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

Comparing libev/ev.pod (file contents):
Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs.
Revision 1.98 by root, Sat Dec 22 06:10:25 2007 UTC

…		…
48	return 0;	48	return 0;
49	}	49	}
50		50
51	=head1 DESCRIPTION	51	=head1 DESCRIPTION
52		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>.
		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 occurring), 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
57	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
58	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
59	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
94	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
97	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
98	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
99	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
100		106
101	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
102		108
103	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
104	library in any way.	110	library in any way.
…		…
109		115
110	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
111	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
112	you actually want to know.	118	you actually want to know.
113		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
114	=item int ev_version_major ()	126	=item int ev_version_major ()
115		127
116	=item int ev_version_minor ()	128	=item int ev_version_minor ()
117		129
118	You can find out the major and minor version numbers of the library	130	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	131	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	132	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	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
122	version of the library your program was compiled against.	134	version of the library your program was compiled against.
123		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
124	Usually, it's a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
125	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
126	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
127	not a problem.	142	not a problem.
128		143
129	Example: Make sure we haven't accidentally been linked against the wrong	144	Example: Make sure we haven't accidentally been linked against the wrong
130	version.	145	version.
…		…
304	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	319	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
305		320
306	=item C<EVBACKEND_EPOLL> (value 4, Linux)	321	=item C<EVBACKEND_EPOLL> (value 4, Linux)
307		322
308	For few fds, this backend is a bit little slower than poll and select,	323	For few fds, this backend is a bit little slower than poll and select,
309	but it scales phenomenally better. While poll and select usually scale like	324	but it scales phenomenally better. While poll and select usually scale
310	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	325	like O(total_fds) where n is the total number of fds (or the highest fd),
311	either O(1) or O(active_fds).	326	epoll scales either O(1) or O(active_fds). The epoll design has a number
		327	of shortcomings, such as silently dropping events in some hard-to-detect
		328	cases and rewiring a syscall per fd change, no fork support and bad
		329	support for dup:
312		330
313	While stopping and starting an I/O watcher in the same iteration will	331	While stopping, setting and starting an I/O watcher in the same iteration
314	result in some caching, there is still a syscall per such incident	332	will result in some caching, there is still a syscall per such incident
315	(because the fd could point to a different file description now), so its	333	(because the fd could point to a different file description now), so its
316	best to avoid that. Also, dup()ed file descriptors might not work very	334	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
317	well if you register events for both fds.	335	very well if you register events for both fds.
318		336
319	Please note that epoll sometimes generates spurious notifications, so you	337	Please note that epoll sometimes generates spurious notifications, so you
320	need to use non-blocking I/O or other means to avoid blocking when no data	338	need to use non-blocking I/O or other means to avoid blocking when no data
321	(or space) is available.	339	(or space) is available.
322		340
323	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
324		342
325	Kqueue deserves special mention, as at the time of this writing, it	343	Kqueue deserves special mention, as at the time of this writing, it
326	was broken on all BSDs except NetBSD (usually it doesn't work with	344	was broken on I<all> BSDs (usually it doesn't work with anything but
327	anything but sockets and pipes, except on Darwin, where of course its	345	sockets and pipes, except on Darwin, where of course it's completely
		346	useless. On NetBSD, it seems to work for all the FD types I tested, so it
328	completely useless). For this reason its not being "autodetected"	347	is used by default there). For this reason it's not being "autodetected"
329	unless you explicitly specify it explicitly in the flags (i.e. using	348	unless you explicitly specify it explicitly in the flags (i.e. using
330	C<EVBACKEND_KQUEUE>).	349	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		350	system like NetBSD.
331		351
332	It scales in the same way as the epoll backend, but the interface to the	352	It scales in the same way as the epoll backend, but the interface to the
333	kernel is more efficient (which says nothing about its actual speed, of	353	kernel is more efficient (which says nothing about its actual speed,
334	course). While starting and stopping an I/O watcher does not cause an	354	of course). While stopping, setting and starting an I/O watcher does
335	extra syscall as with epoll, it still adds up to four event changes per	355	never cause an extra syscall as with epoll, it still adds up to two event
336	incident, so its best to avoid that.	356	changes per incident, support for C<fork ()> is very bad and it drops fds
		357	silently in similarly hard-to-detetc cases.
337		358
338	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	359	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
339		360
340	This is not implemented yet (and might never be).	361	This is not implemented yet (and might never be).
341		362
342	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	363	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
343		364
344	This uses the Solaris 10 port mechanism. As with everything on Solaris,	365	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
345	it's really slow, but it still scales very well (O(active_fds)).	366	it's really slow, but it still scales very well (O(active_fds)).
346		367
347	Please note that solaris ports can result in a lot of spurious	368	Please note that solaris event ports can deliver a lot of spurious
348	notifications, so you need to use non-blocking I/O or other means to avoid	369	notifications, so you need to use non-blocking I/O or other means to avoid
349	blocking when no data (or space) is available.	370	blocking when no data (or space) is available.
350		371
351	=item C<EVBACKEND_ALL>	372	=item C<EVBACKEND_ALL>
352		373
…		…
395	Destroys the default loop again (frees all memory and kernel state	416	Destroys the default loop again (frees all memory and kernel state
396	etc.). None of the active event watchers will be stopped in the normal	417	etc.). None of the active event watchers will be stopped in the normal
397	sense, so e.g. C<ev_is_active> might still return true. It is your	418	sense, so e.g. C<ev_is_active> might still return true. It is your
398	responsibility to either stop all watchers cleanly yoursef I<before>	419	responsibility to either stop all watchers cleanly yoursef I<before>
399	calling this function, or cope with the fact afterwards (which is usually	420	calling this function, or cope with the fact afterwards (which is usually
400	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	421	the easiest thing, you can just ignore the watchers and/or C<free ()> them
401	for example).	422	for example).
		423
		424	Note that certain global state, such as signal state, will not be freed by
		425	this function, and related watchers (such as signal and child watchers)
		426	would need to be stopped manually.
		427
		428	In general it is not advisable to call this function except in the
		429	rare occasion where you really need to free e.g. the signal handling
		430	pipe fds. If you need dynamically allocated loops it is better to use
		431	C<ev_loop_new> and C<ev_loop_destroy>).
402		432
403	=item ev_loop_destroy (loop)	433	=item ev_loop_destroy (loop)
404		434
405	Like C<ev_default_destroy>, but destroys an event loop created by an	435	Like C<ev_default_destroy>, but destroys an event loop created by an
406	earlier call to C<ev_loop_new>.	436	earlier call to C<ev_loop_new>.
…		…
451		481
452	Returns the current "event loop time", which is the time the event loop	482	Returns the current "event loop time", which is the time the event loop
453	received events and started processing them. This timestamp does not	483	received events and started processing them. This timestamp does not
454	change as long as callbacks are being processed, and this is also the base	484	change as long as callbacks are being processed, and this is also the base
455	time used for relative timers. You can treat it as the timestamp of the	485	time used for relative timers. You can treat it as the timestamp of the
456	event occuring (or more correctly, libev finding out about it).	486	event occurring (or more correctly, libev finding out about it).
457		487
458	=item ev_loop (loop, int flags)	488	=item ev_loop (loop, int flags)
459		489
460	Finally, this is it, the event handler. This function usually is called	490	Finally, this is it, the event handler. This function usually is called
461	after you initialised all your watchers and you want to start handling	491	after you initialised all your watchers and you want to start handling
…		…
482	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	512	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
483	usually a better approach for this kind of thing.	513	usually a better approach for this kind of thing.
484		514
485	Here are the gory details of what C<ev_loop> does:	515	Here are the gory details of what C<ev_loop> does:
486		516
		517	- Before the first iteration, call any pending watchers.
487	* If there are no active watchers (reference count is zero), return.	518	* If there are no active watchers (reference count is zero), return.
488	- Queue prepare watchers and then call all outstanding watchers.	519	- Queue all prepare watchers and then call all outstanding watchers.
489	- If we have been forked, recreate the kernel state.	520	- If we have been forked, recreate the kernel state.
490	- Update the kernel state with all outstanding changes.	521	- Update the kernel state with all outstanding changes.
491	- Update the "event loop time".	522	- Update the "event loop time".
492	- Calculate for how long to block.	523	- Calculate for how long to block.
493	- Block the process, waiting for any events.	524	- Block the process, waiting for any events.
…		…
544	Example: For some weird reason, unregister the above signal handler again.	575	Example: For some weird reason, unregister the above signal handler again.
545		576
546	ev_ref (loop);	577	ev_ref (loop);
547	ev_signal_stop (loop, &exitsig);	578	ev_signal_stop (loop, &exitsig);
548		579
		580	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		581
		582	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		583
		584	These advanced functions influence the time that libev will spend waiting
		585	for events. Both are by default C<0>, meaning that libev will try to
		586	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		587
		588	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		589	allows libev to delay invocation of I/O and timer/periodic callbacks to
		590	increase efficiency of loop iterations.
		591
		592	The background is that sometimes your program runs just fast enough to
		593	handle one (or very few) event(s) per loop iteration. While this makes
		594	the program responsive, it also wastes a lot of CPU time to poll for new
		595	events, especially with backends like C<select ()> which have a high
		596	overhead for the actual polling but can deliver many events at once.
		597
		598	By setting a higher I<io collect interval> you allow libev to spend more
		599	time collecting I/O events, so you can handle more events per iteration,
		600	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		601	C<ev_timer>) will be not affected.
		602
		603	Likewise, by setting a higher I<timeout collect interval> you allow libev
		604	to spend more time collecting timeouts, at the expense of increased
		605	latency (the watcher callback will be called later). C<ev_io> watchers
		606	will not be affected.
		607
		608	Many (busy) programs can usually benefit by setting the io collect
		609	interval to a value near C<0.1> or so, which is often enough for
		610	interactive servers (of course not for games), likewise for timeouts. It
		611	usually doesn't make much sense to set it to a lower value than C<0.01>,
		612	as this approsaches the timing granularity of most systems.
		613
549	=back	614	=back
550		615
551		616
552	=head1 ANATOMY OF A WATCHER	617	=head1 ANATOMY OF A WATCHER
553		618
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	797	=item bool ev_is_pending (ev_TYPE *watcher)
733		798
734	Returns a true value iff the watcher is pending, (i.e. it has outstanding	799	Returns a true value iff the watcher is pending, (i.e. it has outstanding
735	events but its callback has not yet been invoked). As long as a watcher	800	events but its callback has not yet been invoked). As long as a watcher
736	is pending (but not active) you must not call an init function on it (but	801	is pending (but not active) you must not call an init function on it (but
737	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	802	C<ev_TYPE_set> is safe), you must not change its priority, and you must
738	libev (e.g. you cnanot C<free ()> it).	803	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		804	it).
739		805
740	=item callback ev_cb (ev_TYPE *watcher)	806	=item callback ev_cb (ev_TYPE *watcher)
741		807
742	Returns the callback currently set on the watcher.	808	Returns the callback currently set on the watcher.
743		809
744	=item ev_cb_set (ev_TYPE *watcher, callback)	810	=item ev_cb_set (ev_TYPE *watcher, callback)
745		811
746	Change the callback. You can change the callback at virtually any time	812	Change the callback. You can change the callback at virtually any time
747	(modulo threads).	813	(modulo threads).
		814
		815	=item ev_set_priority (ev_TYPE *watcher, priority)
		816
		817	=item int ev_priority (ev_TYPE *watcher)
		818
		819	Set and query the priority of the watcher. The priority is a small
		820	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		821	(default: C<-2>). Pending watchers with higher priority will be invoked
		822	before watchers with lower priority, but priority will not keep watchers
		823	from being executed (except for C<ev_idle> watchers).
		824
		825	This means that priorities are I<only> used for ordering callback
		826	invocation after new events have been received. This is useful, for
		827	example, to reduce latency after idling, or more often, to bind two
		828	watchers on the same event and make sure one is called first.
		829
		830	If you need to suppress invocation when higher priority events are pending
		831	you need to look at C<ev_idle> watchers, which provide this functionality.
		832
		833	You I<must not> change the priority of a watcher as long as it is active or
		834	pending.
		835
		836	The default priority used by watchers when no priority has been set is
		837	always C<0>, which is supposed to not be too high and not be too low :).
		838
		839	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		840	fine, as long as you do not mind that the priority value you query might
		841	or might not have been adjusted to be within valid range.
		842
		843	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		844
		845	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		846	C<loop> nor C<revents> need to be valid as long as the watcher callback
		847	can deal with that fact.
		848
		849	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		850
		851	If the watcher is pending, this function returns clears its pending status
		852	and returns its C<revents> bitset (as if its callback was invoked). If the
		853	watcher isn't pending it does nothing and returns C<0>.
748		854
749	=back	855	=back
750		856
751		857
752	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	858	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
858	it is best to always use non-blocking I/O: An extra C<read>(2) returning	964	it is best to always use non-blocking I/O: An extra C<read>(2) returning
859	C<EAGAIN> is far preferable to a program hanging until some data arrives.	965	C<EAGAIN> is far preferable to a program hanging until some data arrives.
860		966
861	If you cannot run the fd in non-blocking mode (for example you should not	967	If you cannot run the fd in non-blocking mode (for example you should not
862	play around with an Xlib connection), then you have to seperately re-test	968	play around with an Xlib connection), then you have to seperately re-test
863	wether a file descriptor is really ready with a known-to-be good interface	969	whether a file descriptor is really ready with a known-to-be good interface
864	such as poll (fortunately in our Xlib example, Xlib already does this on	970	such as poll (fortunately in our Xlib example, Xlib already does this on
865	its own, so its quite safe to use).	971	its own, so its quite safe to use).
		972
		973	=head3 The special problem of disappearing file descriptors
		974
		975	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		976	descriptor (either by calling C<close> explicitly or by any other means,
		977	such as C<dup>). The reason is that you register interest in some file
		978	descriptor, but when it goes away, the operating system will silently drop
		979	this interest. If another file descriptor with the same number then is
		980	registered with libev, there is no efficient way to see that this is, in
		981	fact, a different file descriptor.
		982
		983	To avoid having to explicitly tell libev about such cases, libev follows
		984	the following policy: Each time C<ev_io_set> is being called, libev
		985	will assume that this is potentially a new file descriptor, otherwise
		986	it is assumed that the file descriptor stays the same. That means that
		987	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		988	descriptor even if the file descriptor number itself did not change.
		989
		990	This is how one would do it normally anyway, the important point is that
		991	the libev application should not optimise around libev but should leave
		992	optimisations to libev.
		993
		994	=head3 The special problem of dup'ed file descriptors
		995
		996	Some backends (e.g. epoll), cannot register events for file descriptors,
		997	but only events for the underlying file descriptions. That menas when you
		998	have C<dup ()>'ed file descriptors and register events for them, only one
		999	file descriptor might actually receive events.
		1000
		1001	There is no workaorund possible except not registering events
		1002	for potentially C<dup ()>'ed file descriptors or to resort to
		1003	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1004
		1005	=head3 The special problem of fork
		1006
		1007	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1008	useless behaviour. Libev fully supports fork, but needs to be told about
		1009	it in the child.
		1010
		1011	To support fork in your programs, you either have to call
		1012	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1013	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1014	C<EVBACKEND_POLL>.
		1015
		1016
		1017	=head3 Watcher-Specific Functions
866		1018
867	=over 4	1019	=over 4
868		1020
869	=item ev_io_init (ev_io *, callback, int fd, int events)	1021	=item ev_io_init (ev_io *, callback, int fd, int events)
870		1022
…		…
923	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1075	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
924		1076
925	The callback is guarenteed to be invoked only when its timeout has passed,	1077	The callback is guarenteed to be invoked only when its timeout has passed,
926	but if multiple timers become ready during the same loop iteration then	1078	but if multiple timers become ready during the same loop iteration then
927	order of execution is undefined.	1079	order of execution is undefined.
		1080
		1081	=head3 Watcher-Specific Functions and Data Members
928		1082
929	=over 4	1083	=over 4
930		1084
931	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1085	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
932		1086
…		…
1028	but on wallclock time (absolute time). You can tell a periodic watcher	1182	but on wallclock time (absolute time). You can tell a periodic watcher
1029	to trigger "at" some specific point in time. For example, if you tell a	1183	to trigger "at" some specific point in time. For example, if you tell a
1030	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1184	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1031	+ 10.>) and then reset your system clock to the last year, then it will	1185	+ 10.>) and then reset your system clock to the last year, then it will
1032	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1186	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1033	roughly 10 seconds later and of course not if you reset your system time	1187	roughly 10 seconds later).
1034	again).
1035		1188
1036	They can also be used to implement vastly more complex timers, such as	1189	They can also be used to implement vastly more complex timers, such as
1037	triggering an event on eahc midnight, local time.	1190	triggering an event on each midnight, local time or other, complicated,
		1191	rules.
1038		1192
1039	As with timers, the callback is guarenteed to be invoked only when the	1193	As with timers, the callback is guarenteed to be invoked only when the
1040	time (C<at>) has been passed, but if multiple periodic timers become ready	1194	time (C<at>) has been passed, but if multiple periodic timers become ready
1041	during the same loop iteration then order of execution is undefined.	1195	during the same loop iteration then order of execution is undefined.
1042		1196
		1197	=head3 Watcher-Specific Functions and Data Members
		1198
1043	=over 4	1199	=over 4
1044		1200
1045	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1201	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1046		1202
1047	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1203	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1049	Lots of arguments, lets sort it out... There are basically three modes of	1205	Lots of arguments, lets sort it out... There are basically three modes of
1050	operation, and we will explain them from simplest to complex:	1206	operation, and we will explain them from simplest to complex:
1051		1207
1052	=over 4	1208	=over 4
1053		1209
1054	=item * absolute timer (interval = reschedule_cb = 0)	1210	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1055		1211
1056	In this configuration the watcher triggers an event at the wallclock time	1212	In this configuration the watcher triggers an event at the wallclock time
1057	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1213	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1058	that is, if it is to be run at January 1st 2011 then it will run when the	1214	that is, if it is to be run at January 1st 2011 then it will run when the
1059	system time reaches or surpasses this time.	1215	system time reaches or surpasses this time.
1060		1216
1061	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1217	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1062		1218
1063	In this mode the watcher will always be scheduled to time out at the next	1219	In this mode the watcher will always be scheduled to time out at the next
1064	C<at + N * interval> time (for some integer N) and then repeat, regardless	1220	C<at + N * interval> time (for some integer N, which can also be negative)
1065	of any time jumps.	1221	and then repeat, regardless of any time jumps.
1066		1222
1067	This can be used to create timers that do not drift with respect to system	1223	This can be used to create timers that do not drift with respect to system
1068	time:	1224	time:
1069		1225
1070	ev_periodic_set (&periodic, 0., 3600., 0);	1226	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1076		1232
1077	Another way to think about it (for the mathematically inclined) is that	1233	Another way to think about it (for the mathematically inclined) is that
1078	C<ev_periodic> will try to run the callback in this mode at the next possible	1234	C<ev_periodic> will try to run the callback in this mode at the next possible
1079	time where C<time = at (mod interval)>, regardless of any time jumps.	1235	time where C<time = at (mod interval)>, regardless of any time jumps.
1080		1236
		1237	For numerical stability it is preferable that the C<at> value is near
		1238	C<ev_now ()> (the current time), but there is no range requirement for
		1239	this value.
		1240
1081	=item * manual reschedule mode (reschedule_cb = callback)	1241	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1082		1242
1083	In this mode the values for C<interval> and C<at> are both being	1243	In this mode the values for C<interval> and C<at> are both being
1084	ignored. Instead, each time the periodic watcher gets scheduled, the	1244	ignored. Instead, each time the periodic watcher gets scheduled, the
1085	reschedule callback will be called with the watcher as first, and the	1245	reschedule callback will be called with the watcher as first, and the
1086	current time as second argument.	1246	current time as second argument.
1087		1247
1088	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1248	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1089	ever, or make any event loop modifications>. If you need to stop it,	1249	ever, or make any event loop modifications>. If you need to stop it,
1090	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1250	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1091	starting a prepare watcher).	1251	starting an C<ev_prepare> watcher, which is legal).
1092		1252
1093	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1253	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1094	ev_tstamp now)>, e.g.:	1254	ev_tstamp now)>, e.g.:
1095		1255
1096	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1256	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1119	Simply stops and restarts the periodic watcher again. This is only useful	1279	Simply stops and restarts the periodic watcher again. This is only useful
1120	when you changed some parameters or the reschedule callback would return	1280	when you changed some parameters or the reschedule callback would return
1121	a different time than the last time it was called (e.g. in a crond like	1281	a different time than the last time it was called (e.g. in a crond like
1122	program when the crontabs have changed).	1282	program when the crontabs have changed).
1123		1283
		1284	=item ev_tstamp offset [read-write]
		1285
		1286	When repeating, this contains the offset value, otherwise this is the
		1287	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1288
		1289	Can be modified any time, but changes only take effect when the periodic
		1290	timer fires or C<ev_periodic_again> is being called.
		1291
1124	=item ev_tstamp interval [read-write]	1292	=item ev_tstamp interval [read-write]
1125		1293
1126	The current interval value. Can be modified any time, but changes only	1294	The current interval value. Can be modified any time, but changes only
1127	take effect when the periodic timer fires or C<ev_periodic_again> is being	1295	take effect when the periodic timer fires or C<ev_periodic_again> is being
1128	called.	1296	called.
…		…
1130	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1298	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
1131		1299
1132	The current reschedule callback, or C<0>, if this functionality is	1300	The current reschedule callback, or C<0>, if this functionality is
1133	switched off. Can be changed any time, but changes only take effect when	1301	switched off. Can be changed any time, but changes only take effect when
1134	the periodic timer fires or C<ev_periodic_again> is being called.	1302	the periodic timer fires or C<ev_periodic_again> is being called.
		1303
		1304	=item ev_tstamp at [read-only]
		1305
		1306	When active, contains the absolute time that the watcher is supposed to
		1307	trigger next.
1135		1308
1136	=back	1309	=back
1137		1310
1138	Example: Call a callback every hour, or, more precisely, whenever the	1311	Example: Call a callback every hour, or, more precisely, whenever the
1139	system clock is divisible by 3600. The callback invocation times have	1312	system clock is divisible by 3600. The callback invocation times have
…		…
1181	with the kernel (thus it coexists with your own signal handlers as long	1354	with the kernel (thus it coexists with your own signal handlers as long
1182	as you don't register any with libev). Similarly, when the last signal	1355	as you don't register any with libev). Similarly, when the last signal
1183	watcher for a signal is stopped libev will reset the signal handler to	1356	watcher for a signal is stopped libev will reset the signal handler to
1184	SIG_DFL (regardless of what it was set to before).	1357	SIG_DFL (regardless of what it was set to before).
1185		1358
		1359	=head3 Watcher-Specific Functions and Data Members
		1360
1186	=over 4	1361	=over 4
1187		1362
1188	=item ev_signal_init (ev_signal *, callback, int signum)	1363	=item ev_signal_init (ev_signal *, callback, int signum)
1189		1364
1190	=item ev_signal_set (ev_signal *, int signum)	1365	=item ev_signal_set (ev_signal *, int signum)
…		…
1201		1376
1202	=head2 C<ev_child> - watch out for process status changes	1377	=head2 C<ev_child> - watch out for process status changes
1203		1378
1204	Child watchers trigger when your process receives a SIGCHLD in response to	1379	Child watchers trigger when your process receives a SIGCHLD in response to
1205	some child status changes (most typically when a child of yours dies).	1380	some child status changes (most typically when a child of yours dies).
		1381
		1382	=head3 Watcher-Specific Functions and Data Members
1206		1383
1207	=over 4	1384	=over 4
1208		1385
1209	=item ev_child_init (ev_child *, callback, int pid)	1386	=item ev_child_init (ev_child *, callback, int pid)
1210		1387
…		…
1278	reader). Inotify will be used to give hints only and should not change the	1455	reader). Inotify will be used to give hints only and should not change the
1279	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1456	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1280	to fall back to regular polling again even with inotify, but changes are	1457	to fall back to regular polling again even with inotify, but changes are
1281	usually detected immediately, and if the file exists there will be no	1458	usually detected immediately, and if the file exists there will be no
1282	polling.	1459	polling.
		1460
		1461	=head3 Watcher-Specific Functions and Data Members
1283		1462
1284	=over 4	1463	=over 4
1285		1464
1286	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1465	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1287		1466
…		…
1351	ev_stat_start (loop, &passwd);	1530	ev_stat_start (loop, &passwd);
1352		1531
1353		1532
1354	=head2 C<ev_idle> - when you've got nothing better to do...	1533	=head2 C<ev_idle> - when you've got nothing better to do...
1355		1534
1356	Idle watchers trigger events when there are no other events are pending	1535	Idle watchers trigger events when no other events of the same or higher
1357	(prepare, check and other idle watchers do not count). That is, as long	1536	priority are pending (prepare, check and other idle watchers do not
1358	as your process is busy handling sockets or timeouts (or even signals,	1537	count).
1359	imagine) it will not be triggered. But when your process is idle all idle	1538
1360	watchers are being called again and again, once per event loop iteration -	1539	That is, as long as your process is busy handling sockets or timeouts
		1540	(or even signals, imagine) of the same or higher priority it will not be
		1541	triggered. But when your process is idle (or only lower-priority watchers
		1542	are pending), the idle watchers are being called once per event loop
1361	until stopped, that is, or your process receives more events and becomes	1543	iteration - until stopped, that is, or your process receives more events
1362	busy.	1544	and becomes busy again with higher priority stuff.
1363		1545
1364	The most noteworthy effect is that as long as any idle watchers are	1546	The most noteworthy effect is that as long as any idle watchers are
1365	active, the process will not block when waiting for new events.	1547	active, the process will not block when waiting for new events.
1366		1548
1367	Apart from keeping your process non-blocking (which is a useful	1549	Apart from keeping your process non-blocking (which is a useful
1368	effect on its own sometimes), idle watchers are a good place to do	1550	effect on its own sometimes), idle watchers are a good place to do
1369	"pseudo-background processing", or delay processing stuff to after the	1551	"pseudo-background processing", or delay processing stuff to after the
1370	event loop has handled all outstanding events.	1552	event loop has handled all outstanding events.
		1553
		1554	=head3 Watcher-Specific Functions and Data Members
1371		1555
1372	=over 4	1556	=over 4
1373		1557
1374	=item ev_idle_init (ev_signal *, callback)	1558	=item ev_idle_init (ev_signal *, callback)
1375		1559
…		…
1433	with priority higher than or equal to the event loop and one coroutine	1617	with priority higher than or equal to the event loop and one coroutine
1434	of lower priority, but only once, using idle watchers to keep the event	1618	of lower priority, but only once, using idle watchers to keep the event
1435	loop from blocking if lower-priority coroutines are active, thus mapping	1619	loop from blocking if lower-priority coroutines are active, thus mapping
1436	low-priority coroutines to idle/background tasks).	1620	low-priority coroutines to idle/background tasks).
1437		1621
		1622	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1623	priority, to ensure that they are being run before any other watchers
		1624	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1625	too) should not activate ("feed") events into libev. While libev fully
		1626	supports this, they will be called before other C<ev_check> watchers did
		1627	their job. As C<ev_check> watchers are often used to embed other event
		1628	loops those other event loops might be in an unusable state until their
		1629	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1630	others).
		1631
		1632	=head3 Watcher-Specific Functions and Data Members
		1633
1438	=over 4	1634	=over 4
1439		1635
1440	=item ev_prepare_init (ev_prepare *, callback)	1636	=item ev_prepare_init (ev_prepare *, callback)
1441		1637
1442	=item ev_check_init (ev_check *, callback)	1638	=item ev_check_init (ev_check *, callback)
…		…
1445	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1641	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1446	macros, but using them is utterly, utterly and completely pointless.	1642	macros, but using them is utterly, utterly and completely pointless.
1447		1643
1448	=back	1644	=back
1449		1645
1450	Example: To include a library such as adns, you would add IO watchers	1646	There are a number of principal ways to embed other event loops or modules
1451	and a timeout watcher in a prepare handler, as required by libadns, and	1647	into libev. Here are some ideas on how to include libadns into libev
		1648	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1649	use for an actually working example. Another Perl module named C<EV::Glib>
		1650	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1651	into the Glib event loop).
		1652
		1653	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1452	in a check watcher, destroy them and call into libadns. What follows is	1654	and in a check watcher, destroy them and call into libadns. What follows
1453	pseudo-code only of course:	1655	is pseudo-code only of course. This requires you to either use a low
		1656	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1657	the callbacks for the IO/timeout watchers might not have been called yet.
1454		1658
1455	static ev_io iow [nfd];	1659	static ev_io iow [nfd];
1456	static ev_timer tw;	1660	static ev_timer tw;
1457		1661
1458	static void	1662	static void
1459	io_cb (ev_loop loop, ev_io w, int revents)	1663	io_cb (ev_loop loop, ev_io w, int revents)
1460	{	1664	{
1461	// set the relevant poll flags
1462	// could also call adns_processreadable etc. here
1463	struct pollfd fd = (struct pollfd )w->data;
1464	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1465	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1466	}	1665	}
1467		1666
1468	// create io watchers for each fd and a timer before blocking	1667	// create io watchers for each fd and a timer before blocking
1469	static void	1668	static void
1470	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1669	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1476		1675
1477	/* the callback is illegal, but won't be called as we stop during check */	1676	/* the callback is illegal, but won't be called as we stop during check */
1478	ev_timer_init (&tw, 0, timeout * 1e-3);	1677	ev_timer_init (&tw, 0, timeout * 1e-3);
1479	ev_timer_start (loop, &tw);	1678	ev_timer_start (loop, &tw);
1480		1679
1481	// create on ev_io per pollfd	1680	// create one ev_io per pollfd
1482	for (int i = 0; i < nfd; ++i)	1681	for (int i = 0; i < nfd; ++i)
1483	{	1682	{
1484	ev_io_init (iow + i, io_cb, fds [i].fd,	1683	ev_io_init (iow + i, io_cb, fds [i].fd,
1485	((fds [i].events & POLLIN ? EV_READ : 0)	1684	((fds [i].events & POLLIN ? EV_READ : 0)
1486	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1685	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1487		1686
1488	fds [i].revents = 0;	1687	fds [i].revents = 0;
1489	iow [i].data = fds + i;
1490	ev_io_start (loop, iow + i);	1688	ev_io_start (loop, iow + i);
1491	}	1689	}
1492	}	1690	}
1493		1691
1494	// stop all watchers after blocking	1692	// stop all watchers after blocking
…		…
1496	adns_check_cb (ev_loop loop, ev_check w, int revents)	1694	adns_check_cb (ev_loop loop, ev_check w, int revents)
1497	{	1695	{
1498	ev_timer_stop (loop, &tw);	1696	ev_timer_stop (loop, &tw);
1499		1697
1500	for (int i = 0; i < nfd; ++i)	1698	for (int i = 0; i < nfd; ++i)
		1699	{
		1700	// set the relevant poll flags
		1701	// could also call adns_processreadable etc. here
		1702	struct pollfd *fd = fds + i;
		1703	int revents = ev_clear_pending (iow + i);
		1704	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1705	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1706
		1707	// now stop the watcher
1501	ev_io_stop (loop, iow + i);	1708	ev_io_stop (loop, iow + i);
		1709	}
1502		1710
1503	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1711	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1712	}
		1713
		1714	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1715	in the prepare watcher and would dispose of the check watcher.
		1716
		1717	Method 3: If the module to be embedded supports explicit event
		1718	notification (adns does), you can also make use of the actual watcher
		1719	callbacks, and only destroy/create the watchers in the prepare watcher.
		1720
		1721	static void
		1722	timer_cb (EV_P_ ev_timer *w, int revents)
		1723	{
		1724	adns_state ads = (adns_state)w->data;
		1725	update_now (EV_A);
		1726
		1727	adns_processtimeouts (ads, &tv_now);
		1728	}
		1729
		1730	static void
		1731	io_cb (EV_P_ ev_io *w, int revents)
		1732	{
		1733	adns_state ads = (adns_state)w->data;
		1734	update_now (EV_A);
		1735
		1736	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1737	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1738	}
		1739
		1740	// do not ever call adns_afterpoll
		1741
		1742	Method 4: Do not use a prepare or check watcher because the module you
		1743	want to embed is too inflexible to support it. Instead, youc na override
		1744	their poll function. The drawback with this solution is that the main
		1745	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1746	this.
		1747
		1748	static gint
		1749	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1750	{
		1751	int got_events = 0;
		1752
		1753	for (n = 0; n < nfds; ++n)
		1754	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1755
		1756	if (timeout >= 0)
		1757	// create/start timer
		1758
		1759	// poll
		1760	ev_loop (EV_A_ 0);
		1761
		1762	// stop timer again
		1763	if (timeout >= 0)
		1764	ev_timer_stop (EV_A_ &to);
		1765
		1766	// stop io watchers again - their callbacks should have set
		1767	for (n = 0; n < nfds; ++n)
		1768	ev_io_stop (EV_A_ iow [n]);
		1769
		1770	return got_events;
1504	}	1771	}
1505		1772
1506		1773
1507	=head2 C<ev_embed> - when one backend isn't enough...	1774	=head2 C<ev_embed> - when one backend isn't enough...
1508		1775
1509	This is a rather advanced watcher type that lets you embed one event loop	1776	This is a rather advanced watcher type that lets you embed one event loop
1510	into another (currently only C<ev_io> events are supported in the embedded	1777	into another (currently only C<ev_io> events are supported in the embedded
1511	loop, other types of watchers might be handled in a delayed or incorrect	1778	loop, other types of watchers might be handled in a delayed or incorrect
1512	fashion and must not be used).	1779	fashion and must not be used). (See portability notes, below).
1513		1780
1514	There are primarily two reasons you would want that: work around bugs and	1781	There are primarily two reasons you would want that: work around bugs and
1515	prioritise I/O.	1782	prioritise I/O.
1516		1783
1517	As an example for a bug workaround, the kqueue backend might only support	1784	As an example for a bug workaround, the kqueue backend might only support
…		…
1572	ev_embed_start (loop_hi, &embed);	1839	ev_embed_start (loop_hi, &embed);
1573	}	1840	}
1574	else	1841	else
1575	loop_lo = loop_hi;	1842	loop_lo = loop_hi;
1576		1843
		1844	=head2 Portability notes
		1845
		1846	Kqueue is nominally embeddable, but this is broken on all BSDs that I
		1847	tried, in various ways. Usually the embedded event loop will simply never
		1848	receive events, sometimes it will only trigger a few times, sometimes in a
		1849	loop. Epoll is also nominally embeddable, but many Linux kernel versions
		1850	will always eport the epoll fd as ready, even when no events are pending.
		1851
		1852	While libev allows embedding these backends (they are contained in
		1853	C<ev_embeddable_backends ()>), take extreme care that it will actually
		1854	work.
		1855
		1856	When in doubt, create a dynamic event loop forced to use sockets (this
		1857	usually works) and possibly another thread and a pipe or so to report to
		1858	your main event loop.
		1859
		1860	=head3 Watcher-Specific Functions and Data Members
		1861
1577	=over 4	1862	=over 4
1578		1863
1579	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1864	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1580		1865
1581	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	1866	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
…		…
1590		1875
1591	Make a single, non-blocking sweep over the embedded loop. This works	1876	Make a single, non-blocking sweep over the embedded loop. This works
1592	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1877	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1593	apropriate way for embedded loops.	1878	apropriate way for embedded loops.
1594		1879
1595	=item struct ev_loop *loop [read-only]	1880	=item struct ev_loop *other [read-only]
1596		1881
1597	The embedded event loop.	1882	The embedded event loop.
1598		1883
1599	=back	1884	=back
1600		1885
…		…
1607	event loop blocks next and before C<ev_check> watchers are being called,	1892	event loop blocks next and before C<ev_check> watchers are being called,
1608	and only in the child after the fork. If whoever good citizen calling	1893	and only in the child after the fork. If whoever good citizen calling
1609	C<ev_default_fork> cheats and calls it in the wrong process, the fork	1894	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1610	handlers will be invoked, too, of course.	1895	handlers will be invoked, too, of course.
1611		1896
		1897	=head3 Watcher-Specific Functions and Data Members
		1898
1612	=over 4	1899	=over 4
1613		1900
1614	=item ev_fork_init (ev_signal *, callback)	1901	=item ev_fork_init (ev_signal *, callback)
1615		1902
1616	Initialises and configures the fork watcher - it has no parameters of any	1903	Initialises and configures the fork watcher - it has no parameters of any
…		…
1712		1999
1713	To use it,	2000	To use it,
1714		2001
1715	#include <ev++.h>	2002	#include <ev++.h>
1716		2003
1717	(it is not installed by default). This automatically includes F<ev.h>	2004	This automatically includes F<ev.h> and puts all of its definitions (many
1718	and puts all of its definitions (many of them macros) into the global	2005	of them macros) into the global namespace. All C++ specific things are
1719	namespace. All C++ specific things are put into the C<ev> namespace.	2006	put into the C<ev> namespace. It should support all the same embedding
		2007	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1720		2008
1721	It should support all the same embedding options as F<ev.h>, most notably	2009	Care has been taken to keep the overhead low. The only data member the C++
1722	C<EV_MULTIPLICITY>.	2010	classes add (compared to plain C-style watchers) is the event loop pointer
		2011	that the watcher is associated with (or no additional members at all if
		2012	you disable C<EV_MULTIPLICITY> when embedding libev).
		2013
		2014	Currently, functions, and static and non-static member functions can be
		2015	used as callbacks. Other types should be easy to add as long as they only
		2016	need one additional pointer for context. If you need support for other
		2017	types of functors please contact the author (preferably after implementing
		2018	it).
1723		2019
1724	Here is a list of things available in the C<ev> namespace:	2020	Here is a list of things available in the C<ev> namespace:
1725		2021
1726	=over 4	2022	=over 4
1727		2023
…		…
1743		2039
1744	All of those classes have these methods:	2040	All of those classes have these methods:
1745		2041
1746	=over 4	2042	=over 4
1747		2043
1748	=item ev::TYPE::TYPE (object , object::method )	2044	=item ev::TYPE::TYPE ()
1749		2045
1750	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	2046	=item ev::TYPE::TYPE (struct ev_loop *)
1751		2047
1752	=item ev::TYPE::~TYPE	2048	=item ev::TYPE::~TYPE
1753		2049
1754	The constructor takes a pointer to an object and a method pointer to	2050	The constructor (optionally) takes an event loop to associate the watcher
1755	the event handler callback to call in this class. The constructor calls	2051	with. If it is omitted, it will use C<EV_DEFAULT>.
1756	C<ev_init> for you, which means you have to call the C<set> method	2052
1757	before starting it. If you do not specify a loop then the constructor	2053	The constructor calls C<ev_init> for you, which means you have to call the
1758	automatically associates the default loop with this watcher.	2054	C<set> method before starting it.
		2055
		2056	It will not set a callback, however: You have to call the templated C<set>
		2057	method to set a callback before you can start the watcher.
		2058
		2059	(The reason why you have to use a method is a limitation in C++ which does
		2060	not allow explicit template arguments for constructors).
1759		2061
1760	The destructor automatically stops the watcher if it is active.	2062	The destructor automatically stops the watcher if it is active.
		2063
		2064	=item w->set<class, &class::method> (object *)
		2065
		2066	This method sets the callback method to call. The method has to have a
		2067	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2068	first argument and the C<revents> as second. The object must be given as
		2069	parameter and is stored in the C<data> member of the watcher.
		2070
		2071	This method synthesizes efficient thunking code to call your method from
		2072	the C callback that libev requires. If your compiler can inline your
		2073	callback (i.e. it is visible to it at the place of the C<set> call and
		2074	your compiler is good :), then the method will be fully inlined into the
		2075	thunking function, making it as fast as a direct C callback.
		2076
		2077	Example: simple class declaration and watcher initialisation
		2078
		2079	struct myclass
		2080	{
		2081	void io_cb (ev::io &w, int revents) { }
		2082	}
		2083
		2084	myclass obj;
		2085	ev::io iow;
		2086	iow.set <myclass, &myclass::io_cb> (&obj);
		2087
		2088	=item w->set<function> (void *data = 0)
		2089
		2090	Also sets a callback, but uses a static method or plain function as
		2091	callback. The optional C<data> argument will be stored in the watcher's
		2092	C<data> member and is free for you to use.
		2093
		2094	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2095
		2096	See the method-C<set> above for more details.
		2097
		2098	Example:
		2099
		2100	static void io_cb (ev::io &w, int revents) { }
		2101	iow.set <io_cb> ();
1761		2102
1762	=item w->set (struct ev_loop *)	2103	=item w->set (struct ev_loop *)
1763		2104
1764	Associates a different C<struct ev_loop> with this watcher. You can only	2105	Associates a different C<struct ev_loop> with this watcher. You can only
1765	do this when the watcher is inactive (and not pending either).	2106	do this when the watcher is inactive (and not pending either).
1766		2107
1767	=item w->set ([args])	2108	=item w->set ([args])
1768		2109
1769	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2110	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1770	called at least once. Unlike the C counterpart, an active watcher gets	2111	called at least once. Unlike the C counterpart, an active watcher gets
1771	automatically stopped and restarted.	2112	automatically stopped and restarted when reconfiguring it with this
		2113	method.
1772		2114
1773	=item w->start ()	2115	=item w->start ()
1774		2116
1775	Starts the watcher. Note that there is no C<loop> argument as the	2117	Starts the watcher. Note that there is no C<loop> argument, as the
1776	constructor already takes the loop.	2118	constructor already stores the event loop.
1777		2119
1778	=item w->stop ()	2120	=item w->stop ()
1779		2121
1780	Stops the watcher if it is active. Again, no C<loop> argument.	2122	Stops the watcher if it is active. Again, no C<loop> argument.
1781		2123
1782	=item w->again () C<ev::timer>, C<ev::periodic> only	2124	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1783		2125
1784	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2126	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1785	C<ev_TYPE_again> function.	2127	C<ev_TYPE_again> function.
1786		2128
1787	=item w->sweep () C<ev::embed> only	2129	=item w->sweep () (C<ev::embed> only)
1788		2130
1789	Invokes C<ev_embed_sweep>.	2131	Invokes C<ev_embed_sweep>.
1790		2132
1791	=item w->update () C<ev::stat> only	2133	=item w->update () (C<ev::stat> only)
1792		2134
1793	Invokes C<ev_stat_stat>.	2135	Invokes C<ev_stat_stat>.
1794		2136
1795	=back	2137	=back
1796		2138
…		…
1806		2148
1807	myclass ();	2149	myclass ();
1808	}	2150	}
1809		2151
1810	myclass::myclass (int fd)	2152	myclass::myclass (int fd)
1811	: io (this, &myclass::io_cb),
1812	idle (this, &myclass::idle_cb)
1813	{	2153	{
		2154	io .set <myclass, &myclass::io_cb > (this);
		2155	idle.set <myclass, &myclass::idle_cb> (this);
		2156
1814	io.start (fd, ev::READ);	2157	io.start (fd, ev::READ);
1815	}	2158	}
1816		2159
1817		2160
1818	=head1 MACRO MAGIC	2161	=head1 MACRO MAGIC
1819		2162
1820	Libev can be compiled with a variety of options, the most fundemantal is	2163	Libev can be compiled with a variety of options, the most fundamantal
1821	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2164	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1822	callbacks have an initial C<struct ev_loop *> argument.	2165	functions and callbacks have an initial C<struct ev_loop *> argument.
1823		2166
1824	To make it easier to write programs that cope with either variant, the	2167	To make it easier to write programs that cope with either variant, the
1825	following macros are defined:	2168	following macros are defined:
1826		2169
1827	=over 4	2170	=over 4
…		…
1860	loop, if multiple loops are supported ("ev loop default").	2203	loop, if multiple loops are supported ("ev loop default").
1861		2204
1862	=back	2205	=back
1863		2206
1864	Example: Declare and initialise a check watcher, utilising the above	2207	Example: Declare and initialise a check watcher, utilising the above
1865	macros so it will work regardless of wether multiple loops are supported	2208	macros so it will work regardless of whether multiple loops are supported
1866	or not.	2209	or not.
1867		2210
1868	static void	2211	static void
1869	check_cb (EV_P_ ev_timer *w, int revents)	2212	check_cb (EV_P_ ev_timer *w, int revents)
1870	{	2213	{
…		…
1881	Libev can (and often is) directly embedded into host	2224	Libev can (and often is) directly embedded into host
1882	applications. Examples of applications that embed it include the Deliantra	2225	applications. Examples of applications that embed it include the Deliantra
1883	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2226	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1884	and rxvt-unicode.	2227	and rxvt-unicode.
1885		2228
1886	The goal is to enable you to just copy the neecssary files into your	2229	The goal is to enable you to just copy the necessary files into your
1887	source directory without having to change even a single line in them, so	2230	source directory without having to change even a single line in them, so
1888	you can easily upgrade by simply copying (or having a checked-out copy of	2231	you can easily upgrade by simply copying (or having a checked-out copy of
1889	libev somewhere in your source tree).	2232	libev somewhere in your source tree).
1890		2233
1891	=head2 FILESETS	2234	=head2 FILESETS
…		…
1981		2324
1982	If defined to be C<1>, libev will try to detect the availability of the	2325	If defined to be C<1>, libev will try to detect the availability of the
1983	monotonic clock option at both compiletime and runtime. Otherwise no use	2326	monotonic clock option at both compiletime and runtime. Otherwise no use
1984	of the monotonic clock option will be attempted. If you enable this, you	2327	of the monotonic clock option will be attempted. If you enable this, you
1985	usually have to link against librt or something similar. Enabling it when	2328	usually have to link against librt or something similar. Enabling it when
1986	the functionality isn't available is safe, though, althoguh you have	2329	the functionality isn't available is safe, though, although you have
1987	to make sure you link against any libraries where the C<clock_gettime>	2330	to make sure you link against any libraries where the C<clock_gettime>
1988	function is hiding in (often F<-lrt>).	2331	function is hiding in (often F<-lrt>).
1989		2332
1990	=item EV_USE_REALTIME	2333	=item EV_USE_REALTIME
1991		2334
1992	If defined to be C<1>, libev will try to detect the availability of the	2335	If defined to be C<1>, libev will try to detect the availability of the
1993	realtime clock option at compiletime (and assume its availability at	2336	realtime clock option at compiletime (and assume its availability at
1994	runtime if successful). Otherwise no use of the realtime clock option will	2337	runtime if successful). Otherwise no use of the realtime clock option will
1995	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2338	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1996	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2339	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1997	in the description of C<EV_USE_MONOTONIC>, though.	2340	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2341
		2342	=item EV_USE_NANOSLEEP
		2343
		2344	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2345	and will use it for delays. Otherwise it will use C<select ()>.
1998		2346
1999	=item EV_USE_SELECT	2347	=item EV_USE_SELECT
2000		2348
2001	If undefined or defined to be C<1>, libev will compile in support for the	2349	If undefined or defined to be C<1>, libev will compile in support for the
2002	C<select>(2) backend. No attempt at autodetection will be done: if no	2350	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2095	will have the C<struct ev_loop *> as first argument, and you can create	2443	will have the C<struct ev_loop *> as first argument, and you can create
2096	additional independent event loops. Otherwise there will be no support	2444	additional independent event loops. Otherwise there will be no support
2097	for multiple event loops and there is no first event loop pointer	2445	for multiple event loops and there is no first event loop pointer
2098	argument. Instead, all functions act on the single default loop.	2446	argument. Instead, all functions act on the single default loop.
2099		2447
		2448	=item EV_MINPRI
		2449
		2450	=item EV_MAXPRI
		2451
		2452	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2453	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2454	provide for more priorities by overriding those symbols (usually defined
		2455	to be C<-2> and C<2>, respectively).
		2456
		2457	When doing priority-based operations, libev usually has to linearly search
		2458	all the priorities, so having many of them (hundreds) uses a lot of space
		2459	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2460	fine.
		2461
		2462	If your embedding app does not need any priorities, defining these both to
		2463	C<0> will save some memory and cpu.
		2464
2100	=item EV_PERIODIC_ENABLE	2465	=item EV_PERIODIC_ENABLE
2101		2466
2102	If undefined or defined to be C<1>, then periodic timers are supported. If	2467	If undefined or defined to be C<1>, then periodic timers are supported. If
		2468	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2469	code.
		2470
		2471	=item EV_IDLE_ENABLE
		2472
		2473	If undefined or defined to be C<1>, then idle watchers are supported. If
2103	defined to be C<0>, then they are not. Disabling them saves a few kB of	2474	defined to be C<0>, then they are not. Disabling them saves a few kB of
2104	code.	2475	code.
2105		2476
2106	=item EV_EMBED_ENABLE	2477	=item EV_EMBED_ENABLE
2107		2478
…		…
2158		2529
2159	=item ev_set_cb (ev, cb)	2530	=item ev_set_cb (ev, cb)
2160		2531
2161	Can be used to change the callback member declaration in each watcher,	2532	Can be used to change the callback member declaration in each watcher,
2162	and the way callbacks are invoked and set. Must expand to a struct member	2533	and the way callbacks are invoked and set. Must expand to a struct member
2163	definition and a statement, respectively. See the F<ev.v> header file for	2534	definition and a statement, respectively. See the F<ev.h> header file for
2164	their default definitions. One possible use for overriding these is to	2535	their default definitions. One possible use for overriding these is to
2165	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2536	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2166	method calls instead of plain function calls in C++.	2537	method calls instead of plain function calls in C++.
		2538
		2539	=head2 EXPORTED API SYMBOLS
		2540
		2541	If you need to re-export the API (e.g. via a dll) and you need a list of
		2542	exported symbols, you can use the provided F<Symbol.*> files which list
		2543	all public symbols, one per line:
		2544
		2545	Symbols.ev for libev proper
		2546	Symbols.event for the libevent emulation
		2547
		2548	This can also be used to rename all public symbols to avoid clashes with
		2549	multiple versions of libev linked together (which is obviously bad in
		2550	itself, but sometimes it is inconvinient to avoid this).
		2551
		2552	A sed command like this will create wrapper C<#define>'s that you need to
		2553	include before including F<ev.h>:
		2554
		2555	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2556
		2557	This would create a file F<wrap.h> which essentially looks like this:
		2558
		2559	#define ev_backend myprefix_ev_backend
		2560	#define ev_check_start myprefix_ev_check_start
		2561	#define ev_check_stop myprefix_ev_check_stop
		2562	...
2167		2563
2168	=head2 EXAMPLES	2564	=head2 EXAMPLES
2169		2565
2170	For a real-world example of a program the includes libev	2566	For a real-world example of a program the includes libev
2171	verbatim, you can have a look at the EV perl module	2567	verbatim, you can have a look at the EV perl module
…		…
2200		2596
2201	In this section the complexities of (many of) the algorithms used inside	2597	In this section the complexities of (many of) the algorithms used inside
2202	libev will be explained. For complexity discussions about backends see the	2598	libev will be explained. For complexity discussions about backends see the
2203	documentation for C<ev_default_init>.	2599	documentation for C<ev_default_init>.
2204		2600
		2601	All of the following are about amortised time: If an array needs to be
		2602	extended, libev needs to realloc and move the whole array, but this
		2603	happens asymptotically never with higher number of elements, so O(1) might
		2604	mean it might do a lengthy realloc operation in rare cases, but on average
		2605	it is much faster and asymptotically approaches constant time.
		2606
2205	=over 4	2607	=over 4
2206		2608
2207	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2609	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2208		2610
		2611	This means that, when you have a watcher that triggers in one hour and
		2612	there are 100 watchers that would trigger before that then inserting will
		2613	have to skip those 100 watchers.
		2614
2209	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2615	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2210		2616
		2617	That means that for changing a timer costs less than removing/adding them
		2618	as only the relative motion in the event queue has to be paid for.
		2619
2211	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2620	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2212		2621
		2622	These just add the watcher into an array or at the head of a list.
2213	=item Stopping check/prepare/idle watchers: O(1)	2623	=item Stopping check/prepare/idle watchers: O(1)
2214		2624
2215	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2625	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2216		2626
		2627	These watchers are stored in lists then need to be walked to find the
		2628	correct watcher to remove. The lists are usually short (you don't usually
		2629	have many watchers waiting for the same fd or signal).
		2630
2217	=item Finding the next timer per loop iteration: O(1)	2631	=item Finding the next timer per loop iteration: O(1)
2218		2632
2219	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2633	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2220		2634
		2635	A change means an I/O watcher gets started or stopped, which requires
		2636	libev to recalculate its status (and possibly tell the kernel).
		2637
2221	=item Activating one watcher: O(1)	2638	=item Activating one watcher: O(1)
2222		2639
		2640	=item Priority handling: O(number_of_priorities)
		2641
		2642	Priorities are implemented by allocating some space for each
		2643	priority. When doing priority-based operations, libev usually has to
		2644	linearly search all the priorities.
		2645
2223	=back	2646	=back
2224		2647
2225		2648
2226	=head1 AUTHOR	2649	=head1 AUTHOR
2227		2650

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Comparing libev/ev.pod (file contents): Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs. Revision 1.98 by root, Sat Dec 22 06:10:25 2007 UTC

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Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs.
Revision 1.98 by root, Sat Dec 22 06:10:25 2007 UTC