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

Comparing libev/ev.pod (file contents):
Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs.
Revision 1.86 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
744	=item ev_cb_set (ev_TYPE *watcher, callback)	755	=item ev_cb_set (ev_TYPE *watcher, callback)
745		756
746	Change the callback. You can change the callback at virtually any time	757	Change the callback. You can change the callback at virtually any time
747	(modulo threads).	758	(modulo threads).
		759
		760	=item ev_set_priority (ev_TYPE *watcher, priority)
		761
		762	=item int ev_priority (ev_TYPE *watcher)
		763
		764	Set and query the priority of the watcher. The priority is a small
		765	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		766	(default: C<-2>). Pending watchers with higher priority will be invoked
		767	before watchers with lower priority, but priority will not keep watchers
		768	from being executed (except for C<ev_idle> watchers).
		769
		770	This means that priorities are I<only> used for ordering callback
		771	invocation after new events have been received. This is useful, for
		772	example, to reduce latency after idling, or more often, to bind two
		773	watchers on the same event and make sure one is called first.
		774
		775	If you need to suppress invocation when higher priority events are pending
		776	you need to look at C<ev_idle> watchers, which provide this functionality.
		777
		778	You I<must not> change the priority of a watcher as long as it is active or
		779	pending.
		780
		781	The default priority used by watchers when no priority has been set is
		782	always C<0>, which is supposed to not be too high and not be too low :).
		783
		784	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		785	fine, as long as you do not mind that the priority value you query might
		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>.
748		799
749	=back	800	=back
750		801
751		802
752	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	803	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
858	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
859	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.
860		911
861	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
862	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
863	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
864	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
865	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
866		941
867	=over 4	942	=over 4
868		943
869	=item ev_io_init (ev_io *, callback, int fd, int events)	944	=item ev_io_init (ev_io *, callback, int fd, int events)
870		945
…		…
923	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	998	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
924		999
925	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,
926	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
927	order of execution is undefined.	1002	order of execution is undefined.
		1003
		1004	=head3 Watcher-Specific Functions and Data Members
928		1005
929	=over 4	1006	=over 4
930		1007
931	=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)
932		1009
…		…
1028	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
1029	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
1030	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 ()
1031	+ 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
1032	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
1033	roughly 10 seconds later and of course not if you reset your system time	1110	roughly 10 seconds later).
1034	again).
1035		1111
1036	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
1037	triggering an event on eahc midnight, local time.	1113	triggering an event on each midnight, local time or other, complicated,
		1114	rules.
1038		1115
1039	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
1040	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
1041	during the same loop iteration then order of execution is undefined.	1118	during the same loop iteration then order of execution is undefined.
1042		1119
		1120	=head3 Watcher-Specific Functions and Data Members
		1121
1043	=over 4	1122	=over 4
1044		1123
1045	=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)
1046		1125
1047	=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)
…		…
1049	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
1050	operation, and we will explain them from simplest to complex:	1129	operation, and we will explain them from simplest to complex:
1051		1130
1052	=over 4	1131	=over 4
1053		1132
1054	=item * absolute timer (interval = reschedule_cb = 0)	1133	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1055		1134
1056	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
1057	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,
1058	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
1059	system time reaches or surpasses this time.	1138	system time reaches or surpasses this time.
1060		1139
1061	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1140	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1062		1141
1063	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
1064	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)
1065	of any time jumps.	1144	and then repeat, regardless of any time jumps.
1066		1145
1067	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
1068	time:	1147	time:
1069		1148
1070	ev_periodic_set (&periodic, 0., 3600., 0);	1149	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1076		1155
1077	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
1078	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
1079	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.
1080		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
1081	=item * manual reschedule mode (reschedule_cb = callback)	1164	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1082		1165
1083	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
1084	ignored. Instead, each time the periodic watcher gets scheduled, the	1167	ignored. Instead, each time the periodic watcher gets scheduled, the
1085	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
1086	current time as second argument.	1169	current time as second argument.
1087		1170
1088	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,
1089	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,
1090	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
1091	starting a prepare watcher).	1174	starting an C<ev_prepare> watcher, which is legal).
1092		1175
1093	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,
1094	ev_tstamp now)>, e.g.:	1177	ev_tstamp now)>, e.g.:
1095		1178
1096	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)
…		…
1119	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
1120	when you changed some parameters or the reschedule callback would return	1203	when you changed some parameters or the reschedule callback would return
1121	a different time than the last time it was called (e.g. in a crond like	1204	a different time than the last time it was called (e.g. in a crond like
1122	program when the crontabs have changed).	1205	program when the crontabs have changed).
1123		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
1124	=item ev_tstamp interval [read-write]	1215	=item ev_tstamp interval [read-write]
1125		1216
1126	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
1127	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
1128	called.	1219	called.
…		…
1130	=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]
1131		1222
1132	The current reschedule callback, or C<0>, if this functionality is	1223	The current reschedule callback, or C<0>, if this functionality is
1133	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
1134	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.
1135		1231
1136	=back	1232	=back
1137		1233
1138	Example: Call a callback every hour, or, more precisely, whenever the	1234	Example: Call a callback every hour, or, more precisely, whenever the
1139	system clock is divisible by 3600. The callback invocation times have	1235	system clock is divisible by 3600. The callback invocation times have
…		…
1181	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
1182	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
1183	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
1184	SIG_DFL (regardless of what it was set to before).	1280	SIG_DFL (regardless of what it was set to before).
1185		1281
		1282	=head3 Watcher-Specific Functions and Data Members
		1283
1186	=over 4	1284	=over 4
1187		1285
1188	=item ev_signal_init (ev_signal *, callback, int signum)	1286	=item ev_signal_init (ev_signal *, callback, int signum)
1189		1287
1190	=item ev_signal_set (ev_signal *, int signum)	1288	=item ev_signal_set (ev_signal *, int signum)
…		…
1201		1299
1202	=head2 C<ev_child> - watch out for process status changes	1300	=head2 C<ev_child> - watch out for process status changes
1203		1301
1204	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
1205	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
1206		1306
1207	=over 4	1307	=over 4
1208		1308
1209	=item ev_child_init (ev_child *, callback, int pid)	1309	=item ev_child_init (ev_child *, callback, int pid)
1210		1310
…		…
1278	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
1279	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
1280	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
1281	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
1282	polling.	1382	polling.
		1383
		1384	=head3 Watcher-Specific Functions and Data Members
1283		1385
1284	=over 4	1386	=over 4
1285		1387
1286	=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)
1287		1389
…		…
1351	ev_stat_start (loop, &passwd);	1453	ev_stat_start (loop, &passwd);
1352		1454
1353		1455
1354	=head2 C<ev_idle> - when you've got nothing better to do...	1456	=head2 C<ev_idle> - when you've got nothing better to do...
1355		1457
1356	Idle watchers trigger events when there are no other events are pending	1458	Idle watchers trigger events when no other events of the same or higher
1357	(prepare, check and other idle watchers do not count). That is, as long	1459	priority are pending (prepare, check and other idle watchers do not
1358	as your process is busy handling sockets or timeouts (or even signals,	1460	count).
1359	imagine) it will not be triggered. But when your process is idle all idle	1461
1360	watchers are being called again and again, once per event loop iteration -	1462	That is, as long as your process is busy handling sockets or timeouts
		1463	(or even signals, imagine) of the same or higher priority it will not be
		1464	triggered. But when your process is idle (or only lower-priority watchers
		1465	are pending), the idle watchers are being called once per event loop
1361	until stopped, that is, or your process receives more events and becomes	1466	iteration - until stopped, that is, or your process receives more events
1362	busy.	1467	and becomes busy again with higher priority stuff.
1363		1468
1364	The most noteworthy effect is that as long as any idle watchers are	1469	The most noteworthy effect is that as long as any idle watchers are
1365	active, the process will not block when waiting for new events.	1470	active, the process will not block when waiting for new events.
1366		1471
1367	Apart from keeping your process non-blocking (which is a useful	1472	Apart from keeping your process non-blocking (which is a useful
1368	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
1369	"pseudo-background processing", or delay processing stuff to after the	1474	"pseudo-background processing", or delay processing stuff to after the
1370	event loop has handled all outstanding events.	1475	event loop has handled all outstanding events.
		1476
		1477	=head3 Watcher-Specific Functions and Data Members
1371		1478
1372	=over 4	1479	=over 4
1373		1480
1374	=item ev_idle_init (ev_signal *, callback)	1481	=item ev_idle_init (ev_signal *, callback)
1375		1482
…		…
1433	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
1434	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
1435	loop from blocking if lower-priority coroutines are active, thus mapping	1542	loop from blocking if lower-priority coroutines are active, thus mapping
1436	low-priority coroutines to idle/background tasks).	1543	low-priority coroutines to idle/background tasks).
1437		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
1438	=over 4	1557	=over 4
1439		1558
1440	=item ev_prepare_init (ev_prepare *, callback)	1559	=item ev_prepare_init (ev_prepare *, callback)
1441		1560
1442	=item ev_check_init (ev_check *, callback)	1561	=item ev_check_init (ev_check *, callback)
…		…
1445	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>
1446	macros, but using them is utterly, utterly and completely pointless.	1565	macros, but using them is utterly, utterly and completely pointless.
1447		1566
1448	=back	1567	=back
1449		1568
1450	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
1451	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,
1452	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
1453	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.
1454		1581
1455	static ev_io iow [nfd];	1582	static ev_io iow [nfd];
1456	static ev_timer tw;	1583	static ev_timer tw;
1457		1584
1458	static void	1585	static void
1459	io_cb (ev_loop loop, ev_io w, int revents)	1586	io_cb (ev_loop loop, ev_io w, int revents)
1460	{	1587	{
1461	// set the relevant poll flags
1462	// could also call adns_processreadable etc. here
1463	struct pollfd fd = (struct pollfd )w->data;
1464	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1465	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1466	}	1588	}
1467		1589
1468	// create io watchers for each fd and a timer before blocking	1590	// create io watchers for each fd and a timer before blocking
1469	static void	1591	static void
1470	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1592	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1476		1598
1477	/* 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 */
1478	ev_timer_init (&tw, 0, timeout * 1e-3);	1600	ev_timer_init (&tw, 0, timeout * 1e-3);
1479	ev_timer_start (loop, &tw);	1601	ev_timer_start (loop, &tw);
1480		1602
1481	// create on ev_io per pollfd	1603	// create one ev_io per pollfd
1482	for (int i = 0; i < nfd; ++i)	1604	for (int i = 0; i < nfd; ++i)
1483	{	1605	{
1484	ev_io_init (iow + i, io_cb, fds [i].fd,	1606	ev_io_init (iow + i, io_cb, fds [i].fd,
1485	((fds [i].events & POLLIN ? EV_READ : 0)	1607	((fds [i].events & POLLIN ? EV_READ : 0)
1486	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1608	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1487		1609
1488	fds [i].revents = 0;	1610	fds [i].revents = 0;
1489	iow [i].data = fds + i;
1490	ev_io_start (loop, iow + i);	1611	ev_io_start (loop, iow + i);
1491	}	1612	}
1492	}	1613	}
1493		1614
1494	// stop all watchers after blocking	1615	// stop all watchers after blocking
…		…
1496	adns_check_cb (ev_loop loop, ev_check w, int revents)	1617	adns_check_cb (ev_loop loop, ev_check w, int revents)
1497	{	1618	{
1498	ev_timer_stop (loop, &tw);	1619	ev_timer_stop (loop, &tw);
1499		1620
1500	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
1501	ev_io_stop (loop, iow + i);	1631	ev_io_stop (loop, iow + i);
		1632	}
1502		1633
1503	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;
1504	}	1694	}
1505		1695
1506		1696
1507	=head2 C<ev_embed> - when one backend isn't enough...	1697	=head2 C<ev_embed> - when one backend isn't enough...
1508		1698
…		…
1572	ev_embed_start (loop_hi, &embed);	1762	ev_embed_start (loop_hi, &embed);
1573	}	1763	}
1574	else	1764	else
1575	loop_lo = loop_hi;	1765	loop_lo = loop_hi;
1576		1766
		1767	=head3 Watcher-Specific Functions and Data Members
		1768
1577	=over 4	1769	=over 4
1578		1770
1579	=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)
1580		1772
1581	=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)
…		…
1607	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,
1608	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
1609	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
1610	handlers will be invoked, too, of course.	1802	handlers will be invoked, too, of course.
1611		1803
		1804	=head3 Watcher-Specific Functions and Data Members
		1805
1612	=over 4	1806	=over 4
1613		1807
1614	=item ev_fork_init (ev_signal *, callback)	1808	=item ev_fork_init (ev_signal *, callback)
1615		1809
1616	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
…		…
1712		1906
1713	To use it,	1907	To use it,
1714		1908
1715	#include <ev++.h>	1909	#include <ev++.h>
1716		1910
1717	(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
1718	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
1719	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>.
1720		1915
1721	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++
1722	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).
1723		1926
1724	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:
1725		1928
1726	=over 4	1929	=over 4
1727		1930
…		…
1743		1946
1744	All of those classes have these methods:	1947	All of those classes have these methods:
1745		1948
1746	=over 4	1949	=over 4
1747		1950
1748	=item ev::TYPE::TYPE (object , object::method )	1951	=item ev::TYPE::TYPE ()
1749		1952
1750	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1953	=item ev::TYPE::TYPE (struct ev_loop *)
1751		1954
1752	=item ev::TYPE::~TYPE	1955	=item ev::TYPE::~TYPE
1753		1956
1754	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
1755	the event handler callback to call in this class. The constructor calls	1958	with. If it is omitted, it will use C<EV_DEFAULT>.
1756	C<ev_init> for you, which means you have to call the C<set> method	1959
1757	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
1758	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).
1759		1968
1760	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> ();
1761		2009
1762	=item w->set (struct ev_loop *)	2010	=item w->set (struct ev_loop *)
1763		2011
1764	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
1765	do this when the watcher is inactive (and not pending either).	2013	do this when the watcher is inactive (and not pending either).
1766		2014
1767	=item w->set ([args])	2015	=item w->set ([args])
1768		2016
1769	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
1770	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
1771	automatically stopped and restarted.	2019	automatically stopped and restarted when reconfiguring it with this
		2020	method.
1772		2021
1773	=item w->start ()	2022	=item w->start ()
1774		2023
1775	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
1776	constructor already takes the loop.	2025	constructor already stores the event loop.
1777		2026
1778	=item w->stop ()	2027	=item w->stop ()
1779		2028
1780	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.
1781		2030
1782	=item w->again () C<ev::timer>, C<ev::periodic> only	2031	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1783		2032
1784	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
1785	C<ev_TYPE_again> function.	2034	C<ev_TYPE_again> function.
1786		2035
1787	=item w->sweep () C<ev::embed> only	2036	=item w->sweep () (C<ev::embed> only)
1788		2037
1789	Invokes C<ev_embed_sweep>.	2038	Invokes C<ev_embed_sweep>.
1790		2039
1791	=item w->update () C<ev::stat> only	2040	=item w->update () (C<ev::stat> only)
1792		2041
1793	Invokes C<ev_stat_stat>.	2042	Invokes C<ev_stat_stat>.
1794		2043
1795	=back	2044	=back
1796		2045
…		…
1806		2055
1807	myclass ();	2056	myclass ();
1808	}	2057	}
1809		2058
1810	myclass::myclass (int fd)	2059	myclass::myclass (int fd)
1811	: io (this, &myclass::io_cb),
1812	idle (this, &myclass::idle_cb)
1813	{	2060	{
		2061	io .set <myclass, &myclass::io_cb > (this);
		2062	idle.set <myclass, &myclass::idle_cb> (this);
		2063
1814	io.start (fd, ev::READ);	2064	io.start (fd, ev::READ);
1815	}	2065	}
1816		2066
1817		2067
1818	=head1 MACRO MAGIC	2068	=head1 MACRO MAGIC
1819		2069
1820	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
1821	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2071	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1822	callbacks have an initial C<struct ev_loop *> argument.	2072	functions and callbacks have an initial C<struct ev_loop *> argument.
1823		2073
1824	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
1825	following macros are defined:	2075	following macros are defined:
1826		2076
1827	=over 4	2077	=over 4
…		…
1860	loop, if multiple loops are supported ("ev loop default").	2110	loop, if multiple loops are supported ("ev loop default").
1861		2111
1862	=back	2112	=back
1863		2113
1864	Example: Declare and initialise a check watcher, utilising the above	2114	Example: Declare and initialise a check watcher, utilising the above
1865	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
1866	or not.	2116	or not.
1867		2117
1868	static void	2118	static void
1869	check_cb (EV_P_ ev_timer *w, int revents)	2119	check_cb (EV_P_ ev_timer *w, int revents)
1870	{	2120	{
…		…
2095	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
2096	additional independent event loops. Otherwise there will be no support	2346	additional independent event loops. Otherwise there will be no support
2097	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
2098	argument. Instead, all functions act on the single default loop.	2348	argument. Instead, all functions act on the single default loop.
2099		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
2100	=item EV_PERIODIC_ENABLE	2367	=item EV_PERIODIC_ENABLE
2101		2368
2102	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
		2370	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2371	code.
		2372
		2373	=item EV_IDLE_ENABLE
		2374
		2375	If undefined or defined to be C<1>, then idle watchers are supported. If
2103	defined to be C<0>, then they are not. Disabling them saves a few kB of	2376	defined to be C<0>, then they are not. Disabling them saves a few kB of
2104	code.	2377	code.
2105		2378
2106	=item EV_EMBED_ENABLE	2379	=item EV_EMBED_ENABLE
2107		2380
…		…
2200		2473
2201	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
2202	libev will be explained. For complexity discussions about backends see the	2475	libev will be explained. For complexity discussions about backends see the
2203	documentation for C<ev_default_init>.	2476	documentation for C<ev_default_init>.
2204		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
2205	=over 4	2484	=over 4
2206		2485
2207	=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)
2208		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
2209	=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)
2210		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
2211	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2497	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2212		2498
		2499	These just add the watcher into an array or at the head of a list.
2213	=item Stopping check/prepare/idle watchers: O(1)	2500	=item Stopping check/prepare/idle watchers: O(1)
2214		2501
2215	=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))
2216		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
2217	=item Finding the next timer per loop iteration: O(1)	2508	=item Finding the next timer per loop iteration: O(1)
2218		2509
2219	=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)
2220		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
2221	=item Activating one watcher: O(1)	2515	=item Activating one watcher: O(1)
2222		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
2223	=back	2523	=back
2224		2524
2225		2525
2226	=head1 AUTHOR	2526	=head1 AUTHOR
2227		2527

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Comparing libev/ev.pod (file contents): Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs. Revision 1.86 by root, Tue Dec 18 01:20:33 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs.
Revision 1.86 by root, Tue Dec 18 01:20:33 2007 UTC