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

Comparing libev/ev.pod (file contents):
Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC vs.
Revision 1.81 by root, Wed Dec 12 04:53:58 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
…		…
63	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
64	watcher.	68	watcher.
65		69
66	=head1 FEATURES	70	=head1 FEATURES
67		71
68	Libev supports C<select>, C<poll>, the linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
69	bsd-specific C<kqueue> and the solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70	for file descriptor events (C<ev_io>), relative timers (C<ev_timer>),	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
		75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
71	absolute timers with customised rescheduling (C<ev_periodic>), synchronous	76	with customised rescheduling (C<ev_periodic>), synchronous signals
72	signals (C<ev_signal>), process status change events (C<ev_child>), and	77	(C<ev_signal>), process status change events (C<ev_child>), and event
73	event watchers dealing with the event loop mechanism itself (C<ev_idle>,	78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
74	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
75	file watchers (C<ev_stat>) and even limited support for fork events	80	file watchers (C<ev_stat>) and even limited support for fork events
76	(C<ev_fork>).	81	(C<ev_fork>).
77		82
78	It also is quite fast (see this	83	It also is quite fast (see this
…		…
112		117
113	=item int ev_version_major ()	118	=item int ev_version_major ()
114		119
115	=item int ev_version_minor ()	120	=item int ev_version_minor ()
116		121
117	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
118	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
119	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
120	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
121	version of the library your program was compiled against.	126	version of the library your program was compiled against.
122		127
		128	These version numbers refer to the ABI version of the library, not the
		129	release version.
		130
123	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,
124	as this indicates an incompatible change. Minor versions are usually	132	as this indicates an incompatible change. Minor versions are usually
125	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
126	not a problem.	134	not a problem.
127		135
128	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
129	version.	137	version.
…		…
162	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	170	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
163	recommended ones.	171	recommended ones.
164		172
165	See the description of C<ev_embed> watchers for more info.	173	See the description of C<ev_embed> watchers for more info.
166		174
167	=item ev_set_allocator (void (cb)(void *ptr, size_t size))	175	=item ev_set_allocator (void (cb)(void *ptr, long size))
168		176
169	Sets the allocation function to use (the prototype and semantics are	177	Sets the allocation function to use (the prototype is similar - the
170	identical to the realloc C function). It is used to allocate and free	178	semantics is identical - to the realloc C function). It is used to
171	memory (no surprises here). If it returns zero when memory needs to be	179	allocate and free memory (no surprises here). If it returns zero when
172	allocated, the library might abort or take some potentially destructive	180	memory needs to be allocated, the library might abort or take some
173	action. The default is your system realloc function.	181	potentially destructive action. The default is your system realloc
		182	function.
174		183
175	You could override this function in high-availability programs to, say,	184	You could override this function in high-availability programs to, say,
176	free some memory if it cannot allocate memory, to use a special allocator,	185	free some memory if it cannot allocate memory, to use a special allocator,
177	or even to sleep a while and retry until some memory is available.	186	or even to sleep a while and retry until some memory is available.
178		187
…		…
264	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	273	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
265	override the flags completely if it is found in the environment. This is	274	override the flags completely if it is found in the environment. This is
266	useful to try out specific backends to test their performance, or to work	275	useful to try out specific backends to test their performance, or to work
267	around bugs.	276	around bugs.
268		277
		278	=item C<EVFLAG_FORKCHECK>
		279
		280	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		281	a fork, you can also make libev check for a fork in each iteration by
		282	enabling this flag.
		283
		284	This works by calling C<getpid ()> on every iteration of the loop,
		285	and thus this might slow down your event loop if you do a lot of loop
		286	iterations and little real work, but is usually not noticeable (on my
		287	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		288	without a syscall and thus I<very> fast, but my Linux system also has
		289	C<pthread_atfork> which is even faster).
		290
		291	The big advantage of this flag is that you can forget about fork (and
		292	forget about forgetting to tell libev about forking) when you use this
		293	flag.
		294
		295	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		296	environment variable.
		297
269	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
270		299
271	This is your standard select(2) backend. Not I<completely> standard, as	300	This is your standard select(2) backend. Not I<completely> standard, as
272	libev tries to roll its own fd_set with no limits on the number of fds,	301	libev tries to roll its own fd_set with no limits on the number of fds,
273	but if that fails, expect a fairly low limit on the number of fds when	302	but if that fails, expect a fairly low limit on the number of fds when
…		…
408		437
409	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
410	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
411	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.
412		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
413	=item unsigned int ev_backend (loop)	452	=item unsigned int ev_backend (loop)
414		453
415	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
416	use.	455	use.
417		456
…		…
450	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
451	usually a better approach for this kind of thing.	490	usually a better approach for this kind of thing.
452		491
453	Here are the gory details of what C<ev_loop> does:	492	Here are the gory details of what C<ev_loop> does:
454		493
		494	- Before the first iteration, call any pending watchers.
455	* If there are no active watchers (reference count is zero), return.	495	* If there are no active watchers (reference count is zero), return.
456	- Queue prepare watchers and then call all outstanding watchers.	496	- Queue all prepare watchers and then call all outstanding watchers.
457	- If we have been forked, recreate the kernel state.	497	- If we have been forked, recreate the kernel state.
458	- Update the kernel state with all outstanding changes.	498	- Update the kernel state with all outstanding changes.
459	- Update the "event loop time".	499	- Update the "event loop time".
460	- Calculate for how long to block.	500	- Calculate for how long to block.
461	- Block the process, waiting for any events.	501	- Block the process, waiting for any events.
…		…
700	=item bool ev_is_pending (ev_TYPE *watcher)	740	=item bool ev_is_pending (ev_TYPE *watcher)
701		741
702	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
703	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
704	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
705	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
706	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).
707		748
708	=item callback ev_cb (ev_TYPE *watcher)	749	=item callback ev_cb (ev_TYPE *watcher)
709		750
710	Returns the callback currently set on the watcher.	751	Returns the callback currently set on the watcher.
711		752
712	=item ev_cb_set (ev_TYPE *watcher, callback)	753	=item ev_cb_set (ev_TYPE *watcher, callback)
713		754
714	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
715	(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>.
716		797
717	=back	798	=back
718		799
719		800
720	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
826	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
827	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.
828		909
829	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
830	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
831	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
832	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
833	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
834		937
835	=over 4	938	=over 4
836		939
837	=item ev_io_init (ev_io *, callback, int fd, int events)	940	=item ev_io_init (ev_io *, callback, int fd, int events)
838		941
…		…
914	=item ev_timer_again (loop)	1017	=item ev_timer_again (loop)
915		1018
916	This will act as if the timer timed out and restart it again if it is	1019	This will act as if the timer timed out and restart it again if it is
917	repeating. The exact semantics are:	1020	repeating. The exact semantics are:
918		1021
		1022	If the timer is pending, its pending status is cleared.
		1023
919	If the timer is started but nonrepeating, stop it.	1024	If the timer is started but nonrepeating, stop it (as if it timed out).
920		1025
921	If the timer is repeating, either start it if necessary (with the repeat	1026	If the timer is repeating, either start it if necessary (with the
922	value), or reset the running timer to the repeat value.	1027	C<repeat> value), or reset the running timer to the C<repeat> value.
923		1028
924	This sounds a bit complicated, but here is a useful and typical	1029	This sounds a bit complicated, but here is a useful and typical
925	example: Imagine you have a tcp connection and you want a so-called	1030	example: Imagine you have a tcp connection and you want a so-called idle
926	idle timeout, that is, you want to be called when there have been,	1031	timeout, that is, you want to be called when there have been, say, 60
927	say, 60 seconds of inactivity on the socket. The easiest way to do	1032	seconds of inactivity on the socket. The easiest way to do this is to
928	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1033	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
929	C<ev_timer_again> each time you successfully read or write some data. If	1034	C<ev_timer_again> each time you successfully read or write some data. If
930	you go into an idle state where you do not expect data to travel on the	1035	you go into an idle state where you do not expect data to travel on the
931	socket, you can stop the timer, and again will automatically restart it if	1036	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
932	need be.	1037	automatically restart it if need be.
933		1038
934	You can also ignore the C<after> value and C<ev_timer_start> altogether	1039	That means you can ignore the C<after> value and C<ev_timer_start>
935	and only ever use the C<repeat> value:	1040	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
936		1041
937	ev_timer_init (timer, callback, 0., 5.);	1042	ev_timer_init (timer, callback, 0., 5.);
938	ev_timer_again (loop, timer);	1043	ev_timer_again (loop, timer);
939	...	1044	...
940	timer->again = 17.;	1045	timer->again = 17.;
941	ev_timer_again (loop, timer);	1046	ev_timer_again (loop, timer);
942	...	1047	...
943	timer->again = 10.;	1048	timer->again = 10.;
944	ev_timer_again (loop, timer);	1049	ev_timer_again (loop, timer);
945		1050
946	This is more efficient then stopping/starting the timer eahc time you want	1051	This is more slightly efficient then stopping/starting the timer each time
947	to modify its timeout value.	1052	you want to modify its timeout value.
948		1053
949	=item ev_tstamp repeat [read-write]	1054	=item ev_tstamp repeat [read-write]
950		1055
951	The current C<repeat> value. Will be used each time the watcher times out	1056	The current C<repeat> value. Will be used each time the watcher times out
952	or C<ev_timer_again> is called and determines the next timeout (if any),	1057	or C<ev_timer_again> is called and determines the next timeout (if any),
…		…
994	but on wallclock time (absolute time). You can tell a periodic watcher	1099	but on wallclock time (absolute time). You can tell a periodic watcher
995	to trigger "at" some specific point in time. For example, if you tell a	1100	to trigger "at" some specific point in time. For example, if you tell a
996	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1101	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
997	+ 10.>) and then reset your system clock to the last year, then it will	1102	+ 10.>) and then reset your system clock to the last year, then it will
998	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1103	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
999	roughly 10 seconds later and of course not if you reset your system time	1104	roughly 10 seconds later).
1000	again).
1001		1105
1002	They can also be used to implement vastly more complex timers, such as	1106	They can also be used to implement vastly more complex timers, such as
1003	triggering an event on eahc midnight, local time.	1107	triggering an event on each midnight, local time or other, complicated,
		1108	rules.
1004		1109
1005	As with timers, the callback is guarenteed to be invoked only when the	1110	As with timers, the callback is guarenteed to be invoked only when the
1006	time (C<at>) has been passed, but if multiple periodic timers become ready	1111	time (C<at>) has been passed, but if multiple periodic timers become ready
1007	during the same loop iteration then order of execution is undefined.	1112	during the same loop iteration then order of execution is undefined.
1008		1113
…		…
1015	Lots of arguments, lets sort it out... There are basically three modes of	1120	Lots of arguments, lets sort it out... There are basically three modes of
1016	operation, and we will explain them from simplest to complex:	1121	operation, and we will explain them from simplest to complex:
1017		1122
1018	=over 4	1123	=over 4
1019		1124
1020	=item * absolute timer (interval = reschedule_cb = 0)	1125	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1021		1126
1022	In this configuration the watcher triggers an event at the wallclock time	1127	In this configuration the watcher triggers an event at the wallclock time
1023	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1128	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1024	that is, if it is to be run at January 1st 2011 then it will run when the	1129	that is, if it is to be run at January 1st 2011 then it will run when the
1025	system time reaches or surpasses this time.	1130	system time reaches or surpasses this time.
1026		1131
1027	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1132	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1028		1133
1029	In this mode the watcher will always be scheduled to time out at the next	1134	In this mode the watcher will always be scheduled to time out at the next
1030	C<at + N * interval> time (for some integer N) and then repeat, regardless	1135	C<at + N * interval> time (for some integer N, which can also be negative)
1031	of any time jumps.	1136	and then repeat, regardless of any time jumps.
1032		1137
1033	This can be used to create timers that do not drift with respect to system	1138	This can be used to create timers that do not drift with respect to system
1034	time:	1139	time:
1035		1140
1036	ev_periodic_set (&periodic, 0., 3600., 0);	1141	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1042		1147
1043	Another way to think about it (for the mathematically inclined) is that	1148	Another way to think about it (for the mathematically inclined) is that
1044	C<ev_periodic> will try to run the callback in this mode at the next possible	1149	C<ev_periodic> will try to run the callback in this mode at the next possible
1045	time where C<time = at (mod interval)>, regardless of any time jumps.	1150	time where C<time = at (mod interval)>, regardless of any time jumps.
1046		1151
		1152	For numerical stability it is preferable that the C<at> value is near
		1153	C<ev_now ()> (the current time), but there is no range requirement for
		1154	this value.
		1155
1047	=item * manual reschedule mode (reschedule_cb = callback)	1156	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1048		1157
1049	In this mode the values for C<interval> and C<at> are both being	1158	In this mode the values for C<interval> and C<at> are both being
1050	ignored. Instead, each time the periodic watcher gets scheduled, the	1159	ignored. Instead, each time the periodic watcher gets scheduled, the
1051	reschedule callback will be called with the watcher as first, and the	1160	reschedule callback will be called with the watcher as first, and the
1052	current time as second argument.	1161	current time as second argument.
1053		1162
1054	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1163	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1055	ever, or make any event loop modifications>. If you need to stop it,	1164	ever, or make any event loop modifications>. If you need to stop it,
1056	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1165	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1057	starting a prepare watcher).	1166	starting an C<ev_prepare> watcher, which is legal).
1058		1167
1059	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1168	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1060	ev_tstamp now)>, e.g.:	1169	ev_tstamp now)>, e.g.:
1061		1170
1062	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1171	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1084		1193
1085	Simply stops and restarts the periodic watcher again. This is only useful	1194	Simply stops and restarts the periodic watcher again. This is only useful
1086	when you changed some parameters or the reschedule callback would return	1195	when you changed some parameters or the reschedule callback would return
1087	a different time than the last time it was called (e.g. in a crond like	1196	a different time than the last time it was called (e.g. in a crond like
1088	program when the crontabs have changed).	1197	program when the crontabs have changed).
		1198
		1199	=item ev_tstamp offset [read-write]
		1200
		1201	When repeating, this contains the offset value, otherwise this is the
		1202	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1203
		1204	Can be modified any time, but changes only take effect when the periodic
		1205	timer fires or C<ev_periodic_again> is being called.
1089		1206
1090	=item ev_tstamp interval [read-write]	1207	=item ev_tstamp interval [read-write]
1091		1208
1092	The current interval value. Can be modified any time, but changes only	1209	The current interval value. Can be modified any time, but changes only
1093	take effect when the periodic timer fires or C<ev_periodic_again> is being	1210	take effect when the periodic timer fires or C<ev_periodic_again> is being
…		…
1220	The path does not need to exist: changing from "path exists" to "path does	1337	The path does not need to exist: changing from "path exists" to "path does
1221	not exist" is a status change like any other. The condition "path does	1338	not exist" is a status change like any other. The condition "path does
1222	not exist" is signified by the C<st_nlink> field being zero (which is	1339	not exist" is signified by the C<st_nlink> field being zero (which is
1223	otherwise always forced to be at least one) and all the other fields of	1340	otherwise always forced to be at least one) and all the other fields of
1224	the stat buffer having unspecified contents.	1341	the stat buffer having unspecified contents.
		1342
		1343	The path I<should> be absolute and I<must not> end in a slash. If it is
		1344	relative and your working directory changes, the behaviour is undefined.
1225		1345
1226	Since there is no standard to do this, the portable implementation simply	1346	Since there is no standard to do this, the portable implementation simply
1227	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1347	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1228	can specify a recommended polling interval for this case. If you specify	1348	can specify a recommended polling interval for this case. If you specify
1229	a polling interval of C<0> (highly recommended!) then a I<suitable,	1349	a polling interval of C<0> (highly recommended!) then a I<suitable,
…		…
1314	ev_stat_start (loop, &passwd);	1434	ev_stat_start (loop, &passwd);
1315		1435
1316		1436
1317	=head2 C<ev_idle> - when you've got nothing better to do...	1437	=head2 C<ev_idle> - when you've got nothing better to do...
1318		1438
1319	Idle watchers trigger events when there are no other events are pending	1439	Idle watchers trigger events when no other events of the same or higher
1320	(prepare, check and other idle watchers do not count). That is, as long	1440	priority are pending (prepare, check and other idle watchers do not
1321	as your process is busy handling sockets or timeouts (or even signals,	1441	count).
1322	imagine) it will not be triggered. But when your process is idle all idle	1442
1323	watchers are being called again and again, once per event loop iteration -	1443	That is, as long as your process is busy handling sockets or timeouts
		1444	(or even signals, imagine) of the same or higher priority it will not be
		1445	triggered. But when your process is idle (or only lower-priority watchers
		1446	are pending), the idle watchers are being called once per event loop
1324	until stopped, that is, or your process receives more events and becomes	1447	iteration - until stopped, that is, or your process receives more events
1325	busy.	1448	and becomes busy again with higher priority stuff.
1326		1449
1327	The most noteworthy effect is that as long as any idle watchers are	1450	The most noteworthy effect is that as long as any idle watchers are
1328	active, the process will not block when waiting for new events.	1451	active, the process will not block when waiting for new events.
1329		1452
1330	Apart from keeping your process non-blocking (which is a useful	1453	Apart from keeping your process non-blocking (which is a useful
…		…
1396	with priority higher than or equal to the event loop and one coroutine	1519	with priority higher than or equal to the event loop and one coroutine
1397	of lower priority, but only once, using idle watchers to keep the event	1520	of lower priority, but only once, using idle watchers to keep the event
1398	loop from blocking if lower-priority coroutines are active, thus mapping	1521	loop from blocking if lower-priority coroutines are active, thus mapping
1399	low-priority coroutines to idle/background tasks).	1522	low-priority coroutines to idle/background tasks).
1400		1523
		1524	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1525	priority, to ensure that they are being run before any other watchers
		1526	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1527	too) should not activate ("feed") events into libev. While libev fully
		1528	supports this, they will be called before other C<ev_check> watchers did
		1529	their job. As C<ev_check> watchers are often used to embed other event
		1530	loops those other event loops might be in an unusable state until their
		1531	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1532	others).
		1533
1401	=over 4	1534	=over 4
1402		1535
1403	=item ev_prepare_init (ev_prepare *, callback)	1536	=item ev_prepare_init (ev_prepare *, callback)
1404		1537
1405	=item ev_check_init (ev_check *, callback)	1538	=item ev_check_init (ev_check *, callback)
…		…
1408	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1541	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1409	macros, but using them is utterly, utterly and completely pointless.	1542	macros, but using them is utterly, utterly and completely pointless.
1410		1543
1411	=back	1544	=back
1412		1545
1413	Example: To include a library such as adns, you would add IO watchers	1546	There are a number of principal ways to embed other event loops or modules
1414	and a timeout watcher in a prepare handler, as required by libadns, and	1547	into libev. Here are some ideas on how to include libadns into libev
		1548	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1549	use for an actually working example. Another Perl module named C<EV::Glib>
		1550	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1551	into the Glib event loop).
		1552
		1553	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1415	in a check watcher, destroy them and call into libadns. What follows is	1554	and in a check watcher, destroy them and call into libadns. What follows
1416	pseudo-code only of course:	1555	is pseudo-code only of course. This requires you to either use a low
		1556	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1557	the callbacks for the IO/timeout watchers might not have been called yet.
1417		1558
1418	static ev_io iow [nfd];	1559	static ev_io iow [nfd];
1419	static ev_timer tw;	1560	static ev_timer tw;
1420		1561
1421	static void	1562	static void
1422	io_cb (ev_loop loop, ev_io w, int revents)	1563	io_cb (ev_loop loop, ev_io w, int revents)
1423	{	1564	{
1424	// set the relevant poll flags
1425	// could also call adns_processreadable etc. here
1426	struct pollfd fd = (struct pollfd )w->data;
1427	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1428	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1429	}	1565	}
1430		1566
1431	// create io watchers for each fd and a timer before blocking	1567	// create io watchers for each fd and a timer before blocking
1432	static void	1568	static void
1433	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1569	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1434	{	1570	{
1435	int timeout = 3600000;truct pollfd fds [nfd];	1571	int timeout = 3600000;
		1572	struct pollfd fds [nfd];
1436	// actual code will need to loop here and realloc etc.	1573	// actual code will need to loop here and realloc etc.
1437	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1574	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1438		1575
1439	/* the callback is illegal, but won't be called as we stop during check */	1576	/* the callback is illegal, but won't be called as we stop during check */
1440	ev_timer_init (&tw, 0, timeout * 1e-3);	1577	ev_timer_init (&tw, 0, timeout * 1e-3);
1441	ev_timer_start (loop, &tw);	1578	ev_timer_start (loop, &tw);
1442		1579
1443	// create on ev_io per pollfd	1580	// create one ev_io per pollfd
1444	for (int i = 0; i < nfd; ++i)	1581	for (int i = 0; i < nfd; ++i)
1445	{	1582	{
1446	ev_io_init (iow + i, io_cb, fds [i].fd,	1583	ev_io_init (iow + i, io_cb, fds [i].fd,
1447	((fds [i].events & POLLIN ? EV_READ : 0)	1584	((fds [i].events & POLLIN ? EV_READ : 0)
1448	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1585	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1449		1586
1450	fds [i].revents = 0;	1587	fds [i].revents = 0;
1451	iow [i].data = fds + i;
1452	ev_io_start (loop, iow + i);	1588	ev_io_start (loop, iow + i);
1453	}	1589	}
1454	}	1590	}
1455		1591
1456	// stop all watchers after blocking	1592	// stop all watchers after blocking
…		…
1458	adns_check_cb (ev_loop loop, ev_check w, int revents)	1594	adns_check_cb (ev_loop loop, ev_check w, int revents)
1459	{	1595	{
1460	ev_timer_stop (loop, &tw);	1596	ev_timer_stop (loop, &tw);
1461		1597
1462	for (int i = 0; i < nfd; ++i)	1598	for (int i = 0; i < nfd; ++i)
		1599	{
		1600	// set the relevant poll flags
		1601	// could also call adns_processreadable etc. here
		1602	struct pollfd *fd = fds + i;
		1603	int revents = ev_clear_pending (iow + i);
		1604	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1605	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1606
		1607	// now stop the watcher
1463	ev_io_stop (loop, iow + i);	1608	ev_io_stop (loop, iow + i);
		1609	}
1464		1610
1465	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1611	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1612	}
		1613
		1614	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1615	in the prepare watcher and would dispose of the check watcher.
		1616
		1617	Method 3: If the module to be embedded supports explicit event
		1618	notification (adns does), you can also make use of the actual watcher
		1619	callbacks, and only destroy/create the watchers in the prepare watcher.
		1620
		1621	static void
		1622	timer_cb (EV_P_ ev_timer *w, int revents)
		1623	{
		1624	adns_state ads = (adns_state)w->data;
		1625	update_now (EV_A);
		1626
		1627	adns_processtimeouts (ads, &tv_now);
		1628	}
		1629
		1630	static void
		1631	io_cb (EV_P_ ev_io *w, int revents)
		1632	{
		1633	adns_state ads = (adns_state)w->data;
		1634	update_now (EV_A);
		1635
		1636	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1637	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1638	}
		1639
		1640	// do not ever call adns_afterpoll
		1641
		1642	Method 4: Do not use a prepare or check watcher because the module you
		1643	want to embed is too inflexible to support it. Instead, youc na override
		1644	their poll function. The drawback with this solution is that the main
		1645	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1646	this.
		1647
		1648	static gint
		1649	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1650	{
		1651	int got_events = 0;
		1652
		1653	for (n = 0; n < nfds; ++n)
		1654	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1655
		1656	if (timeout >= 0)
		1657	// create/start timer
		1658
		1659	// poll
		1660	ev_loop (EV_A_ 0);
		1661
		1662	// stop timer again
		1663	if (timeout >= 0)
		1664	ev_timer_stop (EV_A_ &to);
		1665
		1666	// stop io watchers again - their callbacks should have set
		1667	for (n = 0; n < nfds; ++n)
		1668	ev_io_stop (EV_A_ iow [n]);
		1669
		1670	return got_events;
1466	}	1671	}
1467		1672
1468		1673
1469	=head2 C<ev_embed> - when one backend isn't enough...	1674	=head2 C<ev_embed> - when one backend isn't enough...
1470		1675
…		…
1674		1879
1675	To use it,	1880	To use it,
1676		1881
1677	#include <ev++.h>	1882	#include <ev++.h>
1678		1883
1679	(it is not installed by default). This automatically includes F<ev.h>	1884	This automatically includes F<ev.h> and puts all of its definitions (many
1680	and puts all of its definitions (many of them macros) into the global	1885	of them macros) into the global namespace. All C++ specific things are
1681	namespace. All C++ specific things are put into the C<ev> namespace.	1886	put into the C<ev> namespace. It should support all the same embedding
		1887	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1682		1888
1683	It should support all the same embedding options as F<ev.h>, most notably	1889	Care has been taken to keep the overhead low. The only data member the C++
1684	C<EV_MULTIPLICITY>.	1890	classes add (compared to plain C-style watchers) is the event loop pointer
		1891	that the watcher is associated with (or no additional members at all if
		1892	you disable C<EV_MULTIPLICITY> when embedding libev).
		1893
		1894	Currently, functions, and static and non-static member functions can be
		1895	used as callbacks. Other types should be easy to add as long as they only
		1896	need one additional pointer for context. If you need support for other
		1897	types of functors please contact the author (preferably after implementing
		1898	it).
1685		1899
1686	Here is a list of things available in the C<ev> namespace:	1900	Here is a list of things available in the C<ev> namespace:
1687		1901
1688	=over 4	1902	=over 4
1689		1903
…		…
1705		1919
1706	All of those classes have these methods:	1920	All of those classes have these methods:
1707		1921
1708	=over 4	1922	=over 4
1709		1923
1710	=item ev::TYPE::TYPE (object , object::method )	1924	=item ev::TYPE::TYPE ()
1711		1925
1712	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1926	=item ev::TYPE::TYPE (struct ev_loop *)
1713		1927
1714	=item ev::TYPE::~TYPE	1928	=item ev::TYPE::~TYPE
1715		1929
1716	The constructor takes a pointer to an object and a method pointer to	1930	The constructor (optionally) takes an event loop to associate the watcher
1717	the event handler callback to call in this class. The constructor calls	1931	with. If it is omitted, it will use C<EV_DEFAULT>.
1718	C<ev_init> for you, which means you have to call the C<set> method	1932
1719	before starting it. If you do not specify a loop then the constructor	1933	The constructor calls C<ev_init> for you, which means you have to call the
1720	automatically associates the default loop with this watcher.	1934	C<set> method before starting it.
		1935
		1936	It will not set a callback, however: You have to call the templated C<set>
		1937	method to set a callback before you can start the watcher.
		1938
		1939	(The reason why you have to use a method is a limitation in C++ which does
		1940	not allow explicit template arguments for constructors).
1721		1941
1722	The destructor automatically stops the watcher if it is active.	1942	The destructor automatically stops the watcher if it is active.
		1943
		1944	=item w->set<class, &class::method> (object *)
		1945
		1946	This method sets the callback method to call. The method has to have a
		1947	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1948	first argument and the C<revents> as second. The object must be given as
		1949	parameter and is stored in the C<data> member of the watcher.
		1950
		1951	This method synthesizes efficient thunking code to call your method from
		1952	the C callback that libev requires. If your compiler can inline your
		1953	callback (i.e. it is visible to it at the place of the C<set> call and
		1954	your compiler is good :), then the method will be fully inlined into the
		1955	thunking function, making it as fast as a direct C callback.
		1956
		1957	Example: simple class declaration and watcher initialisation
		1958
		1959	struct myclass
		1960	{
		1961	void io_cb (ev::io &w, int revents) { }
		1962	}
		1963
		1964	myclass obj;
		1965	ev::io iow;
		1966	iow.set <myclass, &myclass::io_cb> (&obj);
		1967
		1968	=item w->set<function> (void *data = 0)
		1969
		1970	Also sets a callback, but uses a static method or plain function as
		1971	callback. The optional C<data> argument will be stored in the watcher's
		1972	C<data> member and is free for you to use.
		1973
		1974	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1975
		1976	See the method-C<set> above for more details.
		1977
		1978	Example:
		1979
		1980	static void io_cb (ev::io &w, int revents) { }
		1981	iow.set <io_cb> ();
1723		1982
1724	=item w->set (struct ev_loop *)	1983	=item w->set (struct ev_loop *)
1725		1984
1726	Associates a different C<struct ev_loop> with this watcher. You can only	1985	Associates a different C<struct ev_loop> with this watcher. You can only
1727	do this when the watcher is inactive (and not pending either).	1986	do this when the watcher is inactive (and not pending either).
1728		1987
1729	=item w->set ([args])	1988	=item w->set ([args])
1730		1989
1731	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1990	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1732	called at least once. Unlike the C counterpart, an active watcher gets	1991	called at least once. Unlike the C counterpart, an active watcher gets
1733	automatically stopped and restarted.	1992	automatically stopped and restarted when reconfiguring it with this
		1993	method.
1734		1994
1735	=item w->start ()	1995	=item w->start ()
1736		1996
1737	Starts the watcher. Note that there is no C<loop> argument as the	1997	Starts the watcher. Note that there is no C<loop> argument, as the
1738	constructor already takes the loop.	1998	constructor already stores the event loop.
1739		1999
1740	=item w->stop ()	2000	=item w->stop ()
1741		2001
1742	Stops the watcher if it is active. Again, no C<loop> argument.	2002	Stops the watcher if it is active. Again, no C<loop> argument.
1743		2003
…		…
1768		2028
1769	myclass ();	2029	myclass ();
1770	}	2030	}
1771		2031
1772	myclass::myclass (int fd)	2032	myclass::myclass (int fd)
1773	: io (this, &myclass::io_cb),
1774	idle (this, &myclass::idle_cb)
1775	{	2033	{
		2034	io .set <myclass, &myclass::io_cb > (this);
		2035	idle.set <myclass, &myclass::idle_cb> (this);
		2036
1776	io.start (fd, ev::READ);	2037	io.start (fd, ev::READ);
1777	}	2038	}
1778		2039
1779		2040
1780	=head1 MACRO MAGIC	2041	=head1 MACRO MAGIC
1781		2042
1782	Libev can be compiled with a variety of options, the most fundemantal is	2043	Libev can be compiled with a variety of options, the most fundemantal is
1783	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2044	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1784	callbacks have an initial C<struct ev_loop *> argument.	2045	callbacks have an initial C<struct ev_loop *> argument.
1785		2046
1786	To make it easier to write programs that cope with either variant, the	2047	To make it easier to write programs that cope with either variant, the
1787	following macros are defined:	2048	following macros are defined:
1788		2049
…		…
1821	Similar to the other two macros, this gives you the value of the default	2082	Similar to the other two macros, this gives you the value of the default
1822	loop, if multiple loops are supported ("ev loop default").	2083	loop, if multiple loops are supported ("ev loop default").
1823		2084
1824	=back	2085	=back
1825		2086
1826	Example: Declare and initialise a check watcher, working regardless of	2087	Example: Declare and initialise a check watcher, utilising the above
1827	wether multiple loops are supported or not.	2088	macros so it will work regardless of whether multiple loops are supported
		2089	or not.
1828		2090
1829	static void	2091	static void
1830	check_cb (EV_P_ ev_timer *w, int revents)	2092	check_cb (EV_P_ ev_timer *w, int revents)
1831	{	2093	{
1832	ev_check_stop (EV_A_ w);	2094	ev_check_stop (EV_A_ w);
…		…
1834		2096
1835	ev_check check;	2097	ev_check check;
1836	ev_check_init (&check, check_cb);	2098	ev_check_init (&check, check_cb);
1837	ev_check_start (EV_DEFAULT_ &check);	2099	ev_check_start (EV_DEFAULT_ &check);
1838	ev_loop (EV_DEFAULT_ 0);	2100	ev_loop (EV_DEFAULT_ 0);
1839
1840		2101
1841	=head1 EMBEDDING	2102	=head1 EMBEDDING
1842		2103
1843	Libev can (and often is) directly embedded into host	2104	Libev can (and often is) directly embedded into host
1844	applications. Examples of applications that embed it include the Deliantra	2105	applications. Examples of applications that embed it include the Deliantra
…		…
1884	ev_vars.h	2145	ev_vars.h
1885	ev_wrap.h	2146	ev_wrap.h
1886		2147
1887	ev_win32.c required on win32 platforms only	2148	ev_win32.c required on win32 platforms only
1888		2149
1889	ev_select.c only when select backend is enabled (which is by default)	2150	ev_select.c only when select backend is enabled (which is enabled by default)
1890	ev_poll.c only when poll backend is enabled (disabled by default)	2151	ev_poll.c only when poll backend is enabled (disabled by default)
1891	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2152	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1892	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2153	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1893	ev_port.c only when the solaris port backend is enabled (disabled by default)	2154	ev_port.c only when the solaris port backend is enabled (disabled by default)
1894		2155
…		…
2057	will have the C<struct ev_loop *> as first argument, and you can create	2318	will have the C<struct ev_loop *> as first argument, and you can create
2058	additional independent event loops. Otherwise there will be no support	2319	additional independent event loops. Otherwise there will be no support
2059	for multiple event loops and there is no first event loop pointer	2320	for multiple event loops and there is no first event loop pointer
2060	argument. Instead, all functions act on the single default loop.	2321	argument. Instead, all functions act on the single default loop.
2061		2322
		2323	=item EV_MINPRI
		2324
		2325	=item EV_MAXPRI
		2326
		2327	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2328	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2329	provide for more priorities by overriding those symbols (usually defined
		2330	to be C<-2> and C<2>, respectively).
		2331
		2332	When doing priority-based operations, libev usually has to linearly search
		2333	all the priorities, so having many of them (hundreds) uses a lot of space
		2334	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2335	fine.
		2336
		2337	If your embedding app does not need any priorities, defining these both to
		2338	C<0> will save some memory and cpu.
		2339
2062	=item EV_PERIODIC_ENABLE	2340	=item EV_PERIODIC_ENABLE
2063		2341
2064	If undefined or defined to be C<1>, then periodic timers are supported. If	2342	If undefined or defined to be C<1>, then periodic timers are supported. If
		2343	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2344	code.
		2345
		2346	=item EV_IDLE_ENABLE
		2347
		2348	If undefined or defined to be C<1>, then idle watchers are supported. If
2065	defined to be C<0>, then they are not. Disabling them saves a few kB of	2349	defined to be C<0>, then they are not. Disabling them saves a few kB of
2066	code.	2350	code.
2067		2351
2068	=item EV_EMBED_ENABLE	2352	=item EV_EMBED_ENABLE
2069		2353
…		…
2136	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2420	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2137	will be compiled. It is pretty complex because it provides its own header	2421	will be compiled. It is pretty complex because it provides its own header
2138	file.	2422	file.
2139		2423
2140	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2424	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2141	that everybody includes and which overrides some autoconf choices:	2425	that everybody includes and which overrides some configure choices:
2142		2426
		2427	#define EV_MINIMAL 1
2143	#define EV_USE_POLL 0	2428	#define EV_USE_POLL 0
2144	#define EV_MULTIPLICITY 0	2429	#define EV_MULTIPLICITY 0
2145	#define EV_PERIODICS 0	2430	#define EV_PERIODIC_ENABLE 0
		2431	#define EV_STAT_ENABLE 0
		2432	#define EV_FORK_ENABLE 0
2146	#define EV_CONFIG_H <config.h>	2433	#define EV_CONFIG_H <config.h>
		2434	#define EV_MINPRI 0
		2435	#define EV_MAXPRI 0
2147		2436
2148	#include "ev++.h"	2437	#include "ev++.h"
2149		2438
2150	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2439	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2151		2440
…		…
2157		2446
2158	In this section the complexities of (many of) the algorithms used inside	2447	In this section the complexities of (many of) the algorithms used inside
2159	libev will be explained. For complexity discussions about backends see the	2448	libev will be explained. For complexity discussions about backends see the
2160	documentation for C<ev_default_init>.	2449	documentation for C<ev_default_init>.
2161		2450
		2451	All of the following are about amortised time: If an array needs to be
		2452	extended, libev needs to realloc and move the whole array, but this
		2453	happens asymptotically never with higher number of elements, so O(1) might
		2454	mean it might do a lengthy realloc operation in rare cases, but on average
		2455	it is much faster and asymptotically approaches constant time.
		2456
2162	=over 4	2457	=over 4
2163		2458
2164	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2459	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2165		2460
		2461	This means that, when you have a watcher that triggers in one hour and
		2462	there are 100 watchers that would trigger before that then inserting will
		2463	have to skip those 100 watchers.
		2464
2166	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2465	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2167		2466
		2467	That means that for changing a timer costs less than removing/adding them
		2468	as only the relative motion in the event queue has to be paid for.
		2469
2168	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2470	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2169		2471
		2472	These just add the watcher into an array or at the head of a list.
2170	=item Stopping check/prepare/idle watchers: O(1)	2473	=item Stopping check/prepare/idle watchers: O(1)
2171		2474
2172	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2475	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2173		2476
		2477	These watchers are stored in lists then need to be walked to find the
		2478	correct watcher to remove. The lists are usually short (you don't usually
		2479	have many watchers waiting for the same fd or signal).
		2480
2174	=item Finding the next timer per loop iteration: O(1)	2481	=item Finding the next timer per loop iteration: O(1)
2175		2482
2176	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2483	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2177		2484
		2485	A change means an I/O watcher gets started or stopped, which requires
		2486	libev to recalculate its status (and possibly tell the kernel).
		2487
2178	=item Activating one watcher: O(1)	2488	=item Activating one watcher: O(1)
2179		2489
		2490	=item Priority handling: O(number_of_priorities)
		2491
		2492	Priorities are implemented by allocating some space for each
		2493	priority. When doing priority-based operations, libev usually has to
		2494	linearly search all the priorities.
		2495
2180	=back	2496	=back
2181		2497
2182		2498
2183	=head1 AUTHOR	2499	=head1 AUTHOR
2184		2500

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Comparing libev/ev.pod (file contents): Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC vs. Revision 1.81 by root, Wed Dec 12 04:53:58 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC vs.
Revision 1.81 by root, Wed Dec 12 04:53:58 2007 UTC