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

Comparing libev/ev.pod (file contents):
Revision 1.67 by root, Fri Dec 7 16:44:12 2007 UTC vs.
Revision 1.86 by root, Tue Dec 18 01:20:33 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
…		…
94	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
97	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
98	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
99	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
100		106
101	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
102		108
103	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
104	library in any way.	110	library in any way.
…		…
113		119
114	=item int ev_version_major ()	120	=item int ev_version_major ()
115		121
116	=item int ev_version_minor ()	122	=item int ev_version_minor ()
117		123
118	You can find out the major and minor version numbers of the library	124	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	125	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	126	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	127	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
122	version of the library your program was compiled against.	128	version of the library your program was compiled against.
123		129
		130	These version numbers refer to the ABI version of the library, not the
		131	release version.
		132
124	Usually, it's a good idea to terminate if the major versions mismatch,	133	Usually, it's a good idea to terminate if the major versions mismatch,
125	as this indicates an incompatible change. Minor versions are usually	134	as this indicates an incompatible change. Minor versions are usually
126	compatible to older versions, so a larger minor version alone is usually	135	compatible to older versions, so a larger minor version alone is usually
127	not a problem.	136	not a problem.
128		137
129	Example: Make sure we haven't accidentally been linked against the wrong	138	Example: Make sure we haven't accidentally been linked against the wrong
130	version.	139	version.
…		…
482	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	491	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
483	usually a better approach for this kind of thing.	492	usually a better approach for this kind of thing.
484		493
485	Here are the gory details of what C<ev_loop> does:	494	Here are the gory details of what C<ev_loop> does:
486		495
		496	- Before the first iteration, call any pending watchers.
487	* If there are no active watchers (reference count is zero), return.	497	* If there are no active watchers (reference count is zero), return.
488	- Queue prepare watchers and then call all outstanding watchers.	498	- Queue all prepare watchers and then call all outstanding watchers.
489	- If we have been forked, recreate the kernel state.	499	- If we have been forked, recreate the kernel state.
490	- Update the kernel state with all outstanding changes.	500	- Update the kernel state with all outstanding changes.
491	- Update the "event loop time".	501	- Update the "event loop time".
492	- Calculate for how long to block.	502	- Calculate for how long to block.
493	- Block the process, waiting for any events.	503	- Block the process, waiting for any events.
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	742	=item bool ev_is_pending (ev_TYPE *watcher)
733		743
734	Returns a true value iff the watcher is pending, (i.e. it has outstanding	744	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	745	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	746	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	747	C<ev_TYPE_set> is safe), you must not change its priority, and you must
738	libev (e.g. you cnanot C<free ()> it).	748	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		749	it).
739		750
740	=item callback ev_cb (ev_TYPE *watcher)	751	=item callback ev_cb (ev_TYPE *watcher)
741		752
742	Returns the callback currently set on the watcher.	753	Returns the callback currently set on the watcher.
743		754
…		…
762	watchers on the same event and make sure one is called first.	773	watchers on the same event and make sure one is called first.
763		774
764	If you need to suppress invocation when higher priority events are pending	775	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.	776	you need to look at C<ev_idle> watchers, which provide this functionality.
766		777
		778	You I<must not> change the priority of a watcher as long as it is active or
		779	pending.
		780
767	The default priority used by watchers when no priority has been set is	781	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 :).	782	always C<0>, which is supposed to not be too high and not be too low :).
769		783
770	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	784	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	785	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.	786	or might not have been adjusted to be within valid range.
		787
		788	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		789
		790	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		791	C<loop> nor C<revents> need to be valid as long as the watcher callback
		792	can deal with that fact.
		793
		794	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		795
		796	If the watcher is pending, this function returns clears its pending status
		797	and returns its C<revents> bitset (as if its callback was invoked). If the
		798	watcher isn't pending it does nothing and returns C<0>.
773		799
774	=back	800	=back
775		801
776		802
777	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	803	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
883	it is best to always use non-blocking I/O: An extra C<read>(2) returning	909	it is best to always use non-blocking I/O: An extra C<read>(2) returning
884	C<EAGAIN> is far preferable to a program hanging until some data arrives.	910	C<EAGAIN> is far preferable to a program hanging until some data arrives.
885		911
886	If you cannot run the fd in non-blocking mode (for example you should not	912	If you cannot run the fd in non-blocking mode (for example you should not
887	play around with an Xlib connection), then you have to seperately re-test	913	play around with an Xlib connection), then you have to seperately re-test
888	wether a file descriptor is really ready with a known-to-be good interface	914	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	915	such as poll (fortunately in our Xlib example, Xlib already does this on
890	its own, so its quite safe to use).	916	its own, so its quite safe to use).
		917
		918	=head3 The special problem of disappearing file descriptors
		919
		920	Some backends (e.g kqueue, epoll) need to be told about closing a file
		921	descriptor (either by calling C<close> explicitly or by any other means,
		922	such as C<dup>). The reason is that you register interest in some file
		923	descriptor, but when it goes away, the operating system will silently drop
		924	this interest. If another file descriptor with the same number then is
		925	registered with libev, there is no efficient way to see that this is, in
		926	fact, a different file descriptor.
		927
		928	To avoid having to explicitly tell libev about such cases, libev follows
		929	the following policy: Each time C<ev_io_set> is being called, libev
		930	will assume that this is potentially a new file descriptor, otherwise
		931	it is assumed that the file descriptor stays the same. That means that
		932	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		933	descriptor even if the file descriptor number itself did not change.
		934
		935	This is how one would do it normally anyway, the important point is that
		936	the libev application should not optimise around libev but should leave
		937	optimisations to libev.
		938
		939
		940	=head3 Watcher-Specific Functions
891		941
892	=over 4	942	=over 4
893		943
894	=item ev_io_init (ev_io *, callback, int fd, int events)	944	=item ev_io_init (ev_io *, callback, int fd, int events)
895		945
…		…
948	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	998	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
949		999
950	The callback is guarenteed to be invoked only when its timeout has passed,	1000	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	1001	but if multiple timers become ready during the same loop iteration then
952	order of execution is undefined.	1002	order of execution is undefined.
		1003
		1004	=head3 Watcher-Specific Functions and Data Members
953		1005
954	=over 4	1006	=over 4
955		1007
956	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1008	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
957		1009
…		…
1053	but on wallclock time (absolute time). You can tell a periodic watcher	1105	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	1106	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 ()	1107	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	1108	+ 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	1109	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	1110	roughly 10 seconds later).
1059	again).
1060		1111
1061	They can also be used to implement vastly more complex timers, such as	1112	They can also be used to implement vastly more complex timers, such as
1062	triggering an event on eahc midnight, local time.	1113	triggering an event on each midnight, local time or other, complicated,
		1114	rules.
1063		1115
1064	As with timers, the callback is guarenteed to be invoked only when the	1116	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	1117	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.	1118	during the same loop iteration then order of execution is undefined.
1067		1119
		1120	=head3 Watcher-Specific Functions and Data Members
		1121
1068	=over 4	1122	=over 4
1069		1123
1070	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1124	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1071		1125
1072	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1126	=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	1128	Lots of arguments, lets sort it out... There are basically three modes of
1075	operation, and we will explain them from simplest to complex:	1129	operation, and we will explain them from simplest to complex:
1076		1130
1077	=over 4	1131	=over 4
1078		1132
1079	=item * absolute timer (interval = reschedule_cb = 0)	1133	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1080		1134
1081	In this configuration the watcher triggers an event at the wallclock time	1135	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,	1136	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	1137	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.	1138	system time reaches or surpasses this time.
1085		1139
1086	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1140	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1087		1141
1088	In this mode the watcher will always be scheduled to time out at the next	1142	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	1143	C<at + N * interval> time (for some integer N, which can also be negative)
1090	of any time jumps.	1144	and then repeat, regardless of any time jumps.
1091		1145
1092	This can be used to create timers that do not drift with respect to system	1146	This can be used to create timers that do not drift with respect to system
1093	time:	1147	time:
1094		1148
1095	ev_periodic_set (&periodic, 0., 3600., 0);	1149	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1101		1155
1102	Another way to think about it (for the mathematically inclined) is that	1156	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	1157	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.	1158	time where C<time = at (mod interval)>, regardless of any time jumps.
1105		1159
		1160	For numerical stability it is preferable that the C<at> value is near
		1161	C<ev_now ()> (the current time), but there is no range requirement for
		1162	this value.
		1163
1106	=item * manual reschedule mode (reschedule_cb = callback)	1164	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1107		1165
1108	In this mode the values for C<interval> and C<at> are both being	1166	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	1167	ignored. Instead, each time the periodic watcher gets scheduled, the
1110	reschedule callback will be called with the watcher as first, and the	1168	reschedule callback will be called with the watcher as first, and the
1111	current time as second argument.	1169	current time as second argument.
1112		1170
1113	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1171	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,	1172	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	1173	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1116	starting a prepare watcher).	1174	starting an C<ev_prepare> watcher, which is legal).
1117		1175
1118	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1176	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1119	ev_tstamp now)>, e.g.:	1177	ev_tstamp now)>, e.g.:
1120		1178
1121	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1179	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	1202	Simply stops and restarts the periodic watcher again. This is only useful
1145	when you changed some parameters or the reschedule callback would return	1203	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	1204	a different time than the last time it was called (e.g. in a crond like
1147	program when the crontabs have changed).	1205	program when the crontabs have changed).
1148		1206
		1207	=item ev_tstamp offset [read-write]
		1208
		1209	When repeating, this contains the offset value, otherwise this is the
		1210	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1211
		1212	Can be modified any time, but changes only take effect when the periodic
		1213	timer fires or C<ev_periodic_again> is being called.
		1214
1149	=item ev_tstamp interval [read-write]	1215	=item ev_tstamp interval [read-write]
1150		1216
1151	The current interval value. Can be modified any time, but changes only	1217	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	1218	take effect when the periodic timer fires or C<ev_periodic_again> is being
1153	called.	1219	called.
…		…
1155	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1221	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
1156		1222
1157	The current reschedule callback, or C<0>, if this functionality is	1223	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	1224	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.	1225	the periodic timer fires or C<ev_periodic_again> is being called.
		1226
		1227	=item ev_tstamp at [read-only]
		1228
		1229	When active, contains the absolute time that the watcher is supposed to
		1230	trigger next.
1160		1231
1161	=back	1232	=back
1162		1233
1163	Example: Call a callback every hour, or, more precisely, whenever the	1234	Example: Call a callback every hour, or, more precisely, whenever the
1164	system clock is divisible by 3600. The callback invocation times have	1235	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	1277	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	1278	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	1279	watcher for a signal is stopped libev will reset the signal handler to
1209	SIG_DFL (regardless of what it was set to before).	1280	SIG_DFL (regardless of what it was set to before).
1210		1281
		1282	=head3 Watcher-Specific Functions and Data Members
		1283
1211	=over 4	1284	=over 4
1212		1285
1213	=item ev_signal_init (ev_signal *, callback, int signum)	1286	=item ev_signal_init (ev_signal *, callback, int signum)
1214		1287
1215	=item ev_signal_set (ev_signal *, int signum)	1288	=item ev_signal_set (ev_signal *, int signum)
…		…
1226		1299
1227	=head2 C<ev_child> - watch out for process status changes	1300	=head2 C<ev_child> - watch out for process status changes
1228		1301
1229	Child watchers trigger when your process receives a SIGCHLD in response to	1302	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).	1303	some child status changes (most typically when a child of yours dies).
		1304
		1305	=head3 Watcher-Specific Functions and Data Members
1231		1306
1232	=over 4	1307	=over 4
1233		1308
1234	=item ev_child_init (ev_child *, callback, int pid)	1309	=item ev_child_init (ev_child *, callback, int pid)
1235		1310
…		…
1303	reader). Inotify will be used to give hints only and should not change the	1378	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	1379	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	1380	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	1381	usually detected immediately, and if the file exists there will be no
1307	polling.	1382	polling.
		1383
		1384	=head3 Watcher-Specific Functions and Data Members
1308		1385
1309	=over 4	1386	=over 4
1310		1387
1311	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1388	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1312		1389
…		…
1395	Apart from keeping your process non-blocking (which is a useful	1472	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	1473	effect on its own sometimes), idle watchers are a good place to do
1397	"pseudo-background processing", or delay processing stuff to after the	1474	"pseudo-background processing", or delay processing stuff to after the
1398	event loop has handled all outstanding events.	1475	event loop has handled all outstanding events.
1399		1476
		1477	=head3 Watcher-Specific Functions and Data Members
		1478
1400	=over 4	1479	=over 4
1401		1480
1402	=item ev_idle_init (ev_signal *, callback)	1481	=item ev_idle_init (ev_signal *, callback)
1403		1482
1404	Initialises and configures the idle watcher - it has no parameters of any	1483	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	1540	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	1541	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	1542	loop from blocking if lower-priority coroutines are active, thus mapping
1464	low-priority coroutines to idle/background tasks).	1543	low-priority coroutines to idle/background tasks).
1465		1544
		1545	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1546	priority, to ensure that they are being run before any other watchers
		1547	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1548	too) should not activate ("feed") events into libev. While libev fully
		1549	supports this, they will be called before other C<ev_check> watchers did
		1550	their job. As C<ev_check> watchers are often used to embed other event
		1551	loops those other event loops might be in an unusable state until their
		1552	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1553	others).
		1554
		1555	=head3 Watcher-Specific Functions and Data Members
		1556
1466	=over 4	1557	=over 4
1467		1558
1468	=item ev_prepare_init (ev_prepare *, callback)	1559	=item ev_prepare_init (ev_prepare *, callback)
1469		1560
1470	=item ev_check_init (ev_check *, callback)	1561	=item ev_check_init (ev_check *, callback)
…		…
1473	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1564	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.	1565	macros, but using them is utterly, utterly and completely pointless.
1475		1566
1476	=back	1567	=back
1477		1568
1478	Example: To include a library such as adns, you would add IO watchers	1569	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	1570	into libev. Here are some ideas on how to include libadns into libev
		1571	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1572	use for an actually working example. Another Perl module named C<EV::Glib>
		1573	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1574	into the Glib event loop).
		1575
		1576	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	1577	and in a check watcher, destroy them and call into libadns. What follows
1481	pseudo-code only of course:	1578	is pseudo-code only of course. This requires you to either use a low
		1579	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1580	the callbacks for the IO/timeout watchers might not have been called yet.
1482		1581
1483	static ev_io iow [nfd];	1582	static ev_io iow [nfd];
1484	static ev_timer tw;	1583	static ev_timer tw;
1485		1584
1486	static void	1585	static void
1487	io_cb (ev_loop loop, ev_io w, int revents)	1586	io_cb (ev_loop loop, ev_io w, int revents)
1488	{	1587	{
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	}	1588	}
1495		1589
1496	// create io watchers for each fd and a timer before blocking	1590	// create io watchers for each fd and a timer before blocking
1497	static void	1591	static void
1498	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1592	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1504		1598
1505	/* the callback is illegal, but won't be called as we stop during check */	1599	/* the callback is illegal, but won't be called as we stop during check */
1506	ev_timer_init (&tw, 0, timeout * 1e-3);	1600	ev_timer_init (&tw, 0, timeout * 1e-3);
1507	ev_timer_start (loop, &tw);	1601	ev_timer_start (loop, &tw);
1508		1602
1509	// create on ev_io per pollfd	1603	// create one ev_io per pollfd
1510	for (int i = 0; i < nfd; ++i)	1604	for (int i = 0; i < nfd; ++i)
1511	{	1605	{
1512	ev_io_init (iow + i, io_cb, fds [i].fd,	1606	ev_io_init (iow + i, io_cb, fds [i].fd,
1513	((fds [i].events & POLLIN ? EV_READ : 0)	1607	((fds [i].events & POLLIN ? EV_READ : 0)
1514	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1608	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1515		1609
1516	fds [i].revents = 0;	1610	fds [i].revents = 0;
1517	iow [i].data = fds + i;
1518	ev_io_start (loop, iow + i);	1611	ev_io_start (loop, iow + i);
1519	}	1612	}
1520	}	1613	}
1521		1614
1522	// stop all watchers after blocking	1615	// stop all watchers after blocking
…		…
1524	adns_check_cb (ev_loop loop, ev_check w, int revents)	1617	adns_check_cb (ev_loop loop, ev_check w, int revents)
1525	{	1618	{
1526	ev_timer_stop (loop, &tw);	1619	ev_timer_stop (loop, &tw);
1527		1620
1528	for (int i = 0; i < nfd; ++i)	1621	for (int i = 0; i < nfd; ++i)
		1622	{
		1623	// set the relevant poll flags
		1624	// could also call adns_processreadable etc. here
		1625	struct pollfd *fd = fds + i;
		1626	int revents = ev_clear_pending (iow + i);
		1627	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1628	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1629
		1630	// now stop the watcher
1529	ev_io_stop (loop, iow + i);	1631	ev_io_stop (loop, iow + i);
		1632	}
1530		1633
1531	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1634	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1635	}
		1636
		1637	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1638	in the prepare watcher and would dispose of the check watcher.
		1639
		1640	Method 3: If the module to be embedded supports explicit event
		1641	notification (adns does), you can also make use of the actual watcher
		1642	callbacks, and only destroy/create the watchers in the prepare watcher.
		1643
		1644	static void
		1645	timer_cb (EV_P_ ev_timer *w, int revents)
		1646	{
		1647	adns_state ads = (adns_state)w->data;
		1648	update_now (EV_A);
		1649
		1650	adns_processtimeouts (ads, &tv_now);
		1651	}
		1652
		1653	static void
		1654	io_cb (EV_P_ ev_io *w, int revents)
		1655	{
		1656	adns_state ads = (adns_state)w->data;
		1657	update_now (EV_A);
		1658
		1659	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1660	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1661	}
		1662
		1663	// do not ever call adns_afterpoll
		1664
		1665	Method 4: Do not use a prepare or check watcher because the module you
		1666	want to embed is too inflexible to support it. Instead, youc na override
		1667	their poll function. The drawback with this solution is that the main
		1668	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1669	this.
		1670
		1671	static gint
		1672	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1673	{
		1674	int got_events = 0;
		1675
		1676	for (n = 0; n < nfds; ++n)
		1677	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1678
		1679	if (timeout >= 0)
		1680	// create/start timer
		1681
		1682	// poll
		1683	ev_loop (EV_A_ 0);
		1684
		1685	// stop timer again
		1686	if (timeout >= 0)
		1687	ev_timer_stop (EV_A_ &to);
		1688
		1689	// stop io watchers again - their callbacks should have set
		1690	for (n = 0; n < nfds; ++n)
		1691	ev_io_stop (EV_A_ iow [n]);
		1692
		1693	return got_events;
1532	}	1694	}
1533		1695
1534		1696
1535	=head2 C<ev_embed> - when one backend isn't enough...	1697	=head2 C<ev_embed> - when one backend isn't enough...
1536		1698
…		…
1600	ev_embed_start (loop_hi, &embed);	1762	ev_embed_start (loop_hi, &embed);
1601	}	1763	}
1602	else	1764	else
1603	loop_lo = loop_hi;	1765	loop_lo = loop_hi;
1604		1766
		1767	=head3 Watcher-Specific Functions and Data Members
		1768
1605	=over 4	1769	=over 4
1606		1770
1607	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1771	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1608		1772
1609	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	1773	=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,	1799	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	1800	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	1801	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1638	handlers will be invoked, too, of course.	1802	handlers will be invoked, too, of course.
1639		1803
		1804	=head3 Watcher-Specific Functions and Data Members
		1805
1640	=over 4	1806	=over 4
1641		1807
1642	=item ev_fork_init (ev_signal *, callback)	1808	=item ev_fork_init (ev_signal *, callback)
1643		1809
1644	Initialises and configures the fork watcher - it has no parameters of any	1810	Initialises and configures the fork watcher - it has no parameters of any
…		…
1740		1906
1741	To use it,	1907	To use it,
1742		1908
1743	#include <ev++.h>	1909	#include <ev++.h>
1744		1910
1745	(it is not installed by default). This automatically includes F<ev.h>	1911	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	1912	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.	1913	put into the C<ev> namespace. It should support all the same embedding
		1914	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1748		1915
1749	It should support all the same embedding options as F<ev.h>, most notably	1916	Care has been taken to keep the overhead low. The only data member the C++
1750	C<EV_MULTIPLICITY>.	1917	classes add (compared to plain C-style watchers) is the event loop pointer
		1918	that the watcher is associated with (or no additional members at all if
		1919	you disable C<EV_MULTIPLICITY> when embedding libev).
		1920
		1921	Currently, functions, and static and non-static member functions can be
		1922	used as callbacks. Other types should be easy to add as long as they only
		1923	need one additional pointer for context. If you need support for other
		1924	types of functors please contact the author (preferably after implementing
		1925	it).
1751		1926
1752	Here is a list of things available in the C<ev> namespace:	1927	Here is a list of things available in the C<ev> namespace:
1753		1928
1754	=over 4	1929	=over 4
1755		1930
…		…
1771		1946
1772	All of those classes have these methods:	1947	All of those classes have these methods:
1773		1948
1774	=over 4	1949	=over 4
1775		1950
1776	=item ev::TYPE::TYPE (object , object::method )	1951	=item ev::TYPE::TYPE ()
1777		1952
1778	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1953	=item ev::TYPE::TYPE (struct ev_loop *)
1779		1954
1780	=item ev::TYPE::~TYPE	1955	=item ev::TYPE::~TYPE
1781		1956
1782	The constructor takes a pointer to an object and a method pointer to	1957	The constructor (optionally) takes an event loop to associate the watcher
1783	the event handler callback to call in this class. The constructor calls	1958	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	1959
1785	before starting it. If you do not specify a loop then the constructor	1960	The constructor calls C<ev_init> for you, which means you have to call the
1786	automatically associates the default loop with this watcher.	1961	C<set> method before starting it.
		1962
		1963	It will not set a callback, however: You have to call the templated C<set>
		1964	method to set a callback before you can start the watcher.
		1965
		1966	(The reason why you have to use a method is a limitation in C++ which does
		1967	not allow explicit template arguments for constructors).
1787		1968
1788	The destructor automatically stops the watcher if it is active.	1969	The destructor automatically stops the watcher if it is active.
		1970
		1971	=item w->set<class, &class::method> (object *)
		1972
		1973	This method sets the callback method to call. The method has to have a
		1974	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1975	first argument and the C<revents> as second. The object must be given as
		1976	parameter and is stored in the C<data> member of the watcher.
		1977
		1978	This method synthesizes efficient thunking code to call your method from
		1979	the C callback that libev requires. If your compiler can inline your
		1980	callback (i.e. it is visible to it at the place of the C<set> call and
		1981	your compiler is good :), then the method will be fully inlined into the
		1982	thunking function, making it as fast as a direct C callback.
		1983
		1984	Example: simple class declaration and watcher initialisation
		1985
		1986	struct myclass
		1987	{
		1988	void io_cb (ev::io &w, int revents) { }
		1989	}
		1990
		1991	myclass obj;
		1992	ev::io iow;
		1993	iow.set <myclass, &myclass::io_cb> (&obj);
		1994
		1995	=item w->set<function> (void *data = 0)
		1996
		1997	Also sets a callback, but uses a static method or plain function as
		1998	callback. The optional C<data> argument will be stored in the watcher's
		1999	C<data> member and is free for you to use.
		2000
		2001	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2002
		2003	See the method-C<set> above for more details.
		2004
		2005	Example:
		2006
		2007	static void io_cb (ev::io &w, int revents) { }
		2008	iow.set <io_cb> ();
1789		2009
1790	=item w->set (struct ev_loop *)	2010	=item w->set (struct ev_loop *)
1791		2011
1792	Associates a different C<struct ev_loop> with this watcher. You can only	2012	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).	2013	do this when the watcher is inactive (and not pending either).
1794		2014
1795	=item w->set ([args])	2015	=item w->set ([args])
1796		2016
1797	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2017	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	2018	called at least once. Unlike the C counterpart, an active watcher gets
1799	automatically stopped and restarted.	2019	automatically stopped and restarted when reconfiguring it with this
		2020	method.
1800		2021
1801	=item w->start ()	2022	=item w->start ()
1802		2023
1803	Starts the watcher. Note that there is no C<loop> argument as the	2024	Starts the watcher. Note that there is no C<loop> argument, as the
1804	constructor already takes the loop.	2025	constructor already stores the event loop.
1805		2026
1806	=item w->stop ()	2027	=item w->stop ()
1807		2028
1808	Stops the watcher if it is active. Again, no C<loop> argument.	2029	Stops the watcher if it is active. Again, no C<loop> argument.
1809		2030
1810	=item w->again () C<ev::timer>, C<ev::periodic> only	2031	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1811		2032
1812	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2033	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1813	C<ev_TYPE_again> function.	2034	C<ev_TYPE_again> function.
1814		2035
1815	=item w->sweep () C<ev::embed> only	2036	=item w->sweep () (C<ev::embed> only)
1816		2037
1817	Invokes C<ev_embed_sweep>.	2038	Invokes C<ev_embed_sweep>.
1818		2039
1819	=item w->update () C<ev::stat> only	2040	=item w->update () (C<ev::stat> only)
1820		2041
1821	Invokes C<ev_stat_stat>.	2042	Invokes C<ev_stat_stat>.
1822		2043
1823	=back	2044	=back
1824		2045
…		…
1834		2055
1835	myclass ();	2056	myclass ();
1836	}	2057	}
1837		2058
1838	myclass::myclass (int fd)	2059	myclass::myclass (int fd)
1839	: io (this, &myclass::io_cb),
1840	idle (this, &myclass::idle_cb)
1841	{	2060	{
		2061	io .set <myclass, &myclass::io_cb > (this);
		2062	idle.set <myclass, &myclass::idle_cb> (this);
		2063
1842	io.start (fd, ev::READ);	2064	io.start (fd, ev::READ);
1843	}	2065	}
1844		2066
1845		2067
1846	=head1 MACRO MAGIC	2068	=head1 MACRO MAGIC
1847		2069
1848	Libev can be compiled with a variety of options, the most fundemantal is	2070	Libev can be compiled with a variety of options, the most fundamantal
1849	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2071	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1850	callbacks have an initial C<struct ev_loop *> argument.	2072	functions and callbacks have an initial C<struct ev_loop *> argument.
1851		2073
1852	To make it easier to write programs that cope with either variant, the	2074	To make it easier to write programs that cope with either variant, the
1853	following macros are defined:	2075	following macros are defined:
1854		2076
1855	=over 4	2077	=over 4
…		…
1888	loop, if multiple loops are supported ("ev loop default").	2110	loop, if multiple loops are supported ("ev loop default").
1889		2111
1890	=back	2112	=back
1891		2113
1892	Example: Declare and initialise a check watcher, utilising the above	2114	Example: Declare and initialise a check watcher, utilising the above
1893	macros so it will work regardless of wether multiple loops are supported	2115	macros so it will work regardless of whether multiple loops are supported
1894	or not.	2116	or not.
1895		2117
1896	static void	2118	static void
1897	check_cb (EV_P_ ev_timer *w, int revents)	2119	check_cb (EV_P_ ev_timer *w, int revents)
1898	{	2120	{
…		…
2123	will have the C<struct ev_loop *> as first argument, and you can create	2345	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	2346	additional independent event loops. Otherwise there will be no support
2125	for multiple event loops and there is no first event loop pointer	2347	for multiple event loops and there is no first event loop pointer
2126	argument. Instead, all functions act on the single default loop.	2348	argument. Instead, all functions act on the single default loop.
2127		2349
		2350	=item EV_MINPRI
		2351
		2352	=item EV_MAXPRI
		2353
		2354	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2355	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2356	provide for more priorities by overriding those symbols (usually defined
		2357	to be C<-2> and C<2>, respectively).
		2358
		2359	When doing priority-based operations, libev usually has to linearly search
		2360	all the priorities, so having many of them (hundreds) uses a lot of space
		2361	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2362	fine.
		2363
		2364	If your embedding app does not need any priorities, defining these both to
		2365	C<0> will save some memory and cpu.
		2366
2128	=item EV_PERIODIC_ENABLE	2367	=item EV_PERIODIC_ENABLE
2129		2368
2130	If undefined or defined to be C<1>, then periodic timers are supported. If	2369	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	2370	defined to be C<0>, then they are not. Disabling them saves a few kB of
2132	code.	2371	code.
…		…
2234		2473
2235	In this section the complexities of (many of) the algorithms used inside	2474	In this section the complexities of (many of) the algorithms used inside
2236	libev will be explained. For complexity discussions about backends see the	2475	libev will be explained. For complexity discussions about backends see the
2237	documentation for C<ev_default_init>.	2476	documentation for C<ev_default_init>.
2238		2477
		2478	All of the following are about amortised time: If an array needs to be
		2479	extended, libev needs to realloc and move the whole array, but this
		2480	happens asymptotically never with higher number of elements, so O(1) might
		2481	mean it might do a lengthy realloc operation in rare cases, but on average
		2482	it is much faster and asymptotically approaches constant time.
		2483
2239	=over 4	2484	=over 4
2240		2485
2241	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2486	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2242		2487
		2488	This means that, when you have a watcher that triggers in one hour and
		2489	there are 100 watchers that would trigger before that then inserting will
		2490	have to skip those 100 watchers.
		2491
2243	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2492	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2244		2493
		2494	That means that for changing a timer costs less than removing/adding them
		2495	as only the relative motion in the event queue has to be paid for.
		2496
2245	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2497	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2246		2498
		2499	These just add the watcher into an array or at the head of a list.
2247	=item Stopping check/prepare/idle watchers: O(1)	2500	=item Stopping check/prepare/idle watchers: O(1)
2248		2501
2249	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2502	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2250		2503
		2504	These watchers are stored in lists then need to be walked to find the
		2505	correct watcher to remove. The lists are usually short (you don't usually
		2506	have many watchers waiting for the same fd or signal).
		2507
2251	=item Finding the next timer per loop iteration: O(1)	2508	=item Finding the next timer per loop iteration: O(1)
2252		2509
2253	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2510	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2254		2511
		2512	A change means an I/O watcher gets started or stopped, which requires
		2513	libev to recalculate its status (and possibly tell the kernel).
		2514
2255	=item Activating one watcher: O(1)	2515	=item Activating one watcher: O(1)
2256		2516
		2517	=item Priority handling: O(number_of_priorities)
		2518
		2519	Priorities are implemented by allocating some space for each
		2520	priority. When doing priority-based operations, libev usually has to
		2521	linearly search all the priorities.
		2522
2257	=back	2523	=back
2258		2524
2259		2525
2260	=head1 AUTHOR	2526	=head1 AUTHOR
2261		2527

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Comparing libev/ev.pod (file contents): Revision 1.67 by root, Fri Dec 7 16:44:12 2007 UTC vs. Revision 1.86 by root, Tue Dec 18 01:20:33 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.67 by root, Fri Dec 7 16:44:12 2007 UTC vs.
Revision 1.86 by root, Tue Dec 18 01:20:33 2007 UTC