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Revision 1.32 by root, Fri Nov 23 08:36:35 2007 UTC vs.
Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC

…		…
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
8		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
11	Libev is an event loop: you register interest in certain events (such as a	53	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	54	file descriptor being readable or a timeout occuring), and it will manage
…		…
21	details of the event, and then hand it over to libev by I<starting> the	63	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	64	watcher.
23		65
24	=head1 FEATURES	66	=head1 FEATURES
25		67
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	68	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	70	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	72	with customised rescheduling (C<ev_periodic>), synchronous signals
		73	(C<ev_signal>), process status change events (C<ev_child>), and event
		74	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		75	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		76	file watchers (C<ev_stat>) and even limited support for fork events
		77	(C<ev_fork>).
		78
		79	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	80	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	81	for example).
33		82
34	=head1 CONVENTIONS	83	=head1 CONVENTIONS
35		84
36	Libev is very configurable. In this manual the default configuration	85	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	86	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	87	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	88	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	89	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	90	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		91
44	=head1 TIME REPRESENTATION	92	=head1 TIME REPRESENTATION
45		93
46	Libev represents time as a single floating point number, representing the	94	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	95	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	96	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	97	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	98	to the C<double> type in C, and when you need to do any calculations on
		99	it, you should treat it as such.
51		100
52	=head1 GLOBAL FUNCTIONS	101	=head1 GLOBAL FUNCTIONS
53		102
54	These functions can be called anytime, even before initialising the	103	These functions can be called anytime, even before initialising the
55	library in any way.	104	library in any way.
…		…
75	Usually, it's a good idea to terminate if the major versions mismatch,	124	Usually, it's a good idea to terminate if the major versions mismatch,
76	as this indicates an incompatible change. Minor versions are usually	125	as this indicates an incompatible change. Minor versions are usually
77	compatible to older versions, so a larger minor version alone is usually	126	compatible to older versions, so a larger minor version alone is usually
78	not a problem.	127	not a problem.
79		128
		129	Example: Make sure we haven't accidentally been linked against the wrong
		130	version.
		131
		132	assert (("libev version mismatch",
		133	ev_version_major () == EV_VERSION_MAJOR
		134	&& ev_version_minor () >= EV_VERSION_MINOR));
		135
80	=item unsigned int ev_supported_backends ()	136	=item unsigned int ev_supported_backends ()
81		137
82	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	138	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
83	value) compiled into this binary of libev (independent of their	139	value) compiled into this binary of libev (independent of their
84	availability on the system you are running on). See C<ev_default_loop> for	140	availability on the system you are running on). See C<ev_default_loop> for
85	a description of the set values.	141	a description of the set values.
		142
		143	Example: make sure we have the epoll method, because yeah this is cool and
		144	a must have and can we have a torrent of it please!!!11
		145
		146	assert (("sorry, no epoll, no sex",
		147	ev_supported_backends () & EVBACKEND_EPOLL));
86		148
87	=item unsigned int ev_recommended_backends ()	149	=item unsigned int ev_recommended_backends ()
88		150
89	Return the set of all backends compiled into this binary of libev and also	151	Return the set of all backends compiled into this binary of libev and also
90	recommended for this platform. This set is often smaller than the one	152	recommended for this platform. This set is often smaller than the one
91	returned by C<ev_supported_backends>, as for example kqueue is broken on	153	returned by C<ev_supported_backends>, as for example kqueue is broken on
92	most BSDs and will not be autodetected unless you explicitly request it	154	most BSDs and will not be autodetected unless you explicitly request it
93	(assuming you know what you are doing). This is the set of backends that	155	(assuming you know what you are doing). This is the set of backends that
94	C<EVFLAG_AUTO> will probe for.	156	libev will probe for if you specify no backends explicitly.
		157
		158	=item unsigned int ev_embeddable_backends ()
		159
		160	Returns the set of backends that are embeddable in other event loops. This
		161	is the theoretical, all-platform, value. To find which backends
		162	might be supported on the current system, you would need to look at
		163	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		164	recommended ones.
		165
		166	See the description of C<ev_embed> watchers for more info.
95		167
96	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	168	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
97		169
98	Sets the allocation function to use (the prototype is similar to the	170	Sets the allocation function to use (the prototype is similar - the
99	realloc C function, the semantics are identical). It is used to allocate	171	semantics is identical - to the realloc C function). It is used to
100	and free memory (no surprises here). If it returns zero when memory	172	allocate and free memory (no surprises here). If it returns zero when
101	needs to be allocated, the library might abort or take some potentially	173	memory needs to be allocated, the library might abort or take some
102	destructive action. The default is your system realloc function.	174	potentially destructive action. The default is your system realloc
		175	function.
103		176
104	You could override this function in high-availability programs to, say,	177	You could override this function in high-availability programs to, say,
105	free some memory if it cannot allocate memory, to use a special allocator,	178	free some memory if it cannot allocate memory, to use a special allocator,
106	or even to sleep a while and retry until some memory is available.	179	or even to sleep a while and retry until some memory is available.
		180
		181	Example: Replace the libev allocator with one that waits a bit and then
		182	retries).
		183
		184	static void *
		185	persistent_realloc (void *ptr, size_t size)
		186	{
		187	for (;;)
		188	{
		189	void *newptr = realloc (ptr, size);
		190
		191	if (newptr)
		192	return newptr;
		193
		194	sleep (60);
		195	}
		196	}
		197
		198	...
		199	ev_set_allocator (persistent_realloc);
107		200
108	=item ev_set_syserr_cb (void (*cb)(const char *msg));	201	=item ev_set_syserr_cb (void (*cb)(const char *msg));
109		202
110	Set the callback function to call on a retryable syscall error (such	203	Set the callback function to call on a retryable syscall error (such
111	as failed select, poll, epoll_wait). The message is a printable string	204	as failed select, poll, epoll_wait). The message is a printable string
…		…
113	callback is set, then libev will expect it to remedy the sitution, no	206	callback is set, then libev will expect it to remedy the sitution, no
114	matter what, when it returns. That is, libev will generally retry the	207	matter what, when it returns. That is, libev will generally retry the
115	requested operation, or, if the condition doesn't go away, do bad stuff	208	requested operation, or, if the condition doesn't go away, do bad stuff
116	(such as abort).	209	(such as abort).
117		210
		211	Example: This is basically the same thing that libev does internally, too.
		212
		213	static void
		214	fatal_error (const char *msg)
		215	{
		216	perror (msg);
		217	abort ();
		218	}
		219
		220	...
		221	ev_set_syserr_cb (fatal_error);
		222
118	=back	223	=back
119		224
120	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	225	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
121		226
122	An event loop is described by a C<struct ev_loop *>. The library knows two	227	An event loop is described by a C<struct ev_loop *>. The library knows two
…		…
141		246
142	If you don't know what event loop to use, use the one returned from this	247	If you don't know what event loop to use, use the one returned from this
143	function.	248	function.
144		249
145	The flags argument can be used to specify special behaviour or specific	250	The flags argument can be used to specify special behaviour or specific
146	backends to use, and is usually specified as C<0> (or EVFLAG_AUTO).	251	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
147		252
148	It supports the following flags:	253	The following flags are supported:
149		254
150	=over 4	255	=over 4
151		256
152	=item C<EVFLAG_AUTO>	257	=item C<EVFLAG_AUTO>
153		258
…		…
161	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	266	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
162	override the flags completely if it is found in the environment. This is	267	override the flags completely if it is found in the environment. This is
163	useful to try out specific backends to test their performance, or to work	268	useful to try out specific backends to test their performance, or to work
164	around bugs.	269	around bugs.
165		270
		271	=item C<EVFLAG_FORKCHECK>
		272
		273	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		274	a fork, you can also make libev check for a fork in each iteration by
		275	enabling this flag.
		276
		277	This works by calling C<getpid ()> on every iteration of the loop,
		278	and thus this might slow down your event loop if you do a lot of loop
		279	iterations and little real work, but is usually not noticeable (on my
		280	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		281	without a syscall and thus I<very> fast, but my Linux system also has
		282	C<pthread_atfork> which is even faster).
		283
		284	The big advantage of this flag is that you can forget about fork (and
		285	forget about forgetting to tell libev about forking) when you use this
		286	flag.
		287
		288	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		289	environment variable.
		290
166	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	291	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
167		292
168	This is your standard select(2) backend. Not I<completely> standard, as	293	This is your standard select(2) backend. Not I<completely> standard, as
169	libev tries to roll its own fd_set with no limits on the number of fds,	294	libev tries to roll its own fd_set with no limits on the number of fds,
170	but if that fails, expect a fairly low limit on the number of fds when	295	but if that fails, expect a fairly low limit on the number of fds when
…		…
198	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	323	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
199		324
200	Kqueue deserves special mention, as at the time of this writing, it	325	Kqueue deserves special mention, as at the time of this writing, it
201	was broken on all BSDs except NetBSD (usually it doesn't work with	326	was broken on all BSDs except NetBSD (usually it doesn't work with
202	anything but sockets and pipes, except on Darwin, where of course its	327	anything but sockets and pipes, except on Darwin, where of course its
203	completely useless). For this reason its not being "autodetected" unless	328	completely useless). For this reason its not being "autodetected"
204	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).	329	unless you explicitly specify it explicitly in the flags (i.e. using
		330	C<EVBACKEND_KQUEUE>).
205		331
206	It scales in the same way as the epoll backend, but the interface to the	332	It scales in the same way as the epoll backend, but the interface to the
207	kernel is more efficient (which says nothing about its actual speed, of	333	kernel is more efficient (which says nothing about its actual speed, of
208	course). While starting and stopping an I/O watcher does not cause an	334	course). While starting and stopping an I/O watcher does not cause an
209	extra syscall as with epoll, it still adds up to four event changes per	335	extra syscall as with epoll, it still adds up to four event changes per
…		…
233	If one or more of these are ored into the flags value, then only these	359	If one or more of these are ored into the flags value, then only these
234	backends will be tried (in the reverse order as given here). If none are	360	backends will be tried (in the reverse order as given here). If none are
235	specified, most compiled-in backend will be tried, usually in reverse	361	specified, most compiled-in backend will be tried, usually in reverse
236	order of their flag values :)	362	order of their flag values :)
237		363
		364	The most typical usage is like this:
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	Use whatever libev has to offer, but make sure that kqueue is used if
		375	available (warning, breaks stuff, best use only with your own private
		376	event loop and only if you know the OS supports your types of fds):
		377
		378	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
		379
238	=item struct ev_loop *ev_loop_new (unsigned int flags)	380	=item struct ev_loop *ev_loop_new (unsigned int flags)
239		381
240	Similar to C<ev_default_loop>, but always creates a new event loop that is	382	Similar to C<ev_default_loop>, but always creates a new event loop that is
241	always distinct from the default loop. Unlike the default loop, it cannot	383	always distinct from the default loop. Unlike the default loop, it cannot
242	handle signal and child watchers, and attempts to do so will be greeted by	384	handle signal and child watchers, and attempts to do so will be greeted by
243	undefined behaviour (or a failed assertion if assertions are enabled).	385	undefined behaviour (or a failed assertion if assertions are enabled).
244		386
		387	Example: Try to create a event loop that uses epoll and nothing else.
		388
		389	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
		390	if (!epoller)
		391	fatal ("no epoll found here, maybe it hides under your chair");
		392
245	=item ev_default_destroy ()	393	=item ev_default_destroy ()
246		394
247	Destroys the default loop again (frees all memory and kernel state	395	Destroys the default loop again (frees all memory and kernel state
248	etc.). This stops all registered event watchers (by not touching them in	396	etc.). None of the active event watchers will be stopped in the normal
249	any way whatsoever, although you cannot rely on this :).	397	sense, so e.g. C<ev_is_active> might still return true. It is your
		398	responsibility to either stop all watchers cleanly yoursef I<before>
		399	calling this function, or cope with the fact afterwards (which is usually
		400	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		401	for example).
250		402
251	=item ev_loop_destroy (loop)	403	=item ev_loop_destroy (loop)
252		404
253	Like C<ev_default_destroy>, but destroys an event loop created by an	405	Like C<ev_default_destroy>, but destroys an event loop created by an
254	earlier call to C<ev_loop_new>.	406	earlier call to C<ev_loop_new>.
…		…
278		430
279	Like C<ev_default_fork>, but acts on an event loop created by	431	Like C<ev_default_fork>, but acts on an event loop created by
280	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	432	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
281	after fork, and how you do this is entirely your own problem.	433	after fork, and how you do this is entirely your own problem.
282		434
		435	=item unsigned int ev_loop_count (loop)
		436
		437	Returns the count of loop iterations for the loop, which is identical to
		438	the number of times libev did poll for new events. It starts at C<0> and
		439	happily wraps around with enough iterations.
		440
		441	This value can sometimes be useful as a generation counter of sorts (it
		442	"ticks" the number of loop iterations), as it roughly corresponds with
		443	C<ev_prepare> and C<ev_check> calls.
		444
283	=item unsigned int ev_backend (loop)	445	=item unsigned int ev_backend (loop)
284		446
285	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	447	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
286	use.	448	use.
287		449
288	=item ev_tstamp ev_now (loop)	450	=item ev_tstamp ev_now (loop)
289		451
290	Returns the current "event loop time", which is the time the event loop	452	Returns the current "event loop time", which is the time the event loop
291	got events and started processing them. This timestamp does not change	453	received events and started processing them. This timestamp does not
292	as long as callbacks are being processed, and this is also the base time	454	change as long as callbacks are being processed, and this is also the base
293	used for relative timers. You can treat it as the timestamp of the event	455	time used for relative timers. You can treat it as the timestamp of the
294	occuring (or more correctly, the mainloop finding out about it).	456	event occuring (or more correctly, libev finding out about it).
295		457
296	=item ev_loop (loop, int flags)	458	=item ev_loop (loop, int flags)
297		459
298	Finally, this is it, the event handler. This function usually is called	460	Finally, this is it, the event handler. This function usually is called
299	after you initialised all your watchers and you want to start handling	461	after you initialised all your watchers and you want to start handling
300	events.	462	events.
301		463
302	If the flags argument is specified as 0, it will not return until either	464	If the flags argument is specified as C<0>, it will not return until
303	no event watchers are active anymore or C<ev_unloop> was called.	465	either no event watchers are active anymore or C<ev_unloop> was called.
		466
		467	Please note that an explicit C<ev_unloop> is usually better than
		468	relying on all watchers to be stopped when deciding when a program has
		469	finished (especially in interactive programs), but having a program that
		470	automatically loops as long as it has to and no longer by virtue of
		471	relying on its watchers stopping correctly is a thing of beauty.
304		472
305	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	473	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
306	those events and any outstanding ones, but will not block your process in	474	those events and any outstanding ones, but will not block your process in
307	case there are no events and will return after one iteration of the loop.	475	case there are no events and will return after one iteration of the loop.
308		476
309	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	477	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
310	neccessary) and will handle those and any outstanding ones. It will block	478	neccessary) and will handle those and any outstanding ones. It will block
311	your process until at least one new event arrives, and will return after	479	your process until at least one new event arrives, and will return after
312	one iteration of the loop.	480	one iteration of the loop. This is useful if you are waiting for some
		481	external event in conjunction with something not expressible using other
		482	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		483	usually a better approach for this kind of thing.
313		484
314	This flags value could be used to implement alternative looping
315	constructs, but the C<prepare> and C<check> watchers provide a better and
316	more generic mechanism.
317
318	Here are the gory details of what ev_loop does:	485	Here are the gory details of what C<ev_loop> does:
319		486
320	1. If there are no active watchers (reference count is zero), return.	487	* If there are no active watchers (reference count is zero), return.
321	2. Queue and immediately call all prepare watchers.	488	- Queue prepare watchers and then call all outstanding watchers.
322	3. If we have been forked, recreate the kernel state.	489	- If we have been forked, recreate the kernel state.
323	4. Update the kernel state with all outstanding changes.	490	- Update the kernel state with all outstanding changes.
324	5. Update the "event loop time".	491	- Update the "event loop time".
325	6. Calculate for how long to block.	492	- Calculate for how long to block.
326	7. Block the process, waiting for events.	493	- Block the process, waiting for any events.
		494	- Queue all outstanding I/O (fd) events.
327	8. Update the "event loop time" and do time jump handling.	495	- Update the "event loop time" and do time jump handling.
328	9. Queue all outstanding timers.	496	- Queue all outstanding timers.
329	10. Queue all outstanding periodics.	497	- Queue all outstanding periodics.
330	11. If no events are pending now, queue all idle watchers.	498	- If no events are pending now, queue all idle watchers.
331	12. Queue all check watchers.	499	- Queue all check watchers.
332	13. Call all queued watchers in reverse order (i.e. check watchers first).	500	- Call all queued watchers in reverse order (i.e. check watchers first).
		501	Signals and child watchers are implemented as I/O watchers, and will
		502	be handled here by queueing them when their watcher gets executed.
333	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	503	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
334	was used, return, otherwise continue with step #1.	504	were used, return, otherwise continue with step *.
		505
		506	Example: Queue some jobs and then loop until no events are outsanding
		507	anymore.
		508
		509	... queue jobs here, make sure they register event watchers as long
		510	... as they still have work to do (even an idle watcher will do..)
		511	ev_loop (my_loop, 0);
		512	... jobs done. yeah!
335		513
336	=item ev_unloop (loop, how)	514	=item ev_unloop (loop, how)
337		515
338	Can be used to make a call to C<ev_loop> return early (but only after it	516	Can be used to make a call to C<ev_loop> return early (but only after it
339	has processed all outstanding events). The C<how> argument must be either	517	has processed all outstanding events). The C<how> argument must be either
…		…
353	visible to the libev user and should not keep C<ev_loop> from exiting if	531	visible to the libev user and should not keep C<ev_loop> from exiting if
354	no event watchers registered by it are active. It is also an excellent	532	no event watchers registered by it are active. It is also an excellent
355	way to do this for generic recurring timers or from within third-party	533	way to do this for generic recurring timers or from within third-party
356	libraries. Just remember to I<unref after start> and I<ref before stop>.	534	libraries. Just remember to I<unref after start> and I<ref before stop>.
357		535
		536	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
		537	running when nothing else is active.
		538
		539	struct ev_signal exitsig;
		540	ev_signal_init (&exitsig, sig_cb, SIGINT);
		541	ev_signal_start (loop, &exitsig);
		542	evf_unref (loop);
		543
		544	Example: For some weird reason, unregister the above signal handler again.
		545
		546	ev_ref (loop);
		547	ev_signal_stop (loop, &exitsig);
		548
358	=back	549	=back
		550
359		551
360	=head1 ANATOMY OF A WATCHER	552	=head1 ANATOMY OF A WATCHER
361		553
362	A watcher is a structure that you create and register to record your	554	A watcher is a structure that you create and register to record your
363	interest in some event. For instance, if you want to wait for STDIN to	555	interest in some event. For instance, if you want to wait for STDIN to
…		…
396	*) >>), and you can stop watching for events at any time by calling the	588	*) >>), and you can stop watching for events at any time by calling the
397	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	589	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
398		590
399	As long as your watcher is active (has been started but not stopped) you	591	As long as your watcher is active (has been started but not stopped) you
400	must not touch the values stored in it. Most specifically you must never	592	must not touch the values stored in it. Most specifically you must never
401	reinitialise it or call its set macro.	593	reinitialise it or call its C<set> macro.
402
403	You can check whether an event is active by calling the C<ev_is_active
404	(watcher *)> macro. To see whether an event is outstanding (but the
405	callback for it has not been called yet) you can use the C<ev_is_pending
406	(watcher *)> macro.
407		594
408	Each and every callback receives the event loop pointer as first, the	595	Each and every callback receives the event loop pointer as first, the
409	registered watcher structure as second, and a bitset of received events as	596	registered watcher structure as second, and a bitset of received events as
410	third argument.	597	third argument.
411		598
…		…
435	The signal specified in the C<ev_signal> watcher has been received by a thread.	622	The signal specified in the C<ev_signal> watcher has been received by a thread.
436		623
437	=item C<EV_CHILD>	624	=item C<EV_CHILD>
438		625
439	The pid specified in the C<ev_child> watcher has received a status change.	626	The pid specified in the C<ev_child> watcher has received a status change.
		627
		628	=item C<EV_STAT>
		629
		630	The path specified in the C<ev_stat> watcher changed its attributes somehow.
440		631
441	=item C<EV_IDLE>	632	=item C<EV_IDLE>
442		633
443	The C<ev_idle> watcher has determined that you have nothing better to do.	634	The C<ev_idle> watcher has determined that you have nothing better to do.
444		635
…		…
452	received events. Callbacks of both watcher types can start and stop as	643	received events. Callbacks of both watcher types can start and stop as
453	many watchers as they want, and all of them will be taken into account	644	many watchers as they want, and all of them will be taken into account
454	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	645	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
455	C<ev_loop> from blocking).	646	C<ev_loop> from blocking).
456		647
		648	=item C<EV_EMBED>
		649
		650	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		651
		652	=item C<EV_FORK>
		653
		654	The event loop has been resumed in the child process after fork (see
		655	C<ev_fork>).
		656
457	=item C<EV_ERROR>	657	=item C<EV_ERROR>
458		658
459	An unspecified error has occured, the watcher has been stopped. This might	659	An unspecified error has occured, the watcher has been stopped. This might
460	happen because the watcher could not be properly started because libev	660	happen because the watcher could not be properly started because libev
461	ran out of memory, a file descriptor was found to be closed or any other	661	ran out of memory, a file descriptor was found to be closed or any other
…		…
467	your callbacks is well-written it can just attempt the operation and cope	667	your callbacks is well-written it can just attempt the operation and cope
468	with the error from read() or write(). This will not work in multithreaded	668	with the error from read() or write(). This will not work in multithreaded
469	programs, though, so beware.	669	programs, though, so beware.
470		670
471	=back	671	=back
		672
		673	=head2 GENERIC WATCHER FUNCTIONS
		674
		675	In the following description, C<TYPE> stands for the watcher type,
		676	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		677
		678	=over 4
		679
		680	=item C<ev_init> (ev_TYPE *watcher, callback)
		681
		682	This macro initialises the generic portion of a watcher. The contents
		683	of the watcher object can be arbitrary (so C<malloc> will do). Only
		684	the generic parts of the watcher are initialised, you I<need> to call
		685	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		686	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		687	which rolls both calls into one.
		688
		689	You can reinitialise a watcher at any time as long as it has been stopped
		690	(or never started) and there are no pending events outstanding.
		691
		692	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		693	int revents)>.
		694
		695	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		696
		697	This macro initialises the type-specific parts of a watcher. You need to
		698	call C<ev_init> at least once before you call this macro, but you can
		699	call C<ev_TYPE_set> any number of times. You must not, however, call this
		700	macro on a watcher that is active (it can be pending, however, which is a
		701	difference to the C<ev_init> macro).
		702
		703	Although some watcher types do not have type-specific arguments
		704	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		705
		706	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		707
		708	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		709	calls into a single call. This is the most convinient method to initialise
		710	a watcher. The same limitations apply, of course.
		711
		712	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		713
		714	Starts (activates) the given watcher. Only active watchers will receive
		715	events. If the watcher is already active nothing will happen.
		716
		717	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		718
		719	Stops the given watcher again (if active) and clears the pending
		720	status. It is possible that stopped watchers are pending (for example,
		721	non-repeating timers are being stopped when they become pending), but
		722	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		723	you want to free or reuse the memory used by the watcher it is therefore a
		724	good idea to always call its C<ev_TYPE_stop> function.
		725
		726	=item bool ev_is_active (ev_TYPE *watcher)
		727
		728	Returns a true value iff the watcher is active (i.e. it has been started
		729	and not yet been stopped). As long as a watcher is active you must not modify
		730	it.
		731
		732	=item bool ev_is_pending (ev_TYPE *watcher)
		733
		734	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		735	events but its callback has not yet been invoked). As long as a watcher
		736	is pending (but not active) you must not call an init function on it (but
		737	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		738	libev (e.g. you cnanot C<free ()> it).
		739
		740	=item callback ev_cb (ev_TYPE *watcher)
		741
		742	Returns the callback currently set on the watcher.
		743
		744	=item ev_cb_set (ev_TYPE *watcher, callback)
		745
		746	Change the callback. You can change the callback at virtually any time
		747	(modulo threads).
		748
		749	=back
		750
472		751
473	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	752	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
474		753
475	Each watcher has, by default, a member C<void *data> that you can change	754	Each watcher has, by default, a member C<void *data> that you can change
476	and read at any time, libev will completely ignore it. This can be used	755	and read at any time, libev will completely ignore it. This can be used
…		…
494	{	773	{
495	struct my_io *w = (struct my_io *)w_;	774	struct my_io *w = (struct my_io *)w_;
496	...	775	...
497	}	776	}
498		777
499	More interesting and less C-conformant ways of catsing your callback type	778	More interesting and less C-conformant ways of casting your callback type
500	have been omitted....	779	instead have been omitted.
		780
		781	Another common scenario is having some data structure with multiple
		782	watchers:
		783
		784	struct my_biggy
		785	{
		786	int some_data;
		787	ev_timer t1;
		788	ev_timer t2;
		789	}
		790
		791	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		792	you need to use C<offsetof>:
		793
		794	#include <stddef.h>
		795
		796	static void
		797	t1_cb (EV_P_ struct ev_timer *w, int revents)
		798	{
		799	struct my_biggy big = (struct my_biggy *
		800	(((char *)w) - offsetof (struct my_biggy, t1));
		801	}
		802
		803	static void
		804	t2_cb (EV_P_ struct ev_timer *w, int revents)
		805	{
		806	struct my_biggy big = (struct my_biggy *
		807	(((char *)w) - offsetof (struct my_biggy, t2));
		808	}
501		809
502		810
503	=head1 WATCHER TYPES	811	=head1 WATCHER TYPES
504		812
505	This section describes each watcher in detail, but will not repeat	813	This section describes each watcher in detail, but will not repeat
506	information given in the last section.	814	information given in the last section. Any initialisation/set macros,
		815	functions and members specific to the watcher type are explained.
507		816
		817	Members are additionally marked with either I<[read-only]>, meaning that,
		818	while the watcher is active, you can look at the member and expect some
		819	sensible content, but you must not modify it (you can modify it while the
		820	watcher is stopped to your hearts content), or I<[read-write]>, which
		821	means you can expect it to have some sensible content while the watcher
		822	is active, but you can also modify it. Modifying it may not do something
		823	sensible or take immediate effect (or do anything at all), but libev will
		824	not crash or malfunction in any way.
		825
		826
508	=head2 C<ev_io> - is this file descriptor readable or writable	827	=head2 C<ev_io> - is this file descriptor readable or writable?
509		828
510	I/O watchers check whether a file descriptor is readable or writable	829	I/O watchers check whether a file descriptor is readable or writable
511	in each iteration of the event loop (This behaviour is called	830	in each iteration of the event loop, or, more precisely, when reading
512	level-triggering because you keep receiving events as long as the	831	would not block the process and writing would at least be able to write
513	condition persists. Remember you can stop the watcher if you don't want to	832	some data. This behaviour is called level-triggering because you keep
514	act on the event and neither want to receive future events).	833	receiving events as long as the condition persists. Remember you can stop
		834	the watcher if you don't want to act on the event and neither want to
		835	receive future events.
515		836
516	In general you can register as many read and/or write event watchers per	837	In general you can register as many read and/or write event watchers per
517	fd as you want (as long as you don't confuse yourself). Setting all file	838	fd as you want (as long as you don't confuse yourself). Setting all file
518	descriptors to non-blocking mode is also usually a good idea (but not	839	descriptors to non-blocking mode is also usually a good idea (but not
519	required if you know what you are doing).	840	required if you know what you are doing).
520		841
521	You have to be careful with dup'ed file descriptors, though. Some backends	842	You have to be careful with dup'ed file descriptors, though. Some backends
522	(the linux epoll backend is a notable example) cannot handle dup'ed file	843	(the linux epoll backend is a notable example) cannot handle dup'ed file
523	descriptors correctly if you register interest in two or more fds pointing	844	descriptors correctly if you register interest in two or more fds pointing
524	to the same underlying file/socket etc. description (that is, they share	845	to the same underlying file/socket/etc. description (that is, they share
525	the same underlying "file open").	846	the same underlying "file open").
526		847
527	If you must do this, then force the use of a known-to-be-good backend	848	If you must do this, then force the use of a known-to-be-good backend
528	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	849	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
529	C<EVBACKEND_POLL>).	850	C<EVBACKEND_POLL>).
530		851
		852	Another thing you have to watch out for is that it is quite easy to
		853	receive "spurious" readyness notifications, that is your callback might
		854	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		855	because there is no data. Not only are some backends known to create a
		856	lot of those (for example solaris ports), it is very easy to get into
		857	this situation even with a relatively standard program structure. Thus
		858	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		859	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		860
		861	If you cannot run the fd in non-blocking mode (for example you should not
		862	play around with an Xlib connection), then you have to seperately re-test
		863	wether a file descriptor is really ready with a known-to-be good interface
		864	such as poll (fortunately in our Xlib example, Xlib already does this on
		865	its own, so its quite safe to use).
		866
531	=over 4	867	=over 4
532		868
533	=item ev_io_init (ev_io *, callback, int fd, int events)	869	=item ev_io_init (ev_io *, callback, int fd, int events)
534		870
535	=item ev_io_set (ev_io *, int fd, int events)	871	=item ev_io_set (ev_io *, int fd, int events)
536		872
537	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	873	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
538	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	874	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
539	EV_WRITE> to receive the given events.	875	C<EV_READ | EV_WRITE> to receive the given events.
540		876
541	Please note that most of the more scalable backend mechanisms (for example	877	=item int fd [read-only]
542	epoll and solaris ports) can result in spurious readyness notifications	878
543	for file descriptors, so you practically need to use non-blocking I/O (and	879	The file descriptor being watched.
544	treat callback invocation as hint only), or retest separately with a safe	880
545	interface before doing I/O (XLib can do this), or force the use of either	881	=item int events [read-only]
546	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	882
547	problem. Also note that it is quite easy to have your callback invoked	883	The events being watched.
548	when the readyness condition is no longer valid even when employing
549	typical ways of handling events, so its a good idea to use non-blocking
550	I/O unconditionally.
551		884
552	=back	885	=back
553		886
		887	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
		888	readable, but only once. Since it is likely line-buffered, you could
		889	attempt to read a whole line in the callback.
		890
		891	static void
		892	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		893	{
		894	ev_io_stop (loop, w);
		895	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		896	}
		897
		898	...
		899	struct ev_loop *loop = ev_default_init (0);
		900	struct ev_io stdin_readable;
		901	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		902	ev_io_start (loop, &stdin_readable);
		903	ev_loop (loop, 0);
		904
		905
554	=head2 C<ev_timer> - relative and optionally recurring timeouts	906	=head2 C<ev_timer> - relative and optionally repeating timeouts
555		907
556	Timer watchers are simple relative timers that generate an event after a	908	Timer watchers are simple relative timers that generate an event after a
557	given time, and optionally repeating in regular intervals after that.	909	given time, and optionally repeating in regular intervals after that.
558		910
559	The timers are based on real time, that is, if you register an event that	911	The timers are based on real time, that is, if you register an event that
…		…
594	=item ev_timer_again (loop)	946	=item ev_timer_again (loop)
595		947
596	This will act as if the timer timed out and restart it again if it is	948	This will act as if the timer timed out and restart it again if it is
597	repeating. The exact semantics are:	949	repeating. The exact semantics are:
598		950
		951	If the timer is pending, its pending status is cleared.
		952
599	If the timer is started but nonrepeating, stop it.	953	If the timer is started but nonrepeating, stop it (as if it timed out).
600		954
601	If the timer is repeating, either start it if necessary (with the repeat	955	If the timer is repeating, either start it if necessary (with the
602	value), or reset the running timer to the repeat value.	956	C<repeat> value), or reset the running timer to the C<repeat> value.
603		957
604	This sounds a bit complicated, but here is a useful and typical	958	This sounds a bit complicated, but here is a useful and typical
605	example: Imagine you have a tcp connection and you want a so-called idle	959	example: Imagine you have a tcp connection and you want a so-called idle
606	timeout, that is, you want to be called when there have been, say, 60	960	timeout, that is, you want to be called when there have been, say, 60
607	seconds of inactivity on the socket. The easiest way to do this is to	961	seconds of inactivity on the socket. The easiest way to do this is to
608	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	962	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
609	time you successfully read or write some data. If you go into an idle	963	C<ev_timer_again> each time you successfully read or write some data. If
610	state where you do not expect data to travel on the socket, you can stop	964	you go into an idle state where you do not expect data to travel on the
611	the timer, and again will automatically restart it if need be.	965	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		966	automatically restart it if need be.
		967
		968	That means you can ignore the C<after> value and C<ev_timer_start>
		969	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		970
		971	ev_timer_init (timer, callback, 0., 5.);
		972	ev_timer_again (loop, timer);
		973	...
		974	timer->again = 17.;
		975	ev_timer_again (loop, timer);
		976	...
		977	timer->again = 10.;
		978	ev_timer_again (loop, timer);
		979
		980	This is more slightly efficient then stopping/starting the timer each time
		981	you want to modify its timeout value.
		982
		983	=item ev_tstamp repeat [read-write]
		984
		985	The current C<repeat> value. Will be used each time the watcher times out
		986	or C<ev_timer_again> is called and determines the next timeout (if any),
		987	which is also when any modifications are taken into account.
612		988
613	=back	989	=back
614		990
		991	Example: Create a timer that fires after 60 seconds.
		992
		993	static void
		994	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		995	{
		996	.. one minute over, w is actually stopped right here
		997	}
		998
		999	struct ev_timer mytimer;
		1000	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		1001	ev_timer_start (loop, &mytimer);
		1002
		1003	Example: Create a timeout timer that times out after 10 seconds of
		1004	inactivity.
		1005
		1006	static void
		1007	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
		1008	{
		1009	.. ten seconds without any activity
		1010	}
		1011
		1012	struct ev_timer mytimer;
		1013	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		1014	ev_timer_again (&mytimer); /* start timer */
		1015	ev_loop (loop, 0);
		1016
		1017	// and in some piece of code that gets executed on any "activity":
		1018	// reset the timeout to start ticking again at 10 seconds
		1019	ev_timer_again (&mytimer);
		1020
		1021
615	=head2 C<ev_periodic> - to cron or not to cron	1022	=head2 C<ev_periodic> - to cron or not to cron?
616		1023
617	Periodic watchers are also timers of a kind, but they are very versatile	1024	Periodic watchers are also timers of a kind, but they are very versatile
618	(and unfortunately a bit complex).	1025	(and unfortunately a bit complex).
619		1026
620	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1027	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
621	but on wallclock time (absolute time). You can tell a periodic watcher	1028	but on wallclock time (absolute time). You can tell a periodic watcher
622	to trigger "at" some specific point in time. For example, if you tell a	1029	to trigger "at" some specific point in time. For example, if you tell a
623	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1030	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
624	+ 10.>) and then reset your system clock to the last year, then it will	1031	+ 10.>) and then reset your system clock to the last year, then it will
625	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1032	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
626	roughly 10 seconds later and of course not if you reset your system time	1033	roughly 10 seconds later and of course not if you reset your system time
627	again).	1034	again).
628		1035
…		…
712	Simply stops and restarts the periodic watcher again. This is only useful	1119	Simply stops and restarts the periodic watcher again. This is only useful
713	when you changed some parameters or the reschedule callback would return	1120	when you changed some parameters or the reschedule callback would return
714	a different time than the last time it was called (e.g. in a crond like	1121	a different time than the last time it was called (e.g. in a crond like
715	program when the crontabs have changed).	1122	program when the crontabs have changed).
716		1123
		1124	=item ev_tstamp interval [read-write]
		1125
		1126	The current interval value. Can be modified any time, but changes only
		1127	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1128	called.
		1129
		1130	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1131
		1132	The current reschedule callback, or C<0>, if this functionality is
		1133	switched off. Can be changed any time, but changes only take effect when
		1134	the periodic timer fires or C<ev_periodic_again> is being called.
		1135
717	=back	1136	=back
718		1137
		1138	Example: Call a callback every hour, or, more precisely, whenever the
		1139	system clock is divisible by 3600. The callback invocation times have
		1140	potentially a lot of jittering, but good long-term stability.
		1141
		1142	static void
		1143	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
		1144	{
		1145	... its now a full hour (UTC, or TAI or whatever your clock follows)
		1146	}
		1147
		1148	struct ev_periodic hourly_tick;
		1149	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1150	ev_periodic_start (loop, &hourly_tick);
		1151
		1152	Example: The same as above, but use a reschedule callback to do it:
		1153
		1154	#include <math.h>
		1155
		1156	static ev_tstamp
		1157	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1158	{
		1159	return fmod (now, 3600.) + 3600.;
		1160	}
		1161
		1162	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1163
		1164	Example: Call a callback every hour, starting now:
		1165
		1166	struct ev_periodic hourly_tick;
		1167	ev_periodic_init (&hourly_tick, clock_cb,
		1168	fmod (ev_now (loop), 3600.), 3600., 0);
		1169	ev_periodic_start (loop, &hourly_tick);
		1170
		1171
719	=head2 C<ev_signal> - signal me when a signal gets signalled	1172	=head2 C<ev_signal> - signal me when a signal gets signalled!
720		1173
721	Signal watchers will trigger an event when the process receives a specific	1174	Signal watchers will trigger an event when the process receives a specific
722	signal one or more times. Even though signals are very asynchronous, libev	1175	signal one or more times. Even though signals are very asynchronous, libev
723	will try it's best to deliver signals synchronously, i.e. as part of the	1176	will try it's best to deliver signals synchronously, i.e. as part of the
724	normal event processing, like any other event.	1177	normal event processing, like any other event.
…		…
737	=item ev_signal_set (ev_signal *, int signum)	1190	=item ev_signal_set (ev_signal *, int signum)
738		1191
739	Configures the watcher to trigger on the given signal number (usually one	1192	Configures the watcher to trigger on the given signal number (usually one
740	of the C<SIGxxx> constants).	1193	of the C<SIGxxx> constants).
741		1194
		1195	=item int signum [read-only]
		1196
		1197	The signal the watcher watches out for.
		1198
742	=back	1199	=back
743		1200
		1201
744	=head2 C<ev_child> - wait for pid status changes	1202	=head2 C<ev_child> - watch out for process status changes
745		1203
746	Child watchers trigger when your process receives a SIGCHLD in response to	1204	Child watchers trigger when your process receives a SIGCHLD in response to
747	some child status changes (most typically when a child of yours dies).	1205	some child status changes (most typically when a child of yours dies).
748		1206
749	=over 4	1207	=over 4
…		…
757	at the C<rstatus> member of the C<ev_child> watcher structure to see	1215	at the C<rstatus> member of the C<ev_child> watcher structure to see
758	the status word (use the macros from C<sys/wait.h> and see your systems	1216	the status word (use the macros from C<sys/wait.h> and see your systems
759	C<waitpid> documentation). The C<rpid> member contains the pid of the	1217	C<waitpid> documentation). The C<rpid> member contains the pid of the
760	process causing the status change.	1218	process causing the status change.
761		1219
		1220	=item int pid [read-only]
		1221
		1222	The process id this watcher watches out for, or C<0>, meaning any process id.
		1223
		1224	=item int rpid [read-write]
		1225
		1226	The process id that detected a status change.
		1227
		1228	=item int rstatus [read-write]
		1229
		1230	The process exit/trace status caused by C<rpid> (see your systems
		1231	C<waitpid> and C<sys/wait.h> documentation for details).
		1232
762	=back	1233	=back
763		1234
		1235	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1236
		1237	static void
		1238	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1239	{
		1240	ev_unloop (loop, EVUNLOOP_ALL);
		1241	}
		1242
		1243	struct ev_signal signal_watcher;
		1244	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1245	ev_signal_start (loop, &sigint_cb);
		1246
		1247
		1248	=head2 C<ev_stat> - did the file attributes just change?
		1249
		1250	This watches a filesystem path for attribute changes. That is, it calls
		1251	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1252	compared to the last time, invoking the callback if it did.
		1253
		1254	The path does not need to exist: changing from "path exists" to "path does
		1255	not exist" is a status change like any other. The condition "path does
		1256	not exist" is signified by the C<st_nlink> field being zero (which is
		1257	otherwise always forced to be at least one) and all the other fields of
		1258	the stat buffer having unspecified contents.
		1259
		1260	The path I<should> be absolute and I<must not> end in a slash. If it is
		1261	relative and your working directory changes, the behaviour is undefined.
		1262
		1263	Since there is no standard to do this, the portable implementation simply
		1264	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1265	can specify a recommended polling interval for this case. If you specify
		1266	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1267	unspecified default> value will be used (which you can expect to be around
		1268	five seconds, although this might change dynamically). Libev will also
		1269	impose a minimum interval which is currently around C<0.1>, but thats
		1270	usually overkill.
		1271
		1272	This watcher type is not meant for massive numbers of stat watchers,
		1273	as even with OS-supported change notifications, this can be
		1274	resource-intensive.
		1275
		1276	At the time of this writing, only the Linux inotify interface is
		1277	implemented (implementing kqueue support is left as an exercise for the
		1278	reader). Inotify will be used to give hints only and should not change the
		1279	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1280	to fall back to regular polling again even with inotify, but changes are
		1281	usually detected immediately, and if the file exists there will be no
		1282	polling.
		1283
		1284	=over 4
		1285
		1286	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1287
		1288	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1289
		1290	Configures the watcher to wait for status changes of the given
		1291	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1292	be detected and should normally be specified as C<0> to let libev choose
		1293	a suitable value. The memory pointed to by C<path> must point to the same
		1294	path for as long as the watcher is active.
		1295
		1296	The callback will be receive C<EV_STAT> when a change was detected,
		1297	relative to the attributes at the time the watcher was started (or the
		1298	last change was detected).
		1299
		1300	=item ev_stat_stat (ev_stat *)
		1301
		1302	Updates the stat buffer immediately with new values. If you change the
		1303	watched path in your callback, you could call this fucntion to avoid
		1304	detecting this change (while introducing a race condition). Can also be
		1305	useful simply to find out the new values.
		1306
		1307	=item ev_statdata attr [read-only]
		1308
		1309	The most-recently detected attributes of the file. Although the type is of
		1310	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1311	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1312	was some error while C<stat>ing the file.
		1313
		1314	=item ev_statdata prev [read-only]
		1315
		1316	The previous attributes of the file. The callback gets invoked whenever
		1317	C<prev> != C<attr>.
		1318
		1319	=item ev_tstamp interval [read-only]
		1320
		1321	The specified interval.
		1322
		1323	=item const char *path [read-only]
		1324
		1325	The filesystem path that is being watched.
		1326
		1327	=back
		1328
		1329	Example: Watch C</etc/passwd> for attribute changes.
		1330
		1331	static void
		1332	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1333	{
		1334	/* /etc/passwd changed in some way */
		1335	if (w->attr.st_nlink)
		1336	{
		1337	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1338	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1339	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1340	}
		1341	else
		1342	/* you shalt not abuse printf for puts */
		1343	puts ("wow, /etc/passwd is not there, expect problems. "
		1344	"if this is windows, they already arrived\n");
		1345	}
		1346
		1347	...
		1348	ev_stat passwd;
		1349
		1350	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1351	ev_stat_start (loop, &passwd);
		1352
		1353
764	=head2 C<ev_idle> - when you've got nothing better to do	1354	=head2 C<ev_idle> - when you've got nothing better to do...
765		1355
766	Idle watchers trigger events when there are no other events are pending	1356	Idle watchers trigger events when there are no other events are pending
767	(prepare, check and other idle watchers do not count). That is, as long	1357	(prepare, check and other idle watchers do not count). That is, as long
768	as your process is busy handling sockets or timeouts (or even signals,	1358	as your process is busy handling sockets or timeouts (or even signals,
769	imagine) it will not be triggered. But when your process is idle all idle	1359	imagine) it will not be triggered. But when your process is idle all idle
…		…
787	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1377	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
788	believe me.	1378	believe me.
789		1379
790	=back	1380	=back
791		1381
		1382	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
		1383	callback, free it. Also, use no error checking, as usual.
		1384
		1385	static void
		1386	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
		1387	{
		1388	free (w);
		1389	// now do something you wanted to do when the program has
		1390	// no longer asnything immediate to do.
		1391	}
		1392
		1393	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1394	ev_idle_init (idle_watcher, idle_cb);
		1395	ev_idle_start (loop, idle_cb);
		1396
		1397
792	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1398	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
793		1399
794	Prepare and check watchers are usually (but not always) used in tandem:	1400	Prepare and check watchers are usually (but not always) used in tandem:
795	prepare watchers get invoked before the process blocks and check watchers	1401	prepare watchers get invoked before the process blocks and check watchers
796	afterwards.	1402	afterwards.
797		1403
		1404	You I<must not> call C<ev_loop> or similar functions that enter
		1405	the current event loop from either C<ev_prepare> or C<ev_check>
		1406	watchers. Other loops than the current one are fine, however. The
		1407	rationale behind this is that you do not need to check for recursion in
		1408	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1409	C<ev_check> so if you have one watcher of each kind they will always be
		1410	called in pairs bracketing the blocking call.
		1411
798	Their main purpose is to integrate other event mechanisms into libev. This	1412	Their main purpose is to integrate other event mechanisms into libev and
799	could be used, for example, to track variable changes, implement your own	1413	their use is somewhat advanced. This could be used, for example, to track
800	watchers, integrate net-snmp or a coroutine library and lots more.	1414	variable changes, implement your own watchers, integrate net-snmp or a
		1415	coroutine library and lots more. They are also occasionally useful if
		1416	you cache some data and want to flush it before blocking (for example,
		1417	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1418	watcher).
801		1419
802	This is done by examining in each prepare call which file descriptors need	1420	This is done by examining in each prepare call which file descriptors need
803	to be watched by the other library, registering C<ev_io> watchers for	1421	to be watched by the other library, registering C<ev_io> watchers for
804	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1422	them and starting an C<ev_timer> watcher for any timeouts (many libraries
805	provide just this functionality). Then, in the check watcher you check for	1423	provide just this functionality). Then, in the check watcher you check for
…		…
827	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1445	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
828	macros, but using them is utterly, utterly and completely pointless.	1446	macros, but using them is utterly, utterly and completely pointless.
829		1447
830	=back	1448	=back
831		1449
		1450	Example: To include a library such as adns, you would add IO watchers
		1451	and a timeout watcher in a prepare handler, as required by libadns, and
		1452	in a check watcher, destroy them and call into libadns. What follows is
		1453	pseudo-code only of course:
		1454
		1455	static ev_io iow [nfd];
		1456	static ev_timer tw;
		1457
		1458	static void
		1459	io_cb (ev_loop *loop, ev_io *w, int revents)
		1460	{
		1461	// set the relevant poll flags
		1462	// could also call adns_processreadable etc. here
		1463	struct pollfd *fd = (struct pollfd *)w->data;
		1464	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1465	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1466	}
		1467
		1468	// create io watchers for each fd and a timer before blocking
		1469	static void
		1470	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1471	{
		1472	int timeout = 3600000;
		1473	struct pollfd fds [nfd];
		1474	// actual code will need to loop here and realloc etc.
		1475	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1476
		1477	/* the callback is illegal, but won't be called as we stop during check */
		1478	ev_timer_init (&tw, 0, timeout * 1e-3);
		1479	ev_timer_start (loop, &tw);
		1480
		1481	// create on ev_io per pollfd
		1482	for (int i = 0; i < nfd; ++i)
		1483	{
		1484	ev_io_init (iow + i, io_cb, fds [i].fd,
		1485	((fds [i].events & POLLIN ? EV_READ : 0)
		1486	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1487
		1488	fds [i].revents = 0;
		1489	iow [i].data = fds + i;
		1490	ev_io_start (loop, iow + i);
		1491	}
		1492	}
		1493
		1494	// stop all watchers after blocking
		1495	static void
		1496	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1497	{
		1498	ev_timer_stop (loop, &tw);
		1499
		1500	for (int i = 0; i < nfd; ++i)
		1501	ev_io_stop (loop, iow + i);
		1502
		1503	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1504	}
		1505
		1506
		1507	=head2 C<ev_embed> - when one backend isn't enough...
		1508
		1509	This is a rather advanced watcher type that lets you embed one event loop
		1510	into another (currently only C<ev_io> events are supported in the embedded
		1511	loop, other types of watchers might be handled in a delayed or incorrect
		1512	fashion and must not be used).
		1513
		1514	There are primarily two reasons you would want that: work around bugs and
		1515	prioritise I/O.
		1516
		1517	As an example for a bug workaround, the kqueue backend might only support
		1518	sockets on some platform, so it is unusable as generic backend, but you
		1519	still want to make use of it because you have many sockets and it scales
		1520	so nicely. In this case, you would create a kqueue-based loop and embed it
		1521	into your default loop (which might use e.g. poll). Overall operation will
		1522	be a bit slower because first libev has to poll and then call kevent, but
		1523	at least you can use both at what they are best.
		1524
		1525	As for prioritising I/O: rarely you have the case where some fds have
		1526	to be watched and handled very quickly (with low latency), and even
		1527	priorities and idle watchers might have too much overhead. In this case
		1528	you would put all the high priority stuff in one loop and all the rest in
		1529	a second one, and embed the second one in the first.
		1530
		1531	As long as the watcher is active, the callback will be invoked every time
		1532	there might be events pending in the embedded loop. The callback must then
		1533	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1534	their callbacks (you could also start an idle watcher to give the embedded
		1535	loop strictly lower priority for example). You can also set the callback
		1536	to C<0>, in which case the embed watcher will automatically execute the
		1537	embedded loop sweep.
		1538
		1539	As long as the watcher is started it will automatically handle events. The
		1540	callback will be invoked whenever some events have been handled. You can
		1541	set the callback to C<0> to avoid having to specify one if you are not
		1542	interested in that.
		1543
		1544	Also, there have not currently been made special provisions for forking:
		1545	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1546	but you will also have to stop and restart any C<ev_embed> watchers
		1547	yourself.
		1548
		1549	Unfortunately, not all backends are embeddable, only the ones returned by
		1550	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1551	portable one.
		1552
		1553	So when you want to use this feature you will always have to be prepared
		1554	that you cannot get an embeddable loop. The recommended way to get around
		1555	this is to have a separate variables for your embeddable loop, try to
		1556	create it, and if that fails, use the normal loop for everything:
		1557
		1558	struct ev_loop *loop_hi = ev_default_init (0);
		1559	struct ev_loop *loop_lo = 0;
		1560	struct ev_embed embed;
		1561
		1562	// see if there is a chance of getting one that works
		1563	// (remember that a flags value of 0 means autodetection)
		1564	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1565	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1566	: 0;
		1567
		1568	// if we got one, then embed it, otherwise default to loop_hi
		1569	if (loop_lo)
		1570	{
		1571	ev_embed_init (&embed, 0, loop_lo);
		1572	ev_embed_start (loop_hi, &embed);
		1573	}
		1574	else
		1575	loop_lo = loop_hi;
		1576
		1577	=over 4
		1578
		1579	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1580
		1581	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1582
		1583	Configures the watcher to embed the given loop, which must be
		1584	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1585	invoked automatically, otherwise it is the responsibility of the callback
		1586	to invoke it (it will continue to be called until the sweep has been done,
		1587	if you do not want thta, you need to temporarily stop the embed watcher).
		1588
		1589	=item ev_embed_sweep (loop, ev_embed *)
		1590
		1591	Make a single, non-blocking sweep over the embedded loop. This works
		1592	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1593	apropriate way for embedded loops.
		1594
		1595	=item struct ev_loop *loop [read-only]
		1596
		1597	The embedded event loop.
		1598
		1599	=back
		1600
		1601
		1602	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1603
		1604	Fork watchers are called when a C<fork ()> was detected (usually because
		1605	whoever is a good citizen cared to tell libev about it by calling
		1606	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1607	event loop blocks next and before C<ev_check> watchers are being called,
		1608	and only in the child after the fork. If whoever good citizen calling
		1609	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1610	handlers will be invoked, too, of course.
		1611
		1612	=over 4
		1613
		1614	=item ev_fork_init (ev_signal *, callback)
		1615
		1616	Initialises and configures the fork watcher - it has no parameters of any
		1617	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1618	believe me.
		1619
		1620	=back
		1621
		1622
832	=head1 OTHER FUNCTIONS	1623	=head1 OTHER FUNCTIONS
833		1624
834	There are some other functions of possible interest. Described. Here. Now.	1625	There are some other functions of possible interest. Described. Here. Now.
835		1626
836	=over 4	1627	=over 4
…		…
865	/* stdin might have data for us, joy! */;	1656	/* stdin might have data for us, joy! */;
866	}	1657	}
867		1658
868	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1659	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
869		1660
870	=item ev_feed_event (loop, watcher, int events)	1661	=item ev_feed_event (ev_loop *, watcher *, int revents)
871		1662
872	Feeds the given event set into the event loop, as if the specified event	1663	Feeds the given event set into the event loop, as if the specified event
873	had happened for the specified watcher (which must be a pointer to an	1664	had happened for the specified watcher (which must be a pointer to an
874	initialised but not necessarily started event watcher).	1665	initialised but not necessarily started event watcher).
875		1666
876	=item ev_feed_fd_event (loop, int fd, int revents)	1667	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
877		1668
878	Feed an event on the given fd, as if a file descriptor backend detected	1669	Feed an event on the given fd, as if a file descriptor backend detected
879	the given events it.	1670	the given events it.
880		1671
881	=item ev_feed_signal_event (loop, int signum)	1672	=item ev_feed_signal_event (ev_loop *loop, int signum)
882		1673
883	Feed an event as if the given signal occured (loop must be the default loop!).	1674	Feed an event as if the given signal occured (C<loop> must be the default
		1675	loop!).
884		1676
885	=back	1677	=back
		1678
886		1679
887	=head1 LIBEVENT EMULATION	1680	=head1 LIBEVENT EMULATION
888		1681
889	Libev offers a compatibility emulation layer for libevent. It cannot	1682	Libev offers a compatibility emulation layer for libevent. It cannot
890	emulate the internals of libevent, so here are some usage hints:	1683	emulate the internals of libevent, so here are some usage hints:
…		…
911		1704
912	=back	1705	=back
913		1706
914	=head1 C++ SUPPORT	1707	=head1 C++ SUPPORT
915		1708
916	TBD.	1709	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1710	you to use some convinience methods to start/stop watchers and also change
		1711	the callback model to a model using method callbacks on objects.
		1712
		1713	To use it,
		1714
		1715	#include <ev++.h>
		1716
		1717	(it is not installed by default). This automatically includes F<ev.h>
		1718	and puts all of its definitions (many of them macros) into the global
		1719	namespace. All C++ specific things are put into the C<ev> namespace.
		1720
		1721	It should support all the same embedding options as F<ev.h>, most notably
		1722	C<EV_MULTIPLICITY>.
		1723
		1724	Here is a list of things available in the C<ev> namespace:
		1725
		1726	=over 4
		1727
		1728	=item C<ev::READ>, C<ev::WRITE> etc.
		1729
		1730	These are just enum values with the same values as the C<EV_READ> etc.
		1731	macros from F<ev.h>.
		1732
		1733	=item C<ev::tstamp>, C<ev::now>
		1734
		1735	Aliases to the same types/functions as with the C<ev_> prefix.
		1736
		1737	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1738
		1739	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1740	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1741	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1742	defines by many implementations.
		1743
		1744	All of those classes have these methods:
		1745
		1746	=over 4
		1747
		1748	=item ev::TYPE::TYPE (object *, object::method *)
		1749
		1750	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
		1751
		1752	=item ev::TYPE::~TYPE
		1753
		1754	The constructor takes a pointer to an object and a method pointer to
		1755	the event handler callback to call in this class. The constructor calls
		1756	C<ev_init> for you, which means you have to call the C<set> method
		1757	before starting it. If you do not specify a loop then the constructor
		1758	automatically associates the default loop with this watcher.
		1759
		1760	The destructor automatically stops the watcher if it is active.
		1761
		1762	=item w->set (struct ev_loop *)
		1763
		1764	Associates a different C<struct ev_loop> with this watcher. You can only
		1765	do this when the watcher is inactive (and not pending either).
		1766
		1767	=item w->set ([args])
		1768
		1769	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1770	called at least once. Unlike the C counterpart, an active watcher gets
		1771	automatically stopped and restarted.
		1772
		1773	=item w->start ()
		1774
		1775	Starts the watcher. Note that there is no C<loop> argument as the
		1776	constructor already takes the loop.
		1777
		1778	=item w->stop ()
		1779
		1780	Stops the watcher if it is active. Again, no C<loop> argument.
		1781
		1782	=item w->again () C<ev::timer>, C<ev::periodic> only
		1783
		1784	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1785	C<ev_TYPE_again> function.
		1786
		1787	=item w->sweep () C<ev::embed> only
		1788
		1789	Invokes C<ev_embed_sweep>.
		1790
		1791	=item w->update () C<ev::stat> only
		1792
		1793	Invokes C<ev_stat_stat>.
		1794
		1795	=back
		1796
		1797	=back
		1798
		1799	Example: Define a class with an IO and idle watcher, start one of them in
		1800	the constructor.
		1801
		1802	class myclass
		1803	{
		1804	ev_io io; void io_cb (ev::io &w, int revents);
		1805	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1806
		1807	myclass ();
		1808	}
		1809
		1810	myclass::myclass (int fd)
		1811	: io (this, &myclass::io_cb),
		1812	idle (this, &myclass::idle_cb)
		1813	{
		1814	io.start (fd, ev::READ);
		1815	}
		1816
		1817
		1818	=head1 MACRO MAGIC
		1819
		1820	Libev can be compiled with a variety of options, the most fundemantal is
		1821	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1822	callbacks have an initial C<struct ev_loop *> argument.
		1823
		1824	To make it easier to write programs that cope with either variant, the
		1825	following macros are defined:
		1826
		1827	=over 4
		1828
		1829	=item C<EV_A>, C<EV_A_>
		1830
		1831	This provides the loop I<argument> for functions, if one is required ("ev
		1832	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1833	C<EV_A_> is used when other arguments are following. Example:
		1834
		1835	ev_unref (EV_A);
		1836	ev_timer_add (EV_A_ watcher);
		1837	ev_loop (EV_A_ 0);
		1838
		1839	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1840	which is often provided by the following macro.
		1841
		1842	=item C<EV_P>, C<EV_P_>
		1843
		1844	This provides the loop I<parameter> for functions, if one is required ("ev
		1845	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1846	C<EV_P_> is used when other parameters are following. Example:
		1847
		1848	// this is how ev_unref is being declared
		1849	static void ev_unref (EV_P);
		1850
		1851	// this is how you can declare your typical callback
		1852	static void cb (EV_P_ ev_timer *w, int revents)
		1853
		1854	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1855	suitable for use with C<EV_A>.
		1856
		1857	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1858
		1859	Similar to the other two macros, this gives you the value of the default
		1860	loop, if multiple loops are supported ("ev loop default").
		1861
		1862	=back
		1863
		1864	Example: Declare and initialise a check watcher, utilising the above
		1865	macros so it will work regardless of wether multiple loops are supported
		1866	or not.
		1867
		1868	static void
		1869	check_cb (EV_P_ ev_timer *w, int revents)
		1870	{
		1871	ev_check_stop (EV_A_ w);
		1872	}
		1873
		1874	ev_check check;
		1875	ev_check_init (&check, check_cb);
		1876	ev_check_start (EV_DEFAULT_ &check);
		1877	ev_loop (EV_DEFAULT_ 0);
		1878
		1879	=head1 EMBEDDING
		1880
		1881	Libev can (and often is) directly embedded into host
		1882	applications. Examples of applications that embed it include the Deliantra
		1883	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		1884	and rxvt-unicode.
		1885
		1886	The goal is to enable you to just copy the neecssary files into your
		1887	source directory without having to change even a single line in them, so
		1888	you can easily upgrade by simply copying (or having a checked-out copy of
		1889	libev somewhere in your source tree).
		1890
		1891	=head2 FILESETS
		1892
		1893	Depending on what features you need you need to include one or more sets of files
		1894	in your app.
		1895
		1896	=head3 CORE EVENT LOOP
		1897
		1898	To include only the libev core (all the C<ev_*> functions), with manual
		1899	configuration (no autoconf):
		1900
		1901	#define EV_STANDALONE 1
		1902	#include "ev.c"
		1903
		1904	This will automatically include F<ev.h>, too, and should be done in a
		1905	single C source file only to provide the function implementations. To use
		1906	it, do the same for F<ev.h> in all files wishing to use this API (best
		1907	done by writing a wrapper around F<ev.h> that you can include instead and
		1908	where you can put other configuration options):
		1909
		1910	#define EV_STANDALONE 1
		1911	#include "ev.h"
		1912
		1913	Both header files and implementation files can be compiled with a C++
		1914	compiler (at least, thats a stated goal, and breakage will be treated
		1915	as a bug).
		1916
		1917	You need the following files in your source tree, or in a directory
		1918	in your include path (e.g. in libev/ when using -Ilibev):
		1919
		1920	ev.h
		1921	ev.c
		1922	ev_vars.h
		1923	ev_wrap.h
		1924
		1925	ev_win32.c required on win32 platforms only
		1926
		1927	ev_select.c only when select backend is enabled (which is enabled by default)
		1928	ev_poll.c only when poll backend is enabled (disabled by default)
		1929	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		1930	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		1931	ev_port.c only when the solaris port backend is enabled (disabled by default)
		1932
		1933	F<ev.c> includes the backend files directly when enabled, so you only need
		1934	to compile this single file.
		1935
		1936	=head3 LIBEVENT COMPATIBILITY API
		1937
		1938	To include the libevent compatibility API, also include:
		1939
		1940	#include "event.c"
		1941
		1942	in the file including F<ev.c>, and:
		1943
		1944	#include "event.h"
		1945
		1946	in the files that want to use the libevent API. This also includes F<ev.h>.
		1947
		1948	You need the following additional files for this:
		1949
		1950	event.h
		1951	event.c
		1952
		1953	=head3 AUTOCONF SUPPORT
		1954
		1955	Instead of using C<EV_STANDALONE=1> and providing your config in
		1956	whatever way you want, you can also C<m4_include([libev.m4])> in your
		1957	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		1958	include F<config.h> and configure itself accordingly.
		1959
		1960	For this of course you need the m4 file:
		1961
		1962	libev.m4
		1963
		1964	=head2 PREPROCESSOR SYMBOLS/MACROS
		1965
		1966	Libev can be configured via a variety of preprocessor symbols you have to define
		1967	before including any of its files. The default is not to build for multiplicity
		1968	and only include the select backend.
		1969
		1970	=over 4
		1971
		1972	=item EV_STANDALONE
		1973
		1974	Must always be C<1> if you do not use autoconf configuration, which
		1975	keeps libev from including F<config.h>, and it also defines dummy
		1976	implementations for some libevent functions (such as logging, which is not
		1977	supported). It will also not define any of the structs usually found in
		1978	F<event.h> that are not directly supported by the libev core alone.
		1979
		1980	=item EV_USE_MONOTONIC
		1981
		1982	If defined to be C<1>, libev will try to detect the availability of the
		1983	monotonic clock option at both compiletime and runtime. Otherwise no use
		1984	of the monotonic clock option will be attempted. If you enable this, you
		1985	usually have to link against librt or something similar. Enabling it when
		1986	the functionality isn't available is safe, though, althoguh you have
		1987	to make sure you link against any libraries where the C<clock_gettime>
		1988	function is hiding in (often F<-lrt>).
		1989
		1990	=item EV_USE_REALTIME
		1991
		1992	If defined to be C<1>, libev will try to detect the availability of the
		1993	realtime clock option at compiletime (and assume its availability at
		1994	runtime if successful). Otherwise no use of the realtime clock option will
		1995	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		1996	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
		1997	in the description of C<EV_USE_MONOTONIC>, though.
		1998
		1999	=item EV_USE_SELECT
		2000
		2001	If undefined or defined to be C<1>, libev will compile in support for the
		2002	C<select>(2) backend. No attempt at autodetection will be done: if no
		2003	other method takes over, select will be it. Otherwise the select backend
		2004	will not be compiled in.
		2005
		2006	=item EV_SELECT_USE_FD_SET
		2007
		2008	If defined to C<1>, then the select backend will use the system C<fd_set>
		2009	structure. This is useful if libev doesn't compile due to a missing
		2010	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2011	exotic systems. This usually limits the range of file descriptors to some
		2012	low limit such as 1024 or might have other limitations (winsocket only
		2013	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2014	influence the size of the C<fd_set> used.
		2015
		2016	=item EV_SELECT_IS_WINSOCKET
		2017
		2018	When defined to C<1>, the select backend will assume that
		2019	select/socket/connect etc. don't understand file descriptors but
		2020	wants osf handles on win32 (this is the case when the select to
		2021	be used is the winsock select). This means that it will call
		2022	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2023	it is assumed that all these functions actually work on fds, even
		2024	on win32. Should not be defined on non-win32 platforms.
		2025
		2026	=item EV_USE_POLL
		2027
		2028	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2029	backend. Otherwise it will be enabled on non-win32 platforms. It
		2030	takes precedence over select.
		2031
		2032	=item EV_USE_EPOLL
		2033
		2034	If defined to be C<1>, libev will compile in support for the Linux
		2035	C<epoll>(7) backend. Its availability will be detected at runtime,
		2036	otherwise another method will be used as fallback. This is the
		2037	preferred backend for GNU/Linux systems.
		2038
		2039	=item EV_USE_KQUEUE
		2040
		2041	If defined to be C<1>, libev will compile in support for the BSD style
		2042	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2043	otherwise another method will be used as fallback. This is the preferred
		2044	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2045	supports some types of fds correctly (the only platform we found that
		2046	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2047	not be used unless explicitly requested. The best way to use it is to find
		2048	out whether kqueue supports your type of fd properly and use an embedded
		2049	kqueue loop.
		2050
		2051	=item EV_USE_PORT
		2052
		2053	If defined to be C<1>, libev will compile in support for the Solaris
		2054	10 port style backend. Its availability will be detected at runtime,
		2055	otherwise another method will be used as fallback. This is the preferred
		2056	backend for Solaris 10 systems.
		2057
		2058	=item EV_USE_DEVPOLL
		2059
		2060	reserved for future expansion, works like the USE symbols above.
		2061
		2062	=item EV_USE_INOTIFY
		2063
		2064	If defined to be C<1>, libev will compile in support for the Linux inotify
		2065	interface to speed up C<ev_stat> watchers. Its actual availability will
		2066	be detected at runtime.
		2067
		2068	=item EV_H
		2069
		2070	The name of the F<ev.h> header file used to include it. The default if
		2071	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2072	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2073
		2074	=item EV_CONFIG_H
		2075
		2076	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2077	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2078	C<EV_H>, above.
		2079
		2080	=item EV_EVENT_H
		2081
		2082	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2083	of how the F<event.h> header can be found.
		2084
		2085	=item EV_PROTOTYPES
		2086
		2087	If defined to be C<0>, then F<ev.h> will not define any function
		2088	prototypes, but still define all the structs and other symbols. This is
		2089	occasionally useful if you want to provide your own wrapper functions
		2090	around libev functions.
		2091
		2092	=item EV_MULTIPLICITY
		2093
		2094	If undefined or defined to C<1>, then all event-loop-specific functions
		2095	will have the C<struct ev_loop *> as first argument, and you can create
		2096	additional independent event loops. Otherwise there will be no support
		2097	for multiple event loops and there is no first event loop pointer
		2098	argument. Instead, all functions act on the single default loop.
		2099
		2100	=item EV_PERIODIC_ENABLE
		2101
		2102	If undefined or defined to be C<1>, then periodic timers are supported. If
		2103	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2104	code.
		2105
		2106	=item EV_EMBED_ENABLE
		2107
		2108	If undefined or defined to be C<1>, then embed watchers are supported. If
		2109	defined to be C<0>, then they are not.
		2110
		2111	=item EV_STAT_ENABLE
		2112
		2113	If undefined or defined to be C<1>, then stat watchers are supported. If
		2114	defined to be C<0>, then they are not.
		2115
		2116	=item EV_FORK_ENABLE
		2117
		2118	If undefined or defined to be C<1>, then fork watchers are supported. If
		2119	defined to be C<0>, then they are not.
		2120
		2121	=item EV_MINIMAL
		2122
		2123	If you need to shave off some kilobytes of code at the expense of some
		2124	speed, define this symbol to C<1>. Currently only used for gcc to override
		2125	some inlining decisions, saves roughly 30% codesize of amd64.
		2126
		2127	=item EV_PID_HASHSIZE
		2128
		2129	C<ev_child> watchers use a small hash table to distribute workload by
		2130	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2131	than enough. If you need to manage thousands of children you might want to
		2132	increase this value (I<must> be a power of two).
		2133
		2134	=item EV_INOTIFY_HASHSIZE
		2135
		2136	C<ev_staz> watchers use a small hash table to distribute workload by
		2137	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2138	usually more than enough. If you need to manage thousands of C<ev_stat>
		2139	watchers you might want to increase this value (I<must> be a power of
		2140	two).
		2141
		2142	=item EV_COMMON
		2143
		2144	By default, all watchers have a C<void *data> member. By redefining
		2145	this macro to a something else you can include more and other types of
		2146	members. You have to define it each time you include one of the files,
		2147	though, and it must be identical each time.
		2148
		2149	For example, the perl EV module uses something like this:
		2150
		2151	#define EV_COMMON \
		2152	SV *self; /* contains this struct */ \
		2153	SV *cb_sv, *fh /* note no trailing ";" */
		2154
		2155	=item EV_CB_DECLARE (type)
		2156
		2157	=item EV_CB_INVOKE (watcher, revents)
		2158
		2159	=item ev_set_cb (ev, cb)
		2160
		2161	Can be used to change the callback member declaration in each watcher,
		2162	and the way callbacks are invoked and set. Must expand to a struct member
		2163	definition and a statement, respectively. See the F<ev.v> header file for
		2164	their default definitions. One possible use for overriding these is to
		2165	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2166	method calls instead of plain function calls in C++.
		2167
		2168	=head2 EXAMPLES
		2169
		2170	For a real-world example of a program the includes libev
		2171	verbatim, you can have a look at the EV perl module
		2172	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2173	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2174	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2175	will be compiled. It is pretty complex because it provides its own header
		2176	file.
		2177
		2178	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2179	that everybody includes and which overrides some configure choices:
		2180
		2181	#define EV_MINIMAL 1
		2182	#define EV_USE_POLL 0
		2183	#define EV_MULTIPLICITY 0
		2184	#define EV_PERIODIC_ENABLE 0
		2185	#define EV_STAT_ENABLE 0
		2186	#define EV_FORK_ENABLE 0
		2187	#define EV_CONFIG_H <config.h>
		2188	#define EV_MINPRI 0
		2189	#define EV_MAXPRI 0
		2190
		2191	#include "ev++.h"
		2192
		2193	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2194
		2195	#include "ev_cpp.h"
		2196	#include "ev.c"
		2197
		2198
		2199	=head1 COMPLEXITIES
		2200
		2201	In this section the complexities of (many of) the algorithms used inside
		2202	libev will be explained. For complexity discussions about backends see the
		2203	documentation for C<ev_default_init>.
		2204
		2205	=over 4
		2206
		2207	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2208
		2209	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2210
		2211	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2212
		2213	=item Stopping check/prepare/idle watchers: O(1)
		2214
		2215	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2216
		2217	=item Finding the next timer per loop iteration: O(1)
		2218
		2219	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2220
		2221	=item Activating one watcher: O(1)
		2222
		2223	=back
		2224
917		2225
918	=head1 AUTHOR	2226	=head1 AUTHOR
919		2227
920	Marc Lehmann <libev@schmorp.de>.	2228	Marc Lehmann <libev@schmorp.de>.
921		2229

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