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

Comparing libev/ev.pod (file contents):
Revision 1.64 by root, Sat Dec 1 15:32:53 2007 UTC vs.
Revision 1.84 by root, Wed Dec 12 22:26:37 2007 UTC

…		…
47		47
48	return 0;	48	return 0;
49	}	49	}
50		50
51	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
52		56
53	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
54	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
55	these event sources and provide your program with events.	59	these event sources and provide your program with events.
56		60
…		…
113		117
114	=item int ev_version_major ()	118	=item int ev_version_major ()
115		119
116	=item int ev_version_minor ()	120	=item int ev_version_minor ()
117		121
118	You can find out the major and minor version numbers of the library	122	You can find out the major and minor ABI version numbers of the library
119	you linked against by calling the functions C<ev_version_major> and	123	you linked against by calling the functions C<ev_version_major> and
120	C<ev_version_minor>. If you want, you can compare against the global	124	C<ev_version_minor>. If you want, you can compare against the global
121	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
122	version of the library your program was compiled against.	126	version of the library your program was compiled against.
123		127
		128	These version numbers refer to the ABI version of the library, not the
		129	release version.
		130
124	Usually, it's a good idea to terminate if the major versions mismatch,	131	Usually, it's a good idea to terminate if the major versions mismatch,
125	as this indicates an incompatible change. Minor versions are usually	132	as this indicates an incompatible change. Minor versions are usually
126	compatible to older versions, so a larger minor version alone is usually	133	compatible to older versions, so a larger minor version alone is usually
127	not a problem.	134	not a problem.
128		135
129	Example: Make sure we haven't accidentally been linked against the wrong	136	Example: Make sure we haven't accidentally been linked against the wrong
130	version.	137	version.
…		…
274	a fork, you can also make libev check for a fork in each iteration by	281	a fork, you can also make libev check for a fork in each iteration by
275	enabling this flag.	282	enabling this flag.
276		283
277	This works by calling C<getpid ()> on every iteration of the loop,	284	This works by calling C<getpid ()> on every iteration of the loop,
278	and thus this might slow down your event loop if you do a lot of loop	285	and thus this might slow down your event loop if you do a lot of loop
279	iterations and little real work, but is usually not noticable (on my	286	iterations and little real work, but is usually not noticeable (on my
280	Linux system for example, C<getpid> is actually a simple 5-insn sequence	287	Linux system for example, C<getpid> is actually a simple 5-insn sequence
281	without a syscall and thus I<very> fast, but my Linux system also has	288	without a syscall and thus I<very> fast, but my Linux system also has
282	C<pthread_atfork> which is even faster).	289	C<pthread_atfork> which is even faster).
283		290
284	The big advantage of this flag is that you can forget about fork (and	291	The big advantage of this flag is that you can forget about fork (and
…		…
430		437
431	Like C<ev_default_fork>, but acts on an event loop created by	438	Like C<ev_default_fork>, but acts on an event loop created by
432	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	439	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
433	after fork, and how you do this is entirely your own problem.	440	after fork, and how you do this is entirely your own problem.
434		441
		442	=item unsigned int ev_loop_count (loop)
		443
		444	Returns the count of loop iterations for the loop, which is identical to
		445	the number of times libev did poll for new events. It starts at C<0> and
		446	happily wraps around with enough iterations.
		447
		448	This value can sometimes be useful as a generation counter of sorts (it
		449	"ticks" the number of loop iterations), as it roughly corresponds with
		450	C<ev_prepare> and C<ev_check> calls.
		451
435	=item unsigned int ev_backend (loop)	452	=item unsigned int ev_backend (loop)
436		453
437	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	454	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
438	use.	455	use.
439		456
…		…
472	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
473	usually a better approach for this kind of thing.	490	usually a better approach for this kind of thing.
474		491
475	Here are the gory details of what C<ev_loop> does:	492	Here are the gory details of what C<ev_loop> does:
476		493
		494	- Before the first iteration, call any pending watchers.
477	* If there are no active watchers (reference count is zero), return.	495	* If there are no active watchers (reference count is zero), return.
478	- Queue prepare watchers and then call all outstanding watchers.	496	- Queue all prepare watchers and then call all outstanding watchers.
479	- If we have been forked, recreate the kernel state.	497	- If we have been forked, recreate the kernel state.
480	- Update the kernel state with all outstanding changes.	498	- Update the kernel state with all outstanding changes.
481	- Update the "event loop time".	499	- Update the "event loop time".
482	- Calculate for how long to block.	500	- Calculate for how long to block.
483	- Block the process, waiting for any events.	501	- Block the process, waiting for any events.
…		…
722	=item bool ev_is_pending (ev_TYPE *watcher)	740	=item bool ev_is_pending (ev_TYPE *watcher)
723		741
724	Returns a true value iff the watcher is pending, (i.e. it has outstanding	742	Returns a true value iff the watcher is pending, (i.e. it has outstanding
725	events but its callback has not yet been invoked). As long as a watcher	743	events but its callback has not yet been invoked). As long as a watcher
726	is pending (but not active) you must not call an init function on it (but	744	is pending (but not active) you must not call an init function on it (but
727	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	745	C<ev_TYPE_set> is safe), you must not change its priority, and you must
728	libev (e.g. you cnanot C<free ()> it).	746	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		747	it).
729		748
730	=item callback ev_cb (ev_TYPE *watcher)	749	=item callback ev_cb (ev_TYPE *watcher)
731		750
732	Returns the callback currently set on the watcher.	751	Returns the callback currently set on the watcher.
733		752
734	=item ev_cb_set (ev_TYPE *watcher, callback)	753	=item ev_cb_set (ev_TYPE *watcher, callback)
735		754
736	Change the callback. You can change the callback at virtually any time	755	Change the callback. You can change the callback at virtually any time
737	(modulo threads).	756	(modulo threads).
		757
		758	=item ev_set_priority (ev_TYPE *watcher, priority)
		759
		760	=item int ev_priority (ev_TYPE *watcher)
		761
		762	Set and query the priority of the watcher. The priority is a small
		763	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		764	(default: C<-2>). Pending watchers with higher priority will be invoked
		765	before watchers with lower priority, but priority will not keep watchers
		766	from being executed (except for C<ev_idle> watchers).
		767
		768	This means that priorities are I<only> used for ordering callback
		769	invocation after new events have been received. This is useful, for
		770	example, to reduce latency after idling, or more often, to bind two
		771	watchers on the same event and make sure one is called first.
		772
		773	If you need to suppress invocation when higher priority events are pending
		774	you need to look at C<ev_idle> watchers, which provide this functionality.
		775
		776	You I<must not> change the priority of a watcher as long as it is active or
		777	pending.
		778
		779	The default priority used by watchers when no priority has been set is
		780	always C<0>, which is supposed to not be too high and not be too low :).
		781
		782	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		783	fine, as long as you do not mind that the priority value you query might
		784	or might not have been adjusted to be within valid range.
		785
		786	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		787
		788	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		789	C<loop> nor C<revents> need to be valid as long as the watcher callback
		790	can deal with that fact.
		791
		792	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		793
		794	If the watcher is pending, this function returns clears its pending status
		795	and returns its C<revents> bitset (as if its callback was invoked). If the
		796	watcher isn't pending it does nothing and returns C<0>.
738		797
739	=back	798	=back
740		799
741		800
742	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
848	it is best to always use non-blocking I/O: An extra C<read>(2) returning	907	it is best to always use non-blocking I/O: An extra C<read>(2) returning
849	C<EAGAIN> is far preferable to a program hanging until some data arrives.	908	C<EAGAIN> is far preferable to a program hanging until some data arrives.
850		909
851	If you cannot run the fd in non-blocking mode (for example you should not	910	If you cannot run the fd in non-blocking mode (for example you should not
852	play around with an Xlib connection), then you have to seperately re-test	911	play around with an Xlib connection), then you have to seperately re-test
853	wether a file descriptor is really ready with a known-to-be good interface	912	whether a file descriptor is really ready with a known-to-be good interface
854	such as poll (fortunately in our Xlib example, Xlib already does this on	913	such as poll (fortunately in our Xlib example, Xlib already does this on
855	its own, so its quite safe to use).	914	its own, so its quite safe to use).
		915
		916	=head3 The special problem of disappearing file descriptors
		917
		918	Some backends (e.g kqueue, epoll) need to be told about closing a file
		919	descriptor (either by calling C<close> explicitly or by any other means,
		920	such as C<dup>). The reason is that you register interest in some file
		921	descriptor, but when it goes away, the operating system will silently drop
		922	this interest. If another file descriptor with the same number then is
		923	registered with libev, there is no efficient way to see that this is, in
		924	fact, a different file descriptor.
		925
		926	To avoid having to explicitly tell libev about such cases, libev follows
		927	the following policy: Each time C<ev_io_set> is being called, libev
		928	will assume that this is potentially a new file descriptor, otherwise
		929	it is assumed that the file descriptor stays the same. That means that
		930	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		931	descriptor even if the file descriptor number itself did not change.
		932
		933	This is how one would do it normally anyway, the important point is that
		934	the libev application should not optimise around libev but should leave
		935	optimisations to libev.
		936
		937
		938	=head3 Watcher-Specific Functions
856		939
857	=over 4	940	=over 4
858		941
859	=item ev_io_init (ev_io *, callback, int fd, int events)	942	=item ev_io_init (ev_io *, callback, int fd, int events)
860		943
…		…
913	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	996	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
914		997
915	The callback is guarenteed to be invoked only when its timeout has passed,	998	The callback is guarenteed to be invoked only when its timeout has passed,
916	but if multiple timers become ready during the same loop iteration then	999	but if multiple timers become ready during the same loop iteration then
917	order of execution is undefined.	1000	order of execution is undefined.
		1001
		1002	=head3 Watcher-Specific Functions and Data Members
918		1003
919	=over 4	1004	=over 4
920		1005
921	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1006	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
922		1007
…		…
1018	but on wallclock time (absolute time). You can tell a periodic watcher	1103	but on wallclock time (absolute time). You can tell a periodic watcher
1019	to trigger "at" some specific point in time. For example, if you tell a	1104	to trigger "at" some specific point in time. For example, if you tell a
1020	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1105	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1021	+ 10.>) and then reset your system clock to the last year, then it will	1106	+ 10.>) and then reset your system clock to the last year, then it will
1022	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1107	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1023	roughly 10 seconds later and of course not if you reset your system time	1108	roughly 10 seconds later).
1024	again).
1025		1109
1026	They can also be used to implement vastly more complex timers, such as	1110	They can also be used to implement vastly more complex timers, such as
1027	triggering an event on eahc midnight, local time.	1111	triggering an event on each midnight, local time or other, complicated,
		1112	rules.
1028		1113
1029	As with timers, the callback is guarenteed to be invoked only when the	1114	As with timers, the callback is guarenteed to be invoked only when the
1030	time (C<at>) has been passed, but if multiple periodic timers become ready	1115	time (C<at>) has been passed, but if multiple periodic timers become ready
1031	during the same loop iteration then order of execution is undefined.	1116	during the same loop iteration then order of execution is undefined.
1032		1117
		1118	=head3 Watcher-Specific Functions and Data Members
		1119
1033	=over 4	1120	=over 4
1034		1121
1035	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1122	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1036		1123
1037	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1124	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1039	Lots of arguments, lets sort it out... There are basically three modes of	1126	Lots of arguments, lets sort it out... There are basically three modes of
1040	operation, and we will explain them from simplest to complex:	1127	operation, and we will explain them from simplest to complex:
1041		1128
1042	=over 4	1129	=over 4
1043		1130
1044	=item * absolute timer (interval = reschedule_cb = 0)	1131	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1045		1132
1046	In this configuration the watcher triggers an event at the wallclock time	1133	In this configuration the watcher triggers an event at the wallclock time
1047	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1134	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1048	that is, if it is to be run at January 1st 2011 then it will run when the	1135	that is, if it is to be run at January 1st 2011 then it will run when the
1049	system time reaches or surpasses this time.	1136	system time reaches or surpasses this time.
1050		1137
1051	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1138	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1052		1139
1053	In this mode the watcher will always be scheduled to time out at the next	1140	In this mode the watcher will always be scheduled to time out at the next
1054	C<at + N * interval> time (for some integer N) and then repeat, regardless	1141	C<at + N * interval> time (for some integer N, which can also be negative)
1055	of any time jumps.	1142	and then repeat, regardless of any time jumps.
1056		1143
1057	This can be used to create timers that do not drift with respect to system	1144	This can be used to create timers that do not drift with respect to system
1058	time:	1145	time:
1059		1146
1060	ev_periodic_set (&periodic, 0., 3600., 0);	1147	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1066		1153
1067	Another way to think about it (for the mathematically inclined) is that	1154	Another way to think about it (for the mathematically inclined) is that
1068	C<ev_periodic> will try to run the callback in this mode at the next possible	1155	C<ev_periodic> will try to run the callback in this mode at the next possible
1069	time where C<time = at (mod interval)>, regardless of any time jumps.	1156	time where C<time = at (mod interval)>, regardless of any time jumps.
1070		1157
		1158	For numerical stability it is preferable that the C<at> value is near
		1159	C<ev_now ()> (the current time), but there is no range requirement for
		1160	this value.
		1161
1071	=item * manual reschedule mode (reschedule_cb = callback)	1162	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1072		1163
1073	In this mode the values for C<interval> and C<at> are both being	1164	In this mode the values for C<interval> and C<at> are both being
1074	ignored. Instead, each time the periodic watcher gets scheduled, the	1165	ignored. Instead, each time the periodic watcher gets scheduled, the
1075	reschedule callback will be called with the watcher as first, and the	1166	reschedule callback will be called with the watcher as first, and the
1076	current time as second argument.	1167	current time as second argument.
1077		1168
1078	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1169	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1079	ever, or make any event loop modifications>. If you need to stop it,	1170	ever, or make any event loop modifications>. If you need to stop it,
1080	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1171	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1081	starting a prepare watcher).	1172	starting an C<ev_prepare> watcher, which is legal).
1082		1173
1083	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1174	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1084	ev_tstamp now)>, e.g.:	1175	ev_tstamp now)>, e.g.:
1085		1176
1086	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1177	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1108		1199
1109	Simply stops and restarts the periodic watcher again. This is only useful	1200	Simply stops and restarts the periodic watcher again. This is only useful
1110	when you changed some parameters or the reschedule callback would return	1201	when you changed some parameters or the reschedule callback would return
1111	a different time than the last time it was called (e.g. in a crond like	1202	a different time than the last time it was called (e.g. in a crond like
1112	program when the crontabs have changed).	1203	program when the crontabs have changed).
		1204
		1205	=item ev_tstamp offset [read-write]
		1206
		1207	When repeating, this contains the offset value, otherwise this is the
		1208	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1209
		1210	Can be modified any time, but changes only take effect when the periodic
		1211	timer fires or C<ev_periodic_again> is being called.
1113		1212
1114	=item ev_tstamp interval [read-write]	1213	=item ev_tstamp interval [read-write]
1115		1214
1116	The current interval value. Can be modified any time, but changes only	1215	The current interval value. Can be modified any time, but changes only
1117	take effect when the periodic timer fires or C<ev_periodic_again> is being	1216	take effect when the periodic timer fires or C<ev_periodic_again> is being
…		…
1171	with the kernel (thus it coexists with your own signal handlers as long	1270	with the kernel (thus it coexists with your own signal handlers as long
1172	as you don't register any with libev). Similarly, when the last signal	1271	as you don't register any with libev). Similarly, when the last signal
1173	watcher for a signal is stopped libev will reset the signal handler to	1272	watcher for a signal is stopped libev will reset the signal handler to
1174	SIG_DFL (regardless of what it was set to before).	1273	SIG_DFL (regardless of what it was set to before).
1175		1274
		1275	=head3 Watcher-Specific Functions and Data Members
		1276
1176	=over 4	1277	=over 4
1177		1278
1178	=item ev_signal_init (ev_signal *, callback, int signum)	1279	=item ev_signal_init (ev_signal *, callback, int signum)
1179		1280
1180	=item ev_signal_set (ev_signal *, int signum)	1281	=item ev_signal_set (ev_signal *, int signum)
…		…
1191		1292
1192	=head2 C<ev_child> - watch out for process status changes	1293	=head2 C<ev_child> - watch out for process status changes
1193		1294
1194	Child watchers trigger when your process receives a SIGCHLD in response to	1295	Child watchers trigger when your process receives a SIGCHLD in response to
1195	some child status changes (most typically when a child of yours dies).	1296	some child status changes (most typically when a child of yours dies).
		1297
		1298	=head3 Watcher-Specific Functions and Data Members
1196		1299
1197	=over 4	1300	=over 4
1198		1301
1199	=item ev_child_init (ev_child *, callback, int pid)	1302	=item ev_child_init (ev_child *, callback, int pid)
1200		1303
…		…
1268	reader). Inotify will be used to give hints only and should not change the	1371	reader). Inotify will be used to give hints only and should not change the
1269	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1372	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1270	to fall back to regular polling again even with inotify, but changes are	1373	to fall back to regular polling again even with inotify, but changes are
1271	usually detected immediately, and if the file exists there will be no	1374	usually detected immediately, and if the file exists there will be no
1272	polling.	1375	polling.
		1376
		1377	=head3 Watcher-Specific Functions and Data Members
1273		1378
1274	=over 4	1379	=over 4
1275		1380
1276	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1381	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1277		1382
…		…
1341	ev_stat_start (loop, &passwd);	1446	ev_stat_start (loop, &passwd);
1342		1447
1343		1448
1344	=head2 C<ev_idle> - when you've got nothing better to do...	1449	=head2 C<ev_idle> - when you've got nothing better to do...
1345		1450
1346	Idle watchers trigger events when there are no other events are pending	1451	Idle watchers trigger events when no other events of the same or higher
1347	(prepare, check and other idle watchers do not count). That is, as long	1452	priority are pending (prepare, check and other idle watchers do not
1348	as your process is busy handling sockets or timeouts (or even signals,	1453	count).
1349	imagine) it will not be triggered. But when your process is idle all idle	1454
1350	watchers are being called again and again, once per event loop iteration -	1455	That is, as long as your process is busy handling sockets or timeouts
		1456	(or even signals, imagine) of the same or higher priority it will not be
		1457	triggered. But when your process is idle (or only lower-priority watchers
		1458	are pending), the idle watchers are being called once per event loop
1351	until stopped, that is, or your process receives more events and becomes	1459	iteration - until stopped, that is, or your process receives more events
1352	busy.	1460	and becomes busy again with higher priority stuff.
1353		1461
1354	The most noteworthy effect is that as long as any idle watchers are	1462	The most noteworthy effect is that as long as any idle watchers are
1355	active, the process will not block when waiting for new events.	1463	active, the process will not block when waiting for new events.
1356		1464
1357	Apart from keeping your process non-blocking (which is a useful	1465	Apart from keeping your process non-blocking (which is a useful
1358	effect on its own sometimes), idle watchers are a good place to do	1466	effect on its own sometimes), idle watchers are a good place to do
1359	"pseudo-background processing", or delay processing stuff to after the	1467	"pseudo-background processing", or delay processing stuff to after the
1360	event loop has handled all outstanding events.	1468	event loop has handled all outstanding events.
		1469
		1470	=head3 Watcher-Specific Functions and Data Members
1361		1471
1362	=over 4	1472	=over 4
1363		1473
1364	=item ev_idle_init (ev_signal *, callback)	1474	=item ev_idle_init (ev_signal *, callback)
1365		1475
…		…
1423	with priority higher than or equal to the event loop and one coroutine	1533	with priority higher than or equal to the event loop and one coroutine
1424	of lower priority, but only once, using idle watchers to keep the event	1534	of lower priority, but only once, using idle watchers to keep the event
1425	loop from blocking if lower-priority coroutines are active, thus mapping	1535	loop from blocking if lower-priority coroutines are active, thus mapping
1426	low-priority coroutines to idle/background tasks).	1536	low-priority coroutines to idle/background tasks).
1427		1537
		1538	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1539	priority, to ensure that they are being run before any other watchers
		1540	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1541	too) should not activate ("feed") events into libev. While libev fully
		1542	supports this, they will be called before other C<ev_check> watchers did
		1543	their job. As C<ev_check> watchers are often used to embed other event
		1544	loops those other event loops might be in an unusable state until their
		1545	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1546	others).
		1547
		1548	=head3 Watcher-Specific Functions and Data Members
		1549
1428	=over 4	1550	=over 4
1429		1551
1430	=item ev_prepare_init (ev_prepare *, callback)	1552	=item ev_prepare_init (ev_prepare *, callback)
1431		1553
1432	=item ev_check_init (ev_check *, callback)	1554	=item ev_check_init (ev_check *, callback)
…		…
1435	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1557	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1436	macros, but using them is utterly, utterly and completely pointless.	1558	macros, but using them is utterly, utterly and completely pointless.
1437		1559
1438	=back	1560	=back
1439		1561
1440	Example: To include a library such as adns, you would add IO watchers	1562	There are a number of principal ways to embed other event loops or modules
1441	and a timeout watcher in a prepare handler, as required by libadns, and	1563	into libev. Here are some ideas on how to include libadns into libev
		1564	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1565	use for an actually working example. Another Perl module named C<EV::Glib>
		1566	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1567	into the Glib event loop).
		1568
		1569	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1442	in a check watcher, destroy them and call into libadns. What follows is	1570	and in a check watcher, destroy them and call into libadns. What follows
1443	pseudo-code only of course:	1571	is pseudo-code only of course. This requires you to either use a low
		1572	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1573	the callbacks for the IO/timeout watchers might not have been called yet.
1444		1574
1445	static ev_io iow [nfd];	1575	static ev_io iow [nfd];
1446	static ev_timer tw;	1576	static ev_timer tw;
1447		1577
1448	static void	1578	static void
1449	io_cb (ev_loop loop, ev_io w, int revents)	1579	io_cb (ev_loop loop, ev_io w, int revents)
1450	{	1580	{
1451	// set the relevant poll flags
1452	// could also call adns_processreadable etc. here
1453	struct pollfd fd = (struct pollfd )w->data;
1454	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1455	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1456	}	1581	}
1457		1582
1458	// create io watchers for each fd and a timer before blocking	1583	// create io watchers for each fd and a timer before blocking
1459	static void	1584	static void
1460	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1585	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1466		1591
1467	/* the callback is illegal, but won't be called as we stop during check */	1592	/* the callback is illegal, but won't be called as we stop during check */
1468	ev_timer_init (&tw, 0, timeout * 1e-3);	1593	ev_timer_init (&tw, 0, timeout * 1e-3);
1469	ev_timer_start (loop, &tw);	1594	ev_timer_start (loop, &tw);
1470		1595
1471	// create on ev_io per pollfd	1596	// create one ev_io per pollfd
1472	for (int i = 0; i < nfd; ++i)	1597	for (int i = 0; i < nfd; ++i)
1473	{	1598	{
1474	ev_io_init (iow + i, io_cb, fds [i].fd,	1599	ev_io_init (iow + i, io_cb, fds [i].fd,
1475	((fds [i].events & POLLIN ? EV_READ : 0)	1600	((fds [i].events & POLLIN ? EV_READ : 0)
1476	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1601	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1477		1602
1478	fds [i].revents = 0;	1603	fds [i].revents = 0;
1479	iow [i].data = fds + i;
1480	ev_io_start (loop, iow + i);	1604	ev_io_start (loop, iow + i);
1481	}	1605	}
1482	}	1606	}
1483		1607
1484	// stop all watchers after blocking	1608	// stop all watchers after blocking
…		…
1486	adns_check_cb (ev_loop loop, ev_check w, int revents)	1610	adns_check_cb (ev_loop loop, ev_check w, int revents)
1487	{	1611	{
1488	ev_timer_stop (loop, &tw);	1612	ev_timer_stop (loop, &tw);
1489		1613
1490	for (int i = 0; i < nfd; ++i)	1614	for (int i = 0; i < nfd; ++i)
		1615	{
		1616	// set the relevant poll flags
		1617	// could also call adns_processreadable etc. here
		1618	struct pollfd *fd = fds + i;
		1619	int revents = ev_clear_pending (iow + i);
		1620	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1621	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1622
		1623	// now stop the watcher
1491	ev_io_stop (loop, iow + i);	1624	ev_io_stop (loop, iow + i);
		1625	}
1492		1626
1493	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1627	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1628	}
		1629
		1630	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1631	in the prepare watcher and would dispose of the check watcher.
		1632
		1633	Method 3: If the module to be embedded supports explicit event
		1634	notification (adns does), you can also make use of the actual watcher
		1635	callbacks, and only destroy/create the watchers in the prepare watcher.
		1636
		1637	static void
		1638	timer_cb (EV_P_ ev_timer *w, int revents)
		1639	{
		1640	adns_state ads = (adns_state)w->data;
		1641	update_now (EV_A);
		1642
		1643	adns_processtimeouts (ads, &tv_now);
		1644	}
		1645
		1646	static void
		1647	io_cb (EV_P_ ev_io *w, int revents)
		1648	{
		1649	adns_state ads = (adns_state)w->data;
		1650	update_now (EV_A);
		1651
		1652	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1653	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1654	}
		1655
		1656	// do not ever call adns_afterpoll
		1657
		1658	Method 4: Do not use a prepare or check watcher because the module you
		1659	want to embed is too inflexible to support it. Instead, youc na override
		1660	their poll function. The drawback with this solution is that the main
		1661	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1662	this.
		1663
		1664	static gint
		1665	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1666	{
		1667	int got_events = 0;
		1668
		1669	for (n = 0; n < nfds; ++n)
		1670	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1671
		1672	if (timeout >= 0)
		1673	// create/start timer
		1674
		1675	// poll
		1676	ev_loop (EV_A_ 0);
		1677
		1678	// stop timer again
		1679	if (timeout >= 0)
		1680	ev_timer_stop (EV_A_ &to);
		1681
		1682	// stop io watchers again - their callbacks should have set
		1683	for (n = 0; n < nfds; ++n)
		1684	ev_io_stop (EV_A_ iow [n]);
		1685
		1686	return got_events;
1494	}	1687	}
1495		1688
1496		1689
1497	=head2 C<ev_embed> - when one backend isn't enough...	1690	=head2 C<ev_embed> - when one backend isn't enough...
1498		1691
…		…
1562	ev_embed_start (loop_hi, &embed);	1755	ev_embed_start (loop_hi, &embed);
1563	}	1756	}
1564	else	1757	else
1565	loop_lo = loop_hi;	1758	loop_lo = loop_hi;
1566		1759
		1760	=head3 Watcher-Specific Functions and Data Members
		1761
1567	=over 4	1762	=over 4
1568		1763
1569	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1764	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1570		1765
1571	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	1766	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
…		…
1597	event loop blocks next and before C<ev_check> watchers are being called,	1792	event loop blocks next and before C<ev_check> watchers are being called,
1598	and only in the child after the fork. If whoever good citizen calling	1793	and only in the child after the fork. If whoever good citizen calling
1599	C<ev_default_fork> cheats and calls it in the wrong process, the fork	1794	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1600	handlers will be invoked, too, of course.	1795	handlers will be invoked, too, of course.
1601		1796
		1797	=head3 Watcher-Specific Functions and Data Members
		1798
1602	=over 4	1799	=over 4
1603		1800
1604	=item ev_fork_init (ev_signal *, callback)	1801	=item ev_fork_init (ev_signal *, callback)
1605		1802
1606	Initialises and configures the fork watcher - it has no parameters of any	1803	Initialises and configures the fork watcher - it has no parameters of any
…		…
1702		1899
1703	To use it,	1900	To use it,
1704		1901
1705	#include <ev++.h>	1902	#include <ev++.h>
1706		1903
1707	(it is not installed by default). This automatically includes F<ev.h>	1904	This automatically includes F<ev.h> and puts all of its definitions (many
1708	and puts all of its definitions (many of them macros) into the global	1905	of them macros) into the global namespace. All C++ specific things are
1709	namespace. All C++ specific things are put into the C<ev> namespace.	1906	put into the C<ev> namespace. It should support all the same embedding
		1907	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1710		1908
1711	It should support all the same embedding options as F<ev.h>, most notably	1909	Care has been taken to keep the overhead low. The only data member the C++
1712	C<EV_MULTIPLICITY>.	1910	classes add (compared to plain C-style watchers) is the event loop pointer
		1911	that the watcher is associated with (or no additional members at all if
		1912	you disable C<EV_MULTIPLICITY> when embedding libev).
		1913
		1914	Currently, functions, and static and non-static member functions can be
		1915	used as callbacks. Other types should be easy to add as long as they only
		1916	need one additional pointer for context. If you need support for other
		1917	types of functors please contact the author (preferably after implementing
		1918	it).
1713		1919
1714	Here is a list of things available in the C<ev> namespace:	1920	Here is a list of things available in the C<ev> namespace:
1715		1921
1716	=over 4	1922	=over 4
1717		1923
…		…
1733		1939
1734	All of those classes have these methods:	1940	All of those classes have these methods:
1735		1941
1736	=over 4	1942	=over 4
1737		1943
1738	=item ev::TYPE::TYPE (object , object::method )	1944	=item ev::TYPE::TYPE ()
1739		1945
1740	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1946	=item ev::TYPE::TYPE (struct ev_loop *)
1741		1947
1742	=item ev::TYPE::~TYPE	1948	=item ev::TYPE::~TYPE
1743		1949
1744	The constructor takes a pointer to an object and a method pointer to	1950	The constructor (optionally) takes an event loop to associate the watcher
1745	the event handler callback to call in this class. The constructor calls	1951	with. If it is omitted, it will use C<EV_DEFAULT>.
1746	C<ev_init> for you, which means you have to call the C<set> method	1952
1747	before starting it. If you do not specify a loop then the constructor	1953	The constructor calls C<ev_init> for you, which means you have to call the
1748	automatically associates the default loop with this watcher.	1954	C<set> method before starting it.
		1955
		1956	It will not set a callback, however: You have to call the templated C<set>
		1957	method to set a callback before you can start the watcher.
		1958
		1959	(The reason why you have to use a method is a limitation in C++ which does
		1960	not allow explicit template arguments for constructors).
1749		1961
1750	The destructor automatically stops the watcher if it is active.	1962	The destructor automatically stops the watcher if it is active.
		1963
		1964	=item w->set<class, &class::method> (object *)
		1965
		1966	This method sets the callback method to call. The method has to have a
		1967	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1968	first argument and the C<revents> as second. The object must be given as
		1969	parameter and is stored in the C<data> member of the watcher.
		1970
		1971	This method synthesizes efficient thunking code to call your method from
		1972	the C callback that libev requires. If your compiler can inline your
		1973	callback (i.e. it is visible to it at the place of the C<set> call and
		1974	your compiler is good :), then the method will be fully inlined into the
		1975	thunking function, making it as fast as a direct C callback.
		1976
		1977	Example: simple class declaration and watcher initialisation
		1978
		1979	struct myclass
		1980	{
		1981	void io_cb (ev::io &w, int revents) { }
		1982	}
		1983
		1984	myclass obj;
		1985	ev::io iow;
		1986	iow.set <myclass, &myclass::io_cb> (&obj);
		1987
		1988	=item w->set<function> (void *data = 0)
		1989
		1990	Also sets a callback, but uses a static method or plain function as
		1991	callback. The optional C<data> argument will be stored in the watcher's
		1992	C<data> member and is free for you to use.
		1993
		1994	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1995
		1996	See the method-C<set> above for more details.
		1997
		1998	Example:
		1999
		2000	static void io_cb (ev::io &w, int revents) { }
		2001	iow.set <io_cb> ();
1751		2002
1752	=item w->set (struct ev_loop *)	2003	=item w->set (struct ev_loop *)
1753		2004
1754	Associates a different C<struct ev_loop> with this watcher. You can only	2005	Associates a different C<struct ev_loop> with this watcher. You can only
1755	do this when the watcher is inactive (and not pending either).	2006	do this when the watcher is inactive (and not pending either).
1756		2007
1757	=item w->set ([args])	2008	=item w->set ([args])
1758		2009
1759	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2010	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1760	called at least once. Unlike the C counterpart, an active watcher gets	2011	called at least once. Unlike the C counterpart, an active watcher gets
1761	automatically stopped and restarted.	2012	automatically stopped and restarted when reconfiguring it with this
		2013	method.
1762		2014
1763	=item w->start ()	2015	=item w->start ()
1764		2016
1765	Starts the watcher. Note that there is no C<loop> argument as the	2017	Starts the watcher. Note that there is no C<loop> argument, as the
1766	constructor already takes the loop.	2018	constructor already stores the event loop.
1767		2019
1768	=item w->stop ()	2020	=item w->stop ()
1769		2021
1770	Stops the watcher if it is active. Again, no C<loop> argument.	2022	Stops the watcher if it is active. Again, no C<loop> argument.
1771		2023
1772	=item w->again () C<ev::timer>, C<ev::periodic> only	2024	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1773		2025
1774	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2026	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1775	C<ev_TYPE_again> function.	2027	C<ev_TYPE_again> function.
1776		2028
1777	=item w->sweep () C<ev::embed> only	2029	=item w->sweep () (C<ev::embed> only)
1778		2030
1779	Invokes C<ev_embed_sweep>.	2031	Invokes C<ev_embed_sweep>.
1780		2032
1781	=item w->update () C<ev::stat> only	2033	=item w->update () (C<ev::stat> only)
1782		2034
1783	Invokes C<ev_stat_stat>.	2035	Invokes C<ev_stat_stat>.
1784		2036
1785	=back	2037	=back
1786		2038
…		…
1796		2048
1797	myclass ();	2049	myclass ();
1798	}	2050	}
1799		2051
1800	myclass::myclass (int fd)	2052	myclass::myclass (int fd)
1801	: io (this, &myclass::io_cb),
1802	idle (this, &myclass::idle_cb)
1803	{	2053	{
		2054	io .set <myclass, &myclass::io_cb > (this);
		2055	idle.set <myclass, &myclass::idle_cb> (this);
		2056
1804	io.start (fd, ev::READ);	2057	io.start (fd, ev::READ);
1805	}	2058	}
1806		2059
1807		2060
1808	=head1 MACRO MAGIC	2061	=head1 MACRO MAGIC
1809		2062
1810	Libev can be compiled with a variety of options, the most fundemantal is	2063	Libev can be compiled with a variety of options, the most fundamantal
1811	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2064	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1812	callbacks have an initial C<struct ev_loop *> argument.	2065	functions and callbacks have an initial C<struct ev_loop *> argument.
1813		2066
1814	To make it easier to write programs that cope with either variant, the	2067	To make it easier to write programs that cope with either variant, the
1815	following macros are defined:	2068	following macros are defined:
1816		2069
1817	=over 4	2070	=over 4
…		…
1850	loop, if multiple loops are supported ("ev loop default").	2103	loop, if multiple loops are supported ("ev loop default").
1851		2104
1852	=back	2105	=back
1853		2106
1854	Example: Declare and initialise a check watcher, utilising the above	2107	Example: Declare and initialise a check watcher, utilising the above
1855	macros so it will work regardless of wether multiple loops are supported	2108	macros so it will work regardless of whether multiple loops are supported
1856	or not.	2109	or not.
1857		2110
1858	static void	2111	static void
1859	check_cb (EV_P_ ev_timer *w, int revents)	2112	check_cb (EV_P_ ev_timer *w, int revents)
1860	{	2113	{
…		…
2085	will have the C<struct ev_loop *> as first argument, and you can create	2338	will have the C<struct ev_loop *> as first argument, and you can create
2086	additional independent event loops. Otherwise there will be no support	2339	additional independent event loops. Otherwise there will be no support
2087	for multiple event loops and there is no first event loop pointer	2340	for multiple event loops and there is no first event loop pointer
2088	argument. Instead, all functions act on the single default loop.	2341	argument. Instead, all functions act on the single default loop.
2089		2342
		2343	=item EV_MINPRI
		2344
		2345	=item EV_MAXPRI
		2346
		2347	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2348	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2349	provide for more priorities by overriding those symbols (usually defined
		2350	to be C<-2> and C<2>, respectively).
		2351
		2352	When doing priority-based operations, libev usually has to linearly search
		2353	all the priorities, so having many of them (hundreds) uses a lot of space
		2354	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2355	fine.
		2356
		2357	If your embedding app does not need any priorities, defining these both to
		2358	C<0> will save some memory and cpu.
		2359
2090	=item EV_PERIODIC_ENABLE	2360	=item EV_PERIODIC_ENABLE
2091		2361
2092	If undefined or defined to be C<1>, then periodic timers are supported. If	2362	If undefined or defined to be C<1>, then periodic timers are supported. If
		2363	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2364	code.
		2365
		2366	=item EV_IDLE_ENABLE
		2367
		2368	If undefined or defined to be C<1>, then idle watchers are supported. If
2093	defined to be C<0>, then they are not. Disabling them saves a few kB of	2369	defined to be C<0>, then they are not. Disabling them saves a few kB of
2094	code.	2370	code.
2095		2371
2096	=item EV_EMBED_ENABLE	2372	=item EV_EMBED_ENABLE
2097		2373
…		…
2190		2466
2191	In this section the complexities of (many of) the algorithms used inside	2467	In this section the complexities of (many of) the algorithms used inside
2192	libev will be explained. For complexity discussions about backends see the	2468	libev will be explained. For complexity discussions about backends see the
2193	documentation for C<ev_default_init>.	2469	documentation for C<ev_default_init>.
2194		2470
		2471	All of the following are about amortised time: If an array needs to be
		2472	extended, libev needs to realloc and move the whole array, but this
		2473	happens asymptotically never with higher number of elements, so O(1) might
		2474	mean it might do a lengthy realloc operation in rare cases, but on average
		2475	it is much faster and asymptotically approaches constant time.
		2476
2195	=over 4	2477	=over 4
2196		2478
2197	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2479	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2198		2480
		2481	This means that, when you have a watcher that triggers in one hour and
		2482	there are 100 watchers that would trigger before that then inserting will
		2483	have to skip those 100 watchers.
		2484
2199	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2485	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2200		2486
		2487	That means that for changing a timer costs less than removing/adding them
		2488	as only the relative motion in the event queue has to be paid for.
		2489
2201	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2490	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2202		2491
		2492	These just add the watcher into an array or at the head of a list.
2203	=item Stopping check/prepare/idle watchers: O(1)	2493	=item Stopping check/prepare/idle watchers: O(1)
2204		2494
2205	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2495	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2206		2496
		2497	These watchers are stored in lists then need to be walked to find the
		2498	correct watcher to remove. The lists are usually short (you don't usually
		2499	have many watchers waiting for the same fd or signal).
		2500
2207	=item Finding the next timer per loop iteration: O(1)	2501	=item Finding the next timer per loop iteration: O(1)
2208		2502
2209	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2503	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2210		2504
		2505	A change means an I/O watcher gets started or stopped, which requires
		2506	libev to recalculate its status (and possibly tell the kernel).
		2507
2211	=item Activating one watcher: O(1)	2508	=item Activating one watcher: O(1)
2212		2509
		2510	=item Priority handling: O(number_of_priorities)
		2511
		2512	Priorities are implemented by allocating some space for each
		2513	priority. When doing priority-based operations, libev usually has to
		2514	linearly search all the priorities.
		2515
2213	=back	2516	=back
2214		2517
2215		2518
2216	=head1 AUTHOR	2519	=head1 AUTHOR
2217		2520

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Comparing libev/ev.pod (file contents): Revision 1.64 by root, Sat Dec 1 15:32:53 2007 UTC vs. Revision 1.84 by root, Wed Dec 12 22:26:37 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.64 by root, Sat Dec 1 15:32:53 2007 UTC vs.
Revision 1.84 by root, Wed Dec 12 22:26:37 2007 UTC