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

Comparing libev/ev.pod (file contents):
Revision 1.68 by root, Fri Dec 7 18:09:43 2007 UTC vs.
Revision 1.85 by root, Mon Dec 17 07:24:12 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
…		…
762	watchers on the same event and make sure one is called first.	771	watchers on the same event and make sure one is called first.
763		772
764	If you need to suppress invocation when higher priority events are pending	773	If you need to suppress invocation when higher priority events are pending
765	you need to look at C<ev_idle> watchers, which provide this functionality.	774	you need to look at C<ev_idle> watchers, which provide this functionality.
766		775
		776	You I<must not> change the priority of a watcher as long as it is active or
		777	pending.
		778
767	The default priority used by watchers when no priority has been set is	779	The default priority used by watchers when no priority has been set is
768	always C<0>, which is supposed to not be too high and not be too low :).	780	always C<0>, which is supposed to not be too high and not be too low :).
769		781
770	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	782	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
771	fine, as long as you do not mind that the priority value you query might	783	fine, as long as you do not mind that the priority value you query might
772	or might not have been adjusted to be within valid range.	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>.
773		797
774	=back	798	=back
775		799
776		800
777	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
887	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
888	whether 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
889	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
890	its own, so its quite safe to use).	914	its own, so its quite safe to use).
891		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
		937
		938	=head3 Watcher-Specific Functions
		939
892	=over 4	940	=over 4
893		941
894	=item ev_io_init (ev_io *, callback, int fd, int events)	942	=item ev_io_init (ev_io *, callback, int fd, int events)
895		943
896	=item ev_io_set (ev_io *, int fd, int events)	944	=item ev_io_set (ev_io *, int fd, int events)
…		…
948	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	996	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
949		997
950	The callback is guarenteed to be invoked only when its timeout has passed,	998	The callback is guarenteed to be invoked only when its timeout has passed,
951	but if multiple timers become ready during the same loop iteration then	999	but if multiple timers become ready during the same loop iteration then
952	order of execution is undefined.	1000	order of execution is undefined.
		1001
		1002	=head3 Watcher-Specific Functions and Data Members
953		1003
954	=over 4	1004	=over 4
955		1005
956	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1006	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
957		1007
…		…
1053	but on wallclock time (absolute time). You can tell a periodic watcher	1103	but on wallclock time (absolute time). You can tell a periodic watcher
1054	to trigger "at" some specific point in time. For example, if you tell a	1104	to trigger "at" some specific point in time. For example, if you tell a
1055	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1105	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1056	+ 10.>) and then reset your system clock to the last year, then it will	1106	+ 10.>) and then reset your system clock to the last year, then it will
1057	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1107	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1058	roughly 10 seconds later and of course not if you reset your system time	1108	roughly 10 seconds later).
1059	again).
1060		1109
1061	They can also be used to implement vastly more complex timers, such as	1110	They can also be used to implement vastly more complex timers, such as
1062	triggering an event on eahc midnight, local time.	1111	triggering an event on each midnight, local time or other, complicated,
		1112	rules.
1063		1113
1064	As with timers, the callback is guarenteed to be invoked only when the	1114	As with timers, the callback is guarenteed to be invoked only when the
1065	time (C<at>) has been passed, but if multiple periodic timers become ready	1115	time (C<at>) has been passed, but if multiple periodic timers become ready
1066	during the same loop iteration then order of execution is undefined.	1116	during the same loop iteration then order of execution is undefined.
1067		1117
		1118	=head3 Watcher-Specific Functions and Data Members
		1119
1068	=over 4	1120	=over 4
1069		1121
1070	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1122	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1071		1123
1072	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1124	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1074	Lots of arguments, lets sort it out... There are basically three modes of	1126	Lots of arguments, lets sort it out... There are basically three modes of
1075	operation, and we will explain them from simplest to complex:	1127	operation, and we will explain them from simplest to complex:
1076		1128
1077	=over 4	1129	=over 4
1078		1130
1079	=item * absolute timer (interval = reschedule_cb = 0)	1131	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1080		1132
1081	In this configuration the watcher triggers an event at the wallclock time	1133	In this configuration the watcher triggers an event at the wallclock time
1082	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1134	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1083	that is, if it is to be run at January 1st 2011 then it will run when the	1135	that is, if it is to be run at January 1st 2011 then it will run when the
1084	system time reaches or surpasses this time.	1136	system time reaches or surpasses this time.
1085		1137
1086	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1138	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1087		1139
1088	In this mode the watcher will always be scheduled to time out at the next	1140	In this mode the watcher will always be scheduled to time out at the next
1089	C<at + N * interval> time (for some integer N) and then repeat, regardless	1141	C<at + N * interval> time (for some integer N, which can also be negative)
1090	of any time jumps.	1142	and then repeat, regardless of any time jumps.
1091		1143
1092	This can be used to create timers that do not drift with respect to system	1144	This can be used to create timers that do not drift with respect to system
1093	time:	1145	time:
1094		1146
1095	ev_periodic_set (&periodic, 0., 3600., 0);	1147	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1101		1153
1102	Another way to think about it (for the mathematically inclined) is that	1154	Another way to think about it (for the mathematically inclined) is that
1103	C<ev_periodic> will try to run the callback in this mode at the next possible	1155	C<ev_periodic> will try to run the callback in this mode at the next possible
1104	time where C<time = at (mod interval)>, regardless of any time jumps.	1156	time where C<time = at (mod interval)>, regardless of any time jumps.
1105		1157
		1158	For numerical stability it is preferable that the C<at> value is near
		1159	C<ev_now ()> (the current time), but there is no range requirement for
		1160	this value.
		1161
1106	=item * manual reschedule mode (reschedule_cb = callback)	1162	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1107		1163
1108	In this mode the values for C<interval> and C<at> are both being	1164	In this mode the values for C<interval> and C<at> are both being
1109	ignored. Instead, each time the periodic watcher gets scheduled, the	1165	ignored. Instead, each time the periodic watcher gets scheduled, the
1110	reschedule callback will be called with the watcher as first, and the	1166	reschedule callback will be called with the watcher as first, and the
1111	current time as second argument.	1167	current time as second argument.
1112		1168
1113	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1169	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1114	ever, or make any event loop modifications>. If you need to stop it,	1170	ever, or make any event loop modifications>. If you need to stop it,
1115	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1171	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1116	starting a prepare watcher).	1172	starting an C<ev_prepare> watcher, which is legal).
1117		1173
1118	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1174	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1119	ev_tstamp now)>, e.g.:	1175	ev_tstamp now)>, e.g.:
1120		1176
1121	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1177	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1144	Simply stops and restarts the periodic watcher again. This is only useful	1200	Simply stops and restarts the periodic watcher again. This is only useful
1145	when you changed some parameters or the reschedule callback would return	1201	when you changed some parameters or the reschedule callback would return
1146	a different time than the last time it was called (e.g. in a crond like	1202	a different time than the last time it was called (e.g. in a crond like
1147	program when the crontabs have changed).	1203	program when the crontabs have changed).
1148		1204
		1205	=item ev_tstamp offset [read-write]
		1206
		1207	When repeating, this contains the offset value, otherwise this is the
		1208	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1209
		1210	Can be modified any time, but changes only take effect when the periodic
		1211	timer fires or C<ev_periodic_again> is being called.
		1212
1149	=item ev_tstamp interval [read-write]	1213	=item ev_tstamp interval [read-write]
1150		1214
1151	The current interval value. Can be modified any time, but changes only	1215	The current interval value. Can be modified any time, but changes only
1152	take effect when the periodic timer fires or C<ev_periodic_again> is being	1216	take effect when the periodic timer fires or C<ev_periodic_again> is being
1153	called.	1217	called.
…		…
1155	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1219	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
1156		1220
1157	The current reschedule callback, or C<0>, if this functionality is	1221	The current reschedule callback, or C<0>, if this functionality is
1158	switched off. Can be changed any time, but changes only take effect when	1222	switched off. Can be changed any time, but changes only take effect when
1159	the periodic timer fires or C<ev_periodic_again> is being called.	1223	the periodic timer fires or C<ev_periodic_again> is being called.
		1224
		1225	=item ev_tstamp at [read-only]
		1226
		1227	When active, contains the absolute time that the watcher is supposed to
		1228	trigger next.
1160		1229
1161	=back	1230	=back
1162		1231
1163	Example: Call a callback every hour, or, more precisely, whenever the	1232	Example: Call a callback every hour, or, more precisely, whenever the
1164	system clock is divisible by 3600. The callback invocation times have	1233	system clock is divisible by 3600. The callback invocation times have
…		…
1206	with the kernel (thus it coexists with your own signal handlers as long	1275	with the kernel (thus it coexists with your own signal handlers as long
1207	as you don't register any with libev). Similarly, when the last signal	1276	as you don't register any with libev). Similarly, when the last signal
1208	watcher for a signal is stopped libev will reset the signal handler to	1277	watcher for a signal is stopped libev will reset the signal handler to
1209	SIG_DFL (regardless of what it was set to before).	1278	SIG_DFL (regardless of what it was set to before).
1210		1279
		1280	=head3 Watcher-Specific Functions and Data Members
		1281
1211	=over 4	1282	=over 4
1212		1283
1213	=item ev_signal_init (ev_signal *, callback, int signum)	1284	=item ev_signal_init (ev_signal *, callback, int signum)
1214		1285
1215	=item ev_signal_set (ev_signal *, int signum)	1286	=item ev_signal_set (ev_signal *, int signum)
…		…
1226		1297
1227	=head2 C<ev_child> - watch out for process status changes	1298	=head2 C<ev_child> - watch out for process status changes
1228		1299
1229	Child watchers trigger when your process receives a SIGCHLD in response to	1300	Child watchers trigger when your process receives a SIGCHLD in response to
1230	some child status changes (most typically when a child of yours dies).	1301	some child status changes (most typically when a child of yours dies).
		1302
		1303	=head3 Watcher-Specific Functions and Data Members
1231		1304
1232	=over 4	1305	=over 4
1233		1306
1234	=item ev_child_init (ev_child *, callback, int pid)	1307	=item ev_child_init (ev_child *, callback, int pid)
1235		1308
…		…
1303	reader). Inotify will be used to give hints only and should not change the	1376	reader). Inotify will be used to give hints only and should not change the
1304	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1377	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1305	to fall back to regular polling again even with inotify, but changes are	1378	to fall back to regular polling again even with inotify, but changes are
1306	usually detected immediately, and if the file exists there will be no	1379	usually detected immediately, and if the file exists there will be no
1307	polling.	1380	polling.
		1381
		1382	=head3 Watcher-Specific Functions and Data Members
1308		1383
1309	=over 4	1384	=over 4
1310		1385
1311	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1386	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1312		1387
…		…
1395	Apart from keeping your process non-blocking (which is a useful	1470	Apart from keeping your process non-blocking (which is a useful
1396	effect on its own sometimes), idle watchers are a good place to do	1471	effect on its own sometimes), idle watchers are a good place to do
1397	"pseudo-background processing", or delay processing stuff to after the	1472	"pseudo-background processing", or delay processing stuff to after the
1398	event loop has handled all outstanding events.	1473	event loop has handled all outstanding events.
1399		1474
		1475	=head3 Watcher-Specific Functions and Data Members
		1476
1400	=over 4	1477	=over 4
1401		1478
1402	=item ev_idle_init (ev_signal *, callback)	1479	=item ev_idle_init (ev_signal *, callback)
1403		1480
1404	Initialises and configures the idle watcher - it has no parameters of any	1481	Initialises and configures the idle watcher - it has no parameters of any
…		…
1461	with priority higher than or equal to the event loop and one coroutine	1538	with priority higher than or equal to the event loop and one coroutine
1462	of lower priority, but only once, using idle watchers to keep the event	1539	of lower priority, but only once, using idle watchers to keep the event
1463	loop from blocking if lower-priority coroutines are active, thus mapping	1540	loop from blocking if lower-priority coroutines are active, thus mapping
1464	low-priority coroutines to idle/background tasks).	1541	low-priority coroutines to idle/background tasks).
1465		1542
		1543	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1544	priority, to ensure that they are being run before any other watchers
		1545	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1546	too) should not activate ("feed") events into libev. While libev fully
		1547	supports this, they will be called before other C<ev_check> watchers did
		1548	their job. As C<ev_check> watchers are often used to embed other event
		1549	loops those other event loops might be in an unusable state until their
		1550	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1551	others).
		1552
		1553	=head3 Watcher-Specific Functions and Data Members
		1554
1466	=over 4	1555	=over 4
1467		1556
1468	=item ev_prepare_init (ev_prepare *, callback)	1557	=item ev_prepare_init (ev_prepare *, callback)
1469		1558
1470	=item ev_check_init (ev_check *, callback)	1559	=item ev_check_init (ev_check *, callback)
…		…
1473	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1562	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1474	macros, but using them is utterly, utterly and completely pointless.	1563	macros, but using them is utterly, utterly and completely pointless.
1475		1564
1476	=back	1565	=back
1477		1566
1478	Example: To include a library such as adns, you would add IO watchers	1567	There are a number of principal ways to embed other event loops or modules
1479	and a timeout watcher in a prepare handler, as required by libadns, and	1568	into libev. Here are some ideas on how to include libadns into libev
		1569	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1570	use for an actually working example. Another Perl module named C<EV::Glib>
		1571	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1572	into the Glib event loop).
		1573
		1574	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1480	in a check watcher, destroy them and call into libadns. What follows is	1575	and in a check watcher, destroy them and call into libadns. What follows
1481	pseudo-code only of course:	1576	is pseudo-code only of course. This requires you to either use a low
		1577	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1578	the callbacks for the IO/timeout watchers might not have been called yet.
1482		1579
1483	static ev_io iow [nfd];	1580	static ev_io iow [nfd];
1484	static ev_timer tw;	1581	static ev_timer tw;
1485		1582
1486	static void	1583	static void
1487	io_cb (ev_loop loop, ev_io w, int revents)	1584	io_cb (ev_loop loop, ev_io w, int revents)
1488	{	1585	{
1489	// set the relevant poll flags
1490	// could also call adns_processreadable etc. here
1491	struct pollfd fd = (struct pollfd )w->data;
1492	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1493	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1494	}	1586	}
1495		1587
1496	// create io watchers for each fd and a timer before blocking	1588	// create io watchers for each fd and a timer before blocking
1497	static void	1589	static void
1498	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1590	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1504		1596
1505	/* the callback is illegal, but won't be called as we stop during check */	1597	/* the callback is illegal, but won't be called as we stop during check */
1506	ev_timer_init (&tw, 0, timeout * 1e-3);	1598	ev_timer_init (&tw, 0, timeout * 1e-3);
1507	ev_timer_start (loop, &tw);	1599	ev_timer_start (loop, &tw);
1508		1600
1509	// create on ev_io per pollfd	1601	// create one ev_io per pollfd
1510	for (int i = 0; i < nfd; ++i)	1602	for (int i = 0; i < nfd; ++i)
1511	{	1603	{
1512	ev_io_init (iow + i, io_cb, fds [i].fd,	1604	ev_io_init (iow + i, io_cb, fds [i].fd,
1513	((fds [i].events & POLLIN ? EV_READ : 0)	1605	((fds [i].events & POLLIN ? EV_READ : 0)
1514	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1606	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1515		1607
1516	fds [i].revents = 0;	1608	fds [i].revents = 0;
1517	iow [i].data = fds + i;
1518	ev_io_start (loop, iow + i);	1609	ev_io_start (loop, iow + i);
1519	}	1610	}
1520	}	1611	}
1521		1612
1522	// stop all watchers after blocking	1613	// stop all watchers after blocking
…		…
1524	adns_check_cb (ev_loop loop, ev_check w, int revents)	1615	adns_check_cb (ev_loop loop, ev_check w, int revents)
1525	{	1616	{
1526	ev_timer_stop (loop, &tw);	1617	ev_timer_stop (loop, &tw);
1527		1618
1528	for (int i = 0; i < nfd; ++i)	1619	for (int i = 0; i < nfd; ++i)
		1620	{
		1621	// set the relevant poll flags
		1622	// could also call adns_processreadable etc. here
		1623	struct pollfd *fd = fds + i;
		1624	int revents = ev_clear_pending (iow + i);
		1625	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1626	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1627
		1628	// now stop the watcher
1529	ev_io_stop (loop, iow + i);	1629	ev_io_stop (loop, iow + i);
		1630	}
1530		1631
1531	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1632	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1633	}
		1634
		1635	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1636	in the prepare watcher and would dispose of the check watcher.
		1637
		1638	Method 3: If the module to be embedded supports explicit event
		1639	notification (adns does), you can also make use of the actual watcher
		1640	callbacks, and only destroy/create the watchers in the prepare watcher.
		1641
		1642	static void
		1643	timer_cb (EV_P_ ev_timer *w, int revents)
		1644	{
		1645	adns_state ads = (adns_state)w->data;
		1646	update_now (EV_A);
		1647
		1648	adns_processtimeouts (ads, &tv_now);
		1649	}
		1650
		1651	static void
		1652	io_cb (EV_P_ ev_io *w, int revents)
		1653	{
		1654	adns_state ads = (adns_state)w->data;
		1655	update_now (EV_A);
		1656
		1657	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1658	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1659	}
		1660
		1661	// do not ever call adns_afterpoll
		1662
		1663	Method 4: Do not use a prepare or check watcher because the module you
		1664	want to embed is too inflexible to support it. Instead, youc na override
		1665	their poll function. The drawback with this solution is that the main
		1666	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1667	this.
		1668
		1669	static gint
		1670	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1671	{
		1672	int got_events = 0;
		1673
		1674	for (n = 0; n < nfds; ++n)
		1675	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1676
		1677	if (timeout >= 0)
		1678	// create/start timer
		1679
		1680	// poll
		1681	ev_loop (EV_A_ 0);
		1682
		1683	// stop timer again
		1684	if (timeout >= 0)
		1685	ev_timer_stop (EV_A_ &to);
		1686
		1687	// stop io watchers again - their callbacks should have set
		1688	for (n = 0; n < nfds; ++n)
		1689	ev_io_stop (EV_A_ iow [n]);
		1690
		1691	return got_events;
1532	}	1692	}
1533		1693
1534		1694
1535	=head2 C<ev_embed> - when one backend isn't enough...	1695	=head2 C<ev_embed> - when one backend isn't enough...
1536		1696
…		…
1600	ev_embed_start (loop_hi, &embed);	1760	ev_embed_start (loop_hi, &embed);
1601	}	1761	}
1602	else	1762	else
1603	loop_lo = loop_hi;	1763	loop_lo = loop_hi;
1604		1764
		1765	=head3 Watcher-Specific Functions and Data Members
		1766
1605	=over 4	1767	=over 4
1606		1768
1607	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1769	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1608		1770
1609	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	1771	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
…		…
1635	event loop blocks next and before C<ev_check> watchers are being called,	1797	event loop blocks next and before C<ev_check> watchers are being called,
1636	and only in the child after the fork. If whoever good citizen calling	1798	and only in the child after the fork. If whoever good citizen calling
1637	C<ev_default_fork> cheats and calls it in the wrong process, the fork	1799	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1638	handlers will be invoked, too, of course.	1800	handlers will be invoked, too, of course.
1639		1801
		1802	=head3 Watcher-Specific Functions and Data Members
		1803
1640	=over 4	1804	=over 4
1641		1805
1642	=item ev_fork_init (ev_signal *, callback)	1806	=item ev_fork_init (ev_signal *, callback)
1643		1807
1644	Initialises and configures the fork watcher - it has no parameters of any	1808	Initialises and configures the fork watcher - it has no parameters of any
…		…
1740		1904
1741	To use it,	1905	To use it,
1742		1906
1743	#include <ev++.h>	1907	#include <ev++.h>
1744		1908
1745	(it is not installed by default). This automatically includes F<ev.h>	1909	This automatically includes F<ev.h> and puts all of its definitions (many
1746	and puts all of its definitions (many of them macros) into the global	1910	of them macros) into the global namespace. All C++ specific things are
1747	namespace. All C++ specific things are put into the C<ev> namespace.	1911	put into the C<ev> namespace. It should support all the same embedding
		1912	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1748		1913
1749	It should support all the same embedding options as F<ev.h>, most notably	1914	Care has been taken to keep the overhead low. The only data member the C++
1750	C<EV_MULTIPLICITY>.	1915	classes add (compared to plain C-style watchers) is the event loop pointer
		1916	that the watcher is associated with (or no additional members at all if
		1917	you disable C<EV_MULTIPLICITY> when embedding libev).
		1918
		1919	Currently, functions, and static and non-static member functions can be
		1920	used as callbacks. Other types should be easy to add as long as they only
		1921	need one additional pointer for context. If you need support for other
		1922	types of functors please contact the author (preferably after implementing
		1923	it).
1751		1924
1752	Here is a list of things available in the C<ev> namespace:	1925	Here is a list of things available in the C<ev> namespace:
1753		1926
1754	=over 4	1927	=over 4
1755		1928
…		…
1771		1944
1772	All of those classes have these methods:	1945	All of those classes have these methods:
1773		1946
1774	=over 4	1947	=over 4
1775		1948
1776	=item ev::TYPE::TYPE (object , object::method )	1949	=item ev::TYPE::TYPE ()
1777		1950
1778	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1951	=item ev::TYPE::TYPE (struct ev_loop *)
1779		1952
1780	=item ev::TYPE::~TYPE	1953	=item ev::TYPE::~TYPE
1781		1954
1782	The constructor takes a pointer to an object and a method pointer to	1955	The constructor (optionally) takes an event loop to associate the watcher
1783	the event handler callback to call in this class. The constructor calls	1956	with. If it is omitted, it will use C<EV_DEFAULT>.
1784	C<ev_init> for you, which means you have to call the C<set> method	1957
1785	before starting it. If you do not specify a loop then the constructor	1958	The constructor calls C<ev_init> for you, which means you have to call the
1786	automatically associates the default loop with this watcher.	1959	C<set> method before starting it.
		1960
		1961	It will not set a callback, however: You have to call the templated C<set>
		1962	method to set a callback before you can start the watcher.
		1963
		1964	(The reason why you have to use a method is a limitation in C++ which does
		1965	not allow explicit template arguments for constructors).
1787		1966
1788	The destructor automatically stops the watcher if it is active.	1967	The destructor automatically stops the watcher if it is active.
		1968
		1969	=item w->set<class, &class::method> (object *)
		1970
		1971	This method sets the callback method to call. The method has to have a
		1972	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1973	first argument and the C<revents> as second. The object must be given as
		1974	parameter and is stored in the C<data> member of the watcher.
		1975
		1976	This method synthesizes efficient thunking code to call your method from
		1977	the C callback that libev requires. If your compiler can inline your
		1978	callback (i.e. it is visible to it at the place of the C<set> call and
		1979	your compiler is good :), then the method will be fully inlined into the
		1980	thunking function, making it as fast as a direct C callback.
		1981
		1982	Example: simple class declaration and watcher initialisation
		1983
		1984	struct myclass
		1985	{
		1986	void io_cb (ev::io &w, int revents) { }
		1987	}
		1988
		1989	myclass obj;
		1990	ev::io iow;
		1991	iow.set <myclass, &myclass::io_cb> (&obj);
		1992
		1993	=item w->set<function> (void *data = 0)
		1994
		1995	Also sets a callback, but uses a static method or plain function as
		1996	callback. The optional C<data> argument will be stored in the watcher's
		1997	C<data> member and is free for you to use.
		1998
		1999	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2000
		2001	See the method-C<set> above for more details.
		2002
		2003	Example:
		2004
		2005	static void io_cb (ev::io &w, int revents) { }
		2006	iow.set <io_cb> ();
1789		2007
1790	=item w->set (struct ev_loop *)	2008	=item w->set (struct ev_loop *)
1791		2009
1792	Associates a different C<struct ev_loop> with this watcher. You can only	2010	Associates a different C<struct ev_loop> with this watcher. You can only
1793	do this when the watcher is inactive (and not pending either).	2011	do this when the watcher is inactive (and not pending either).
1794		2012
1795	=item w->set ([args])	2013	=item w->set ([args])
1796		2014
1797	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2015	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1798	called at least once. Unlike the C counterpart, an active watcher gets	2016	called at least once. Unlike the C counterpart, an active watcher gets
1799	automatically stopped and restarted.	2017	automatically stopped and restarted when reconfiguring it with this
		2018	method.
1800		2019
1801	=item w->start ()	2020	=item w->start ()
1802		2021
1803	Starts the watcher. Note that there is no C<loop> argument as the	2022	Starts the watcher. Note that there is no C<loop> argument, as the
1804	constructor already takes the loop.	2023	constructor already stores the event loop.
1805		2024
1806	=item w->stop ()	2025	=item w->stop ()
1807		2026
1808	Stops the watcher if it is active. Again, no C<loop> argument.	2027	Stops the watcher if it is active. Again, no C<loop> argument.
1809		2028
1810	=item w->again () C<ev::timer>, C<ev::periodic> only	2029	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1811		2030
1812	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2031	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1813	C<ev_TYPE_again> function.	2032	C<ev_TYPE_again> function.
1814		2033
1815	=item w->sweep () C<ev::embed> only	2034	=item w->sweep () (C<ev::embed> only)
1816		2035
1817	Invokes C<ev_embed_sweep>.	2036	Invokes C<ev_embed_sweep>.
1818		2037
1819	=item w->update () C<ev::stat> only	2038	=item w->update () (C<ev::stat> only)
1820		2039
1821	Invokes C<ev_stat_stat>.	2040	Invokes C<ev_stat_stat>.
1822		2041
1823	=back	2042	=back
1824		2043
…		…
1834		2053
1835	myclass ();	2054	myclass ();
1836	}	2055	}
1837		2056
1838	myclass::myclass (int fd)	2057	myclass::myclass (int fd)
1839	: io (this, &myclass::io_cb),
1840	idle (this, &myclass::idle_cb)
1841	{	2058	{
		2059	io .set <myclass, &myclass::io_cb > (this);
		2060	idle.set <myclass, &myclass::idle_cb> (this);
		2061
1842	io.start (fd, ev::READ);	2062	io.start (fd, ev::READ);
1843	}	2063	}
1844		2064
1845		2065
1846	=head1 MACRO MAGIC	2066	=head1 MACRO MAGIC
1847		2067
1848	Libev can be compiled with a variety of options, the most fundemantal is	2068	Libev can be compiled with a variety of options, the most fundamantal
1849	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2069	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1850	callbacks have an initial C<struct ev_loop *> argument.	2070	functions and callbacks have an initial C<struct ev_loop *> argument.
1851		2071
1852	To make it easier to write programs that cope with either variant, the	2072	To make it easier to write programs that cope with either variant, the
1853	following macros are defined:	2073	following macros are defined:
1854		2074
1855	=over 4	2075	=over 4
…		…
2123	will have the C<struct ev_loop *> as first argument, and you can create	2343	will have the C<struct ev_loop *> as first argument, and you can create
2124	additional independent event loops. Otherwise there will be no support	2344	additional independent event loops. Otherwise there will be no support
2125	for multiple event loops and there is no first event loop pointer	2345	for multiple event loops and there is no first event loop pointer
2126	argument. Instead, all functions act on the single default loop.	2346	argument. Instead, all functions act on the single default loop.
2127		2347
		2348	=item EV_MINPRI
		2349
		2350	=item EV_MAXPRI
		2351
		2352	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2353	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2354	provide for more priorities by overriding those symbols (usually defined
		2355	to be C<-2> and C<2>, respectively).
		2356
		2357	When doing priority-based operations, libev usually has to linearly search
		2358	all the priorities, so having many of them (hundreds) uses a lot of space
		2359	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2360	fine.
		2361
		2362	If your embedding app does not need any priorities, defining these both to
		2363	C<0> will save some memory and cpu.
		2364
2128	=item EV_PERIODIC_ENABLE	2365	=item EV_PERIODIC_ENABLE
2129		2366
2130	If undefined or defined to be C<1>, then periodic timers are supported. If	2367	If undefined or defined to be C<1>, then periodic timers are supported. If
2131	defined to be C<0>, then they are not. Disabling them saves a few kB of	2368	defined to be C<0>, then they are not. Disabling them saves a few kB of
2132	code.	2369	code.
…		…
2234		2471
2235	In this section the complexities of (many of) the algorithms used inside	2472	In this section the complexities of (many of) the algorithms used inside
2236	libev will be explained. For complexity discussions about backends see the	2473	libev will be explained. For complexity discussions about backends see the
2237	documentation for C<ev_default_init>.	2474	documentation for C<ev_default_init>.
2238		2475
		2476	All of the following are about amortised time: If an array needs to be
		2477	extended, libev needs to realloc and move the whole array, but this
		2478	happens asymptotically never with higher number of elements, so O(1) might
		2479	mean it might do a lengthy realloc operation in rare cases, but on average
		2480	it is much faster and asymptotically approaches constant time.
		2481
2239	=over 4	2482	=over 4
2240		2483
2241	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2484	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2242		2485
		2486	This means that, when you have a watcher that triggers in one hour and
		2487	there are 100 watchers that would trigger before that then inserting will
		2488	have to skip those 100 watchers.
		2489
2243	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2490	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2244		2491
		2492	That means that for changing a timer costs less than removing/adding them
		2493	as only the relative motion in the event queue has to be paid for.
		2494
2245	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2495	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2246		2496
		2497	These just add the watcher into an array or at the head of a list.
2247	=item Stopping check/prepare/idle watchers: O(1)	2498	=item Stopping check/prepare/idle watchers: O(1)
2248		2499
2249	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2500	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2250		2501
		2502	These watchers are stored in lists then need to be walked to find the
		2503	correct watcher to remove. The lists are usually short (you don't usually
		2504	have many watchers waiting for the same fd or signal).
		2505
2251	=item Finding the next timer per loop iteration: O(1)	2506	=item Finding the next timer per loop iteration: O(1)
2252		2507
2253	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2508	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2254		2509
		2510	A change means an I/O watcher gets started or stopped, which requires
		2511	libev to recalculate its status (and possibly tell the kernel).
		2512
2255	=item Activating one watcher: O(1)	2513	=item Activating one watcher: O(1)
2256		2514
		2515	=item Priority handling: O(number_of_priorities)
		2516
		2517	Priorities are implemented by allocating some space for each
		2518	priority. When doing priority-based operations, libev usually has to
		2519	linearly search all the priorities.
		2520
2257	=back	2521	=back
2258		2522
2259		2523
2260	=head1 AUTHOR	2524	=head1 AUTHOR
2261		2525

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Comparing libev/ev.pod (file contents): Revision 1.68 by root, Fri Dec 7 18:09:43 2007 UTC vs. Revision 1.85 by root, Mon Dec 17 07:24:12 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.68 by root, Fri Dec 7 18:09:43 2007 UTC vs.
Revision 1.85 by root, Mon Dec 17 07:24:12 2007 UTC