[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 1.78 by root, Sun Dec 9 19:42:57 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
…		…
482	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
483	usually a better approach for this kind of thing.	487	usually a better approach for this kind of thing.
484		488
485	Here are the gory details of what C<ev_loop> does:	489	Here are the gory details of what C<ev_loop> does:
486		490
		491	- Before the first iteration, call any pending watchers.
487	* If there are no active watchers (reference count is zero), return.	492	* If there are no active watchers (reference count is zero), return.
488	- Queue prepare watchers and then call all outstanding watchers.	493	- Queue all prepare watchers and then call all outstanding watchers.
489	- If we have been forked, recreate the kernel state.	494	- If we have been forked, recreate the kernel state.
490	- Update the kernel state with all outstanding changes.	495	- Update the kernel state with all outstanding changes.
491	- Update the "event loop time".	496	- Update the "event loop time".
492	- Calculate for how long to block.	497	- Calculate for how long to block.
493	- Block the process, waiting for any events.	498	- Block the process, waiting for any events.
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	737	=item bool ev_is_pending (ev_TYPE *watcher)
733		738
734	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
735	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
736	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
737	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
738	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).
739		745
740	=item callback ev_cb (ev_TYPE *watcher)	746	=item callback ev_cb (ev_TYPE *watcher)
741		747
742	Returns the callback currently set on the watcher.	748	Returns the callback currently set on the watcher.
743		749
744	=item ev_cb_set (ev_TYPE *watcher, callback)	750	=item ev_cb_set (ev_TYPE *watcher, callback)
745		751
746	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
747	(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>.
748		794
749	=back	795	=back
750		796
751		797
752	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	798	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
858	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
859	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.
860		906
861	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
862	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
863	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
864	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
865	its own, so its quite safe to use).	911	its own, so its quite safe to use).
866		912
867	=over 4	913	=over 4
868		914
…		…
1028	but on wallclock time (absolute time). You can tell a periodic watcher	1074	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	1075	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 ()	1076	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	1077	+ 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	1078	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	1079	roughly 10 seconds later).
1034	again).
1035		1080
1036	They can also be used to implement vastly more complex timers, such as	1081	They can also be used to implement vastly more complex timers, such as
1037	triggering an event on eahc midnight, local time.	1082	triggering an event on each midnight, local time or other, complicated,
		1083	rules.
1038		1084
1039	As with timers, the callback is guarenteed to be invoked only when the	1085	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	1086	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.	1087	during the same loop iteration then order of execution is undefined.
1042		1088
…		…
1049	Lots of arguments, lets sort it out... There are basically three modes of	1095	Lots of arguments, lets sort it out... There are basically three modes of
1050	operation, and we will explain them from simplest to complex:	1096	operation, and we will explain them from simplest to complex:
1051		1097
1052	=over 4	1098	=over 4
1053		1099
1054	=item * absolute timer (interval = reschedule_cb = 0)	1100	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1055		1101
1056	In this configuration the watcher triggers an event at the wallclock time	1102	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,	1103	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	1104	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.	1105	system time reaches or surpasses this time.
1060		1106
1061	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1107	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1062		1108
1063	In this mode the watcher will always be scheduled to time out at the next	1109	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	1110	C<at + N * interval> time (for some integer N, which can also be negative)
1065	of any time jumps.	1111	and then repeat, regardless of any time jumps.
1066		1112
1067	This can be used to create timers that do not drift with respect to system	1113	This can be used to create timers that do not drift with respect to system
1068	time:	1114	time:
1069		1115
1070	ev_periodic_set (&periodic, 0., 3600., 0);	1116	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1076		1122
1077	Another way to think about it (for the mathematically inclined) is that	1123	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	1124	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.	1125	time where C<time = at (mod interval)>, regardless of any time jumps.
1080		1126
		1127	For numerical stability it is preferable that the C<at> value is near
		1128	C<ev_now ()> (the current time), but there is no range requirement for
		1129	this value.
		1130
1081	=item * manual reschedule mode (reschedule_cb = callback)	1131	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1082		1132
1083	In this mode the values for C<interval> and C<at> are both being	1133	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	1134	ignored. Instead, each time the periodic watcher gets scheduled, the
1085	reschedule callback will be called with the watcher as first, and the	1135	reschedule callback will be called with the watcher as first, and the
1086	current time as second argument.	1136	current time as second argument.
1087		1137
1088	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1138	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,	1139	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	1140	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1091	starting a prepare watcher).	1141	starting an C<ev_prepare> watcher, which is legal).
1092		1142
1093	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1143	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1094	ev_tstamp now)>, e.g.:	1144	ev_tstamp now)>, e.g.:
1095		1145
1096	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1146	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1118		1168
1119	Simply stops and restarts the periodic watcher again. This is only useful	1169	Simply stops and restarts the periodic watcher again. This is only useful
1120	when you changed some parameters or the reschedule callback would return	1170	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	1171	a different time than the last time it was called (e.g. in a crond like
1122	program when the crontabs have changed).	1172	program when the crontabs have changed).
		1173
		1174	=item ev_tstamp offset [read-write]
		1175
		1176	When repeating, this contains the offset value, otherwise this is the
		1177	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1178
		1179	Can be modified any time, but changes only take effect when the periodic
		1180	timer fires or C<ev_periodic_again> is being called.
1123		1181
1124	=item ev_tstamp interval [read-write]	1182	=item ev_tstamp interval [read-write]
1125		1183
1126	The current interval value. Can be modified any time, but changes only	1184	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	1185	take effect when the periodic timer fires or C<ev_periodic_again> is being
…		…
1351	ev_stat_start (loop, &passwd);	1409	ev_stat_start (loop, &passwd);
1352		1410
1353		1411
1354	=head2 C<ev_idle> - when you've got nothing better to do...	1412	=head2 C<ev_idle> - when you've got nothing better to do...
1355		1413
1356	Idle watchers trigger events when there are no other events are pending	1414	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	1415	priority are pending (prepare, check and other idle watchers do not
1358	as your process is busy handling sockets or timeouts (or even signals,	1416	count).
1359	imagine) it will not be triggered. But when your process is idle all idle	1417
1360	watchers are being called again and again, once per event loop iteration -	1418	That is, as long as your process is busy handling sockets or timeouts
		1419	(or even signals, imagine) of the same or higher priority it will not be
		1420	triggered. But when your process is idle (or only lower-priority watchers
		1421	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	1422	iteration - until stopped, that is, or your process receives more events
1362	busy.	1423	and becomes busy again with higher priority stuff.
1363		1424
1364	The most noteworthy effect is that as long as any idle watchers are	1425	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.	1426	active, the process will not block when waiting for new events.
1366		1427
1367	Apart from keeping your process non-blocking (which is a useful	1428	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	1494	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	1495	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	1496	loop from blocking if lower-priority coroutines are active, thus mapping
1436	low-priority coroutines to idle/background tasks).	1497	low-priority coroutines to idle/background tasks).
1437		1498
		1499	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1500	priority, to ensure that they are being run before any other watchers
		1501	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1502	too) should not activate ("feed") events into libev. While libev fully
		1503	supports this, they will be called before other C<ev_check> watchers did
		1504	their job. As C<ev_check> watchers are often used to embed other event
		1505	loops those other event loops might be in an unusable state until their
		1506	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1507	others).
		1508
1438	=over 4	1509	=over 4
1439		1510
1440	=item ev_prepare_init (ev_prepare *, callback)	1511	=item ev_prepare_init (ev_prepare *, callback)
1441		1512
1442	=item ev_check_init (ev_check *, callback)	1513	=item ev_check_init (ev_check *, callback)
…		…
1445	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1516	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.	1517	macros, but using them is utterly, utterly and completely pointless.
1447		1518
1448	=back	1519	=back
1449		1520
1450	Example: To include a library such as adns, you would add IO watchers	1521	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	1522	into libev. Here are some ideas on how to include libadns into libev
		1523	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1524	use for an actually working example. Another Perl module named C<EV::Glib>
		1525	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1526	into the Glib event loop).
		1527
		1528	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	1529	and in a check watcher, destroy them and call into libadns. What follows
1453	pseudo-code only of course:	1530	is pseudo-code only of course. This requires you to either use a low
		1531	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1532	the callbacks for the IO/timeout watchers might not have been called yet.
1454		1533
1455	static ev_io iow [nfd];	1534	static ev_io iow [nfd];
1456	static ev_timer tw;	1535	static ev_timer tw;
1457		1536
1458	static void	1537	static void
1459	io_cb (ev_loop loop, ev_io w, int revents)	1538	io_cb (ev_loop loop, ev_io w, int revents)
1460	{	1539	{
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	}	1540	}
1467		1541
1468	// create io watchers for each fd and a timer before blocking	1542	// create io watchers for each fd and a timer before blocking
1469	static void	1543	static void
1470	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1544	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1476		1550
1477	/* the callback is illegal, but won't be called as we stop during check */	1551	/* the callback is illegal, but won't be called as we stop during check */
1478	ev_timer_init (&tw, 0, timeout * 1e-3);	1552	ev_timer_init (&tw, 0, timeout * 1e-3);
1479	ev_timer_start (loop, &tw);	1553	ev_timer_start (loop, &tw);
1480		1554
1481	// create on ev_io per pollfd	1555	// create one ev_io per pollfd
1482	for (int i = 0; i < nfd; ++i)	1556	for (int i = 0; i < nfd; ++i)
1483	{	1557	{
1484	ev_io_init (iow + i, io_cb, fds [i].fd,	1558	ev_io_init (iow + i, io_cb, fds [i].fd,
1485	((fds [i].events & POLLIN ? EV_READ : 0)	1559	((fds [i].events & POLLIN ? EV_READ : 0)
1486	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1560	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1487		1561
1488	fds [i].revents = 0;	1562	fds [i].revents = 0;
1489	iow [i].data = fds + i;
1490	ev_io_start (loop, iow + i);	1563	ev_io_start (loop, iow + i);
1491	}	1564	}
1492	}	1565	}
1493		1566
1494	// stop all watchers after blocking	1567	// stop all watchers after blocking
…		…
1496	adns_check_cb (ev_loop loop, ev_check w, int revents)	1569	adns_check_cb (ev_loop loop, ev_check w, int revents)
1497	{	1570	{
1498	ev_timer_stop (loop, &tw);	1571	ev_timer_stop (loop, &tw);
1499		1572
1500	for (int i = 0; i < nfd; ++i)	1573	for (int i = 0; i < nfd; ++i)
		1574	{
		1575	// set the relevant poll flags
		1576	// could also call adns_processreadable etc. here
		1577	struct pollfd *fd = fds + i;
		1578	int revents = ev_clear_pending (iow + i);
		1579	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1580	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1581
		1582	// now stop the watcher
1501	ev_io_stop (loop, iow + i);	1583	ev_io_stop (loop, iow + i);
		1584	}
1502		1585
1503	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1586	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1587	}
		1588
		1589	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1590	in the prepare watcher and would dispose of the check watcher.
		1591
		1592	Method 3: If the module to be embedded supports explicit event
		1593	notification (adns does), you can also make use of the actual watcher
		1594	callbacks, and only destroy/create the watchers in the prepare watcher.
		1595
		1596	static void
		1597	timer_cb (EV_P_ ev_timer *w, int revents)
		1598	{
		1599	adns_state ads = (adns_state)w->data;
		1600	update_now (EV_A);
		1601
		1602	adns_processtimeouts (ads, &tv_now);
		1603	}
		1604
		1605	static void
		1606	io_cb (EV_P_ ev_io *w, int revents)
		1607	{
		1608	adns_state ads = (adns_state)w->data;
		1609	update_now (EV_A);
		1610
		1611	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1612	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1613	}
		1614
		1615	// do not ever call adns_afterpoll
		1616
		1617	Method 4: Do not use a prepare or check watcher because the module you
		1618	want to embed is too inflexible to support it. Instead, youc na override
		1619	their poll function. The drawback with this solution is that the main
		1620	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1621	this.
		1622
		1623	static gint
		1624	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1625	{
		1626	int got_events = 0;
		1627
		1628	for (n = 0; n < nfds; ++n)
		1629	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1630
		1631	if (timeout >= 0)
		1632	// create/start timer
		1633
		1634	// poll
		1635	ev_loop (EV_A_ 0);
		1636
		1637	// stop timer again
		1638	if (timeout >= 0)
		1639	ev_timer_stop (EV_A_ &to);
		1640
		1641	// stop io watchers again - their callbacks should have set
		1642	for (n = 0; n < nfds; ++n)
		1643	ev_io_stop (EV_A_ iow [n]);
		1644
		1645	return got_events;
1504	}	1646	}
1505		1647
1506		1648
1507	=head2 C<ev_embed> - when one backend isn't enough...	1649	=head2 C<ev_embed> - when one backend isn't enough...
1508		1650
…		…
1712		1854
1713	To use it,	1855	To use it,
1714		1856
1715	#include <ev++.h>	1857	#include <ev++.h>
1716		1858
1717	(it is not installed by default). This automatically includes F<ev.h>	1859	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	1860	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.	1861	put into the C<ev> namespace. It should support all the same embedding
		1862	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1720		1863
1721	It should support all the same embedding options as F<ev.h>, most notably	1864	Care has been taken to keep the overhead low. The only data member the C++
1722	C<EV_MULTIPLICITY>.	1865	classes add (compared to plain C-style watchers) is the event loop pointer
		1866	that the watcher is associated with (or no additional members at all if
		1867	you disable C<EV_MULTIPLICITY> when embedding libev).
		1868
		1869	Currently, functions, and static and non-static member functions can be
		1870	used as callbacks. Other types should be easy to add as long as they only
		1871	need one additional pointer for context. If you need support for other
		1872	types of functors please contact the author (preferably after implementing
		1873	it).
1723		1874
1724	Here is a list of things available in the C<ev> namespace:	1875	Here is a list of things available in the C<ev> namespace:
1725		1876
1726	=over 4	1877	=over 4
1727		1878
…		…
1743		1894
1744	All of those classes have these methods:	1895	All of those classes have these methods:
1745		1896
1746	=over 4	1897	=over 4
1747		1898
1748	=item ev::TYPE::TYPE (object , object::method )	1899	=item ev::TYPE::TYPE ()
1749		1900
1750	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1901	=item ev::TYPE::TYPE (struct ev_loop *)
1751		1902
1752	=item ev::TYPE::~TYPE	1903	=item ev::TYPE::~TYPE
1753		1904
1754	The constructor takes a pointer to an object and a method pointer to	1905	The constructor (optionally) takes an event loop to associate the watcher
1755	the event handler callback to call in this class. The constructor calls	1906	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	1907
1757	before starting it. If you do not specify a loop then the constructor	1908	The constructor calls C<ev_init> for you, which means you have to call the
1758	automatically associates the default loop with this watcher.	1909	C<set> method before starting it.
		1910
		1911	It will not set a callback, however: You have to call the templated C<set>
		1912	method to set a callback before you can start the watcher.
		1913
		1914	(The reason why you have to use a method is a limitation in C++ which does
		1915	not allow explicit template arguments for constructors).
1759		1916
1760	The destructor automatically stops the watcher if it is active.	1917	The destructor automatically stops the watcher if it is active.
		1918
		1919	=item w->set<class, &class::method> (object *)
		1920
		1921	This method sets the callback method to call. The method has to have a
		1922	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1923	first argument and the C<revents> as second. The object must be given as
		1924	parameter and is stored in the C<data> member of the watcher.
		1925
		1926	This method synthesizes efficient thunking code to call your method from
		1927	the C callback that libev requires. If your compiler can inline your
		1928	callback (i.e. it is visible to it at the place of the C<set> call and
		1929	your compiler is good :), then the method will be fully inlined into the
		1930	thunking function, making it as fast as a direct C callback.
		1931
		1932	Example: simple class declaration and watcher initialisation
		1933
		1934	struct myclass
		1935	{
		1936	void io_cb (ev::io &w, int revents) { }
		1937	}
		1938
		1939	myclass obj;
		1940	ev::io iow;
		1941	iow.set <myclass, &myclass::io_cb> (&obj);
		1942
		1943	=item w->set<function> (void *data = 0)
		1944
		1945	Also sets a callback, but uses a static method or plain function as
		1946	callback. The optional C<data> argument will be stored in the watcher's
		1947	C<data> member and is free for you to use.
		1948
		1949	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1950
		1951	See the method-C<set> above for more details.
		1952
		1953	Example:
		1954
		1955	static void io_cb (ev::io &w, int revents) { }
		1956	iow.set <io_cb> ();
1761		1957
1762	=item w->set (struct ev_loop *)	1958	=item w->set (struct ev_loop *)
1763		1959
1764	Associates a different C<struct ev_loop> with this watcher. You can only	1960	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).	1961	do this when the watcher is inactive (and not pending either).
1766		1962
1767	=item w->set ([args])	1963	=item w->set ([args])
1768		1964
1769	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1965	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	1966	called at least once. Unlike the C counterpart, an active watcher gets
1771	automatically stopped and restarted.	1967	automatically stopped and restarted when reconfiguring it with this
		1968	method.
1772		1969
1773	=item w->start ()	1970	=item w->start ()
1774		1971
1775	Starts the watcher. Note that there is no C<loop> argument as the	1972	Starts the watcher. Note that there is no C<loop> argument, as the
1776	constructor already takes the loop.	1973	constructor already stores the event loop.
1777		1974
1778	=item w->stop ()	1975	=item w->stop ()
1779		1976
1780	Stops the watcher if it is active. Again, no C<loop> argument.	1977	Stops the watcher if it is active. Again, no C<loop> argument.
1781		1978
…		…
1806		2003
1807	myclass ();	2004	myclass ();
1808	}	2005	}
1809		2006
1810	myclass::myclass (int fd)	2007	myclass::myclass (int fd)
1811	: io (this, &myclass::io_cb),
1812	idle (this, &myclass::idle_cb)
1813	{	2008	{
		2009	io .set <myclass, &myclass::io_cb > (this);
		2010	idle.set <myclass, &myclass::idle_cb> (this);
		2011
1814	io.start (fd, ev::READ);	2012	io.start (fd, ev::READ);
1815	}	2013	}
1816		2014
1817		2015
1818	=head1 MACRO MAGIC	2016	=head1 MACRO MAGIC
1819		2017
1820	Libev can be compiled with a variety of options, the most fundemantal is	2018	Libev can be compiled with a variety of options, the most fundemantal is
1821	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2019	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1822	callbacks have an initial C<struct ev_loop *> argument.	2020	callbacks have an initial C<struct ev_loop *> argument.
1823		2021
1824	To make it easier to write programs that cope with either variant, the	2022	To make it easier to write programs that cope with either variant, the
1825	following macros are defined:	2023	following macros are defined:
1826		2024
…		…
1860	loop, if multiple loops are supported ("ev loop default").	2058	loop, if multiple loops are supported ("ev loop default").
1861		2059
1862	=back	2060	=back
1863		2061
1864	Example: Declare and initialise a check watcher, utilising the above	2062	Example: Declare and initialise a check watcher, utilising the above
1865	macros so it will work regardless of wether multiple loops are supported	2063	macros so it will work regardless of whether multiple loops are supported
1866	or not.	2064	or not.
1867		2065
1868	static void	2066	static void
1869	check_cb (EV_P_ ev_timer *w, int revents)	2067	check_cb (EV_P_ ev_timer *w, int revents)
1870	{	2068	{
…		…
2095	will have the C<struct ev_loop *> as first argument, and you can create	2293	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	2294	additional independent event loops. Otherwise there will be no support
2097	for multiple event loops and there is no first event loop pointer	2295	for multiple event loops and there is no first event loop pointer
2098	argument. Instead, all functions act on the single default loop.	2296	argument. Instead, all functions act on the single default loop.
2099		2297
		2298	=item EV_MINPRI
		2299
		2300	=item EV_MAXPRI
		2301
		2302	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2303	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2304	provide for more priorities by overriding those symbols (usually defined
		2305	to be C<-2> and C<2>, respectively).
		2306
		2307	When doing priority-based operations, libev usually has to linearly search
		2308	all the priorities, so having many of them (hundreds) uses a lot of space
		2309	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2310	fine.
		2311
		2312	If your embedding app does not need any priorities, defining these both to
		2313	C<0> will save some memory and cpu.
		2314
2100	=item EV_PERIODIC_ENABLE	2315	=item EV_PERIODIC_ENABLE
2101		2316
2102	If undefined or defined to be C<1>, then periodic timers are supported. If	2317	If undefined or defined to be C<1>, then periodic timers are supported. If
		2318	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2319	code.
		2320
		2321	=item EV_IDLE_ENABLE
		2322
		2323	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	2324	defined to be C<0>, then they are not. Disabling them saves a few kB of
2104	code.	2325	code.
2105		2326
2106	=item EV_EMBED_ENABLE	2327	=item EV_EMBED_ENABLE
2107		2328
…		…
2200		2421
2201	In this section the complexities of (many of) the algorithms used inside	2422	In this section the complexities of (many of) the algorithms used inside
2202	libev will be explained. For complexity discussions about backends see the	2423	libev will be explained. For complexity discussions about backends see the
2203	documentation for C<ev_default_init>.	2424	documentation for C<ev_default_init>.
2204		2425
		2426	All of the following are about amortised time: If an array needs to be
		2427	extended, libev needs to realloc and move the whole array, but this
		2428	happens asymptotically never with higher number of elements, so O(1) might
		2429	mean it might do a lengthy realloc operation in rare cases, but on average
		2430	it is much faster and asymptotically approaches constant time.
		2431
2205	=over 4	2432	=over 4
2206		2433
2207	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2434	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2208		2435
		2436	This means that, when you have a watcher that triggers in one hour and
		2437	there are 100 watchers that would trigger before that then inserting will
		2438	have to skip those 100 watchers.
		2439
2209	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2440	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2210		2441
		2442	That means that for changing a timer costs less than removing/adding them
		2443	as only the relative motion in the event queue has to be paid for.
		2444
2211	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2445	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2212		2446
		2447	These just add the watcher into an array or at the head of a list.
2213	=item Stopping check/prepare/idle watchers: O(1)	2448	=item Stopping check/prepare/idle watchers: O(1)
2214		2449
2215	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2450	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2216		2451
		2452	These watchers are stored in lists then need to be walked to find the
		2453	correct watcher to remove. The lists are usually short (you don't usually
		2454	have many watchers waiting for the same fd or signal).
		2455
2217	=item Finding the next timer per loop iteration: O(1)	2456	=item Finding the next timer per loop iteration: O(1)
2218		2457
2219	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2458	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2220		2459
		2460	A change means an I/O watcher gets started or stopped, which requires
		2461	libev to recalculate its status (and possibly tell the kernel).
		2462
2221	=item Activating one watcher: O(1)	2463	=item Activating one watcher: O(1)
2222		2464
		2465	=item Priority handling: O(number_of_priorities)
		2466
		2467	Priorities are implemented by allocating some space for each
		2468	priority. When doing priority-based operations, libev usually has to
		2469	linearly search all the priorities.
		2470
2223	=back	2471	=back
2224		2472
2225		2473
2226	=head1 AUTHOR	2474	=head1 AUTHOR
2227		2475

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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 1.78 by root, Sun Dec 9 19:42:57 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 1.78 by root, Sun Dec 9 19:42:57 2007 UTC