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

Comparing libev/ev.pod (file contents):
Revision 1.64 by root, Sat Dec 1 15:32:53 2007 UTC vs.
Revision 1.99 by root, Sat Dec 22 06:16:36 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.
…		…
274	a fork, you can also make libev check for a fork in each iteration by	289	a fork, you can also make libev check for a fork in each iteration by
275	enabling this flag.	290	enabling this flag.
276		291
277	This works by calling C<getpid ()> on every iteration of the loop,	292	This works by calling C<getpid ()> on every iteration of the loop,
278	and thus this might slow down your event loop if you do a lot of loop	293	and thus this might slow down your event loop if you do a lot of loop
279	iterations and little real work, but is usually not noticable (on my	294	iterations and little real work, but is usually not noticeable (on my
280	Linux system for example, C<getpid> is actually a simple 5-insn sequence	295	Linux system for example, C<getpid> is actually a simple 5-insn sequence
281	without a syscall and thus I<very> fast, but my Linux system also has	296	without a syscall and thus I<very> fast, but my Linux system also has
282	C<pthread_atfork> which is even faster).	297	C<pthread_atfork> which is even faster).
283		298
284	The big advantage of this flag is that you can forget about fork (and	299	The big advantage of this flag is that you can forget about fork (and
…		…
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>.
…		…
430		460
431	Like C<ev_default_fork>, but acts on an event loop created by	461	Like C<ev_default_fork>, but acts on an event loop created by
432	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	462	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
433	after fork, and how you do this is entirely your own problem.	463	after fork, and how you do this is entirely your own problem.
434		464
		465	=item unsigned int ev_loop_count (loop)
		466
		467	Returns the count of loop iterations for the loop, which is identical to
		468	the number of times libev did poll for new events. It starts at C<0> and
		469	happily wraps around with enough iterations.
		470
		471	This value can sometimes be useful as a generation counter of sorts (it
		472	"ticks" the number of loop iterations), as it roughly corresponds with
		473	C<ev_prepare> and C<ev_check> calls.
		474
435	=item unsigned int ev_backend (loop)	475	=item unsigned int ev_backend (loop)
436		476
437	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	477	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
438	use.	478	use.
439		479
…		…
441		481
442	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
443	received events and started processing them. This timestamp does not	483	received events and started processing them. This timestamp does not
444	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
445	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
446	event occuring (or more correctly, libev finding out about it).	486	event occurring (or more correctly, libev finding out about it).
447		487
448	=item ev_loop (loop, int flags)	488	=item ev_loop (loop, int flags)
449		489
450	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
451	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
…		…
472	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
473	usually a better approach for this kind of thing.	513	usually a better approach for this kind of thing.
474		514
475	Here are the gory details of what C<ev_loop> does:	515	Here are the gory details of what C<ev_loop> does:
476		516
		517	- Before the first iteration, call any pending watchers.
477	* If there are no active watchers (reference count is zero), return.	518	* If there are no active watchers (reference count is zero), return.
478	- Queue prepare watchers and then call all outstanding watchers.	519	- Queue all prepare watchers and then call all outstanding watchers.
479	- If we have been forked, recreate the kernel state.	520	- If we have been forked, recreate the kernel state.
480	- Update the kernel state with all outstanding changes.	521	- Update the kernel state with all outstanding changes.
481	- Update the "event loop time".	522	- Update the "event loop time".
482	- Calculate for how long to block.	523	- Calculate for how long to block.
483	- Block the process, waiting for any events.	524	- Block the process, waiting for any events.
…		…
534	Example: For some weird reason, unregister the above signal handler again.	575	Example: For some weird reason, unregister the above signal handler again.
535		576
536	ev_ref (loop);	577	ev_ref (loop);
537	ev_signal_stop (loop, &exitsig);	578	ev_signal_stop (loop, &exitsig);
538		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. Setting this to a non-null bvalue will
		602	introduce an additional C<ev_sleep ()> call into most loop iterations.
		603
		604	Likewise, by setting a higher I<timeout collect interval> you allow libev
		605	to spend more time collecting timeouts, at the expense of increased
		606	latency (the watcher callback will be called later). C<ev_io> watchers
		607	will not be affected. Setting this to a non-null value will not introduce
		608	any overhead in libev.
		609
		610	Many (busy) programs can usually benefit by setting the io collect
		611	interval to a value near C<0.1> or so, which is often enough for
		612	interactive servers (of course not for games), likewise for timeouts. It
		613	usually doesn't make much sense to set it to a lower value than C<0.01>,
		614	as this approsaches the timing granularity of most systems.
		615
539	=back	616	=back
540		617
541		618
542	=head1 ANATOMY OF A WATCHER	619	=head1 ANATOMY OF A WATCHER
543		620
…		…
722	=item bool ev_is_pending (ev_TYPE *watcher)	799	=item bool ev_is_pending (ev_TYPE *watcher)
723		800
724	Returns a true value iff the watcher is pending, (i.e. it has outstanding	801	Returns a true value iff the watcher is pending, (i.e. it has outstanding
725	events but its callback has not yet been invoked). As long as a watcher	802	events but its callback has not yet been invoked). As long as a watcher
726	is pending (but not active) you must not call an init function on it (but	803	is pending (but not active) you must not call an init function on it (but
727	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	804	C<ev_TYPE_set> is safe), you must not change its priority, and you must
728	libev (e.g. you cnanot C<free ()> it).	805	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		806	it).
729		807
730	=item callback ev_cb (ev_TYPE *watcher)	808	=item callback ev_cb (ev_TYPE *watcher)
731		809
732	Returns the callback currently set on the watcher.	810	Returns the callback currently set on the watcher.
733		811
734	=item ev_cb_set (ev_TYPE *watcher, callback)	812	=item ev_cb_set (ev_TYPE *watcher, callback)
735		813
736	Change the callback. You can change the callback at virtually any time	814	Change the callback. You can change the callback at virtually any time
737	(modulo threads).	815	(modulo threads).
		816
		817	=item ev_set_priority (ev_TYPE *watcher, priority)
		818
		819	=item int ev_priority (ev_TYPE *watcher)
		820
		821	Set and query the priority of the watcher. The priority is a small
		822	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		823	(default: C<-2>). Pending watchers with higher priority will be invoked
		824	before watchers with lower priority, but priority will not keep watchers
		825	from being executed (except for C<ev_idle> watchers).
		826
		827	This means that priorities are I<only> used for ordering callback
		828	invocation after new events have been received. This is useful, for
		829	example, to reduce latency after idling, or more often, to bind two
		830	watchers on the same event and make sure one is called first.
		831
		832	If you need to suppress invocation when higher priority events are pending
		833	you need to look at C<ev_idle> watchers, which provide this functionality.
		834
		835	You I<must not> change the priority of a watcher as long as it is active or
		836	pending.
		837
		838	The default priority used by watchers when no priority has been set is
		839	always C<0>, which is supposed to not be too high and not be too low :).
		840
		841	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		842	fine, as long as you do not mind that the priority value you query might
		843	or might not have been adjusted to be within valid range.
		844
		845	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		846
		847	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		848	C<loop> nor C<revents> need to be valid as long as the watcher callback
		849	can deal with that fact.
		850
		851	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		852
		853	If the watcher is pending, this function returns clears its pending status
		854	and returns its C<revents> bitset (as if its callback was invoked). If the
		855	watcher isn't pending it does nothing and returns C<0>.
738		856
739	=back	857	=back
740		858
741		859
742	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	860	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
848	it is best to always use non-blocking I/O: An extra C<read>(2) returning	966	it is best to always use non-blocking I/O: An extra C<read>(2) returning
849	C<EAGAIN> is far preferable to a program hanging until some data arrives.	967	C<EAGAIN> is far preferable to a program hanging until some data arrives.
850		968
851	If you cannot run the fd in non-blocking mode (for example you should not	969	If you cannot run the fd in non-blocking mode (for example you should not
852	play around with an Xlib connection), then you have to seperately re-test	970	play around with an Xlib connection), then you have to seperately re-test
853	wether a file descriptor is really ready with a known-to-be good interface	971	whether a file descriptor is really ready with a known-to-be good interface
854	such as poll (fortunately in our Xlib example, Xlib already does this on	972	such as poll (fortunately in our Xlib example, Xlib already does this on
855	its own, so its quite safe to use).	973	its own, so its quite safe to use).
		974
		975	=head3 The special problem of disappearing file descriptors
		976
		977	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		978	descriptor (either by calling C<close> explicitly or by any other means,
		979	such as C<dup>). The reason is that you register interest in some file
		980	descriptor, but when it goes away, the operating system will silently drop
		981	this interest. If another file descriptor with the same number then is
		982	registered with libev, there is no efficient way to see that this is, in
		983	fact, a different file descriptor.
		984
		985	To avoid having to explicitly tell libev about such cases, libev follows
		986	the following policy: Each time C<ev_io_set> is being called, libev
		987	will assume that this is potentially a new file descriptor, otherwise
		988	it is assumed that the file descriptor stays the same. That means that
		989	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		990	descriptor even if the file descriptor number itself did not change.
		991
		992	This is how one would do it normally anyway, the important point is that
		993	the libev application should not optimise around libev but should leave
		994	optimisations to libev.
		995
		996	=head3 The special problem of dup'ed file descriptors
		997
		998	Some backends (e.g. epoll), cannot register events for file descriptors,
		999	but only events for the underlying file descriptions. That menas when you
		1000	have C<dup ()>'ed file descriptors and register events for them, only one
		1001	file descriptor might actually receive events.
		1002
		1003	There is no workaorund possible except not registering events
		1004	for potentially C<dup ()>'ed file descriptors or to resort to
		1005	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1006
		1007	=head3 The special problem of fork
		1008
		1009	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1010	useless behaviour. Libev fully supports fork, but needs to be told about
		1011	it in the child.
		1012
		1013	To support fork in your programs, you either have to call
		1014	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1015	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1016	C<EVBACKEND_POLL>.
		1017
		1018
		1019	=head3 Watcher-Specific Functions
856		1020
857	=over 4	1021	=over 4
858		1022
859	=item ev_io_init (ev_io *, callback, int fd, int events)	1023	=item ev_io_init (ev_io *, callback, int fd, int events)
860		1024
…		…
913	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1077	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
914		1078
915	The callback is guarenteed to be invoked only when its timeout has passed,	1079	The callback is guarenteed to be invoked only when its timeout has passed,
916	but if multiple timers become ready during the same loop iteration then	1080	but if multiple timers become ready during the same loop iteration then
917	order of execution is undefined.	1081	order of execution is undefined.
		1082
		1083	=head3 Watcher-Specific Functions and Data Members
918		1084
919	=over 4	1085	=over 4
920		1086
921	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1087	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
922		1088
…		…
1018	but on wallclock time (absolute time). You can tell a periodic watcher	1184	but on wallclock time (absolute time). You can tell a periodic watcher
1019	to trigger "at" some specific point in time. For example, if you tell a	1185	to trigger "at" some specific point in time. For example, if you tell a
1020	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1186	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1021	+ 10.>) and then reset your system clock to the last year, then it will	1187	+ 10.>) and then reset your system clock to the last year, then it will
1022	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1188	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1023	roughly 10 seconds later and of course not if you reset your system time	1189	roughly 10 seconds later).
1024	again).
1025		1190
1026	They can also be used to implement vastly more complex timers, such as	1191	They can also be used to implement vastly more complex timers, such as
1027	triggering an event on eahc midnight, local time.	1192	triggering an event on each midnight, local time or other, complicated,
		1193	rules.
1028		1194
1029	As with timers, the callback is guarenteed to be invoked only when the	1195	As with timers, the callback is guarenteed to be invoked only when the
1030	time (C<at>) has been passed, but if multiple periodic timers become ready	1196	time (C<at>) has been passed, but if multiple periodic timers become ready
1031	during the same loop iteration then order of execution is undefined.	1197	during the same loop iteration then order of execution is undefined.
1032		1198
		1199	=head3 Watcher-Specific Functions and Data Members
		1200
1033	=over 4	1201	=over 4
1034		1202
1035	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1203	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1036		1204
1037	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1205	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1039	Lots of arguments, lets sort it out... There are basically three modes of	1207	Lots of arguments, lets sort it out... There are basically three modes of
1040	operation, and we will explain them from simplest to complex:	1208	operation, and we will explain them from simplest to complex:
1041		1209
1042	=over 4	1210	=over 4
1043		1211
1044	=item * absolute timer (interval = reschedule_cb = 0)	1212	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1045		1213
1046	In this configuration the watcher triggers an event at the wallclock time	1214	In this configuration the watcher triggers an event at the wallclock time
1047	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1215	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1048	that is, if it is to be run at January 1st 2011 then it will run when the	1216	that is, if it is to be run at January 1st 2011 then it will run when the
1049	system time reaches or surpasses this time.	1217	system time reaches or surpasses this time.
1050		1218
1051	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1219	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1052		1220
1053	In this mode the watcher will always be scheduled to time out at the next	1221	In this mode the watcher will always be scheduled to time out at the next
1054	C<at + N * interval> time (for some integer N) and then repeat, regardless	1222	C<at + N * interval> time (for some integer N, which can also be negative)
1055	of any time jumps.	1223	and then repeat, regardless of any time jumps.
1056		1224
1057	This can be used to create timers that do not drift with respect to system	1225	This can be used to create timers that do not drift with respect to system
1058	time:	1226	time:
1059		1227
1060	ev_periodic_set (&periodic, 0., 3600., 0);	1228	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1066		1234
1067	Another way to think about it (for the mathematically inclined) is that	1235	Another way to think about it (for the mathematically inclined) is that
1068	C<ev_periodic> will try to run the callback in this mode at the next possible	1236	C<ev_periodic> will try to run the callback in this mode at the next possible
1069	time where C<time = at (mod interval)>, regardless of any time jumps.	1237	time where C<time = at (mod interval)>, regardless of any time jumps.
1070		1238
		1239	For numerical stability it is preferable that the C<at> value is near
		1240	C<ev_now ()> (the current time), but there is no range requirement for
		1241	this value.
		1242
1071	=item * manual reschedule mode (reschedule_cb = callback)	1243	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1072		1244
1073	In this mode the values for C<interval> and C<at> are both being	1245	In this mode the values for C<interval> and C<at> are both being
1074	ignored. Instead, each time the periodic watcher gets scheduled, the	1246	ignored. Instead, each time the periodic watcher gets scheduled, the
1075	reschedule callback will be called with the watcher as first, and the	1247	reschedule callback will be called with the watcher as first, and the
1076	current time as second argument.	1248	current time as second argument.
1077		1249
1078	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1250	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1079	ever, or make any event loop modifications>. If you need to stop it,	1251	ever, or make any event loop modifications>. If you need to stop it,
1080	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1252	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1081	starting a prepare watcher).	1253	starting an C<ev_prepare> watcher, which is legal).
1082		1254
1083	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1255	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1084	ev_tstamp now)>, e.g.:	1256	ev_tstamp now)>, e.g.:
1085		1257
1086	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1258	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1109	Simply stops and restarts the periodic watcher again. This is only useful	1281	Simply stops and restarts the periodic watcher again. This is only useful
1110	when you changed some parameters or the reschedule callback would return	1282	when you changed some parameters or the reschedule callback would return
1111	a different time than the last time it was called (e.g. in a crond like	1283	a different time than the last time it was called (e.g. in a crond like
1112	program when the crontabs have changed).	1284	program when the crontabs have changed).
1113		1285
		1286	=item ev_tstamp offset [read-write]
		1287
		1288	When repeating, this contains the offset value, otherwise this is the
		1289	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1290
		1291	Can be modified any time, but changes only take effect when the periodic
		1292	timer fires or C<ev_periodic_again> is being called.
		1293
1114	=item ev_tstamp interval [read-write]	1294	=item ev_tstamp interval [read-write]
1115		1295
1116	The current interval value. Can be modified any time, but changes only	1296	The current interval value. Can be modified any time, but changes only
1117	take effect when the periodic timer fires or C<ev_periodic_again> is being	1297	take effect when the periodic timer fires or C<ev_periodic_again> is being
1118	called.	1298	called.
…		…
1120	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1300	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
1121		1301
1122	The current reschedule callback, or C<0>, if this functionality is	1302	The current reschedule callback, or C<0>, if this functionality is
1123	switched off. Can be changed any time, but changes only take effect when	1303	switched off. Can be changed any time, but changes only take effect when
1124	the periodic timer fires or C<ev_periodic_again> is being called.	1304	the periodic timer fires or C<ev_periodic_again> is being called.
		1305
		1306	=item ev_tstamp at [read-only]
		1307
		1308	When active, contains the absolute time that the watcher is supposed to
		1309	trigger next.
1125		1310
1126	=back	1311	=back
1127		1312
1128	Example: Call a callback every hour, or, more precisely, whenever the	1313	Example: Call a callback every hour, or, more precisely, whenever the
1129	system clock is divisible by 3600. The callback invocation times have	1314	system clock is divisible by 3600. The callback invocation times have
…		…
1171	with the kernel (thus it coexists with your own signal handlers as long	1356	with the kernel (thus it coexists with your own signal handlers as long
1172	as you don't register any with libev). Similarly, when the last signal	1357	as you don't register any with libev). Similarly, when the last signal
1173	watcher for a signal is stopped libev will reset the signal handler to	1358	watcher for a signal is stopped libev will reset the signal handler to
1174	SIG_DFL (regardless of what it was set to before).	1359	SIG_DFL (regardless of what it was set to before).
1175		1360
		1361	=head3 Watcher-Specific Functions and Data Members
		1362
1176	=over 4	1363	=over 4
1177		1364
1178	=item ev_signal_init (ev_signal *, callback, int signum)	1365	=item ev_signal_init (ev_signal *, callback, int signum)
1179		1366
1180	=item ev_signal_set (ev_signal *, int signum)	1367	=item ev_signal_set (ev_signal *, int signum)
…		…
1191		1378
1192	=head2 C<ev_child> - watch out for process status changes	1379	=head2 C<ev_child> - watch out for process status changes
1193		1380
1194	Child watchers trigger when your process receives a SIGCHLD in response to	1381	Child watchers trigger when your process receives a SIGCHLD in response to
1195	some child status changes (most typically when a child of yours dies).	1382	some child status changes (most typically when a child of yours dies).
		1383
		1384	=head3 Watcher-Specific Functions and Data Members
1196		1385
1197	=over 4	1386	=over 4
1198		1387
1199	=item ev_child_init (ev_child *, callback, int pid)	1388	=item ev_child_init (ev_child *, callback, int pid)
1200		1389
…		…
1268	reader). Inotify will be used to give hints only and should not change the	1457	reader). Inotify will be used to give hints only and should not change the
1269	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1458	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1270	to fall back to regular polling again even with inotify, but changes are	1459	to fall back to regular polling again even with inotify, but changes are
1271	usually detected immediately, and if the file exists there will be no	1460	usually detected immediately, and if the file exists there will be no
1272	polling.	1461	polling.
		1462
		1463	=head3 Watcher-Specific Functions and Data Members
1273		1464
1274	=over 4	1465	=over 4
1275		1466
1276	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1467	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1277		1468
…		…
1341	ev_stat_start (loop, &passwd);	1532	ev_stat_start (loop, &passwd);
1342		1533
1343		1534
1344	=head2 C<ev_idle> - when you've got nothing better to do...	1535	=head2 C<ev_idle> - when you've got nothing better to do...
1345		1536
1346	Idle watchers trigger events when there are no other events are pending	1537	Idle watchers trigger events when no other events of the same or higher
1347	(prepare, check and other idle watchers do not count). That is, as long	1538	priority are pending (prepare, check and other idle watchers do not
1348	as your process is busy handling sockets or timeouts (or even signals,	1539	count).
1349	imagine) it will not be triggered. But when your process is idle all idle	1540
1350	watchers are being called again and again, once per event loop iteration -	1541	That is, as long as your process is busy handling sockets or timeouts
		1542	(or even signals, imagine) of the same or higher priority it will not be
		1543	triggered. But when your process is idle (or only lower-priority watchers
		1544	are pending), the idle watchers are being called once per event loop
1351	until stopped, that is, or your process receives more events and becomes	1545	iteration - until stopped, that is, or your process receives more events
1352	busy.	1546	and becomes busy again with higher priority stuff.
1353		1547
1354	The most noteworthy effect is that as long as any idle watchers are	1548	The most noteworthy effect is that as long as any idle watchers are
1355	active, the process will not block when waiting for new events.	1549	active, the process will not block when waiting for new events.
1356		1550
1357	Apart from keeping your process non-blocking (which is a useful	1551	Apart from keeping your process non-blocking (which is a useful
1358	effect on its own sometimes), idle watchers are a good place to do	1552	effect on its own sometimes), idle watchers are a good place to do
1359	"pseudo-background processing", or delay processing stuff to after the	1553	"pseudo-background processing", or delay processing stuff to after the
1360	event loop has handled all outstanding events.	1554	event loop has handled all outstanding events.
		1555
		1556	=head3 Watcher-Specific Functions and Data Members
1361		1557
1362	=over 4	1558	=over 4
1363		1559
1364	=item ev_idle_init (ev_signal *, callback)	1560	=item ev_idle_init (ev_signal *, callback)
1365		1561
…		…
1423	with priority higher than or equal to the event loop and one coroutine	1619	with priority higher than or equal to the event loop and one coroutine
1424	of lower priority, but only once, using idle watchers to keep the event	1620	of lower priority, but only once, using idle watchers to keep the event
1425	loop from blocking if lower-priority coroutines are active, thus mapping	1621	loop from blocking if lower-priority coroutines are active, thus mapping
1426	low-priority coroutines to idle/background tasks).	1622	low-priority coroutines to idle/background tasks).
1427		1623
		1624	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1625	priority, to ensure that they are being run before any other watchers
		1626	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1627	too) should not activate ("feed") events into libev. While libev fully
		1628	supports this, they will be called before other C<ev_check> watchers did
		1629	their job. As C<ev_check> watchers are often used to embed other event
		1630	loops those other event loops might be in an unusable state until their
		1631	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1632	others).
		1633
		1634	=head3 Watcher-Specific Functions and Data Members
		1635
1428	=over 4	1636	=over 4
1429		1637
1430	=item ev_prepare_init (ev_prepare *, callback)	1638	=item ev_prepare_init (ev_prepare *, callback)
1431		1639
1432	=item ev_check_init (ev_check *, callback)	1640	=item ev_check_init (ev_check *, callback)
…		…
1435	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1643	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1436	macros, but using them is utterly, utterly and completely pointless.	1644	macros, but using them is utterly, utterly and completely pointless.
1437		1645
1438	=back	1646	=back
1439		1647
1440	Example: To include a library such as adns, you would add IO watchers	1648	There are a number of principal ways to embed other event loops or modules
1441	and a timeout watcher in a prepare handler, as required by libadns, and	1649	into libev. Here are some ideas on how to include libadns into libev
		1650	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1651	use for an actually working example. Another Perl module named C<EV::Glib>
		1652	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1653	into the Glib event loop).
		1654
		1655	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1442	in a check watcher, destroy them and call into libadns. What follows is	1656	and in a check watcher, destroy them and call into libadns. What follows
1443	pseudo-code only of course:	1657	is pseudo-code only of course. This requires you to either use a low
		1658	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1659	the callbacks for the IO/timeout watchers might not have been called yet.
1444		1660
1445	static ev_io iow [nfd];	1661	static ev_io iow [nfd];
1446	static ev_timer tw;	1662	static ev_timer tw;
1447		1663
1448	static void	1664	static void
1449	io_cb (ev_loop loop, ev_io w, int revents)	1665	io_cb (ev_loop loop, ev_io w, int revents)
1450	{	1666	{
1451	// set the relevant poll flags
1452	// could also call adns_processreadable etc. here
1453	struct pollfd fd = (struct pollfd )w->data;
1454	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1455	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1456	}	1667	}
1457		1668
1458	// create io watchers for each fd and a timer before blocking	1669	// create io watchers for each fd and a timer before blocking
1459	static void	1670	static void
1460	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1671	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1466		1677
1467	/* the callback is illegal, but won't be called as we stop during check */	1678	/* the callback is illegal, but won't be called as we stop during check */
1468	ev_timer_init (&tw, 0, timeout * 1e-3);	1679	ev_timer_init (&tw, 0, timeout * 1e-3);
1469	ev_timer_start (loop, &tw);	1680	ev_timer_start (loop, &tw);
1470		1681
1471	// create on ev_io per pollfd	1682	// create one ev_io per pollfd
1472	for (int i = 0; i < nfd; ++i)	1683	for (int i = 0; i < nfd; ++i)
1473	{	1684	{
1474	ev_io_init (iow + i, io_cb, fds [i].fd,	1685	ev_io_init (iow + i, io_cb, fds [i].fd,
1475	((fds [i].events & POLLIN ? EV_READ : 0)	1686	((fds [i].events & POLLIN ? EV_READ : 0)
1476	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1687	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1477		1688
1478	fds [i].revents = 0;	1689	fds [i].revents = 0;
1479	iow [i].data = fds + i;
1480	ev_io_start (loop, iow + i);	1690	ev_io_start (loop, iow + i);
1481	}	1691	}
1482	}	1692	}
1483		1693
1484	// stop all watchers after blocking	1694	// stop all watchers after blocking
…		…
1486	adns_check_cb (ev_loop loop, ev_check w, int revents)	1696	adns_check_cb (ev_loop loop, ev_check w, int revents)
1487	{	1697	{
1488	ev_timer_stop (loop, &tw);	1698	ev_timer_stop (loop, &tw);
1489		1699
1490	for (int i = 0; i < nfd; ++i)	1700	for (int i = 0; i < nfd; ++i)
		1701	{
		1702	// set the relevant poll flags
		1703	// could also call adns_processreadable etc. here
		1704	struct pollfd *fd = fds + i;
		1705	int revents = ev_clear_pending (iow + i);
		1706	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1707	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1708
		1709	// now stop the watcher
1491	ev_io_stop (loop, iow + i);	1710	ev_io_stop (loop, iow + i);
		1711	}
1492		1712
1493	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1713	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1714	}
		1715
		1716	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1717	in the prepare watcher and would dispose of the check watcher.
		1718
		1719	Method 3: If the module to be embedded supports explicit event
		1720	notification (adns does), you can also make use of the actual watcher
		1721	callbacks, and only destroy/create the watchers in the prepare watcher.
		1722
		1723	static void
		1724	timer_cb (EV_P_ ev_timer *w, int revents)
		1725	{
		1726	adns_state ads = (adns_state)w->data;
		1727	update_now (EV_A);
		1728
		1729	adns_processtimeouts (ads, &tv_now);
		1730	}
		1731
		1732	static void
		1733	io_cb (EV_P_ ev_io *w, int revents)
		1734	{
		1735	adns_state ads = (adns_state)w->data;
		1736	update_now (EV_A);
		1737
		1738	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1739	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1740	}
		1741
		1742	// do not ever call adns_afterpoll
		1743
		1744	Method 4: Do not use a prepare or check watcher because the module you
		1745	want to embed is too inflexible to support it. Instead, youc na override
		1746	their poll function. The drawback with this solution is that the main
		1747	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1748	this.
		1749
		1750	static gint
		1751	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1752	{
		1753	int got_events = 0;
		1754
		1755	for (n = 0; n < nfds; ++n)
		1756	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1757
		1758	if (timeout >= 0)
		1759	// create/start timer
		1760
		1761	// poll
		1762	ev_loop (EV_A_ 0);
		1763
		1764	// stop timer again
		1765	if (timeout >= 0)
		1766	ev_timer_stop (EV_A_ &to);
		1767
		1768	// stop io watchers again - their callbacks should have set
		1769	for (n = 0; n < nfds; ++n)
		1770	ev_io_stop (EV_A_ iow [n]);
		1771
		1772	return got_events;
1494	}	1773	}
1495		1774
1496		1775
1497	=head2 C<ev_embed> - when one backend isn't enough...	1776	=head2 C<ev_embed> - when one backend isn't enough...
1498		1777
1499	This is a rather advanced watcher type that lets you embed one event loop	1778	This is a rather advanced watcher type that lets you embed one event loop
1500	into another (currently only C<ev_io> events are supported in the embedded	1779	into another (currently only C<ev_io> events are supported in the embedded
1501	loop, other types of watchers might be handled in a delayed or incorrect	1780	loop, other types of watchers might be handled in a delayed or incorrect
1502	fashion and must not be used).	1781	fashion and must not be used). (See portability notes, below).
1503		1782
1504	There are primarily two reasons you would want that: work around bugs and	1783	There are primarily two reasons you would want that: work around bugs and
1505	prioritise I/O.	1784	prioritise I/O.
1506		1785
1507	As an example for a bug workaround, the kqueue backend might only support	1786	As an example for a bug workaround, the kqueue backend might only support
…		…
1562	ev_embed_start (loop_hi, &embed);	1841	ev_embed_start (loop_hi, &embed);
1563	}	1842	}
1564	else	1843	else
1565	loop_lo = loop_hi;	1844	loop_lo = loop_hi;
1566		1845
		1846	=head2 Portability notes
		1847
		1848	Kqueue is nominally embeddable, but this is broken on all BSDs that I
		1849	tried, in various ways. Usually the embedded event loop will simply never
		1850	receive events, sometimes it will only trigger a few times, sometimes in a
		1851	loop. Epoll is also nominally embeddable, but many Linux kernel versions
		1852	will always eport the epoll fd as ready, even when no events are pending.
		1853
		1854	While libev allows embedding these backends (they are contained in
		1855	C<ev_embeddable_backends ()>), take extreme care that it will actually
		1856	work.
		1857
		1858	When in doubt, create a dynamic event loop forced to use sockets (this
		1859	usually works) and possibly another thread and a pipe or so to report to
		1860	your main event loop.
		1861
		1862	=head3 Watcher-Specific Functions and Data Members
		1863
1567	=over 4	1864	=over 4
1568		1865
1569	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1866	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1570		1867
1571	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	1868	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
…		…
1580		1877
1581	Make a single, non-blocking sweep over the embedded loop. This works	1878	Make a single, non-blocking sweep over the embedded loop. This works
1582	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1879	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1583	apropriate way for embedded loops.	1880	apropriate way for embedded loops.
1584		1881
1585	=item struct ev_loop *loop [read-only]	1882	=item struct ev_loop *other [read-only]
1586		1883
1587	The embedded event loop.	1884	The embedded event loop.
1588		1885
1589	=back	1886	=back
1590		1887
…		…
1597	event loop blocks next and before C<ev_check> watchers are being called,	1894	event loop blocks next and before C<ev_check> watchers are being called,
1598	and only in the child after the fork. If whoever good citizen calling	1895	and only in the child after the fork. If whoever good citizen calling
1599	C<ev_default_fork> cheats and calls it in the wrong process, the fork	1896	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1600	handlers will be invoked, too, of course.	1897	handlers will be invoked, too, of course.
1601		1898
		1899	=head3 Watcher-Specific Functions and Data Members
		1900
1602	=over 4	1901	=over 4
1603		1902
1604	=item ev_fork_init (ev_signal *, callback)	1903	=item ev_fork_init (ev_signal *, callback)
1605		1904
1606	Initialises and configures the fork watcher - it has no parameters of any	1905	Initialises and configures the fork watcher - it has no parameters of any
…		…
1702		2001
1703	To use it,	2002	To use it,
1704		2003
1705	#include <ev++.h>	2004	#include <ev++.h>
1706		2005
1707	(it is not installed by default). This automatically includes F<ev.h>	2006	This automatically includes F<ev.h> and puts all of its definitions (many
1708	and puts all of its definitions (many of them macros) into the global	2007	of them macros) into the global namespace. All C++ specific things are
1709	namespace. All C++ specific things are put into the C<ev> namespace.	2008	put into the C<ev> namespace. It should support all the same embedding
		2009	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1710		2010
1711	It should support all the same embedding options as F<ev.h>, most notably	2011	Care has been taken to keep the overhead low. The only data member the C++
1712	C<EV_MULTIPLICITY>.	2012	classes add (compared to plain C-style watchers) is the event loop pointer
		2013	that the watcher is associated with (or no additional members at all if
		2014	you disable C<EV_MULTIPLICITY> when embedding libev).
		2015
		2016	Currently, functions, and static and non-static member functions can be
		2017	used as callbacks. Other types should be easy to add as long as they only
		2018	need one additional pointer for context. If you need support for other
		2019	types of functors please contact the author (preferably after implementing
		2020	it).
1713		2021
1714	Here is a list of things available in the C<ev> namespace:	2022	Here is a list of things available in the C<ev> namespace:
1715		2023
1716	=over 4	2024	=over 4
1717		2025
…		…
1733		2041
1734	All of those classes have these methods:	2042	All of those classes have these methods:
1735		2043
1736	=over 4	2044	=over 4
1737		2045
1738	=item ev::TYPE::TYPE (object , object::method )	2046	=item ev::TYPE::TYPE ()
1739		2047
1740	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	2048	=item ev::TYPE::TYPE (struct ev_loop *)
1741		2049
1742	=item ev::TYPE::~TYPE	2050	=item ev::TYPE::~TYPE
1743		2051
1744	The constructor takes a pointer to an object and a method pointer to	2052	The constructor (optionally) takes an event loop to associate the watcher
1745	the event handler callback to call in this class. The constructor calls	2053	with. If it is omitted, it will use C<EV_DEFAULT>.
1746	C<ev_init> for you, which means you have to call the C<set> method	2054
1747	before starting it. If you do not specify a loop then the constructor	2055	The constructor calls C<ev_init> for you, which means you have to call the
1748	automatically associates the default loop with this watcher.	2056	C<set> method before starting it.
		2057
		2058	It will not set a callback, however: You have to call the templated C<set>
		2059	method to set a callback before you can start the watcher.
		2060
		2061	(The reason why you have to use a method is a limitation in C++ which does
		2062	not allow explicit template arguments for constructors).
1749		2063
1750	The destructor automatically stops the watcher if it is active.	2064	The destructor automatically stops the watcher if it is active.
		2065
		2066	=item w->set<class, &class::method> (object *)
		2067
		2068	This method sets the callback method to call. The method has to have a
		2069	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2070	first argument and the C<revents> as second. The object must be given as
		2071	parameter and is stored in the C<data> member of the watcher.
		2072
		2073	This method synthesizes efficient thunking code to call your method from
		2074	the C callback that libev requires. If your compiler can inline your
		2075	callback (i.e. it is visible to it at the place of the C<set> call and
		2076	your compiler is good :), then the method will be fully inlined into the
		2077	thunking function, making it as fast as a direct C callback.
		2078
		2079	Example: simple class declaration and watcher initialisation
		2080
		2081	struct myclass
		2082	{
		2083	void io_cb (ev::io &w, int revents) { }
		2084	}
		2085
		2086	myclass obj;
		2087	ev::io iow;
		2088	iow.set <myclass, &myclass::io_cb> (&obj);
		2089
		2090	=item w->set<function> (void *data = 0)
		2091
		2092	Also sets a callback, but uses a static method or plain function as
		2093	callback. The optional C<data> argument will be stored in the watcher's
		2094	C<data> member and is free for you to use.
		2095
		2096	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2097
		2098	See the method-C<set> above for more details.
		2099
		2100	Example:
		2101
		2102	static void io_cb (ev::io &w, int revents) { }
		2103	iow.set <io_cb> ();
1751		2104
1752	=item w->set (struct ev_loop *)	2105	=item w->set (struct ev_loop *)
1753		2106
1754	Associates a different C<struct ev_loop> with this watcher. You can only	2107	Associates a different C<struct ev_loop> with this watcher. You can only
1755	do this when the watcher is inactive (and not pending either).	2108	do this when the watcher is inactive (and not pending either).
1756		2109
1757	=item w->set ([args])	2110	=item w->set ([args])
1758		2111
1759	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2112	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1760	called at least once. Unlike the C counterpart, an active watcher gets	2113	called at least once. Unlike the C counterpart, an active watcher gets
1761	automatically stopped and restarted.	2114	automatically stopped and restarted when reconfiguring it with this
		2115	method.
1762		2116
1763	=item w->start ()	2117	=item w->start ()
1764		2118
1765	Starts the watcher. Note that there is no C<loop> argument as the	2119	Starts the watcher. Note that there is no C<loop> argument, as the
1766	constructor already takes the loop.	2120	constructor already stores the event loop.
1767		2121
1768	=item w->stop ()	2122	=item w->stop ()
1769		2123
1770	Stops the watcher if it is active. Again, no C<loop> argument.	2124	Stops the watcher if it is active. Again, no C<loop> argument.
1771		2125
1772	=item w->again () C<ev::timer>, C<ev::periodic> only	2126	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1773		2127
1774	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2128	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1775	C<ev_TYPE_again> function.	2129	C<ev_TYPE_again> function.
1776		2130
1777	=item w->sweep () C<ev::embed> only	2131	=item w->sweep () (C<ev::embed> only)
1778		2132
1779	Invokes C<ev_embed_sweep>.	2133	Invokes C<ev_embed_sweep>.
1780		2134
1781	=item w->update () C<ev::stat> only	2135	=item w->update () (C<ev::stat> only)
1782		2136
1783	Invokes C<ev_stat_stat>.	2137	Invokes C<ev_stat_stat>.
1784		2138
1785	=back	2139	=back
1786		2140
…		…
1796		2150
1797	myclass ();	2151	myclass ();
1798	}	2152	}
1799		2153
1800	myclass::myclass (int fd)	2154	myclass::myclass (int fd)
1801	: io (this, &myclass::io_cb),
1802	idle (this, &myclass::idle_cb)
1803	{	2155	{
		2156	io .set <myclass, &myclass::io_cb > (this);
		2157	idle.set <myclass, &myclass::idle_cb> (this);
		2158
1804	io.start (fd, ev::READ);	2159	io.start (fd, ev::READ);
1805	}	2160	}
1806		2161
1807		2162
1808	=head1 MACRO MAGIC	2163	=head1 MACRO MAGIC
1809		2164
1810	Libev can be compiled with a variety of options, the most fundemantal is	2165	Libev can be compiled with a variety of options, the most fundamantal
1811	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2166	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1812	callbacks have an initial C<struct ev_loop *> argument.	2167	functions and callbacks have an initial C<struct ev_loop *> argument.
1813		2168
1814	To make it easier to write programs that cope with either variant, the	2169	To make it easier to write programs that cope with either variant, the
1815	following macros are defined:	2170	following macros are defined:
1816		2171
1817	=over 4	2172	=over 4
…		…
1850	loop, if multiple loops are supported ("ev loop default").	2205	loop, if multiple loops are supported ("ev loop default").
1851		2206
1852	=back	2207	=back
1853		2208
1854	Example: Declare and initialise a check watcher, utilising the above	2209	Example: Declare and initialise a check watcher, utilising the above
1855	macros so it will work regardless of wether multiple loops are supported	2210	macros so it will work regardless of whether multiple loops are supported
1856	or not.	2211	or not.
1857		2212
1858	static void	2213	static void
1859	check_cb (EV_P_ ev_timer *w, int revents)	2214	check_cb (EV_P_ ev_timer *w, int revents)
1860	{	2215	{
…		…
1871	Libev can (and often is) directly embedded into host	2226	Libev can (and often is) directly embedded into host
1872	applications. Examples of applications that embed it include the Deliantra	2227	applications. Examples of applications that embed it include the Deliantra
1873	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2228	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1874	and rxvt-unicode.	2229	and rxvt-unicode.
1875		2230
1876	The goal is to enable you to just copy the neecssary files into your	2231	The goal is to enable you to just copy the necessary files into your
1877	source directory without having to change even a single line in them, so	2232	source directory without having to change even a single line in them, so
1878	you can easily upgrade by simply copying (or having a checked-out copy of	2233	you can easily upgrade by simply copying (or having a checked-out copy of
1879	libev somewhere in your source tree).	2234	libev somewhere in your source tree).
1880		2235
1881	=head2 FILESETS	2236	=head2 FILESETS
…		…
1971		2326
1972	If defined to be C<1>, libev will try to detect the availability of the	2327	If defined to be C<1>, libev will try to detect the availability of the
1973	monotonic clock option at both compiletime and runtime. Otherwise no use	2328	monotonic clock option at both compiletime and runtime. Otherwise no use
1974	of the monotonic clock option will be attempted. If you enable this, you	2329	of the monotonic clock option will be attempted. If you enable this, you
1975	usually have to link against librt or something similar. Enabling it when	2330	usually have to link against librt or something similar. Enabling it when
1976	the functionality isn't available is safe, though, althoguh you have	2331	the functionality isn't available is safe, though, although you have
1977	to make sure you link against any libraries where the C<clock_gettime>	2332	to make sure you link against any libraries where the C<clock_gettime>
1978	function is hiding in (often F<-lrt>).	2333	function is hiding in (often F<-lrt>).
1979		2334
1980	=item EV_USE_REALTIME	2335	=item EV_USE_REALTIME
1981		2336
1982	If defined to be C<1>, libev will try to detect the availability of the	2337	If defined to be C<1>, libev will try to detect the availability of the
1983	realtime clock option at compiletime (and assume its availability at	2338	realtime clock option at compiletime (and assume its availability at
1984	runtime if successful). Otherwise no use of the realtime clock option will	2339	runtime if successful). Otherwise no use of the realtime clock option will
1985	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2340	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1986	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2341	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1987	in the description of C<EV_USE_MONOTONIC>, though.	2342	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2343
		2344	=item EV_USE_NANOSLEEP
		2345
		2346	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2347	and will use it for delays. Otherwise it will use C<select ()>.
1988		2348
1989	=item EV_USE_SELECT	2349	=item EV_USE_SELECT
1990		2350
1991	If undefined or defined to be C<1>, libev will compile in support for the	2351	If undefined or defined to be C<1>, libev will compile in support for the
1992	C<select>(2) backend. No attempt at autodetection will be done: if no	2352	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2085	will have the C<struct ev_loop *> as first argument, and you can create	2445	will have the C<struct ev_loop *> as first argument, and you can create
2086	additional independent event loops. Otherwise there will be no support	2446	additional independent event loops. Otherwise there will be no support
2087	for multiple event loops and there is no first event loop pointer	2447	for multiple event loops and there is no first event loop pointer
2088	argument. Instead, all functions act on the single default loop.	2448	argument. Instead, all functions act on the single default loop.
2089		2449
		2450	=item EV_MINPRI
		2451
		2452	=item EV_MAXPRI
		2453
		2454	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2455	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2456	provide for more priorities by overriding those symbols (usually defined
		2457	to be C<-2> and C<2>, respectively).
		2458
		2459	When doing priority-based operations, libev usually has to linearly search
		2460	all the priorities, so having many of them (hundreds) uses a lot of space
		2461	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2462	fine.
		2463
		2464	If your embedding app does not need any priorities, defining these both to
		2465	C<0> will save some memory and cpu.
		2466
2090	=item EV_PERIODIC_ENABLE	2467	=item EV_PERIODIC_ENABLE
2091		2468
2092	If undefined or defined to be C<1>, then periodic timers are supported. If	2469	If undefined or defined to be C<1>, then periodic timers are supported. If
		2470	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2471	code.
		2472
		2473	=item EV_IDLE_ENABLE
		2474
		2475	If undefined or defined to be C<1>, then idle watchers are supported. If
2093	defined to be C<0>, then they are not. Disabling them saves a few kB of	2476	defined to be C<0>, then they are not. Disabling them saves a few kB of
2094	code.	2477	code.
2095		2478
2096	=item EV_EMBED_ENABLE	2479	=item EV_EMBED_ENABLE
2097		2480
…		…
2148		2531
2149	=item ev_set_cb (ev, cb)	2532	=item ev_set_cb (ev, cb)
2150		2533
2151	Can be used to change the callback member declaration in each watcher,	2534	Can be used to change the callback member declaration in each watcher,
2152	and the way callbacks are invoked and set. Must expand to a struct member	2535	and the way callbacks are invoked and set. Must expand to a struct member
2153	definition and a statement, respectively. See the F<ev.v> header file for	2536	definition and a statement, respectively. See the F<ev.h> header file for
2154	their default definitions. One possible use for overriding these is to	2537	their default definitions. One possible use for overriding these is to
2155	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2538	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2156	method calls instead of plain function calls in C++.	2539	method calls instead of plain function calls in C++.
		2540
		2541	=head2 EXPORTED API SYMBOLS
		2542
		2543	If you need to re-export the API (e.g. via a dll) and you need a list of
		2544	exported symbols, you can use the provided F<Symbol.*> files which list
		2545	all public symbols, one per line:
		2546
		2547	Symbols.ev for libev proper
		2548	Symbols.event for the libevent emulation
		2549
		2550	This can also be used to rename all public symbols to avoid clashes with
		2551	multiple versions of libev linked together (which is obviously bad in
		2552	itself, but sometimes it is inconvinient to avoid this).
		2553
		2554	A sed command like this will create wrapper C<#define>'s that you need to
		2555	include before including F<ev.h>:
		2556
		2557	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2558
		2559	This would create a file F<wrap.h> which essentially looks like this:
		2560
		2561	#define ev_backend myprefix_ev_backend
		2562	#define ev_check_start myprefix_ev_check_start
		2563	#define ev_check_stop myprefix_ev_check_stop
		2564	...
2157		2565
2158	=head2 EXAMPLES	2566	=head2 EXAMPLES
2159		2567
2160	For a real-world example of a program the includes libev	2568	For a real-world example of a program the includes libev
2161	verbatim, you can have a look at the EV perl module	2569	verbatim, you can have a look at the EV perl module
…		…
2190		2598
2191	In this section the complexities of (many of) the algorithms used inside	2599	In this section the complexities of (many of) the algorithms used inside
2192	libev will be explained. For complexity discussions about backends see the	2600	libev will be explained. For complexity discussions about backends see the
2193	documentation for C<ev_default_init>.	2601	documentation for C<ev_default_init>.
2194		2602
		2603	All of the following are about amortised time: If an array needs to be
		2604	extended, libev needs to realloc and move the whole array, but this
		2605	happens asymptotically never with higher number of elements, so O(1) might
		2606	mean it might do a lengthy realloc operation in rare cases, but on average
		2607	it is much faster and asymptotically approaches constant time.
		2608
2195	=over 4	2609	=over 4
2196		2610
2197	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2611	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2198		2612
		2613	This means that, when you have a watcher that triggers in one hour and
		2614	there are 100 watchers that would trigger before that then inserting will
		2615	have to skip those 100 watchers.
		2616
2199	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2617	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2200		2618
		2619	That means that for changing a timer costs less than removing/adding them
		2620	as only the relative motion in the event queue has to be paid for.
		2621
2201	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2622	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2202		2623
		2624	These just add the watcher into an array or at the head of a list.
2203	=item Stopping check/prepare/idle watchers: O(1)	2625	=item Stopping check/prepare/idle watchers: O(1)
2204		2626
2205	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2627	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2206		2628
		2629	These watchers are stored in lists then need to be walked to find the
		2630	correct watcher to remove. The lists are usually short (you don't usually
		2631	have many watchers waiting for the same fd or signal).
		2632
2207	=item Finding the next timer per loop iteration: O(1)	2633	=item Finding the next timer per loop iteration: O(1)
2208		2634
2209	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2635	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2210		2636
		2637	A change means an I/O watcher gets started or stopped, which requires
		2638	libev to recalculate its status (and possibly tell the kernel).
		2639
2211	=item Activating one watcher: O(1)	2640	=item Activating one watcher: O(1)
2212		2641
		2642	=item Priority handling: O(number_of_priorities)
		2643
		2644	Priorities are implemented by allocating some space for each
		2645	priority. When doing priority-based operations, libev usually has to
		2646	linearly search all the priorities.
		2647
2213	=back	2648	=back
2214		2649
2215		2650
2216	=head1 AUTHOR	2651	=head1 AUTHOR
2217		2652

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Comparing libev/ev.pod (file contents): Revision 1.64 by root, Sat Dec 1 15:32:53 2007 UTC vs. Revision 1.99 by root, Sat Dec 22 06:16:36 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.64 by root, Sat Dec 1 15:32:53 2007 UTC vs.
Revision 1.99 by root, Sat Dec 22 06:16:36 2007 UTC