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

Comparing libev/ev.pod (file contents):
Revision 1.54 by root, Tue Nov 27 20:26:51 2007 UTC vs.
Revision 1.76 by root, Sat Dec 8 15:30:30 2007 UTC

…		…
47		47
48	return 0;	48	return 0;
49	}	49	}
50		50
51	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
52		56
53	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
54	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
55	these event sources and provide your program with events.	59	these event sources and provide your program with events.
56		60
…		…
63	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
64	watcher.	68	watcher.
65		69
66	=head1 FEATURES	70	=head1 FEATURES
67		71
68	Libev supports C<select>, C<poll>, the linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
69	bsd-specific C<kqueue> and the solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70	for file descriptor events (C<ev_io>), relative timers (C<ev_timer>),	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
		75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
71	absolute timers with customised rescheduling (C<ev_periodic>), synchronous	76	with customised rescheduling (C<ev_periodic>), synchronous signals
72	signals (C<ev_signal>), process status change events (C<ev_child>), and	77	(C<ev_signal>), process status change events (C<ev_child>), and event
73	event watchers dealing with the event loop mechanism itself (C<ev_idle>,	78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
74	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
75	file watchers (C<ev_stat>) and even limited support for fork events	80	file watchers (C<ev_stat>) and even limited support for fork events
76	(C<ev_fork>).	81	(C<ev_fork>).
77		82
78	It also is quite fast (see this	83	It also is quite fast (see this
…		…
162	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	167	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
163	recommended ones.	168	recommended ones.
164		169
165	See the description of C<ev_embed> watchers for more info.	170	See the description of C<ev_embed> watchers for more info.
166		171
167	=item ev_set_allocator (void (cb)(void *ptr, size_t size))	172	=item ev_set_allocator (void (cb)(void *ptr, long size))
168		173
169	Sets the allocation function to use (the prototype and semantics are	174	Sets the allocation function to use (the prototype is similar - the
170	identical to the realloc C function). It is used to allocate and free	175	semantics is identical - to the realloc C function). It is used to
171	memory (no surprises here). If it returns zero when memory needs to be	176	allocate and free memory (no surprises here). If it returns zero when
172	allocated, the library might abort or take some potentially destructive	177	memory needs to be allocated, the library might abort or take some
173	action. The default is your system realloc function.	178	potentially destructive action. The default is your system realloc
		179	function.
174		180
175	You could override this function in high-availability programs to, say,	181	You could override this function in high-availability programs to, say,
176	free some memory if it cannot allocate memory, to use a special allocator,	182	free some memory if it cannot allocate memory, to use a special allocator,
177	or even to sleep a while and retry until some memory is available.	183	or even to sleep a while and retry until some memory is available.
178		184
…		…
264	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
265	override the flags completely if it is found in the environment. This is	271	override the flags completely if it is found in the environment. This is
266	useful to try out specific backends to test their performance, or to work	272	useful to try out specific backends to test their performance, or to work
267	around bugs.	273	around bugs.
268		274
		275	=item C<EVFLAG_FORKCHECK>
		276
		277	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		278	a fork, you can also make libev check for a fork in each iteration by
		279	enabling this flag.
		280
		281	This works by calling C<getpid ()> on every iteration of the loop,
		282	and thus this might slow down your event loop if you do a lot of loop
		283	iterations and little real work, but is usually not noticeable (on my
		284	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		285	without a syscall and thus I<very> fast, but my Linux system also has
		286	C<pthread_atfork> which is even faster).
		287
		288	The big advantage of this flag is that you can forget about fork (and
		289	forget about forgetting to tell libev about forking) when you use this
		290	flag.
		291
		292	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		293	environment variable.
		294
269	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
270		296
271	This is your standard select(2) backend. Not I<completely> standard, as	297	This is your standard select(2) backend. Not I<completely> standard, as
272	libev tries to roll its own fd_set with no limits on the number of fds,	298	libev tries to roll its own fd_set with no limits on the number of fds,
273	but if that fails, expect a fairly low limit on the number of fds when	299	but if that fails, expect a fairly low limit on the number of fds when
…		…
407	=item ev_loop_fork (loop)	433	=item ev_loop_fork (loop)
408		434
409	Like C<ev_default_fork>, but acts on an event loop created by	435	Like C<ev_default_fork>, but acts on an event loop created by
410	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
411	after fork, and how you do this is entirely your own problem.	437	after fork, and how you do this is entirely your own problem.
		438
		439	=item unsigned int ev_loop_count (loop)
		440
		441	Returns the count of loop iterations for the loop, which is identical to
		442	the number of times libev did poll for new events. It starts at C<0> and
		443	happily wraps around with enough iterations.
		444
		445	This value can sometimes be useful as a generation counter of sorts (it
		446	"ticks" the number of loop iterations), as it roughly corresponds with
		447	C<ev_prepare> and C<ev_check> calls.
412		448
413	=item unsigned int ev_backend (loop)	449	=item unsigned int ev_backend (loop)
414		450
415	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	451	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
416	use.	452	use.
…		…
700	=item bool ev_is_pending (ev_TYPE *watcher)	736	=item bool ev_is_pending (ev_TYPE *watcher)
701		737
702	Returns a true value iff the watcher is pending, (i.e. it has outstanding	738	Returns a true value iff the watcher is pending, (i.e. it has outstanding
703	events but its callback has not yet been invoked). As long as a watcher	739	events but its callback has not yet been invoked). As long as a watcher
704	is pending (but not active) you must not call an init function on it (but	740	is pending (but not active) you must not call an init function on it (but
705	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	741	C<ev_TYPE_set> is safe), you must not change its priority, and you must
706	libev (e.g. you cnanot C<free ()> it).	742	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		743	it).
707		744
708	=item callback = ev_cb (ev_TYPE *watcher)	745	=item callback ev_cb (ev_TYPE *watcher)
709		746
710	Returns the callback currently set on the watcher.	747	Returns the callback currently set on the watcher.
711		748
712	=item ev_cb_set (ev_TYPE *watcher, callback)	749	=item ev_cb_set (ev_TYPE *watcher, callback)
713		750
714	Change the callback. You can change the callback at virtually any time	751	Change the callback. You can change the callback at virtually any time
715	(modulo threads).	752	(modulo threads).
		753
		754	=item ev_set_priority (ev_TYPE *watcher, priority)
		755
		756	=item int ev_priority (ev_TYPE *watcher)
		757
		758	Set and query the priority of the watcher. The priority is a small
		759	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		760	(default: C<-2>). Pending watchers with higher priority will be invoked
		761	before watchers with lower priority, but priority will not keep watchers
		762	from being executed (except for C<ev_idle> watchers).
		763
		764	This means that priorities are I<only> used for ordering callback
		765	invocation after new events have been received. This is useful, for
		766	example, to reduce latency after idling, or more often, to bind two
		767	watchers on the same event and make sure one is called first.
		768
		769	If you need to suppress invocation when higher priority events are pending
		770	you need to look at C<ev_idle> watchers, which provide this functionality.
		771
		772	You I<must not> change the priority of a watcher as long as it is active or
		773	pending.
		774
		775	The default priority used by watchers when no priority has been set is
		776	always C<0>, which is supposed to not be too high and not be too low :).
		777
		778	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		779	fine, as long as you do not mind that the priority value you query might
		780	or might not have been adjusted to be within valid range.
		781
		782	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		783
		784	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		785	C<loop> nor C<revents> need to be valid as long as the watcher callback
		786	can deal with that fact.
		787
		788	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		789
		790	If the watcher is pending, this function returns clears its pending status
		791	and returns its C<revents> bitset (as if its callback was invoked). If the
		792	watcher isn't pending it does nothing and returns C<0>.
716		793
717	=back	794	=back
718		795
719		796
720	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	797	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
741	{	818	{
742	struct my_io w = (struct my_io )w_;	819	struct my_io w = (struct my_io )w_;
743	...	820	...
744	}	821	}
745		822
746	More interesting and less C-conformant ways of catsing your callback type	823	More interesting and less C-conformant ways of casting your callback type
747	have been omitted....	824	instead have been omitted.
		825
		826	Another common scenario is having some data structure with multiple
		827	watchers:
		828
		829	struct my_biggy
		830	{
		831	int some_data;
		832	ev_timer t1;
		833	ev_timer t2;
		834	}
		835
		836	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		837	you need to use C<offsetof>:
		838
		839	#include <stddef.h>
		840
		841	static void
		842	t1_cb (EV_P_ struct ev_timer *w, int revents)
		843	{
		844	struct my_biggy big = (struct my_biggy *
		845	(((char *)w) - offsetof (struct my_biggy, t1));
		846	}
		847
		848	static void
		849	t2_cb (EV_P_ struct ev_timer *w, int revents)
		850	{
		851	struct my_biggy big = (struct my_biggy *
		852	(((char *)w) - offsetof (struct my_biggy, t2));
		853	}
748		854
749		855
750	=head1 WATCHER TYPES	856	=head1 WATCHER TYPES
751		857
752	This section describes each watcher in detail, but will not repeat	858	This section describes each watcher in detail, but will not repeat
…		…
797	it is best to always use non-blocking I/O: An extra C<read>(2) returning	903	it is best to always use non-blocking I/O: An extra C<read>(2) returning
798	C<EAGAIN> is far preferable to a program hanging until some data arrives.	904	C<EAGAIN> is far preferable to a program hanging until some data arrives.
799		905
800	If you cannot run the fd in non-blocking mode (for example you should not	906	If you cannot run the fd in non-blocking mode (for example you should not
801	play around with an Xlib connection), then you have to seperately re-test	907	play around with an Xlib connection), then you have to seperately re-test
802	wether a file descriptor is really ready with a known-to-be good interface	908	whether a file descriptor is really ready with a known-to-be good interface
803	such as poll (fortunately in our Xlib example, Xlib already does this on	909	such as poll (fortunately in our Xlib example, Xlib already does this on
804	its own, so its quite safe to use).	910	its own, so its quite safe to use).
805		911
806	=over 4	912	=over 4
807		913
…		…
885	=item ev_timer_again (loop)	991	=item ev_timer_again (loop)
886		992
887	This will act as if the timer timed out and restart it again if it is	993	This will act as if the timer timed out and restart it again if it is
888	repeating. The exact semantics are:	994	repeating. The exact semantics are:
889		995
		996	If the timer is pending, its pending status is cleared.
		997
890	If the timer is started but nonrepeating, stop it.	998	If the timer is started but nonrepeating, stop it (as if it timed out).
891		999
892	If the timer is repeating, either start it if necessary (with the repeat	1000	If the timer is repeating, either start it if necessary (with the
893	value), or reset the running timer to the repeat value.	1001	C<repeat> value), or reset the running timer to the C<repeat> value.
894		1002
895	This sounds a bit complicated, but here is a useful and typical	1003	This sounds a bit complicated, but here is a useful and typical
896	example: Imagine you have a tcp connection and you want a so-called	1004	example: Imagine you have a tcp connection and you want a so-called idle
897	idle timeout, that is, you want to be called when there have been,	1005	timeout, that is, you want to be called when there have been, say, 60
898	say, 60 seconds of inactivity on the socket. The easiest way to do	1006	seconds of inactivity on the socket. The easiest way to do this is to
899	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1007	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
900	C<ev_timer_again> each time you successfully read or write some data. If	1008	C<ev_timer_again> each time you successfully read or write some data. If
901	you go into an idle state where you do not expect data to travel on the	1009	you go into an idle state where you do not expect data to travel on the
902	socket, you can stop the timer, and again will automatically restart it if	1010	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
903	need be.	1011	automatically restart it if need be.
904		1012
905	You can also ignore the C<after> value and C<ev_timer_start> altogether	1013	That means you can ignore the C<after> value and C<ev_timer_start>
906	and only ever use the C<repeat> value:	1014	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
907		1015
908	ev_timer_init (timer, callback, 0., 5.);	1016	ev_timer_init (timer, callback, 0., 5.);
909	ev_timer_again (loop, timer);	1017	ev_timer_again (loop, timer);
910	...	1018	...
911	timer->again = 17.;	1019	timer->again = 17.;
912	ev_timer_again (loop, timer);	1020	ev_timer_again (loop, timer);
913	...	1021	...
914	timer->again = 10.;	1022	timer->again = 10.;
915	ev_timer_again (loop, timer);	1023	ev_timer_again (loop, timer);
916		1024
917	This is more efficient then stopping/starting the timer eahc time you want	1025	This is more slightly efficient then stopping/starting the timer each time
918	to modify its timeout value.	1026	you want to modify its timeout value.
919		1027
920	=item ev_tstamp repeat [read-write]	1028	=item ev_tstamp repeat [read-write]
921		1029
922	The current C<repeat> value. Will be used each time the watcher times out	1030	The current C<repeat> value. Will be used each time the watcher times out
923	or C<ev_timer_again> is called and determines the next timeout (if any),	1031	or C<ev_timer_again> is called and determines the next timeout (if any),
…		…
1192	not exist" is a status change like any other. The condition "path does	1300	not exist" is a status change like any other. The condition "path does
1193	not exist" is signified by the C<st_nlink> field being zero (which is	1301	not exist" is signified by the C<st_nlink> field being zero (which is
1194	otherwise always forced to be at least one) and all the other fields of	1302	otherwise always forced to be at least one) and all the other fields of
1195	the stat buffer having unspecified contents.	1303	the stat buffer having unspecified contents.
1196		1304
		1305	The path I<should> be absolute and I<must not> end in a slash. If it is
		1306	relative and your working directory changes, the behaviour is undefined.
		1307
1197	Since there is no standard to do this, the portable implementation simply	1308	Since there is no standard to do this, the portable implementation simply
1198	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1309	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1199	can specify a recommended polling interval for this case. If you specify	1310	can specify a recommended polling interval for this case. If you specify
1200	a polling interval of C<0> (highly recommended!) then a I<suitable,	1311	a polling interval of C<0> (highly recommended!) then a I<suitable,
1201	unspecified default> value will be used (which you can expect to be around	1312	unspecified default> value will be used (which you can expect to be around
1202	five seconds, although this might change dynamically). Libev will also	1313	five seconds, although this might change dynamically). Libev will also
1203	impose a minimum interval which is currently around C<0.1>, but thats	1314	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1205		1316
1206	This watcher type is not meant for massive numbers of stat watchers,	1317	This watcher type is not meant for massive numbers of stat watchers,
1207	as even with OS-supported change notifications, this can be	1318	as even with OS-supported change notifications, this can be
1208	resource-intensive.	1319	resource-intensive.
1209		1320
1210	At the time of this writing, no specific OS backends are implemented, but	1321	At the time of this writing, only the Linux inotify interface is
1211	if demand increases, at least a kqueue and inotify backend will be added.	1322	implemented (implementing kqueue support is left as an exercise for the
		1323	reader). Inotify will be used to give hints only and should not change the
		1324	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1325	to fall back to regular polling again even with inotify, but changes are
		1326	usually detected immediately, and if the file exists there will be no
		1327	polling.
1212		1328
1213	=over 4	1329	=over 4
1214		1330
1215	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1331	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1216		1332
…		…
1280	ev_stat_start (loop, &passwd);	1396	ev_stat_start (loop, &passwd);
1281		1397
1282		1398
1283	=head2 C<ev_idle> - when you've got nothing better to do...	1399	=head2 C<ev_idle> - when you've got nothing better to do...
1284		1400
1285	Idle watchers trigger events when there are no other events are pending	1401	Idle watchers trigger events when no other events of the same or higher
1286	(prepare, check and other idle watchers do not count). That is, as long	1402	priority are pending (prepare, check and other idle watchers do not
1287	as your process is busy handling sockets or timeouts (or even signals,	1403	count).
1288	imagine) it will not be triggered. But when your process is idle all idle	1404
1289	watchers are being called again and again, once per event loop iteration -	1405	That is, as long as your process is busy handling sockets or timeouts
		1406	(or even signals, imagine) of the same or higher priority it will not be
		1407	triggered. But when your process is idle (or only lower-priority watchers
		1408	are pending), the idle watchers are being called once per event loop
1290	until stopped, that is, or your process receives more events and becomes	1409	iteration - until stopped, that is, or your process receives more events
1291	busy.	1410	and becomes busy again with higher priority stuff.
1292		1411
1293	The most noteworthy effect is that as long as any idle watchers are	1412	The most noteworthy effect is that as long as any idle watchers are
1294	active, the process will not block when waiting for new events.	1413	active, the process will not block when waiting for new events.
1295		1414
1296	Apart from keeping your process non-blocking (which is a useful	1415	Apart from keeping your process non-blocking (which is a useful
…		…
1374	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1493	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1375	macros, but using them is utterly, utterly and completely pointless.	1494	macros, but using them is utterly, utterly and completely pointless.
1376		1495
1377	=back	1496	=back
1378		1497
1379	Example: To include a library such as adns, you would add IO watchers	1498	There are a number of principal ways to embed other event loops or modules
1380	and a timeout watcher in a prepare handler, as required by libadns, and	1499	into libev. Here are some ideas on how to include libadns into libev
		1500	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1501	use for an actually working example. Another Perl module named C<EV::Glib>
		1502	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1503	into the Glib event loop).
		1504
		1505	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1381	in a check watcher, destroy them and call into libadns. What follows is	1506	and in a check watcher, destroy them and call into libadns. What follows
1382	pseudo-code only of course:	1507	is pseudo-code only of course. This requires you to either use a low
		1508	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1509	the callbacks for the IO/timeout watchers might not have been called yet.
1383		1510
1384	static ev_io iow [nfd];	1511	static ev_io iow [nfd];
1385	static ev_timer tw;	1512	static ev_timer tw;
1386		1513
1387	static void	1514	static void
1388	io_cb (ev_loop loop, ev_io w, int revents)	1515	io_cb (ev_loop loop, ev_io w, int revents)
1389	{	1516	{
1390	// set the relevant poll flags
1391	// could also call adns_processreadable etc. here
1392	struct pollfd fd = (struct pollfd )w->data;
1393	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1394	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1395	}	1517	}
1396		1518
1397	// create io watchers for each fd and a timer before blocking	1519	// create io watchers for each fd and a timer before blocking
1398	static void	1520	static void
1399	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1521	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1400	{	1522	{
1401	int timeout = 3600000;truct pollfd fds [nfd];	1523	int timeout = 3600000;
		1524	struct pollfd fds [nfd];
1402	// actual code will need to loop here and realloc etc.	1525	// actual code will need to loop here and realloc etc.
1403	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1526	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1404		1527
1405	/* the callback is illegal, but won't be called as we stop during check */	1528	/* the callback is illegal, but won't be called as we stop during check */
1406	ev_timer_init (&tw, 0, timeout * 1e-3);	1529	ev_timer_init (&tw, 0, timeout * 1e-3);
1407	ev_timer_start (loop, &tw);	1530	ev_timer_start (loop, &tw);
1408		1531
1409	// create on ev_io per pollfd	1532	// create one ev_io per pollfd
1410	for (int i = 0; i < nfd; ++i)	1533	for (int i = 0; i < nfd; ++i)
1411	{	1534	{
1412	ev_io_init (iow + i, io_cb, fds [i].fd,	1535	ev_io_init (iow + i, io_cb, fds [i].fd,
1413	((fds [i].events & POLLIN ? EV_READ : 0)	1536	((fds [i].events & POLLIN ? EV_READ : 0)
1414	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1537	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1415		1538
1416	fds [i].revents = 0;	1539	fds [i].revents = 0;
1417	iow [i].data = fds + i;
1418	ev_io_start (loop, iow + i);	1540	ev_io_start (loop, iow + i);
1419	}	1541	}
1420	}	1542	}
1421		1543
1422	// stop all watchers after blocking	1544	// stop all watchers after blocking
…		…
1424	adns_check_cb (ev_loop loop, ev_check w, int revents)	1546	adns_check_cb (ev_loop loop, ev_check w, int revents)
1425	{	1547	{
1426	ev_timer_stop (loop, &tw);	1548	ev_timer_stop (loop, &tw);
1427		1549
1428	for (int i = 0; i < nfd; ++i)	1550	for (int i = 0; i < nfd; ++i)
		1551	{
		1552	// set the relevant poll flags
		1553	// could also call adns_processreadable etc. here
		1554	struct pollfd *fd = fds + i;
		1555	int revents = ev_clear_pending (iow + i);
		1556	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1557	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1558
		1559	// now stop the watcher
1429	ev_io_stop (loop, iow + i);	1560	ev_io_stop (loop, iow + i);
		1561	}
1430		1562
1431	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1563	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1564	}
		1565
		1566	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1567	in the prepare watcher and would dispose of the check watcher.
		1568
		1569	Method 3: If the module to be embedded supports explicit event
		1570	notification (adns does), you can also make use of the actual watcher
		1571	callbacks, and only destroy/create the watchers in the prepare watcher.
		1572
		1573	static void
		1574	timer_cb (EV_P_ ev_timer *w, int revents)
		1575	{
		1576	adns_state ads = (adns_state)w->data;
		1577	update_now (EV_A);
		1578
		1579	adns_processtimeouts (ads, &tv_now);
		1580	}
		1581
		1582	static void
		1583	io_cb (EV_P_ ev_io *w, int revents)
		1584	{
		1585	adns_state ads = (adns_state)w->data;
		1586	update_now (EV_A);
		1587
		1588	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1589	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1590	}
		1591
		1592	// do not ever call adns_afterpoll
		1593
		1594	Method 4: Do not use a prepare or check watcher because the module you
		1595	want to embed is too inflexible to support it. Instead, youc na override
		1596	their poll function. The drawback with this solution is that the main
		1597	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1598	this.
		1599
		1600	static gint
		1601	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1602	{
		1603	int got_events = 0;
		1604
		1605	for (n = 0; n < nfds; ++n)
		1606	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1607
		1608	if (timeout >= 0)
		1609	// create/start timer
		1610
		1611	// poll
		1612	ev_loop (EV_A_ 0);
		1613
		1614	// stop timer again
		1615	if (timeout >= 0)
		1616	ev_timer_stop (EV_A_ &to);
		1617
		1618	// stop io watchers again - their callbacks should have set
		1619	for (n = 0; n < nfds; ++n)
		1620	ev_io_stop (EV_A_ iow [n]);
		1621
		1622	return got_events;
1432	}	1623	}
1433		1624
1434		1625
1435	=head2 C<ev_embed> - when one backend isn't enough...	1626	=head2 C<ev_embed> - when one backend isn't enough...
1436		1627
…		…
1640		1831
1641	To use it,	1832	To use it,
1642		1833
1643	#include <ev++.h>	1834	#include <ev++.h>
1644		1835
1645	(it is not installed by default). This automatically includes F<ev.h>	1836	This automatically includes F<ev.h> and puts all of its definitions (many
1646	and puts all of its definitions (many of them macros) into the global	1837	of them macros) into the global namespace. All C++ specific things are
1647	namespace. All C++ specific things are put into the C<ev> namespace.	1838	put into the C<ev> namespace. It should support all the same embedding
		1839	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1648		1840
1649	It should support all the same embedding options as F<ev.h>, most notably	1841	Care has been taken to keep the overhead low. The only data member the C++
1650	C<EV_MULTIPLICITY>.	1842	classes add (compared to plain C-style watchers) is the event loop pointer
		1843	that the watcher is associated with (or no additional members at all if
		1844	you disable C<EV_MULTIPLICITY> when embedding libev).
		1845
		1846	Currently, functions, and static and non-static member functions can be
		1847	used as callbacks. Other types should be easy to add as long as they only
		1848	need one additional pointer for context. If you need support for other
		1849	types of functors please contact the author (preferably after implementing
		1850	it).
1651		1851
1652	Here is a list of things available in the C<ev> namespace:	1852	Here is a list of things available in the C<ev> namespace:
1653		1853
1654	=over 4	1854	=over 4
1655		1855
…		…
1671		1871
1672	All of those classes have these methods:	1872	All of those classes have these methods:
1673		1873
1674	=over 4	1874	=over 4
1675		1875
1676	=item ev::TYPE::TYPE (object , object::method )	1876	=item ev::TYPE::TYPE ()
1677		1877
1678	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1878	=item ev::TYPE::TYPE (struct ev_loop *)
1679		1879
1680	=item ev::TYPE::~TYPE	1880	=item ev::TYPE::~TYPE
1681		1881
1682	The constructor takes a pointer to an object and a method pointer to	1882	The constructor (optionally) takes an event loop to associate the watcher
1683	the event handler callback to call in this class. The constructor calls	1883	with. If it is omitted, it will use C<EV_DEFAULT>.
1684	C<ev_init> for you, which means you have to call the C<set> method	1884
1685	before starting it. If you do not specify a loop then the constructor	1885	The constructor calls C<ev_init> for you, which means you have to call the
1686	automatically associates the default loop with this watcher.	1886	C<set> method before starting it.
		1887
		1888	It will not set a callback, however: You have to call the templated C<set>
		1889	method to set a callback before you can start the watcher.
		1890
		1891	(The reason why you have to use a method is a limitation in C++ which does
		1892	not allow explicit template arguments for constructors).
1687		1893
1688	The destructor automatically stops the watcher if it is active.	1894	The destructor automatically stops the watcher if it is active.
		1895
		1896	=item w->set<class, &class::method> (object *)
		1897
		1898	This method sets the callback method to call. The method has to have a
		1899	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1900	first argument and the C<revents> as second. The object must be given as
		1901	parameter and is stored in the C<data> member of the watcher.
		1902
		1903	This method synthesizes efficient thunking code to call your method from
		1904	the C callback that libev requires. If your compiler can inline your
		1905	callback (i.e. it is visible to it at the place of the C<set> call and
		1906	your compiler is good :), then the method will be fully inlined into the
		1907	thunking function, making it as fast as a direct C callback.
		1908
		1909	Example: simple class declaration and watcher initialisation
		1910
		1911	struct myclass
		1912	{
		1913	void io_cb (ev::io &w, int revents) { }
		1914	}
		1915
		1916	myclass obj;
		1917	ev::io iow;
		1918	iow.set <myclass, &myclass::io_cb> (&obj);
		1919
		1920	=item w->set<function> (void *data = 0)
		1921
		1922	Also sets a callback, but uses a static method or plain function as
		1923	callback. The optional C<data> argument will be stored in the watcher's
		1924	C<data> member and is free for you to use.
		1925
		1926	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1927
		1928	See the method-C<set> above for more details.
		1929
		1930	Example:
		1931
		1932	static void io_cb (ev::io &w, int revents) { }
		1933	iow.set <io_cb> ();
1689		1934
1690	=item w->set (struct ev_loop *)	1935	=item w->set (struct ev_loop *)
1691		1936
1692	Associates a different C<struct ev_loop> with this watcher. You can only	1937	Associates a different C<struct ev_loop> with this watcher. You can only
1693	do this when the watcher is inactive (and not pending either).	1938	do this when the watcher is inactive (and not pending either).
1694		1939
1695	=item w->set ([args])	1940	=item w->set ([args])
1696		1941
1697	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1942	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1698	called at least once. Unlike the C counterpart, an active watcher gets	1943	called at least once. Unlike the C counterpart, an active watcher gets
1699	automatically stopped and restarted.	1944	automatically stopped and restarted when reconfiguring it with this
		1945	method.
1700		1946
1701	=item w->start ()	1947	=item w->start ()
1702		1948
1703	Starts the watcher. Note that there is no C<loop> argument as the	1949	Starts the watcher. Note that there is no C<loop> argument, as the
1704	constructor already takes the loop.	1950	constructor already stores the event loop.
1705		1951
1706	=item w->stop ()	1952	=item w->stop ()
1707		1953
1708	Stops the watcher if it is active. Again, no C<loop> argument.	1954	Stops the watcher if it is active. Again, no C<loop> argument.
1709		1955
…		…
1734		1980
1735	myclass ();	1981	myclass ();
1736	}	1982	}
1737		1983
1738	myclass::myclass (int fd)	1984	myclass::myclass (int fd)
1739	: io (this, &myclass::io_cb),
1740	idle (this, &myclass::idle_cb)
1741	{	1985	{
		1986	io .set <myclass, &myclass::io_cb > (this);
		1987	idle.set <myclass, &myclass::idle_cb> (this);
		1988
1742	io.start (fd, ev::READ);	1989	io.start (fd, ev::READ);
1743	}	1990	}
1744		1991
1745		1992
1746	=head1 MACRO MAGIC	1993	=head1 MACRO MAGIC
1747		1994
1748	Libev can be compiled with a variety of options, the most fundemantal is	1995	Libev can be compiled with a variety of options, the most fundemantal is
1749	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	1996	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1750	callbacks have an initial C<struct ev_loop *> argument.	1997	callbacks have an initial C<struct ev_loop *> argument.
1751		1998
1752	To make it easier to write programs that cope with either variant, the	1999	To make it easier to write programs that cope with either variant, the
1753	following macros are defined:	2000	following macros are defined:
1754		2001
…		…
1787	Similar to the other two macros, this gives you the value of the default	2034	Similar to the other two macros, this gives you the value of the default
1788	loop, if multiple loops are supported ("ev loop default").	2035	loop, if multiple loops are supported ("ev loop default").
1789		2036
1790	=back	2037	=back
1791		2038
1792	Example: Declare and initialise a check watcher, working regardless of	2039	Example: Declare and initialise a check watcher, utilising the above
1793	wether multiple loops are supported or not.	2040	macros so it will work regardless of whether multiple loops are supported
		2041	or not.
1794		2042
1795	static void	2043	static void
1796	check_cb (EV_P_ ev_timer *w, int revents)	2044	check_cb (EV_P_ ev_timer *w, int revents)
1797	{	2045	{
1798	ev_check_stop (EV_A_ w);	2046	ev_check_stop (EV_A_ w);
…		…
1800		2048
1801	ev_check check;	2049	ev_check check;
1802	ev_check_init (&check, check_cb);	2050	ev_check_init (&check, check_cb);
1803	ev_check_start (EV_DEFAULT_ &check);	2051	ev_check_start (EV_DEFAULT_ &check);
1804	ev_loop (EV_DEFAULT_ 0);	2052	ev_loop (EV_DEFAULT_ 0);
1805
1806		2053
1807	=head1 EMBEDDING	2054	=head1 EMBEDDING
1808		2055
1809	Libev can (and often is) directly embedded into host	2056	Libev can (and often is) directly embedded into host
1810	applications. Examples of applications that embed it include the Deliantra	2057	applications. Examples of applications that embed it include the Deliantra
…		…
1850	ev_vars.h	2097	ev_vars.h
1851	ev_wrap.h	2098	ev_wrap.h
1852		2099
1853	ev_win32.c required on win32 platforms only	2100	ev_win32.c required on win32 platforms only
1854		2101
1855	ev_select.c only when select backend is enabled (which is by default)	2102	ev_select.c only when select backend is enabled (which is enabled by default)
1856	ev_poll.c only when poll backend is enabled (disabled by default)	2103	ev_poll.c only when poll backend is enabled (disabled by default)
1857	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2104	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1858	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2105	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1859	ev_port.c only when the solaris port backend is enabled (disabled by default)	2106	ev_port.c only when the solaris port backend is enabled (disabled by default)
1860		2107
…		…
1985		2232
1986	=item EV_USE_DEVPOLL	2233	=item EV_USE_DEVPOLL
1987		2234
1988	reserved for future expansion, works like the USE symbols above.	2235	reserved for future expansion, works like the USE symbols above.
1989		2236
		2237	=item EV_USE_INOTIFY
		2238
		2239	If defined to be C<1>, libev will compile in support for the Linux inotify
		2240	interface to speed up C<ev_stat> watchers. Its actual availability will
		2241	be detected at runtime.
		2242
1990	=item EV_H	2243	=item EV_H
1991		2244
1992	The name of the F<ev.h> header file used to include it. The default if	2245	The name of the F<ev.h> header file used to include it. The default if
1993	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2246	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
1994	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2247	can be used to virtually rename the F<ev.h> header file in case of conflicts.
…		…
2017	will have the C<struct ev_loop *> as first argument, and you can create	2270	will have the C<struct ev_loop *> as first argument, and you can create
2018	additional independent event loops. Otherwise there will be no support	2271	additional independent event loops. Otherwise there will be no support
2019	for multiple event loops and there is no first event loop pointer	2272	for multiple event loops and there is no first event loop pointer
2020	argument. Instead, all functions act on the single default loop.	2273	argument. Instead, all functions act on the single default loop.
2021		2274
		2275	=item EV_MINPRI
		2276
		2277	=item EV_MAXPRI
		2278
		2279	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2280	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2281	provide for more priorities by overriding those symbols (usually defined
		2282	to be C<-2> and C<2>, respectively).
		2283
		2284	When doing priority-based operations, libev usually has to linearly search
		2285	all the priorities, so having many of them (hundreds) uses a lot of space
		2286	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2287	fine.
		2288
		2289	If your embedding app does not need any priorities, defining these both to
		2290	C<0> will save some memory and cpu.
		2291
2022	=item EV_PERIODIC_ENABLE	2292	=item EV_PERIODIC_ENABLE
2023		2293
2024	If undefined or defined to be C<1>, then periodic timers are supported. If	2294	If undefined or defined to be C<1>, then periodic timers are supported. If
2025	defined to be C<0>, then they are not. Disabling them saves a few kB of	2295	defined to be C<0>, then they are not. Disabling them saves a few kB of
2026	code.	2296	code.
2027		2297
		2298	=item EV_IDLE_ENABLE
		2299
		2300	If undefined or defined to be C<1>, then idle watchers are supported. If
		2301	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2302	code.
		2303
2028	=item EV_EMBED_ENABLE	2304	=item EV_EMBED_ENABLE
2029		2305
2030	If undefined or defined to be C<1>, then embed watchers are supported. If	2306	If undefined or defined to be C<1>, then embed watchers are supported. If
2031	defined to be C<0>, then they are not.	2307	defined to be C<0>, then they are not.
2032		2308
…		…
2049	=item EV_PID_HASHSIZE	2325	=item EV_PID_HASHSIZE
2050		2326
2051	C<ev_child> watchers use a small hash table to distribute workload by	2327	C<ev_child> watchers use a small hash table to distribute workload by
2052	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	2328	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2053	than enough. If you need to manage thousands of children you might want to	2329	than enough. If you need to manage thousands of children you might want to
2054	increase this value.	2330	increase this value (I<must> be a power of two).
		2331
		2332	=item EV_INOTIFY_HASHSIZE
		2333
		2334	C<ev_staz> watchers use a small hash table to distribute workload by
		2335	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2336	usually more than enough. If you need to manage thousands of C<ev_stat>
		2337	watchers you might want to increase this value (I<must> be a power of
		2338	two).
2055		2339
2056	=item EV_COMMON	2340	=item EV_COMMON
2057		2341
2058	By default, all watchers have a C<void *data> member. By redefining	2342	By default, all watchers have a C<void *data> member. By redefining
2059	this macro to a something else you can include more and other types of	2343	this macro to a something else you can include more and other types of
…		…
2088	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2372	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2089	will be compiled. It is pretty complex because it provides its own header	2373	will be compiled. It is pretty complex because it provides its own header
2090	file.	2374	file.
2091		2375
2092	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2376	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2093	that everybody includes and which overrides some autoconf choices:	2377	that everybody includes and which overrides some configure choices:
2094		2378
		2379	#define EV_MINIMAL 1
2095	#define EV_USE_POLL 0	2380	#define EV_USE_POLL 0
2096	#define EV_MULTIPLICITY 0	2381	#define EV_MULTIPLICITY 0
2097	#define EV_PERIODICS 0	2382	#define EV_PERIODIC_ENABLE 0
		2383	#define EV_STAT_ENABLE 0
		2384	#define EV_FORK_ENABLE 0
2098	#define EV_CONFIG_H <config.h>	2385	#define EV_CONFIG_H <config.h>
		2386	#define EV_MINPRI 0
		2387	#define EV_MAXPRI 0
2099		2388
2100	#include "ev++.h"	2389	#include "ev++.h"
2101		2390
2102	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2391	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2103		2392
…		…
2109		2398
2110	In this section the complexities of (many of) the algorithms used inside	2399	In this section the complexities of (many of) the algorithms used inside
2111	libev will be explained. For complexity discussions about backends see the	2400	libev will be explained. For complexity discussions about backends see the
2112	documentation for C<ev_default_init>.	2401	documentation for C<ev_default_init>.
2113		2402
		2403	All of the following are about amortised time: If an array needs to be
		2404	extended, libev needs to realloc and move the whole array, but this
		2405	happens asymptotically never with higher number of elements, so O(1) might
		2406	mean it might do a lengthy realloc operation in rare cases, but on average
		2407	it is much faster and asymptotically approaches constant time.
		2408
2114	=over 4	2409	=over 4
2115		2410
2116	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2411	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2117		2412
		2413	This means that, when you have a watcher that triggers in one hour and
		2414	there are 100 watchers that would trigger before that then inserting will
		2415	have to skip those 100 watchers.
		2416
2118	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2417	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2119		2418
		2419	That means that for changing a timer costs less than removing/adding them
		2420	as only the relative motion in the event queue has to be paid for.
		2421
2120	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2422	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2121		2423
		2424	These just add the watcher into an array or at the head of a list.
2122	=item Stopping check/prepare/idle watchers: O(1)	2425	=item Stopping check/prepare/idle watchers: O(1)
2123		2426
2124	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2427	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2428
		2429	These watchers are stored in lists then need to be walked to find the
		2430	correct watcher to remove. The lists are usually short (you don't usually
		2431	have many watchers waiting for the same fd or signal).
2125		2432
2126	=item Finding the next timer per loop iteration: O(1)	2433	=item Finding the next timer per loop iteration: O(1)
2127		2434
2128	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2435	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2129		2436
		2437	A change means an I/O watcher gets started or stopped, which requires
		2438	libev to recalculate its status (and possibly tell the kernel).
		2439
2130	=item Activating one watcher: O(1)	2440	=item Activating one watcher: O(1)
2131		2441
		2442	=item Priority handling: O(number_of_priorities)
		2443
		2444	Priorities are implemented by allocating some space for each
		2445	priority. When doing priority-based operations, libev usually has to
		2446	linearly search all the priorities.
		2447
2132	=back	2448	=back
2133		2449
2134		2450
2135	=head1 AUTHOR	2451	=head1 AUTHOR
2136		2452

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Comparing libev/ev.pod (file contents): Revision 1.54 by root, Tue Nov 27 20:26:51 2007 UTC vs. Revision 1.76 by root, Sat Dec 8 15:30:30 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.54 by root, Tue Nov 27 20:26:51 2007 UTC vs.
Revision 1.76 by root, Sat Dec 8 15:30:30 2007 UTC