		1899	When defined to C<1>, the select backend will assume that
		1900	select/socket/connect etc. don't understand file descriptors but
		1901	wants osf handles on win32 (this is the case when the select to
		1902	be used is the winsock select). This means that it will call
		1903	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		1904	it is assumed that all these functions actually work on fds, even
		1905	on win32. Should not be defined on non-win32 platforms.
		1906
		1907	=item EV_USE_POLL
		1908
		1909	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		1910	backend. Otherwise it will be enabled on non-win32 platforms. It
		1911	takes precedence over select.
		1912
		1913	=item EV_USE_EPOLL
		1914
		1915	If defined to be C<1>, libev will compile in support for the Linux
		1916	C<epoll>(7) backend. Its availability will be detected at runtime,
		1917	otherwise another method will be used as fallback. This is the
		1918	preferred backend for GNU/Linux systems.
		1919
		1920	=item EV_USE_KQUEUE
		1921
		1922	If defined to be C<1>, libev will compile in support for the BSD style
		1923	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		1924	otherwise another method will be used as fallback. This is the preferred
		1925	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		1926	supports some types of fds correctly (the only platform we found that
		1927	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		1928	not be used unless explicitly requested. The best way to use it is to find
		1929	out whether kqueue supports your type of fd properly and use an embedded
		1930	kqueue loop.
		1931
		1932	=item EV_USE_PORT
		1933
		1934	If defined to be C<1>, libev will compile in support for the Solaris
		1935	10 port style backend. Its availability will be detected at runtime,
		1936	otherwise another method will be used as fallback. This is the preferred
		1937	backend for Solaris 10 systems.
		1938
		1939	=item EV_USE_DEVPOLL
		1940
		1941	reserved for future expansion, works like the USE symbols above.
		1942
		1943	=item EV_H
		1944
		1945	The name of the F<ev.h> header file used to include it. The default if
		1946	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		1947	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		1948
		1949	=item EV_CONFIG_H
		1950
		1951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		1952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		1953	C<EV_H>, above.
		1954
		1955	=item EV_EVENT_H
		1956
		1957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		1958	of how the F<event.h> header can be found.
		1959
		1960	=item EV_PROTOTYPES
		1961
		1962	If defined to be C<0>, then F<ev.h> will not define any function
		1963	prototypes, but still define all the structs and other symbols. This is
		1964	occasionally useful if you want to provide your own wrapper functions
		1965	around libev functions.
		1966
		1967	=item EV_MULTIPLICITY
		1968
		1969	If undefined or defined to C<1>, then all event-loop-specific functions
		1970	will have the C<struct ev_loop *> as first argument, and you can create
		1971	additional independent event loops. Otherwise there will be no support
		1972	for multiple event loops and there is no first event loop pointer
		1973	argument. Instead, all functions act on the single default loop.
		1974
		1975	=item EV_PERIODIC_ENABLE
		1976
		1977	If undefined or defined to be C<1>, then periodic timers are supported. If
		1978	defined to be C<0>, then they are not. Disabling them saves a few kB of
		1979	code.
		1980
		1981	=item EV_EMBED_ENABLE
		1982
		1983	If undefined or defined to be C<1>, then embed watchers are supported. If
		1984	defined to be C<0>, then they are not.
		1985
		1986	=item EV_STAT_ENABLE
		1987
		1988	If undefined or defined to be C<1>, then stat watchers are supported. If
		1989	defined to be C<0>, then they are not.
		1990
		1991	=item EV_FORK_ENABLE
		1992
		1993	If undefined or defined to be C<1>, then fork watchers are supported. If
		1994	defined to be C<0>, then they are not.
		1995
		1996	=item EV_MINIMAL
		1997
		1998	If you need to shave off some kilobytes of code at the expense of some
		1999	speed, define this symbol to C<1>. Currently only used for gcc to override
		2000	some inlining decisions, saves roughly 30% codesize of amd64.
		2001
		2002	=item EV_PID_HASHSIZE
		2003
		2004	C<ev_child> watchers use a small hash table to distribute workload by
		2005	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2006	than enough. If you need to manage thousands of children you might want to
		2007	increase this value.
		2008
		2009	=item EV_COMMON
		2010
		2011	By default, all watchers have a C<void *data> member. By redefining
		2012	this macro to a something else you can include more and other types of
		2013	members. You have to define it each time you include one of the files,
		2014	though, and it must be identical each time.
		2015
		2016	For example, the perl EV module uses something like this:
		2017
		2018	#define EV_COMMON \
		2019	SV *self; /* contains this struct */ \
		2020	SV *cb_sv, *fh /* note no trailing ";" */
		2021
		2022	=item EV_CB_DECLARE (type)
		2023
		2024	=item EV_CB_INVOKE (watcher, revents)
		2025
		2026	=item ev_set_cb (ev, cb)
		2027
		2028	Can be used to change the callback member declaration in each watcher,
		2029	and the way callbacks are invoked and set. Must expand to a struct member
		2030	definition and a statement, respectively. See the F<ev.v> header file for
		2031	their default definitions. One possible use for overriding these is to
		2032	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2033	method calls instead of plain function calls in C++.
		2034
		2035	=head2 EXAMPLES
		2036
		2037	For a real-world example of a program the includes libev
		2038	verbatim, you can have a look at the EV perl module
		2039	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2040	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2041	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2042	will be compiled. It is pretty complex because it provides its own header
		2043	file.
		2044
		2045	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2046	that everybody includes and which overrides some autoconf choices:
		2047
		2048	#define EV_USE_POLL 0
		2049	#define EV_MULTIPLICITY 0
		2050	#define EV_PERIODICS 0
		2051	#define EV_CONFIG_H <config.h>
		2052
		2053	#include "ev++.h"
		2054
		2055	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2056
		2057	#include "ev_cpp.h"
		2058	#include "ev.c"
		2059
		2060
		2061	=head1 COMPLEXITIES
		2062
		2063	In this section the complexities of (many of) the algorithms used inside
		2064	libev will be explained. For complexity discussions about backends see the
		2065	documentation for C<ev_default_init>.
		2066
		2067	=over 4
		2068
		2069	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2070
		2071	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2072
		2073	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2074
		2075	=item Stopping check/prepare/idle watchers: O(1)
		2076
		2077	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))
		2078
		2079	=item Finding the next timer per loop iteration: O(1)
		2080
		2081	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2082
		2083	=item Activating one watcher: O(1)
		2084
		2085	=back
		2086
878		2087
879	=head1 AUTHOR	2088	=head1 AUTHOR
880		2089
881	Marc Lehmann <libev@schmorp.de>.	2090	Marc Lehmann <libev@schmorp.de>.
882		2091

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