[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 1.79 by root, Sun Dec 9 19:46:56 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 API/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 API and ABI version of the library, not
		129	the 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).
866		915
867	=over 4	916	=over 4
868		917
…		…
1028	but on wallclock time (absolute time). You can tell a periodic watcher	1077	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	1078	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 ()	1079	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	1080	+ 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	1081	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	1082	roughly 10 seconds later).
1034	again).
1035		1083
1036	They can also be used to implement vastly more complex timers, such as	1084	They can also be used to implement vastly more complex timers, such as
1037	triggering an event on eahc midnight, local time.	1085	triggering an event on each midnight, local time or other, complicated,
		1086	rules.
1038		1087
1039	As with timers, the callback is guarenteed to be invoked only when the	1088	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	1089	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.	1090	during the same loop iteration then order of execution is undefined.
1042		1091
…		…
1049	Lots of arguments, lets sort it out... There are basically three modes of	1098	Lots of arguments, lets sort it out... There are basically three modes of
1050	operation, and we will explain them from simplest to complex:	1099	operation, and we will explain them from simplest to complex:
1051		1100
1052	=over 4	1101	=over 4
1053		1102
1054	=item * absolute timer (interval = reschedule_cb = 0)	1103	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1055		1104
1056	In this configuration the watcher triggers an event at the wallclock time	1105	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,	1106	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	1107	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.	1108	system time reaches or surpasses this time.
1060		1109
1061	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1110	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1062		1111
1063	In this mode the watcher will always be scheduled to time out at the next	1112	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	1113	C<at + N * interval> time (for some integer N, which can also be negative)
1065	of any time jumps.	1114	and then repeat, regardless of any time jumps.
1066		1115
1067	This can be used to create timers that do not drift with respect to system	1116	This can be used to create timers that do not drift with respect to system
1068	time:	1117	time:
1069		1118
1070	ev_periodic_set (&periodic, 0., 3600., 0);	1119	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1076		1125
1077	Another way to think about it (for the mathematically inclined) is that	1126	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	1127	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.	1128	time where C<time = at (mod interval)>, regardless of any time jumps.
1080		1129
		1130	For numerical stability it is preferable that the C<at> value is near
		1131	C<ev_now ()> (the current time), but there is no range requirement for
		1132	this value.
		1133
1081	=item * manual reschedule mode (reschedule_cb = callback)	1134	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1082		1135
1083	In this mode the values for C<interval> and C<at> are both being	1136	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	1137	ignored. Instead, each time the periodic watcher gets scheduled, the
1085	reschedule callback will be called with the watcher as first, and the	1138	reschedule callback will be called with the watcher as first, and the
1086	current time as second argument.	1139	current time as second argument.
1087		1140
1088	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1141	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,	1142	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	1143	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1091	starting a prepare watcher).	1144	starting an C<ev_prepare> watcher, which is legal).
1092		1145
1093	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1146	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1094	ev_tstamp now)>, e.g.:	1147	ev_tstamp now)>, e.g.:
1095		1148
1096	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1149	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1118		1171
1119	Simply stops and restarts the periodic watcher again. This is only useful	1172	Simply stops and restarts the periodic watcher again. This is only useful
1120	when you changed some parameters or the reschedule callback would return	1173	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	1174	a different time than the last time it was called (e.g. in a crond like
1122	program when the crontabs have changed).	1175	program when the crontabs have changed).
		1176
		1177	=item ev_tstamp offset [read-write]
		1178
		1179	When repeating, this contains the offset value, otherwise this is the
		1180	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1181
		1182	Can be modified any time, but changes only take effect when the periodic
		1183	timer fires or C<ev_periodic_again> is being called.
1123		1184
1124	=item ev_tstamp interval [read-write]	1185	=item ev_tstamp interval [read-write]
1125		1186
1126	The current interval value. Can be modified any time, but changes only	1187	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	1188	take effect when the periodic timer fires or C<ev_periodic_again> is being
…		…
1351	ev_stat_start (loop, &passwd);	1412	ev_stat_start (loop, &passwd);
1352		1413
1353		1414
1354	=head2 C<ev_idle> - when you've got nothing better to do...	1415	=head2 C<ev_idle> - when you've got nothing better to do...
1355		1416
1356	Idle watchers trigger events when there are no other events are pending	1417	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	1418	priority are pending (prepare, check and other idle watchers do not
1358	as your process is busy handling sockets or timeouts (or even signals,	1419	count).
1359	imagine) it will not be triggered. But when your process is idle all idle	1420
1360	watchers are being called again and again, once per event loop iteration -	1421	That is, as long as your process is busy handling sockets or timeouts
		1422	(or even signals, imagine) of the same or higher priority it will not be
		1423	triggered. But when your process is idle (or only lower-priority watchers
		1424	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	1425	iteration - until stopped, that is, or your process receives more events
1362	busy.	1426	and becomes busy again with higher priority stuff.
1363		1427
1364	The most noteworthy effect is that as long as any idle watchers are	1428	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.	1429	active, the process will not block when waiting for new events.
1366		1430
1367	Apart from keeping your process non-blocking (which is a useful	1431	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	1497	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	1498	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	1499	loop from blocking if lower-priority coroutines are active, thus mapping
1436	low-priority coroutines to idle/background tasks).	1500	low-priority coroutines to idle/background tasks).
1437		1501
		1502	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1503	priority, to ensure that they are being run before any other watchers
		1504	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1505	too) should not activate ("feed") events into libev. While libev fully
		1506	supports this, they will be called before other C<ev_check> watchers did
		1507	their job. As C<ev_check> watchers are often used to embed other event
		1508	loops those other event loops might be in an unusable state until their
		1509	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1510	others).
		1511
1438	=over 4	1512	=over 4
1439		1513
1440	=item ev_prepare_init (ev_prepare *, callback)	1514	=item ev_prepare_init (ev_prepare *, callback)
1441		1515
1442	=item ev_check_init (ev_check *, callback)	1516	=item ev_check_init (ev_check *, callback)
…		…
1445	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1519	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.	1520	macros, but using them is utterly, utterly and completely pointless.
1447		1521
1448	=back	1522	=back
1449		1523
1450	Example: To include a library such as adns, you would add IO watchers	1524	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	1525	into libev. Here are some ideas on how to include libadns into libev
		1526	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1527	use for an actually working example. Another Perl module named C<EV::Glib>
		1528	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1529	into the Glib event loop).
		1530
		1531	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	1532	and in a check watcher, destroy them and call into libadns. What follows
1453	pseudo-code only of course:	1533	is pseudo-code only of course. This requires you to either use a low
		1534	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1535	the callbacks for the IO/timeout watchers might not have been called yet.
1454		1536
1455	static ev_io iow [nfd];	1537	static ev_io iow [nfd];
1456	static ev_timer tw;	1538	static ev_timer tw;
1457		1539
1458	static void	1540	static void
1459	io_cb (ev_loop loop, ev_io w, int revents)	1541	io_cb (ev_loop loop, ev_io w, int revents)
1460	{	1542	{
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	}	1543	}
1467		1544
1468	// create io watchers for each fd and a timer before blocking	1545	// create io watchers for each fd and a timer before blocking
1469	static void	1546	static void
1470	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1547	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1476		1553
1477	/* the callback is illegal, but won't be called as we stop during check */	1554	/* the callback is illegal, but won't be called as we stop during check */
1478	ev_timer_init (&tw, 0, timeout * 1e-3);	1555	ev_timer_init (&tw, 0, timeout * 1e-3);
1479	ev_timer_start (loop, &tw);	1556	ev_timer_start (loop, &tw);
1480		1557
1481	// create on ev_io per pollfd	1558	// create one ev_io per pollfd
1482	for (int i = 0; i < nfd; ++i)	1559	for (int i = 0; i < nfd; ++i)
1483	{	1560	{
1484	ev_io_init (iow + i, io_cb, fds [i].fd,	1561	ev_io_init (iow + i, io_cb, fds [i].fd,
1485	((fds [i].events & POLLIN ? EV_READ : 0)	1562	((fds [i].events & POLLIN ? EV_READ : 0)
1486	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1563	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1487		1564
1488	fds [i].revents = 0;	1565	fds [i].revents = 0;
1489	iow [i].data = fds + i;
1490	ev_io_start (loop, iow + i);	1566	ev_io_start (loop, iow + i);
1491	}	1567	}
1492	}	1568	}
1493		1569
1494	// stop all watchers after blocking	1570	// stop all watchers after blocking
…		…
1496	adns_check_cb (ev_loop loop, ev_check w, int revents)	1572	adns_check_cb (ev_loop loop, ev_check w, int revents)
1497	{	1573	{
1498	ev_timer_stop (loop, &tw);	1574	ev_timer_stop (loop, &tw);
1499		1575
1500	for (int i = 0; i < nfd; ++i)	1576	for (int i = 0; i < nfd; ++i)
		1577	{
		1578	// set the relevant poll flags
		1579	// could also call adns_processreadable etc. here
		1580	struct pollfd *fd = fds + i;
		1581	int revents = ev_clear_pending (iow + i);
		1582	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1583	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1584
		1585	// now stop the watcher
1501	ev_io_stop (loop, iow + i);	1586	ev_io_stop (loop, iow + i);
		1587	}
1502		1588
1503	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1589	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1590	}
		1591
		1592	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1593	in the prepare watcher and would dispose of the check watcher.
		1594
		1595	Method 3: If the module to be embedded supports explicit event
		1596	notification (adns does), you can also make use of the actual watcher
		1597	callbacks, and only destroy/create the watchers in the prepare watcher.
		1598
		1599	static void
		1600	timer_cb (EV_P_ ev_timer *w, int revents)
		1601	{
		1602	adns_state ads = (adns_state)w->data;
		1603	update_now (EV_A);
		1604
		1605	adns_processtimeouts (ads, &tv_now);
		1606	}
		1607
		1608	static void
		1609	io_cb (EV_P_ ev_io *w, int revents)
		1610	{
		1611	adns_state ads = (adns_state)w->data;
		1612	update_now (EV_A);
		1613
		1614	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1615	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1616	}
		1617
		1618	// do not ever call adns_afterpoll
		1619
		1620	Method 4: Do not use a prepare or check watcher because the module you
		1621	want to embed is too inflexible to support it. Instead, youc na override
		1622	their poll function. The drawback with this solution is that the main
		1623	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1624	this.
		1625
		1626	static gint
		1627	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1628	{
		1629	int got_events = 0;
		1630
		1631	for (n = 0; n < nfds; ++n)
		1632	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1633
		1634	if (timeout >= 0)
		1635	// create/start timer
		1636
		1637	// poll
		1638	ev_loop (EV_A_ 0);
		1639
		1640	// stop timer again
		1641	if (timeout >= 0)
		1642	ev_timer_stop (EV_A_ &to);
		1643
		1644	// stop io watchers again - their callbacks should have set
		1645	for (n = 0; n < nfds; ++n)
		1646	ev_io_stop (EV_A_ iow [n]);
		1647
		1648	return got_events;
1504	}	1649	}
1505		1650
1506		1651
1507	=head2 C<ev_embed> - when one backend isn't enough...	1652	=head2 C<ev_embed> - when one backend isn't enough...
1508		1653
…		…
1712		1857
1713	To use it,	1858	To use it,
1714		1859
1715	#include <ev++.h>	1860	#include <ev++.h>
1716		1861
1717	(it is not installed by default). This automatically includes F<ev.h>	1862	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	1863	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.	1864	put into the C<ev> namespace. It should support all the same embedding
		1865	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1720		1866
1721	It should support all the same embedding options as F<ev.h>, most notably	1867	Care has been taken to keep the overhead low. The only data member the C++
1722	C<EV_MULTIPLICITY>.	1868	classes add (compared to plain C-style watchers) is the event loop pointer
		1869	that the watcher is associated with (or no additional members at all if
		1870	you disable C<EV_MULTIPLICITY> when embedding libev).
		1871
		1872	Currently, functions, and static and non-static member functions can be
		1873	used as callbacks. Other types should be easy to add as long as they only
		1874	need one additional pointer for context. If you need support for other
		1875	types of functors please contact the author (preferably after implementing
		1876	it).
1723		1877
1724	Here is a list of things available in the C<ev> namespace:	1878	Here is a list of things available in the C<ev> namespace:
1725		1879
1726	=over 4	1880	=over 4
1727		1881
…		…
1743		1897
1744	All of those classes have these methods:	1898	All of those classes have these methods:
1745		1899
1746	=over 4	1900	=over 4
1747		1901
1748	=item ev::TYPE::TYPE (object , object::method )	1902	=item ev::TYPE::TYPE ()
1749		1903
1750	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1904	=item ev::TYPE::TYPE (struct ev_loop *)
1751		1905
1752	=item ev::TYPE::~TYPE	1906	=item ev::TYPE::~TYPE
1753		1907
1754	The constructor takes a pointer to an object and a method pointer to	1908	The constructor (optionally) takes an event loop to associate the watcher
1755	the event handler callback to call in this class. The constructor calls	1909	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	1910
1757	before starting it. If you do not specify a loop then the constructor	1911	The constructor calls C<ev_init> for you, which means you have to call the
1758	automatically associates the default loop with this watcher.	1912	C<set> method before starting it.
		1913
		1914	It will not set a callback, however: You have to call the templated C<set>
		1915	method to set a callback before you can start the watcher.
		1916
		1917	(The reason why you have to use a method is a limitation in C++ which does
		1918	not allow explicit template arguments for constructors).
1759		1919
1760	The destructor automatically stops the watcher if it is active.	1920	The destructor automatically stops the watcher if it is active.
		1921
		1922	=item w->set<class, &class::method> (object *)
		1923
		1924	This method sets the callback method to call. The method has to have a
		1925	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1926	first argument and the C<revents> as second. The object must be given as
		1927	parameter and is stored in the C<data> member of the watcher.
		1928
		1929	This method synthesizes efficient thunking code to call your method from
		1930	the C callback that libev requires. If your compiler can inline your
		1931	callback (i.e. it is visible to it at the place of the C<set> call and
		1932	your compiler is good :), then the method will be fully inlined into the
		1933	thunking function, making it as fast as a direct C callback.
		1934
		1935	Example: simple class declaration and watcher initialisation
		1936
		1937	struct myclass
		1938	{
		1939	void io_cb (ev::io &w, int revents) { }
		1940	}
		1941
		1942	myclass obj;
		1943	ev::io iow;
		1944	iow.set <myclass, &myclass::io_cb> (&obj);
		1945
		1946	=item w->set<function> (void *data = 0)
		1947
		1948	Also sets a callback, but uses a static method or plain function as
		1949	callback. The optional C<data> argument will be stored in the watcher's
		1950	C<data> member and is free for you to use.
		1951
		1952	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1953
		1954	See the method-C<set> above for more details.
		1955
		1956	Example:
		1957
		1958	static void io_cb (ev::io &w, int revents) { }
		1959	iow.set <io_cb> ();
1761		1960
1762	=item w->set (struct ev_loop *)	1961	=item w->set (struct ev_loop *)
1763		1962
1764	Associates a different C<struct ev_loop> with this watcher. You can only	1963	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).	1964	do this when the watcher is inactive (and not pending either).
1766		1965
1767	=item w->set ([args])	1966	=item w->set ([args])
1768		1967
1769	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1968	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	1969	called at least once. Unlike the C counterpart, an active watcher gets
1771	automatically stopped and restarted.	1970	automatically stopped and restarted when reconfiguring it with this
		1971	method.
1772		1972
1773	=item w->start ()	1973	=item w->start ()
1774		1974
1775	Starts the watcher. Note that there is no C<loop> argument as the	1975	Starts the watcher. Note that there is no C<loop> argument, as the
1776	constructor already takes the loop.	1976	constructor already stores the event loop.
1777		1977
1778	=item w->stop ()	1978	=item w->stop ()
1779		1979
1780	Stops the watcher if it is active. Again, no C<loop> argument.	1980	Stops the watcher if it is active. Again, no C<loop> argument.
1781		1981
…		…
1806		2006
1807	myclass ();	2007	myclass ();
1808	}	2008	}
1809		2009
1810	myclass::myclass (int fd)	2010	myclass::myclass (int fd)
1811	: io (this, &myclass::io_cb),
1812	idle (this, &myclass::idle_cb)
1813	{	2011	{
		2012	io .set <myclass, &myclass::io_cb > (this);
		2013	idle.set <myclass, &myclass::idle_cb> (this);
		2014
1814	io.start (fd, ev::READ);	2015	io.start (fd, ev::READ);
1815	}	2016	}
1816		2017
1817		2018
1818	=head1 MACRO MAGIC	2019	=head1 MACRO MAGIC
1819		2020
1820	Libev can be compiled with a variety of options, the most fundemantal is	2021	Libev can be compiled with a variety of options, the most fundemantal is
1821	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2022	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1822	callbacks have an initial C<struct ev_loop *> argument.	2023	callbacks have an initial C<struct ev_loop *> argument.
1823		2024
1824	To make it easier to write programs that cope with either variant, the	2025	To make it easier to write programs that cope with either variant, the
1825	following macros are defined:	2026	following macros are defined:
1826		2027
…		…
1860	loop, if multiple loops are supported ("ev loop default").	2061	loop, if multiple loops are supported ("ev loop default").
1861		2062
1862	=back	2063	=back
1863		2064
1864	Example: Declare and initialise a check watcher, utilising the above	2065	Example: Declare and initialise a check watcher, utilising the above
1865	macros so it will work regardless of wether multiple loops are supported	2066	macros so it will work regardless of whether multiple loops are supported
1866	or not.	2067	or not.
1867		2068
1868	static void	2069	static void
1869	check_cb (EV_P_ ev_timer *w, int revents)	2070	check_cb (EV_P_ ev_timer *w, int revents)
1870	{	2071	{
…		…
2095	will have the C<struct ev_loop *> as first argument, and you can create	2296	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	2297	additional independent event loops. Otherwise there will be no support
2097	for multiple event loops and there is no first event loop pointer	2298	for multiple event loops and there is no first event loop pointer
2098	argument. Instead, all functions act on the single default loop.	2299	argument. Instead, all functions act on the single default loop.
2099		2300
		2301	=item EV_MINPRI
		2302
		2303	=item EV_MAXPRI
		2304
		2305	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2306	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2307	provide for more priorities by overriding those symbols (usually defined
		2308	to be C<-2> and C<2>, respectively).
		2309
		2310	When doing priority-based operations, libev usually has to linearly search
		2311	all the priorities, so having many of them (hundreds) uses a lot of space
		2312	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2313	fine.
		2314
		2315	If your embedding app does not need any priorities, defining these both to
		2316	C<0> will save some memory and cpu.
		2317
2100	=item EV_PERIODIC_ENABLE	2318	=item EV_PERIODIC_ENABLE
2101		2319
2102	If undefined or defined to be C<1>, then periodic timers are supported. If	2320	If undefined or defined to be C<1>, then periodic timers are supported. If
		2321	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2322	code.
		2323
		2324	=item EV_IDLE_ENABLE
		2325
		2326	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	2327	defined to be C<0>, then they are not. Disabling them saves a few kB of
2104	code.	2328	code.
2105		2329
2106	=item EV_EMBED_ENABLE	2330	=item EV_EMBED_ENABLE
2107		2331
…		…
2200		2424
2201	In this section the complexities of (many of) the algorithms used inside	2425	In this section the complexities of (many of) the algorithms used inside
2202	libev will be explained. For complexity discussions about backends see the	2426	libev will be explained. For complexity discussions about backends see the
2203	documentation for C<ev_default_init>.	2427	documentation for C<ev_default_init>.
2204		2428
		2429	All of the following are about amortised time: If an array needs to be
		2430	extended, libev needs to realloc and move the whole array, but this
		2431	happens asymptotically never with higher number of elements, so O(1) might
		2432	mean it might do a lengthy realloc operation in rare cases, but on average
		2433	it is much faster and asymptotically approaches constant time.
		2434
2205	=over 4	2435	=over 4
2206		2436
2207	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2437	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2208		2438
		2439	This means that, when you have a watcher that triggers in one hour and
		2440	there are 100 watchers that would trigger before that then inserting will
		2441	have to skip those 100 watchers.
		2442
2209	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2443	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2210		2444
		2445	That means that for changing a timer costs less than removing/adding them
		2446	as only the relative motion in the event queue has to be paid for.
		2447
2211	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2448	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2212		2449
		2450	These just add the watcher into an array or at the head of a list.
2213	=item Stopping check/prepare/idle watchers: O(1)	2451	=item Stopping check/prepare/idle watchers: O(1)
2214		2452
2215	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2453	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2216		2454
		2455	These watchers are stored in lists then need to be walked to find the
		2456	correct watcher to remove. The lists are usually short (you don't usually
		2457	have many watchers waiting for the same fd or signal).
		2458
2217	=item Finding the next timer per loop iteration: O(1)	2459	=item Finding the next timer per loop iteration: O(1)
2218		2460
2219	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2461	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2220		2462
		2463	A change means an I/O watcher gets started or stopped, which requires
		2464	libev to recalculate its status (and possibly tell the kernel).
		2465
2221	=item Activating one watcher: O(1)	2466	=item Activating one watcher: O(1)
2222		2467
		2468	=item Priority handling: O(number_of_priorities)
		2469
		2470	Priorities are implemented by allocating some space for each
		2471	priority. When doing priority-based operations, libev usually has to
		2472	linearly search all the priorities.
		2473
2223	=back	2474	=back
2224		2475
2225		2476
2226	=head1 AUTHOR	2477	=head1 AUTHOR
2227		2478

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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 1.79 by root, Sun Dec 9 19:46:56 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 1.79 by root, Sun Dec 9 19:46:56 2007 UTC