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

Comparing libev/ev.pod (file contents):
Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs.
Revision 1.81 by root, Wed Dec 12 04:53:58 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
…		…
113		117
114	=item int ev_version_major ()	118	=item int ev_version_major ()
115		119
116	=item int ev_version_minor ()	120	=item int ev_version_minor ()
117		121
118	You can find out the major and minor version numbers of the library	122	You can find out the major and minor ABI version numbers of the library
119	you linked against by calling the functions C<ev_version_major> and	123	you linked against by calling the functions C<ev_version_major> and
120	C<ev_version_minor>. If you want, you can compare against the global	124	C<ev_version_minor>. If you want, you can compare against the global
121	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
122	version of the library your program was compiled against.	126	version of the library your program was compiled against.
123		127
		128	These version numbers refer to the ABI version of the library, not the
		129	release version.
		130
124	Usually, it's a good idea to terminate if the major versions mismatch,	131	Usually, it's a good idea to terminate if the major versions mismatch,
125	as this indicates an incompatible change. Minor versions are usually	132	as this indicates an incompatible change. Minor versions are usually
126	compatible to older versions, so a larger minor version alone is usually	133	compatible to older versions, so a larger minor version alone is usually
127	not a problem.	134	not a problem.
128		135
129	Example: Make sure we haven't accidentally been linked against the wrong	136	Example: Make sure we haven't accidentally been linked against the wrong
130	version.	137	version.
…		…
482	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
483	usually a better approach for this kind of thing.	490	usually a better approach for this kind of thing.
484		491
485	Here are the gory details of what C<ev_loop> does:	492	Here are the gory details of what C<ev_loop> does:
486		493
		494	- Before the first iteration, call any pending watchers.
487	* If there are no active watchers (reference count is zero), return.	495	* If there are no active watchers (reference count is zero), return.
488	- Queue prepare watchers and then call all outstanding watchers.	496	- Queue all prepare watchers and then call all outstanding watchers.
489	- If we have been forked, recreate the kernel state.	497	- If we have been forked, recreate the kernel state.
490	- Update the kernel state with all outstanding changes.	498	- Update the kernel state with all outstanding changes.
491	- Update the "event loop time".	499	- Update the "event loop time".
492	- Calculate for how long to block.	500	- Calculate for how long to block.
493	- Block the process, waiting for any events.	501	- Block the process, waiting for any events.
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	740	=item bool ev_is_pending (ev_TYPE *watcher)
733		741
734	Returns a true value iff the watcher is pending, (i.e. it has outstanding	742	Returns a true value iff the watcher is pending, (i.e. it has outstanding
735	events but its callback has not yet been invoked). As long as a watcher	743	events but its callback has not yet been invoked). As long as a watcher
736	is pending (but not active) you must not call an init function on it (but	744	is pending (but not active) you must not call an init function on it (but
737	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	745	C<ev_TYPE_set> is safe), you must not change its priority, and you must
738	libev (e.g. you cnanot C<free ()> it).	746	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		747	it).
739		748
740	=item callback ev_cb (ev_TYPE *watcher)	749	=item callback ev_cb (ev_TYPE *watcher)
741		750
742	Returns the callback currently set on the watcher.	751	Returns the callback currently set on the watcher.
743		752
744	=item ev_cb_set (ev_TYPE *watcher, callback)	753	=item ev_cb_set (ev_TYPE *watcher, callback)
745		754
746	Change the callback. You can change the callback at virtually any time	755	Change the callback. You can change the callback at virtually any time
747	(modulo threads).	756	(modulo threads).
		757
		758	=item ev_set_priority (ev_TYPE *watcher, priority)
		759
		760	=item int ev_priority (ev_TYPE *watcher)
		761
		762	Set and query the priority of the watcher. The priority is a small
		763	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		764	(default: C<-2>). Pending watchers with higher priority will be invoked
		765	before watchers with lower priority, but priority will not keep watchers
		766	from being executed (except for C<ev_idle> watchers).
		767
		768	This means that priorities are I<only> used for ordering callback
		769	invocation after new events have been received. This is useful, for
		770	example, to reduce latency after idling, or more often, to bind two
		771	watchers on the same event and make sure one is called first.
		772
		773	If you need to suppress invocation when higher priority events are pending
		774	you need to look at C<ev_idle> watchers, which provide this functionality.
		775
		776	You I<must not> change the priority of a watcher as long as it is active or
		777	pending.
		778
		779	The default priority used by watchers when no priority has been set is
		780	always C<0>, which is supposed to not be too high and not be too low :).
		781
		782	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		783	fine, as long as you do not mind that the priority value you query might
		784	or might not have been adjusted to be within valid range.
		785
		786	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		787
		788	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		789	C<loop> nor C<revents> need to be valid as long as the watcher callback
		790	can deal with that fact.
		791
		792	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		793
		794	If the watcher is pending, this function returns clears its pending status
		795	and returns its C<revents> bitset (as if its callback was invoked). If the
		796	watcher isn't pending it does nothing and returns C<0>.
748		797
749	=back	798	=back
750		799
751		800
752	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
858	it is best to always use non-blocking I/O: An extra C<read>(2) returning	907	it is best to always use non-blocking I/O: An extra C<read>(2) returning
859	C<EAGAIN> is far preferable to a program hanging until some data arrives.	908	C<EAGAIN> is far preferable to a program hanging until some data arrives.
860		909
861	If you cannot run the fd in non-blocking mode (for example you should not	910	If you cannot run the fd in non-blocking mode (for example you should not
862	play around with an Xlib connection), then you have to seperately re-test	911	play around with an Xlib connection), then you have to seperately re-test
863	wether a file descriptor is really ready with a known-to-be good interface	912	whether a file descriptor is really ready with a known-to-be good interface
864	such as poll (fortunately in our Xlib example, Xlib already does this on	913	such as poll (fortunately in our Xlib example, Xlib already does this on
865	its own, so its quite safe to use).	914	its own, so its quite safe to use).
		915
		916	=head3 The special problem of disappearing file descriptors
		917
		918	Some backends (e.g kqueue, epoll) need to be told about closing a file
		919	descriptor (either by calling C<close> explicitly or by any other means,
		920	such as C<dup>). The reason is that you register interest in some file
		921	descriptor, but when it goes away, the operating system will silently drop
		922	this interest. If another file descriptor with the same number then is
		923	registered with libev, there is no efficient way to see that this is, in
		924	fact, a different file descriptor.
		925
		926	To avoid having to explicitly tell libev about such cases, libev follows
		927	the following policy: Each time C<ev_io_set> is being called, libev
		928	will assume that this is potentially a new file descriptor, otherwise
		929	it is assumed that the file descriptor stays the same. That means that
		930	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		931	descriptor even if the file descriptor number itself did not change.
		932
		933	This is how one would do it normally anyway, the important point is that
		934	the libev application should not optimise around libev but should leave
		935	optimisations to libev.
		936
866		937
867	=over 4	938	=over 4
868		939
869	=item ev_io_init (ev_io *, callback, int fd, int events)	940	=item ev_io_init (ev_io *, callback, int fd, int events)
870		941
…		…
1028	but on wallclock time (absolute time). You can tell a periodic watcher	1099	but on wallclock time (absolute time). You can tell a periodic watcher
1029	to trigger "at" some specific point in time. For example, if you tell a	1100	to trigger "at" some specific point in time. For example, if you tell a
1030	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1101	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1031	+ 10.>) and then reset your system clock to the last year, then it will	1102	+ 10.>) and then reset your system clock to the last year, then it will
1032	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1103	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1033	roughly 10 seconds later and of course not if you reset your system time	1104	roughly 10 seconds later).
1034	again).
1035		1105
1036	They can also be used to implement vastly more complex timers, such as	1106	They can also be used to implement vastly more complex timers, such as
1037	triggering an event on eahc midnight, local time.	1107	triggering an event on each midnight, local time or other, complicated,
		1108	rules.
1038		1109
1039	As with timers, the callback is guarenteed to be invoked only when the	1110	As with timers, the callback is guarenteed to be invoked only when the
1040	time (C<at>) has been passed, but if multiple periodic timers become ready	1111	time (C<at>) has been passed, but if multiple periodic timers become ready
1041	during the same loop iteration then order of execution is undefined.	1112	during the same loop iteration then order of execution is undefined.
1042		1113
…		…
1049	Lots of arguments, lets sort it out... There are basically three modes of	1120	Lots of arguments, lets sort it out... There are basically three modes of
1050	operation, and we will explain them from simplest to complex:	1121	operation, and we will explain them from simplest to complex:
1051		1122
1052	=over 4	1123	=over 4
1053		1124
1054	=item * absolute timer (interval = reschedule_cb = 0)	1125	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1055		1126
1056	In this configuration the watcher triggers an event at the wallclock time	1127	In this configuration the watcher triggers an event at the wallclock time
1057	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1128	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1058	that is, if it is to be run at January 1st 2011 then it will run when the	1129	that is, if it is to be run at January 1st 2011 then it will run when the
1059	system time reaches or surpasses this time.	1130	system time reaches or surpasses this time.
1060		1131
1061	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1132	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1062		1133
1063	In this mode the watcher will always be scheduled to time out at the next	1134	In this mode the watcher will always be scheduled to time out at the next
1064	C<at + N * interval> time (for some integer N) and then repeat, regardless	1135	C<at + N * interval> time (for some integer N, which can also be negative)
1065	of any time jumps.	1136	and then repeat, regardless of any time jumps.
1066		1137
1067	This can be used to create timers that do not drift with respect to system	1138	This can be used to create timers that do not drift with respect to system
1068	time:	1139	time:
1069		1140
1070	ev_periodic_set (&periodic, 0., 3600., 0);	1141	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1076		1147
1077	Another way to think about it (for the mathematically inclined) is that	1148	Another way to think about it (for the mathematically inclined) is that
1078	C<ev_periodic> will try to run the callback in this mode at the next possible	1149	C<ev_periodic> will try to run the callback in this mode at the next possible
1079	time where C<time = at (mod interval)>, regardless of any time jumps.	1150	time where C<time = at (mod interval)>, regardless of any time jumps.
1080		1151
		1152	For numerical stability it is preferable that the C<at> value is near
		1153	C<ev_now ()> (the current time), but there is no range requirement for
		1154	this value.
		1155
1081	=item * manual reschedule mode (reschedule_cb = callback)	1156	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1082		1157
1083	In this mode the values for C<interval> and C<at> are both being	1158	In this mode the values for C<interval> and C<at> are both being
1084	ignored. Instead, each time the periodic watcher gets scheduled, the	1159	ignored. Instead, each time the periodic watcher gets scheduled, the
1085	reschedule callback will be called with the watcher as first, and the	1160	reschedule callback will be called with the watcher as first, and the
1086	current time as second argument.	1161	current time as second argument.
1087		1162
1088	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1163	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1089	ever, or make any event loop modifications>. If you need to stop it,	1164	ever, or make any event loop modifications>. If you need to stop it,
1090	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1165	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1091	starting a prepare watcher).	1166	starting an C<ev_prepare> watcher, which is legal).
1092		1167
1093	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1168	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1094	ev_tstamp now)>, e.g.:	1169	ev_tstamp now)>, e.g.:
1095		1170
1096	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1171	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1118		1193
1119	Simply stops and restarts the periodic watcher again. This is only useful	1194	Simply stops and restarts the periodic watcher again. This is only useful
1120	when you changed some parameters or the reschedule callback would return	1195	when you changed some parameters or the reschedule callback would return
1121	a different time than the last time it was called (e.g. in a crond like	1196	a different time than the last time it was called (e.g. in a crond like
1122	program when the crontabs have changed).	1197	program when the crontabs have changed).
		1198
		1199	=item ev_tstamp offset [read-write]
		1200
		1201	When repeating, this contains the offset value, otherwise this is the
		1202	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1203
		1204	Can be modified any time, but changes only take effect when the periodic
		1205	timer fires or C<ev_periodic_again> is being called.
1123		1206
1124	=item ev_tstamp interval [read-write]	1207	=item ev_tstamp interval [read-write]
1125		1208
1126	The current interval value. Can be modified any time, but changes only	1209	The current interval value. Can be modified any time, but changes only
1127	take effect when the periodic timer fires or C<ev_periodic_again> is being	1210	take effect when the periodic timer fires or C<ev_periodic_again> is being
…		…
1351	ev_stat_start (loop, &passwd);	1434	ev_stat_start (loop, &passwd);
1352		1435
1353		1436
1354	=head2 C<ev_idle> - when you've got nothing better to do...	1437	=head2 C<ev_idle> - when you've got nothing better to do...
1355		1438
1356	Idle watchers trigger events when there are no other events are pending	1439	Idle watchers trigger events when no other events of the same or higher
1357	(prepare, check and other idle watchers do not count). That is, as long	1440	priority are pending (prepare, check and other idle watchers do not
1358	as your process is busy handling sockets or timeouts (or even signals,	1441	count).
1359	imagine) it will not be triggered. But when your process is idle all idle	1442
1360	watchers are being called again and again, once per event loop iteration -	1443	That is, as long as your process is busy handling sockets or timeouts
		1444	(or even signals, imagine) of the same or higher priority it will not be
		1445	triggered. But when your process is idle (or only lower-priority watchers
		1446	are pending), the idle watchers are being called once per event loop
1361	until stopped, that is, or your process receives more events and becomes	1447	iteration - until stopped, that is, or your process receives more events
1362	busy.	1448	and becomes busy again with higher priority stuff.
1363		1449
1364	The most noteworthy effect is that as long as any idle watchers are	1450	The most noteworthy effect is that as long as any idle watchers are
1365	active, the process will not block when waiting for new events.	1451	active, the process will not block when waiting for new events.
1366		1452
1367	Apart from keeping your process non-blocking (which is a useful	1453	Apart from keeping your process non-blocking (which is a useful
…		…
1433	with priority higher than or equal to the event loop and one coroutine	1519	with priority higher than or equal to the event loop and one coroutine
1434	of lower priority, but only once, using idle watchers to keep the event	1520	of lower priority, but only once, using idle watchers to keep the event
1435	loop from blocking if lower-priority coroutines are active, thus mapping	1521	loop from blocking if lower-priority coroutines are active, thus mapping
1436	low-priority coroutines to idle/background tasks).	1522	low-priority coroutines to idle/background tasks).
1437		1523
		1524	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1525	priority, to ensure that they are being run before any other watchers
		1526	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1527	too) should not activate ("feed") events into libev. While libev fully
		1528	supports this, they will be called before other C<ev_check> watchers did
		1529	their job. As C<ev_check> watchers are often used to embed other event
		1530	loops those other event loops might be in an unusable state until their
		1531	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1532	others).
		1533
1438	=over 4	1534	=over 4
1439		1535
1440	=item ev_prepare_init (ev_prepare *, callback)	1536	=item ev_prepare_init (ev_prepare *, callback)
1441		1537
1442	=item ev_check_init (ev_check *, callback)	1538	=item ev_check_init (ev_check *, callback)
…		…
1445	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1541	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1446	macros, but using them is utterly, utterly and completely pointless.	1542	macros, but using them is utterly, utterly and completely pointless.
1447		1543
1448	=back	1544	=back
1449		1545
1450	Example: To include a library such as adns, you would add IO watchers	1546	There are a number of principal ways to embed other event loops or modules
1451	and a timeout watcher in a prepare handler, as required by libadns, and	1547	into libev. Here are some ideas on how to include libadns into libev
		1548	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1549	use for an actually working example. Another Perl module named C<EV::Glib>
		1550	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1551	into the Glib event loop).
		1552
		1553	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1452	in a check watcher, destroy them and call into libadns. What follows is	1554	and in a check watcher, destroy them and call into libadns. What follows
1453	pseudo-code only of course:	1555	is pseudo-code only of course. This requires you to either use a low
		1556	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1557	the callbacks for the IO/timeout watchers might not have been called yet.
1454		1558
1455	static ev_io iow [nfd];	1559	static ev_io iow [nfd];
1456	static ev_timer tw;	1560	static ev_timer tw;
1457		1561
1458	static void	1562	static void
1459	io_cb (ev_loop loop, ev_io w, int revents)	1563	io_cb (ev_loop loop, ev_io w, int revents)
1460	{	1564	{
1461	// set the relevant poll flags
1462	// could also call adns_processreadable etc. here
1463	struct pollfd fd = (struct pollfd )w->data;
1464	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1465	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1466	}	1565	}
1467		1566
1468	// create io watchers for each fd and a timer before blocking	1567	// create io watchers for each fd and a timer before blocking
1469	static void	1568	static void
1470	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1569	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1476		1575
1477	/* the callback is illegal, but won't be called as we stop during check */	1576	/* the callback is illegal, but won't be called as we stop during check */
1478	ev_timer_init (&tw, 0, timeout * 1e-3);	1577	ev_timer_init (&tw, 0, timeout * 1e-3);
1479	ev_timer_start (loop, &tw);	1578	ev_timer_start (loop, &tw);
1480		1579
1481	// create on ev_io per pollfd	1580	// create one ev_io per pollfd
1482	for (int i = 0; i < nfd; ++i)	1581	for (int i = 0; i < nfd; ++i)
1483	{	1582	{
1484	ev_io_init (iow + i, io_cb, fds [i].fd,	1583	ev_io_init (iow + i, io_cb, fds [i].fd,
1485	((fds [i].events & POLLIN ? EV_READ : 0)	1584	((fds [i].events & POLLIN ? EV_READ : 0)
1486	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1585	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1487		1586
1488	fds [i].revents = 0;	1587	fds [i].revents = 0;
1489	iow [i].data = fds + i;
1490	ev_io_start (loop, iow + i);	1588	ev_io_start (loop, iow + i);
1491	}	1589	}
1492	}	1590	}
1493		1591
1494	// stop all watchers after blocking	1592	// stop all watchers after blocking
…		…
1496	adns_check_cb (ev_loop loop, ev_check w, int revents)	1594	adns_check_cb (ev_loop loop, ev_check w, int revents)
1497	{	1595	{
1498	ev_timer_stop (loop, &tw);	1596	ev_timer_stop (loop, &tw);
1499		1597
1500	for (int i = 0; i < nfd; ++i)	1598	for (int i = 0; i < nfd; ++i)
		1599	{
		1600	// set the relevant poll flags
		1601	// could also call adns_processreadable etc. here
		1602	struct pollfd *fd = fds + i;
		1603	int revents = ev_clear_pending (iow + i);
		1604	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1605	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1606
		1607	// now stop the watcher
1501	ev_io_stop (loop, iow + i);	1608	ev_io_stop (loop, iow + i);
		1609	}
1502		1610
1503	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1611	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1612	}
		1613
		1614	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1615	in the prepare watcher and would dispose of the check watcher.
		1616
		1617	Method 3: If the module to be embedded supports explicit event
		1618	notification (adns does), you can also make use of the actual watcher
		1619	callbacks, and only destroy/create the watchers in the prepare watcher.
		1620
		1621	static void
		1622	timer_cb (EV_P_ ev_timer *w, int revents)
		1623	{
		1624	adns_state ads = (adns_state)w->data;
		1625	update_now (EV_A);
		1626
		1627	adns_processtimeouts (ads, &tv_now);
		1628	}
		1629
		1630	static void
		1631	io_cb (EV_P_ ev_io *w, int revents)
		1632	{
		1633	adns_state ads = (adns_state)w->data;
		1634	update_now (EV_A);
		1635
		1636	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1637	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1638	}
		1639
		1640	// do not ever call adns_afterpoll
		1641
		1642	Method 4: Do not use a prepare or check watcher because the module you
		1643	want to embed is too inflexible to support it. Instead, youc na override
		1644	their poll function. The drawback with this solution is that the main
		1645	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1646	this.
		1647
		1648	static gint
		1649	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1650	{
		1651	int got_events = 0;
		1652
		1653	for (n = 0; n < nfds; ++n)
		1654	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1655
		1656	if (timeout >= 0)
		1657	// create/start timer
		1658
		1659	// poll
		1660	ev_loop (EV_A_ 0);
		1661
		1662	// stop timer again
		1663	if (timeout >= 0)
		1664	ev_timer_stop (EV_A_ &to);
		1665
		1666	// stop io watchers again - their callbacks should have set
		1667	for (n = 0; n < nfds; ++n)
		1668	ev_io_stop (EV_A_ iow [n]);
		1669
		1670	return got_events;
1504	}	1671	}
1505		1672
1506		1673
1507	=head2 C<ev_embed> - when one backend isn't enough...	1674	=head2 C<ev_embed> - when one backend isn't enough...
1508		1675
…		…
1712		1879
1713	To use it,	1880	To use it,
1714		1881
1715	#include <ev++.h>	1882	#include <ev++.h>
1716		1883
1717	(it is not installed by default). This automatically includes F<ev.h>	1884	This automatically includes F<ev.h> and puts all of its definitions (many
1718	and puts all of its definitions (many of them macros) into the global	1885	of them macros) into the global namespace. All C++ specific things are
1719	namespace. All C++ specific things are put into the C<ev> namespace.	1886	put into the C<ev> namespace. It should support all the same embedding
		1887	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1720		1888
1721	It should support all the same embedding options as F<ev.h>, most notably	1889	Care has been taken to keep the overhead low. The only data member the C++
1722	C<EV_MULTIPLICITY>.	1890	classes add (compared to plain C-style watchers) is the event loop pointer
		1891	that the watcher is associated with (or no additional members at all if
		1892	you disable C<EV_MULTIPLICITY> when embedding libev).
		1893
		1894	Currently, functions, and static and non-static member functions can be
		1895	used as callbacks. Other types should be easy to add as long as they only
		1896	need one additional pointer for context. If you need support for other
		1897	types of functors please contact the author (preferably after implementing
		1898	it).
1723		1899
1724	Here is a list of things available in the C<ev> namespace:	1900	Here is a list of things available in the C<ev> namespace:
1725		1901
1726	=over 4	1902	=over 4
1727		1903
…		…
1743		1919
1744	All of those classes have these methods:	1920	All of those classes have these methods:
1745		1921
1746	=over 4	1922	=over 4
1747		1923
1748	=item ev::TYPE::TYPE (object , object::method )	1924	=item ev::TYPE::TYPE ()
1749		1925
1750	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1926	=item ev::TYPE::TYPE (struct ev_loop *)
1751		1927
1752	=item ev::TYPE::~TYPE	1928	=item ev::TYPE::~TYPE
1753		1929
1754	The constructor takes a pointer to an object and a method pointer to	1930	The constructor (optionally) takes an event loop to associate the watcher
1755	the event handler callback to call in this class. The constructor calls	1931	with. If it is omitted, it will use C<EV_DEFAULT>.
1756	C<ev_init> for you, which means you have to call the C<set> method	1932
1757	before starting it. If you do not specify a loop then the constructor	1933	The constructor calls C<ev_init> for you, which means you have to call the
1758	automatically associates the default loop with this watcher.	1934	C<set> method before starting it.
		1935
		1936	It will not set a callback, however: You have to call the templated C<set>
		1937	method to set a callback before you can start the watcher.
		1938
		1939	(The reason why you have to use a method is a limitation in C++ which does
		1940	not allow explicit template arguments for constructors).
1759		1941
1760	The destructor automatically stops the watcher if it is active.	1942	The destructor automatically stops the watcher if it is active.
		1943
		1944	=item w->set<class, &class::method> (object *)
		1945
		1946	This method sets the callback method to call. The method has to have a
		1947	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1948	first argument and the C<revents> as second. The object must be given as
		1949	parameter and is stored in the C<data> member of the watcher.
		1950
		1951	This method synthesizes efficient thunking code to call your method from
		1952	the C callback that libev requires. If your compiler can inline your
		1953	callback (i.e. it is visible to it at the place of the C<set> call and
		1954	your compiler is good :), then the method will be fully inlined into the
		1955	thunking function, making it as fast as a direct C callback.
		1956
		1957	Example: simple class declaration and watcher initialisation
		1958
		1959	struct myclass
		1960	{
		1961	void io_cb (ev::io &w, int revents) { }
		1962	}
		1963
		1964	myclass obj;
		1965	ev::io iow;
		1966	iow.set <myclass, &myclass::io_cb> (&obj);
		1967
		1968	=item w->set<function> (void *data = 0)
		1969
		1970	Also sets a callback, but uses a static method or plain function as
		1971	callback. The optional C<data> argument will be stored in the watcher's
		1972	C<data> member and is free for you to use.
		1973
		1974	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1975
		1976	See the method-C<set> above for more details.
		1977
		1978	Example:
		1979
		1980	static void io_cb (ev::io &w, int revents) { }
		1981	iow.set <io_cb> ();
1761		1982
1762	=item w->set (struct ev_loop *)	1983	=item w->set (struct ev_loop *)
1763		1984
1764	Associates a different C<struct ev_loop> with this watcher. You can only	1985	Associates a different C<struct ev_loop> with this watcher. You can only
1765	do this when the watcher is inactive (and not pending either).	1986	do this when the watcher is inactive (and not pending either).
1766		1987
1767	=item w->set ([args])	1988	=item w->set ([args])
1768		1989
1769	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1990	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1770	called at least once. Unlike the C counterpart, an active watcher gets	1991	called at least once. Unlike the C counterpart, an active watcher gets
1771	automatically stopped and restarted.	1992	automatically stopped and restarted when reconfiguring it with this
		1993	method.
1772		1994
1773	=item w->start ()	1995	=item w->start ()
1774		1996
1775	Starts the watcher. Note that there is no C<loop> argument as the	1997	Starts the watcher. Note that there is no C<loop> argument, as the
1776	constructor already takes the loop.	1998	constructor already stores the event loop.
1777		1999
1778	=item w->stop ()	2000	=item w->stop ()
1779		2001
1780	Stops the watcher if it is active. Again, no C<loop> argument.	2002	Stops the watcher if it is active. Again, no C<loop> argument.
1781		2003
…		…
1806		2028
1807	myclass ();	2029	myclass ();
1808	}	2030	}
1809		2031
1810	myclass::myclass (int fd)	2032	myclass::myclass (int fd)
1811	: io (this, &myclass::io_cb),
1812	idle (this, &myclass::idle_cb)
1813	{	2033	{
		2034	io .set <myclass, &myclass::io_cb > (this);
		2035	idle.set <myclass, &myclass::idle_cb> (this);
		2036
1814	io.start (fd, ev::READ);	2037	io.start (fd, ev::READ);
1815	}	2038	}
1816		2039
1817		2040
1818	=head1 MACRO MAGIC	2041	=head1 MACRO MAGIC
1819		2042
1820	Libev can be compiled with a variety of options, the most fundemantal is	2043	Libev can be compiled with a variety of options, the most fundemantal is
1821	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2044	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1822	callbacks have an initial C<struct ev_loop *> argument.	2045	callbacks have an initial C<struct ev_loop *> argument.
1823		2046
1824	To make it easier to write programs that cope with either variant, the	2047	To make it easier to write programs that cope with either variant, the
1825	following macros are defined:	2048	following macros are defined:
1826		2049
…		…
1860	loop, if multiple loops are supported ("ev loop default").	2083	loop, if multiple loops are supported ("ev loop default").
1861		2084
1862	=back	2085	=back
1863		2086
1864	Example: Declare and initialise a check watcher, utilising the above	2087	Example: Declare and initialise a check watcher, utilising the above
1865	macros so it will work regardless of wether multiple loops are supported	2088	macros so it will work regardless of whether multiple loops are supported
1866	or not.	2089	or not.
1867		2090
1868	static void	2091	static void
1869	check_cb (EV_P_ ev_timer *w, int revents)	2092	check_cb (EV_P_ ev_timer *w, int revents)
1870	{	2093	{
…		…
2095	will have the C<struct ev_loop *> as first argument, and you can create	2318	will have the C<struct ev_loop *> as first argument, and you can create
2096	additional independent event loops. Otherwise there will be no support	2319	additional independent event loops. Otherwise there will be no support
2097	for multiple event loops and there is no first event loop pointer	2320	for multiple event loops and there is no first event loop pointer
2098	argument. Instead, all functions act on the single default loop.	2321	argument. Instead, all functions act on the single default loop.
2099		2322
		2323	=item EV_MINPRI
		2324
		2325	=item EV_MAXPRI
		2326
		2327	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2328	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2329	provide for more priorities by overriding those symbols (usually defined
		2330	to be C<-2> and C<2>, respectively).
		2331
		2332	When doing priority-based operations, libev usually has to linearly search
		2333	all the priorities, so having many of them (hundreds) uses a lot of space
		2334	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2335	fine.
		2336
		2337	If your embedding app does not need any priorities, defining these both to
		2338	C<0> will save some memory and cpu.
		2339
2100	=item EV_PERIODIC_ENABLE	2340	=item EV_PERIODIC_ENABLE
2101		2341
2102	If undefined or defined to be C<1>, then periodic timers are supported. If	2342	If undefined or defined to be C<1>, then periodic timers are supported. If
		2343	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2344	code.
		2345
		2346	=item EV_IDLE_ENABLE
		2347
		2348	If undefined or defined to be C<1>, then idle watchers are supported. If
2103	defined to be C<0>, then they are not. Disabling them saves a few kB of	2349	defined to be C<0>, then they are not. Disabling them saves a few kB of
2104	code.	2350	code.
2105		2351
2106	=item EV_EMBED_ENABLE	2352	=item EV_EMBED_ENABLE
2107		2353
…		…
2200		2446
2201	In this section the complexities of (many of) the algorithms used inside	2447	In this section the complexities of (many of) the algorithms used inside
2202	libev will be explained. For complexity discussions about backends see the	2448	libev will be explained. For complexity discussions about backends see the
2203	documentation for C<ev_default_init>.	2449	documentation for C<ev_default_init>.
2204		2450
		2451	All of the following are about amortised time: If an array needs to be
		2452	extended, libev needs to realloc and move the whole array, but this
		2453	happens asymptotically never with higher number of elements, so O(1) might
		2454	mean it might do a lengthy realloc operation in rare cases, but on average
		2455	it is much faster and asymptotically approaches constant time.
		2456
2205	=over 4	2457	=over 4
2206		2458
2207	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2459	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2208		2460
		2461	This means that, when you have a watcher that triggers in one hour and
		2462	there are 100 watchers that would trigger before that then inserting will
		2463	have to skip those 100 watchers.
		2464
2209	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2465	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2210		2466
		2467	That means that for changing a timer costs less than removing/adding them
		2468	as only the relative motion in the event queue has to be paid for.
		2469
2211	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2470	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2212		2471
		2472	These just add the watcher into an array or at the head of a list.
2213	=item Stopping check/prepare/idle watchers: O(1)	2473	=item Stopping check/prepare/idle watchers: O(1)
2214		2474
2215	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2475	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2216		2476
		2477	These watchers are stored in lists then need to be walked to find the
		2478	correct watcher to remove. The lists are usually short (you don't usually
		2479	have many watchers waiting for the same fd or signal).
		2480
2217	=item Finding the next timer per loop iteration: O(1)	2481	=item Finding the next timer per loop iteration: O(1)
2218		2482
2219	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2483	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2220		2484
		2485	A change means an I/O watcher gets started or stopped, which requires
		2486	libev to recalculate its status (and possibly tell the kernel).
		2487
2221	=item Activating one watcher: O(1)	2488	=item Activating one watcher: O(1)
2222		2489
		2490	=item Priority handling: O(number_of_priorities)
		2491
		2492	Priorities are implemented by allocating some space for each
		2493	priority. When doing priority-based operations, libev usually has to
		2494	linearly search all the priorities.
		2495
2223	=back	2496	=back
2224		2497
2225		2498
2226	=head1 AUTHOR	2499	=head1 AUTHOR
2227		2500

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Comparing libev/ev.pod (file contents): Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs. Revision 1.81 by root, Wed Dec 12 04:53:58 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs.
Revision 1.81 by root, Wed Dec 12 04:53:58 2007 UTC