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

Comparing libev/ev.pod (file contents):
Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC vs.
Revision 1.77 by root, Sat Dec 8 22:11:14 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
…		…
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.
412		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.
		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.
417		453
…		…
450	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
451	usually a better approach for this kind of thing.	487	usually a better approach for this kind of thing.
452		488
453	Here are the gory details of what C<ev_loop> does:	489	Here are the gory details of what C<ev_loop> does:
454		490
		491	- Before the first iteration, call any pending watchers.
455	* If there are no active watchers (reference count is zero), return.	492	* If there are no active watchers (reference count is zero), return.
456	- Queue prepare watchers and then call all outstanding watchers.	493	- Queue all prepare watchers and then call all outstanding watchers.
457	- If we have been forked, recreate the kernel state.	494	- If we have been forked, recreate the kernel state.
458	- Update the kernel state with all outstanding changes.	495	- Update the kernel state with all outstanding changes.
459	- Update the "event loop time".	496	- Update the "event loop time".
460	- Calculate for how long to block.	497	- Calculate for how long to block.
461	- Block the process, waiting for any events.	498	- Block the process, waiting for any events.
…		…
700	=item bool ev_is_pending (ev_TYPE *watcher)	737	=item bool ev_is_pending (ev_TYPE *watcher)
701		738
702	Returns a true value iff the watcher is pending, (i.e. it has outstanding	739	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	740	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	741	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	742	C<ev_TYPE_set> is safe), you must not change its priority, and you must
706	libev (e.g. you cnanot C<free ()> it).	743	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		744	it).
707		745
708	=item callback ev_cb (ev_TYPE *watcher)	746	=item callback ev_cb (ev_TYPE *watcher)
709		747
710	Returns the callback currently set on the watcher.	748	Returns the callback currently set on the watcher.
711		749
712	=item ev_cb_set (ev_TYPE *watcher, callback)	750	=item ev_cb_set (ev_TYPE *watcher, callback)
713		751
714	Change the callback. You can change the callback at virtually any time	752	Change the callback. You can change the callback at virtually any time
715	(modulo threads).	753	(modulo threads).
		754
		755	=item ev_set_priority (ev_TYPE *watcher, priority)
		756
		757	=item int ev_priority (ev_TYPE *watcher)
		758
		759	Set and query the priority of the watcher. The priority is a small
		760	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		761	(default: C<-2>). Pending watchers with higher priority will be invoked
		762	before watchers with lower priority, but priority will not keep watchers
		763	from being executed (except for C<ev_idle> watchers).
		764
		765	This means that priorities are I<only> used for ordering callback
		766	invocation after new events have been received. This is useful, for
		767	example, to reduce latency after idling, or more often, to bind two
		768	watchers on the same event and make sure one is called first.
		769
		770	If you need to suppress invocation when higher priority events are pending
		771	you need to look at C<ev_idle> watchers, which provide this functionality.
		772
		773	You I<must not> change the priority of a watcher as long as it is active or
		774	pending.
		775
		776	The default priority used by watchers when no priority has been set is
		777	always C<0>, which is supposed to not be too high and not be too low :).
		778
		779	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		780	fine, as long as you do not mind that the priority value you query might
		781	or might not have been adjusted to be within valid range.
		782
		783	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		784
		785	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		786	C<loop> nor C<revents> need to be valid as long as the watcher callback
		787	can deal with that fact.
		788
		789	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		790
		791	If the watcher is pending, this function returns clears its pending status
		792	and returns its C<revents> bitset (as if its callback was invoked). If the
		793	watcher isn't pending it does nothing and returns C<0>.
716		794
717	=back	795	=back
718		796
719		797
720	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	798	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
826	it is best to always use non-blocking I/O: An extra C<read>(2) returning	904	it is best to always use non-blocking I/O: An extra C<read>(2) returning
827	C<EAGAIN> is far preferable to a program hanging until some data arrives.	905	C<EAGAIN> is far preferable to a program hanging until some data arrives.
828		906
829	If you cannot run the fd in non-blocking mode (for example you should not	907	If you cannot run the fd in non-blocking mode (for example you should not
830	play around with an Xlib connection), then you have to seperately re-test	908	play around with an Xlib connection), then you have to seperately re-test
831	wether a file descriptor is really ready with a known-to-be good interface	909	whether a file descriptor is really ready with a known-to-be good interface
832	such as poll (fortunately in our Xlib example, Xlib already does this on	910	such as poll (fortunately in our Xlib example, Xlib already does this on
833	its own, so its quite safe to use).	911	its own, so its quite safe to use).
834		912
835	=over 4	913	=over 4
836		914
…		…
914	=item ev_timer_again (loop)	992	=item ev_timer_again (loop)
915		993
916	This will act as if the timer timed out and restart it again if it is	994	This will act as if the timer timed out and restart it again if it is
917	repeating. The exact semantics are:	995	repeating. The exact semantics are:
918		996
		997	If the timer is pending, its pending status is cleared.
		998
919	If the timer is started but nonrepeating, stop it.	999	If the timer is started but nonrepeating, stop it (as if it timed out).
920		1000
921	If the timer is repeating, either start it if necessary (with the repeat	1001	If the timer is repeating, either start it if necessary (with the
922	value), or reset the running timer to the repeat value.	1002	C<repeat> value), or reset the running timer to the C<repeat> value.
923		1003
924	This sounds a bit complicated, but here is a useful and typical	1004	This sounds a bit complicated, but here is a useful and typical
925	example: Imagine you have a tcp connection and you want a so-called	1005	example: Imagine you have a tcp connection and you want a so-called idle
926	idle timeout, that is, you want to be called when there have been,	1006	timeout, that is, you want to be called when there have been, say, 60
927	say, 60 seconds of inactivity on the socket. The easiest way to do	1007	seconds of inactivity on the socket. The easiest way to do this is to
928	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1008	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
929	C<ev_timer_again> each time you successfully read or write some data. If	1009	C<ev_timer_again> each time you successfully read or write some data. If
930	you go into an idle state where you do not expect data to travel on the	1010	you go into an idle state where you do not expect data to travel on the
931	socket, you can stop the timer, and again will automatically restart it if	1011	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
932	need be.	1012	automatically restart it if need be.
933		1013
934	You can also ignore the C<after> value and C<ev_timer_start> altogether	1014	That means you can ignore the C<after> value and C<ev_timer_start>
935	and only ever use the C<repeat> value:	1015	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
936		1016
937	ev_timer_init (timer, callback, 0., 5.);	1017	ev_timer_init (timer, callback, 0., 5.);
938	ev_timer_again (loop, timer);	1018	ev_timer_again (loop, timer);
939	...	1019	...
940	timer->again = 17.;	1020	timer->again = 17.;
941	ev_timer_again (loop, timer);	1021	ev_timer_again (loop, timer);
942	...	1022	...
943	timer->again = 10.;	1023	timer->again = 10.;
944	ev_timer_again (loop, timer);	1024	ev_timer_again (loop, timer);
945		1025
946	This is more efficient then stopping/starting the timer eahc time you want	1026	This is more slightly efficient then stopping/starting the timer each time
947	to modify its timeout value.	1027	you want to modify its timeout value.
948		1028
949	=item ev_tstamp repeat [read-write]	1029	=item ev_tstamp repeat [read-write]
950		1030
951	The current C<repeat> value. Will be used each time the watcher times out	1031	The current C<repeat> value. Will be used each time the watcher times out
952	or C<ev_timer_again> is called and determines the next timeout (if any),	1032	or C<ev_timer_again> is called and determines the next timeout (if any),
…		…
1220	The path does not need to exist: changing from "path exists" to "path does	1300	The path does not need to exist: changing from "path exists" to "path does
1221	not exist" is a status change like any other. The condition "path does	1301	not exist" is a status change like any other. The condition "path does
1222	not exist" is signified by the C<st_nlink> field being zero (which is	1302	not exist" is signified by the C<st_nlink> field being zero (which is
1223	otherwise always forced to be at least one) and all the other fields of	1303	otherwise always forced to be at least one) and all the other fields of
1224	the stat buffer having unspecified contents.	1304	the stat buffer having unspecified contents.
		1305
		1306	The path I<should> be absolute and I<must not> end in a slash. If it is
		1307	relative and your working directory changes, the behaviour is undefined.
1225		1308
1226	Since there is no standard to do this, the portable implementation simply	1309	Since there is no standard to do this, the portable implementation simply
1227	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1310	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1228	can specify a recommended polling interval for this case. If you specify	1311	can specify a recommended polling interval for this case. If you specify
1229	a polling interval of C<0> (highly recommended!) then a I<suitable,	1312	a polling interval of C<0> (highly recommended!) then a I<suitable,
…		…
1314	ev_stat_start (loop, &passwd);	1397	ev_stat_start (loop, &passwd);
1315		1398
1316		1399
1317	=head2 C<ev_idle> - when you've got nothing better to do...	1400	=head2 C<ev_idle> - when you've got nothing better to do...
1318		1401
1319	Idle watchers trigger events when there are no other events are pending	1402	Idle watchers trigger events when no other events of the same or higher
1320	(prepare, check and other idle watchers do not count). That is, as long	1403	priority are pending (prepare, check and other idle watchers do not
1321	as your process is busy handling sockets or timeouts (or even signals,	1404	count).
1322	imagine) it will not be triggered. But when your process is idle all idle	1405
1323	watchers are being called again and again, once per event loop iteration -	1406	That is, as long as your process is busy handling sockets or timeouts
		1407	(or even signals, imagine) of the same or higher priority it will not be
		1408	triggered. But when your process is idle (or only lower-priority watchers
		1409	are pending), the idle watchers are being called once per event loop
1324	until stopped, that is, or your process receives more events and becomes	1410	iteration - until stopped, that is, or your process receives more events
1325	busy.	1411	and becomes busy again with higher priority stuff.
1326		1412
1327	The most noteworthy effect is that as long as any idle watchers are	1413	The most noteworthy effect is that as long as any idle watchers are
1328	active, the process will not block when waiting for new events.	1414	active, the process will not block when waiting for new events.
1329		1415
1330	Apart from keeping your process non-blocking (which is a useful	1416	Apart from keeping your process non-blocking (which is a useful
…		…
1396	with priority higher than or equal to the event loop and one coroutine	1482	with priority higher than or equal to the event loop and one coroutine
1397	of lower priority, but only once, using idle watchers to keep the event	1483	of lower priority, but only once, using idle watchers to keep the event
1398	loop from blocking if lower-priority coroutines are active, thus mapping	1484	loop from blocking if lower-priority coroutines are active, thus mapping
1399	low-priority coroutines to idle/background tasks).	1485	low-priority coroutines to idle/background tasks).
1400		1486
		1487	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1488	priority, to ensure that they are being run before any other watchers
		1489	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1490	too) should not activate ("feed") events into libev. While libev fully
		1491	supports this, they will be called before other C<ev_check> watchers did
		1492	their job. As C<ev_check> watchers are often used to embed other event
		1493	loops those other event loops might be in an unusable state until their
		1494	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1495	others).
		1496
1401	=over 4	1497	=over 4
1402		1498
1403	=item ev_prepare_init (ev_prepare *, callback)	1499	=item ev_prepare_init (ev_prepare *, callback)
1404		1500
1405	=item ev_check_init (ev_check *, callback)	1501	=item ev_check_init (ev_check *, callback)
…		…
1408	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1504	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1409	macros, but using them is utterly, utterly and completely pointless.	1505	macros, but using them is utterly, utterly and completely pointless.
1410		1506
1411	=back	1507	=back
1412		1508
1413	Example: To include a library such as adns, you would add IO watchers	1509	There are a number of principal ways to embed other event loops or modules
1414	and a timeout watcher in a prepare handler, as required by libadns, and	1510	into libev. Here are some ideas on how to include libadns into libev
		1511	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1512	use for an actually working example. Another Perl module named C<EV::Glib>
		1513	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1514	into the Glib event loop).
		1515
		1516	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1415	in a check watcher, destroy them and call into libadns. What follows is	1517	and in a check watcher, destroy them and call into libadns. What follows
1416	pseudo-code only of course:	1518	is pseudo-code only of course. This requires you to either use a low
		1519	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1520	the callbacks for the IO/timeout watchers might not have been called yet.
1417		1521
1418	static ev_io iow [nfd];	1522	static ev_io iow [nfd];
1419	static ev_timer tw;	1523	static ev_timer tw;
1420		1524
1421	static void	1525	static void
1422	io_cb (ev_loop loop, ev_io w, int revents)	1526	io_cb (ev_loop loop, ev_io w, int revents)
1423	{	1527	{
1424	// set the relevant poll flags
1425	// could also call adns_processreadable etc. here
1426	struct pollfd fd = (struct pollfd )w->data;
1427	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1428	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1429	}	1528	}
1430		1529
1431	// create io watchers for each fd and a timer before blocking	1530	// create io watchers for each fd and a timer before blocking
1432	static void	1531	static void
1433	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1532	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1434	{	1533	{
1435	int timeout = 3600000;truct pollfd fds [nfd];	1534	int timeout = 3600000;
		1535	struct pollfd fds [nfd];
1436	// actual code will need to loop here and realloc etc.	1536	// actual code will need to loop here and realloc etc.
1437	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1537	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1438		1538
1439	/* the callback is illegal, but won't be called as we stop during check */	1539	/* the callback is illegal, but won't be called as we stop during check */
1440	ev_timer_init (&tw, 0, timeout * 1e-3);	1540	ev_timer_init (&tw, 0, timeout * 1e-3);
1441	ev_timer_start (loop, &tw);	1541	ev_timer_start (loop, &tw);
1442		1542
1443	// create on ev_io per pollfd	1543	// create one ev_io per pollfd
1444	for (int i = 0; i < nfd; ++i)	1544	for (int i = 0; i < nfd; ++i)
1445	{	1545	{
1446	ev_io_init (iow + i, io_cb, fds [i].fd,	1546	ev_io_init (iow + i, io_cb, fds [i].fd,
1447	((fds [i].events & POLLIN ? EV_READ : 0)	1547	((fds [i].events & POLLIN ? EV_READ : 0)
1448	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1548	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1449		1549
1450	fds [i].revents = 0;	1550	fds [i].revents = 0;
1451	iow [i].data = fds + i;
1452	ev_io_start (loop, iow + i);	1551	ev_io_start (loop, iow + i);
1453	}	1552	}
1454	}	1553	}
1455		1554
1456	// stop all watchers after blocking	1555	// stop all watchers after blocking
…		…
1458	adns_check_cb (ev_loop loop, ev_check w, int revents)	1557	adns_check_cb (ev_loop loop, ev_check w, int revents)
1459	{	1558	{
1460	ev_timer_stop (loop, &tw);	1559	ev_timer_stop (loop, &tw);
1461		1560
1462	for (int i = 0; i < nfd; ++i)	1561	for (int i = 0; i < nfd; ++i)
		1562	{
		1563	// set the relevant poll flags
		1564	// could also call adns_processreadable etc. here
		1565	struct pollfd *fd = fds + i;
		1566	int revents = ev_clear_pending (iow + i);
		1567	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1568	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1569
		1570	// now stop the watcher
1463	ev_io_stop (loop, iow + i);	1571	ev_io_stop (loop, iow + i);
		1572	}
1464		1573
1465	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1574	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1575	}
		1576
		1577	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1578	in the prepare watcher and would dispose of the check watcher.
		1579
		1580	Method 3: If the module to be embedded supports explicit event
		1581	notification (adns does), you can also make use of the actual watcher
		1582	callbacks, and only destroy/create the watchers in the prepare watcher.
		1583
		1584	static void
		1585	timer_cb (EV_P_ ev_timer *w, int revents)
		1586	{
		1587	adns_state ads = (adns_state)w->data;
		1588	update_now (EV_A);
		1589
		1590	adns_processtimeouts (ads, &tv_now);
		1591	}
		1592
		1593	static void
		1594	io_cb (EV_P_ ev_io *w, int revents)
		1595	{
		1596	adns_state ads = (adns_state)w->data;
		1597	update_now (EV_A);
		1598
		1599	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1600	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1601	}
		1602
		1603	// do not ever call adns_afterpoll
		1604
		1605	Method 4: Do not use a prepare or check watcher because the module you
		1606	want to embed is too inflexible to support it. Instead, youc na override
		1607	their poll function. The drawback with this solution is that the main
		1608	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1609	this.
		1610
		1611	static gint
		1612	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1613	{
		1614	int got_events = 0;
		1615
		1616	for (n = 0; n < nfds; ++n)
		1617	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1618
		1619	if (timeout >= 0)
		1620	// create/start timer
		1621
		1622	// poll
		1623	ev_loop (EV_A_ 0);
		1624
		1625	// stop timer again
		1626	if (timeout >= 0)
		1627	ev_timer_stop (EV_A_ &to);
		1628
		1629	// stop io watchers again - their callbacks should have set
		1630	for (n = 0; n < nfds; ++n)
		1631	ev_io_stop (EV_A_ iow [n]);
		1632
		1633	return got_events;
1466	}	1634	}
1467		1635
1468		1636
1469	=head2 C<ev_embed> - when one backend isn't enough...	1637	=head2 C<ev_embed> - when one backend isn't enough...
1470		1638
…		…
1674		1842
1675	To use it,	1843	To use it,
1676		1844
1677	#include <ev++.h>	1845	#include <ev++.h>
1678		1846
1679	(it is not installed by default). This automatically includes F<ev.h>	1847	This automatically includes F<ev.h> and puts all of its definitions (many
1680	and puts all of its definitions (many of them macros) into the global	1848	of them macros) into the global namespace. All C++ specific things are
1681	namespace. All C++ specific things are put into the C<ev> namespace.	1849	put into the C<ev> namespace. It should support all the same embedding
		1850	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1682		1851
1683	It should support all the same embedding options as F<ev.h>, most notably	1852	Care has been taken to keep the overhead low. The only data member the C++
1684	C<EV_MULTIPLICITY>.	1853	classes add (compared to plain C-style watchers) is the event loop pointer
		1854	that the watcher is associated with (or no additional members at all if
		1855	you disable C<EV_MULTIPLICITY> when embedding libev).
		1856
		1857	Currently, functions, and static and non-static member functions can be
		1858	used as callbacks. Other types should be easy to add as long as they only
		1859	need one additional pointer for context. If you need support for other
		1860	types of functors please contact the author (preferably after implementing
		1861	it).
1685		1862
1686	Here is a list of things available in the C<ev> namespace:	1863	Here is a list of things available in the C<ev> namespace:
1687		1864
1688	=over 4	1865	=over 4
1689		1866
…		…
1705		1882
1706	All of those classes have these methods:	1883	All of those classes have these methods:
1707		1884
1708	=over 4	1885	=over 4
1709		1886
1710	=item ev::TYPE::TYPE (object , object::method )	1887	=item ev::TYPE::TYPE ()
1711		1888
1712	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1889	=item ev::TYPE::TYPE (struct ev_loop *)
1713		1890
1714	=item ev::TYPE::~TYPE	1891	=item ev::TYPE::~TYPE
1715		1892
1716	The constructor takes a pointer to an object and a method pointer to	1893	The constructor (optionally) takes an event loop to associate the watcher
1717	the event handler callback to call in this class. The constructor calls	1894	with. If it is omitted, it will use C<EV_DEFAULT>.
1718	C<ev_init> for you, which means you have to call the C<set> method	1895
1719	before starting it. If you do not specify a loop then the constructor	1896	The constructor calls C<ev_init> for you, which means you have to call the
1720	automatically associates the default loop with this watcher.	1897	C<set> method before starting it.
		1898
		1899	It will not set a callback, however: You have to call the templated C<set>
		1900	method to set a callback before you can start the watcher.
		1901
		1902	(The reason why you have to use a method is a limitation in C++ which does
		1903	not allow explicit template arguments for constructors).
1721		1904
1722	The destructor automatically stops the watcher if it is active.	1905	The destructor automatically stops the watcher if it is active.
		1906
		1907	=item w->set<class, &class::method> (object *)
		1908
		1909	This method sets the callback method to call. The method has to have a
		1910	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1911	first argument and the C<revents> as second. The object must be given as
		1912	parameter and is stored in the C<data> member of the watcher.
		1913
		1914	This method synthesizes efficient thunking code to call your method from
		1915	the C callback that libev requires. If your compiler can inline your
		1916	callback (i.e. it is visible to it at the place of the C<set> call and
		1917	your compiler is good :), then the method will be fully inlined into the
		1918	thunking function, making it as fast as a direct C callback.
		1919
		1920	Example: simple class declaration and watcher initialisation
		1921
		1922	struct myclass
		1923	{
		1924	void io_cb (ev::io &w, int revents) { }
		1925	}
		1926
		1927	myclass obj;
		1928	ev::io iow;
		1929	iow.set <myclass, &myclass::io_cb> (&obj);
		1930
		1931	=item w->set<function> (void *data = 0)
		1932
		1933	Also sets a callback, but uses a static method or plain function as
		1934	callback. The optional C<data> argument will be stored in the watcher's
		1935	C<data> member and is free for you to use.
		1936
		1937	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1938
		1939	See the method-C<set> above for more details.
		1940
		1941	Example:
		1942
		1943	static void io_cb (ev::io &w, int revents) { }
		1944	iow.set <io_cb> ();
1723		1945
1724	=item w->set (struct ev_loop *)	1946	=item w->set (struct ev_loop *)
1725		1947
1726	Associates a different C<struct ev_loop> with this watcher. You can only	1948	Associates a different C<struct ev_loop> with this watcher. You can only
1727	do this when the watcher is inactive (and not pending either).	1949	do this when the watcher is inactive (and not pending either).
1728		1950
1729	=item w->set ([args])	1951	=item w->set ([args])
1730		1952
1731	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1953	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1732	called at least once. Unlike the C counterpart, an active watcher gets	1954	called at least once. Unlike the C counterpart, an active watcher gets
1733	automatically stopped and restarted.	1955	automatically stopped and restarted when reconfiguring it with this
		1956	method.
1734		1957
1735	=item w->start ()	1958	=item w->start ()
1736		1959
1737	Starts the watcher. Note that there is no C<loop> argument as the	1960	Starts the watcher. Note that there is no C<loop> argument, as the
1738	constructor already takes the loop.	1961	constructor already stores the event loop.
1739		1962
1740	=item w->stop ()	1963	=item w->stop ()
1741		1964
1742	Stops the watcher if it is active. Again, no C<loop> argument.	1965	Stops the watcher if it is active. Again, no C<loop> argument.
1743		1966
…		…
1768		1991
1769	myclass ();	1992	myclass ();
1770	}	1993	}
1771		1994
1772	myclass::myclass (int fd)	1995	myclass::myclass (int fd)
1773	: io (this, &myclass::io_cb),
1774	idle (this, &myclass::idle_cb)
1775	{	1996	{
		1997	io .set <myclass, &myclass::io_cb > (this);
		1998	idle.set <myclass, &myclass::idle_cb> (this);
		1999
1776	io.start (fd, ev::READ);	2000	io.start (fd, ev::READ);
1777	}	2001	}
1778		2002
1779		2003
1780	=head1 MACRO MAGIC	2004	=head1 MACRO MAGIC
1781		2005
1782	Libev can be compiled with a variety of options, the most fundemantal is	2006	Libev can be compiled with a variety of options, the most fundemantal is
1783	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2007	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1784	callbacks have an initial C<struct ev_loop *> argument.	2008	callbacks have an initial C<struct ev_loop *> argument.
1785		2009
1786	To make it easier to write programs that cope with either variant, the	2010	To make it easier to write programs that cope with either variant, the
1787	following macros are defined:	2011	following macros are defined:
1788		2012
…		…
1821	Similar to the other two macros, this gives you the value of the default	2045	Similar to the other two macros, this gives you the value of the default
1822	loop, if multiple loops are supported ("ev loop default").	2046	loop, if multiple loops are supported ("ev loop default").
1823		2047
1824	=back	2048	=back
1825		2049
1826	Example: Declare and initialise a check watcher, working regardless of	2050	Example: Declare and initialise a check watcher, utilising the above
1827	wether multiple loops are supported or not.	2051	macros so it will work regardless of whether multiple loops are supported
		2052	or not.
1828		2053
1829	static void	2054	static void
1830	check_cb (EV_P_ ev_timer *w, int revents)	2055	check_cb (EV_P_ ev_timer *w, int revents)
1831	{	2056	{
1832	ev_check_stop (EV_A_ w);	2057	ev_check_stop (EV_A_ w);
…		…
1834		2059
1835	ev_check check;	2060	ev_check check;
1836	ev_check_init (&check, check_cb);	2061	ev_check_init (&check, check_cb);
1837	ev_check_start (EV_DEFAULT_ &check);	2062	ev_check_start (EV_DEFAULT_ &check);
1838	ev_loop (EV_DEFAULT_ 0);	2063	ev_loop (EV_DEFAULT_ 0);
1839
1840		2064
1841	=head1 EMBEDDING	2065	=head1 EMBEDDING
1842		2066
1843	Libev can (and often is) directly embedded into host	2067	Libev can (and often is) directly embedded into host
1844	applications. Examples of applications that embed it include the Deliantra	2068	applications. Examples of applications that embed it include the Deliantra
…		…
1884	ev_vars.h	2108	ev_vars.h
1885	ev_wrap.h	2109	ev_wrap.h
1886		2110
1887	ev_win32.c required on win32 platforms only	2111	ev_win32.c required on win32 platforms only
1888		2112
1889	ev_select.c only when select backend is enabled (which is by default)	2113	ev_select.c only when select backend is enabled (which is enabled by default)
1890	ev_poll.c only when poll backend is enabled (disabled by default)	2114	ev_poll.c only when poll backend is enabled (disabled by default)
1891	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2115	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1892	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2116	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1893	ev_port.c only when the solaris port backend is enabled (disabled by default)	2117	ev_port.c only when the solaris port backend is enabled (disabled by default)
1894		2118
…		…
2057	will have the C<struct ev_loop *> as first argument, and you can create	2281	will have the C<struct ev_loop *> as first argument, and you can create
2058	additional independent event loops. Otherwise there will be no support	2282	additional independent event loops. Otherwise there will be no support
2059	for multiple event loops and there is no first event loop pointer	2283	for multiple event loops and there is no first event loop pointer
2060	argument. Instead, all functions act on the single default loop.	2284	argument. Instead, all functions act on the single default loop.
2061		2285
		2286	=item EV_MINPRI
		2287
		2288	=item EV_MAXPRI
		2289
		2290	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2291	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2292	provide for more priorities by overriding those symbols (usually defined
		2293	to be C<-2> and C<2>, respectively).
		2294
		2295	When doing priority-based operations, libev usually has to linearly search
		2296	all the priorities, so having many of them (hundreds) uses a lot of space
		2297	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2298	fine.
		2299
		2300	If your embedding app does not need any priorities, defining these both to
		2301	C<0> will save some memory and cpu.
		2302
2062	=item EV_PERIODIC_ENABLE	2303	=item EV_PERIODIC_ENABLE
2063		2304
2064	If undefined or defined to be C<1>, then periodic timers are supported. If	2305	If undefined or defined to be C<1>, then periodic timers are supported. If
		2306	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2307	code.
		2308
		2309	=item EV_IDLE_ENABLE
		2310
		2311	If undefined or defined to be C<1>, then idle watchers are supported. If
2065	defined to be C<0>, then they are not. Disabling them saves a few kB of	2312	defined to be C<0>, then they are not. Disabling them saves a few kB of
2066	code.	2313	code.
2067		2314
2068	=item EV_EMBED_ENABLE	2315	=item EV_EMBED_ENABLE
2069		2316
…		…
2136	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2383	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2137	will be compiled. It is pretty complex because it provides its own header	2384	will be compiled. It is pretty complex because it provides its own header
2138	file.	2385	file.
2139		2386
2140	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2387	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2141	that everybody includes and which overrides some autoconf choices:	2388	that everybody includes and which overrides some configure choices:
2142		2389
		2390	#define EV_MINIMAL 1
2143	#define EV_USE_POLL 0	2391	#define EV_USE_POLL 0
2144	#define EV_MULTIPLICITY 0	2392	#define EV_MULTIPLICITY 0
2145	#define EV_PERIODICS 0	2393	#define EV_PERIODIC_ENABLE 0
		2394	#define EV_STAT_ENABLE 0
		2395	#define EV_FORK_ENABLE 0
2146	#define EV_CONFIG_H <config.h>	2396	#define EV_CONFIG_H <config.h>
		2397	#define EV_MINPRI 0
		2398	#define EV_MAXPRI 0
2147		2399
2148	#include "ev++.h"	2400	#include "ev++.h"
2149		2401
2150	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2402	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2151		2403
…		…
2157		2409
2158	In this section the complexities of (many of) the algorithms used inside	2410	In this section the complexities of (many of) the algorithms used inside
2159	libev will be explained. For complexity discussions about backends see the	2411	libev will be explained. For complexity discussions about backends see the
2160	documentation for C<ev_default_init>.	2412	documentation for C<ev_default_init>.
2161		2413
		2414	All of the following are about amortised time: If an array needs to be
		2415	extended, libev needs to realloc and move the whole array, but this
		2416	happens asymptotically never with higher number of elements, so O(1) might
		2417	mean it might do a lengthy realloc operation in rare cases, but on average
		2418	it is much faster and asymptotically approaches constant time.
		2419
2162	=over 4	2420	=over 4
2163		2421
2164	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2422	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2165		2423
		2424	This means that, when you have a watcher that triggers in one hour and
		2425	there are 100 watchers that would trigger before that then inserting will
		2426	have to skip those 100 watchers.
		2427
2166	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2428	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2167		2429
		2430	That means that for changing a timer costs less than removing/adding them
		2431	as only the relative motion in the event queue has to be paid for.
		2432
2168	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2433	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2169		2434
		2435	These just add the watcher into an array or at the head of a list.
2170	=item Stopping check/prepare/idle watchers: O(1)	2436	=item Stopping check/prepare/idle watchers: O(1)
2171		2437
2172	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2438	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2173		2439
		2440	These watchers are stored in lists then need to be walked to find the
		2441	correct watcher to remove. The lists are usually short (you don't usually
		2442	have many watchers waiting for the same fd or signal).
		2443
2174	=item Finding the next timer per loop iteration: O(1)	2444	=item Finding the next timer per loop iteration: O(1)
2175		2445
2176	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2446	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2177		2447
		2448	A change means an I/O watcher gets started or stopped, which requires
		2449	libev to recalculate its status (and possibly tell the kernel).
		2450
2178	=item Activating one watcher: O(1)	2451	=item Activating one watcher: O(1)
2179		2452
		2453	=item Priority handling: O(number_of_priorities)
		2454
		2455	Priorities are implemented by allocating some space for each
		2456	priority. When doing priority-based operations, libev usually has to
		2457	linearly search all the priorities.
		2458
2180	=back	2459	=back
2181		2460
2182		2461
2183	=head1 AUTHOR	2462	=head1 AUTHOR
2184		2463

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Comparing libev/ev.pod (file contents): Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC vs. Revision 1.77 by root, Sat Dec 8 22:11:14 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC vs.
Revision 1.77 by root, Sat Dec 8 22:11:14 2007 UTC