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

Comparing libev/ev.pod (file contents):
Revision 1.16 by root, Mon Nov 12 08:47:14 2007 UTC vs.
Revision 1.27 by root, Wed Nov 14 05:02:07 2007 UTC

…		…
39	F<README.embed> in the libev distribution. If libev was configured without	39	F<README.embed> in the libev distribution. If libev was configured without
40	support for multiple event loops, then all functions taking an initial	40	support for multiple event loops, then all functions taking an initial
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	41	argument of name C<loop> (which is always of type C<struct ev_loop *>)
42	will not have this argument.	42	will not have this argument.
43		43
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	44	=head1 TIME REPRESENTATION
45		45
46	Libev represents time as a single floating point number, representing the	46	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	47	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	48	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	49	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	50	to the double type in C.
51		51
		52	=head1 GLOBAL FUNCTIONS
		53
		54	These functions can be called anytime, even before initialising the
		55	library in any way.
		56
52	=over 4	57	=over 4
53		58
54	=item ev_tstamp ev_time ()	59	=item ev_tstamp ev_time ()
55		60
56	Returns the current time as libev would use it.	61	Returns the current time as libev would use it. Please note that the
		62	C<ev_now> function is usually faster and also often returns the timestamp
		63	you actually want to know.
57		64
58	=item int ev_version_major ()	65	=item int ev_version_major ()
59		66
60	=item int ev_version_minor ()	67	=item int ev_version_minor ()
61		68
…		…
99	An event loop is described by a C<struct ev_loop *>. The library knows two	106	An event loop is described by a C<struct ev_loop *>. The library knows two
100	types of such loops, the I<default> loop, which supports signals and child	107	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	108	events, and dynamically created loops which do not.
102		109
103	If you use threads, a common model is to run the default event loop	110	If you use threads, a common model is to run the default event loop
104	in your main thread (or in a separate thrad) and for each thread you	111	in your main thread (or in a separate thread) and for each thread you
105	create, you also create another event loop. Libev itself does no locking	112	create, you also create another event loop. Libev itself does no locking
106	whatsoever, so if you mix calls to the same event loop in different	113	whatsoever, so if you mix calls to the same event loop in different
107	threads, make sure you lock (this is usually a bad idea, though, even if	114	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because it's hideous and inefficient).	115	done correctly, because it's hideous and inefficient).
109		116
…		…
232		239
233	This flags value could be used to implement alternative looping	240	This flags value could be used to implement alternative looping
234	constructs, but the C<prepare> and C<check> watchers provide a better and	241	constructs, but the C<prepare> and C<check> watchers provide a better and
235	more generic mechanism.	242	more generic mechanism.
236		243
		244	Here are the gory details of what ev_loop does:
		245
		246	1. If there are no active watchers (reference count is zero), return.
		247	2. Queue and immediately call all prepare watchers.
		248	3. If we have been forked, recreate the kernel state.
		249	4. Update the kernel state with all outstanding changes.
		250	5. Update the "event loop time".
		251	6. Calculate for how long to block.
		252	7. Block the process, waiting for events.
		253	8. Update the "event loop time" and do time jump handling.
		254	9. Queue all outstanding timers.
		255	10. Queue all outstanding periodics.
		256	11. If no events are pending now, queue all idle watchers.
		257	12. Queue all check watchers.
		258	13. Call all queued watchers in reverse order (i.e. check watchers first).
		259	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		260	was used, return, otherwise continue with step #1.
		261
237	=item ev_unloop (loop, how)	262	=item ev_unloop (loop, how)
238		263
239	Can be used to make a call to C<ev_loop> return early (but only after it	264	Can be used to make a call to C<ev_loop> return early (but only after it
240	has processed all outstanding events). The C<how> argument must be either	265	has processed all outstanding events). The C<how> argument must be either
241	C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or	266	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
242	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	267	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
243		268
244	=item ev_ref (loop)	269	=item ev_ref (loop)
245		270
246	=item ev_unref (loop)	271	=item ev_unref (loop)
…		…
412	in each iteration of the event loop (This behaviour is called	437	in each iteration of the event loop (This behaviour is called
413	level-triggering because you keep receiving events as long as the	438	level-triggering because you keep receiving events as long as the
414	condition persists. Remember you can stop the watcher if you don't want to	439	condition persists. Remember you can stop the watcher if you don't want to
415	act on the event and neither want to receive future events).	440	act on the event and neither want to receive future events).
416		441
417	In general you can register as many read and/or write event watchers oer	442	In general you can register as many read and/or write event watchers per
418	fd as you want (as long as you don't confuse yourself). Setting all file	443	fd as you want (as long as you don't confuse yourself). Setting all file
419	descriptors to non-blocking mode is also usually a good idea (but not	444	descriptors to non-blocking mode is also usually a good idea (but not
420	required if you know what you are doing).	445	required if you know what you are doing).
421		446
422	You have to be careful with dup'ed file descriptors, though. Some backends	447	You have to be careful with dup'ed file descriptors, though. Some backends
423	(the linux epoll backend is a notable example) cannot handle dup'ed file	448	(the linux epoll backend is a notable example) cannot handle dup'ed file
424	descriptors correctly if you register interest in two or more fds pointing	449	descriptors correctly if you register interest in two or more fds pointing
425	to the same file/socket etc. description.	450	to the same underlying file/socket etc. description (that is, they share
		451	the same underlying "file open").
426		452
427	If you must do this, then force the use of a known-to-be-good backend	453	If you must do this, then force the use of a known-to-be-good backend
428	(at the time of this writing, this includes only EVMETHOD_SELECT and	454	(at the time of this writing, this includes only EVMETHOD_SELECT and
429	EVMETHOD_POLL).	455	EVMETHOD_POLL).
430		456
…		…
444		470
445	Timer watchers are simple relative timers that generate an event after a	471	Timer watchers are simple relative timers that generate an event after a
446	given time, and optionally repeating in regular intervals after that.	472	given time, and optionally repeating in regular intervals after that.
447		473
448	The timers are based on real time, that is, if you register an event that	474	The timers are based on real time, that is, if you register an event that
449	times out after an hour and youreset your system clock to last years	475	times out after an hour and you reset your system clock to last years
450	time, it will still time out after (roughly) and hour. "Roughly" because	476	time, it will still time out after (roughly) and hour. "Roughly" because
451	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	477	detecting time jumps is hard, and soem inaccuracies are unavoidable (the
452	monotonic clock option helps a lot here).	478	monotonic clock option helps a lot here).
453		479
454	The relative timeouts are calculated relative to the C<ev_now ()>	480	The relative timeouts are calculated relative to the C<ev_now ()>
455	time. This is usually the right thing as this timestamp refers to the time	481	time. This is usually the right thing as this timestamp refers to the time
456	of the event triggering whatever timeout you are modifying/starting. If	482	of the event triggering whatever timeout you are modifying/starting. If
457	you suspect event processing to be delayed and you need to base the timeout	483	you suspect event processing to be delayed and you need to base the timeout
458	ion the current time, use something like this to adjust for this:	484	on the current time, use something like this to adjust for this:
459		485
460	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	486	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
461		487
462	=over 4	488	=over 4
463		489
…		…
471	later, again, and again, until stopped manually.	497	later, again, and again, until stopped manually.
472		498
473	The timer itself will do a best-effort at avoiding drift, that is, if you	499	The timer itself will do a best-effort at avoiding drift, that is, if you
474	configure a timer to trigger every 10 seconds, then it will trigger at	500	configure a timer to trigger every 10 seconds, then it will trigger at
475	exactly 10 second intervals. If, however, your program cannot keep up with	501	exactly 10 second intervals. If, however, your program cannot keep up with
476	the timer (ecause it takes longer than those 10 seconds to do stuff) the	502	the timer (because it takes longer than those 10 seconds to do stuff) the
477	timer will not fire more than once per event loop iteration.	503	timer will not fire more than once per event loop iteration.
478		504
479	=item ev_timer_again (loop)	505	=item ev_timer_again (loop)
480		506
481	This will act as if the timer timed out and restart it again if it is	507	This will act as if the timer timed out and restart it again if it is
…		…
558	In this mode the values for C<interval> and C<at> are both being	584	In this mode the values for C<interval> and C<at> are both being
559	ignored. Instead, each time the periodic watcher gets scheduled, the	585	ignored. Instead, each time the periodic watcher gets scheduled, the
560	reschedule callback will be called with the watcher as first, and the	586	reschedule callback will be called with the watcher as first, and the
561	current time as second argument.	587	current time as second argument.
562		588
563	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	589	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
564	periodic watcher, ever, or make any event loop modifications>. If you need	590	ever, or make any event loop modifications>. If you need to stop it,
565	to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards.	591	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
566		592	starting a prepare watcher).
567	Also, I<< this callback must always return a time that is later than the
568	passed C<now> value >>. Not even C<now> itself will be ok.
569		593
570	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	594	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
571	ev_tstamp now)>, e.g.:	595	ev_tstamp now)>, e.g.:
572		596
573	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	597	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
578	It must return the next time to trigger, based on the passed time value	602	It must return the next time to trigger, based on the passed time value
579	(that is, the lowest time value larger than to the second argument). It	603	(that is, the lowest time value larger than to the second argument). It
580	will usually be called just before the callback will be triggered, but	604	will usually be called just before the callback will be triggered, but
581	might be called at other times, too.	605	might be called at other times, too.
582		606
		607	NOTE: I<< This callback must always return a time that is later than the
		608	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		609
583	This can be used to create very complex timers, such as a timer that	610	This can be used to create very complex timers, such as a timer that
584	triggers on each midnight, local time. To do this, you would calculate the	611	triggers on each midnight, local time. To do this, you would calculate the
585	next midnight after C<now> and return the timestamp value for this. How you do this	612	next midnight after C<now> and return the timestamp value for this. How
586	is, again, up to you (but it is not trivial).	613	you do this is, again, up to you (but it is not trivial, which is the main
		614	reason I omitted it as an example).
587		615
588	=back	616	=back
589		617
590	=item ev_periodic_again (loop, ev_periodic *)	618	=item ev_periodic_again (loop, ev_periodic *)
591		619
…		…
670	=back	698	=back
671		699
672	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	700	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
673		701
674	Prepare and check watchers are usually (but not always) used in tandem:	702	Prepare and check watchers are usually (but not always) used in tandem:
675	Prepare watchers get invoked before the process blocks and check watchers	703	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.	704	afterwards.
677		705
678	Their main purpose is to integrate other event mechanisms into libev. This	706	Their main purpose is to integrate other event mechanisms into libev. This
679	could be used, for example, to track variable changes, implement your own	707	could be used, for example, to track variable changes, implement your own
680	watchers, integrate net-snmp or a coroutine library and lots more.	708	watchers, integrate net-snmp or a coroutine library and lots more.
…		…
683	to be watched by the other library, registering C<ev_io> watchers for	711	to be watched by the other library, registering C<ev_io> watchers for
684	them and starting an C<ev_timer> watcher for any timeouts (many libraries	712	them and starting an C<ev_timer> watcher for any timeouts (many libraries
685	provide just this functionality). Then, in the check watcher you check for	713	provide just this functionality). Then, in the check watcher you check for
686	any events that occured (by checking the pending status of all watchers	714	any events that occured (by checking the pending status of all watchers
687	and stopping them) and call back into the library. The I/O and timer	715	and stopping them) and call back into the library. The I/O and timer
688	callbacks will never actually be called (but must be valid neverthelles,	716	callbacks will never actually be called (but must be valid nevertheless,
689	because you never know, you know?).	717	because you never know, you know?).
690		718
691	As another example, the Perl Coro module uses these hooks to integrate	719	As another example, the Perl Coro module uses these hooks to integrate
692	coroutines into libev programs, by yielding to other active coroutines	720	coroutines into libev programs, by yielding to other active coroutines
693	during each prepare and only letting the process block if no coroutines	721	during each prepare and only letting the process block if no coroutines
694	are ready to run (its actually more complicated, it only runs coroutines	722	are ready to run (it's actually more complicated: it only runs coroutines
695	with priority higher than the event loop and one lower priority once,	723	with priority higher than or equal to the event loop and one coroutine
696	using idle watchers to keep the event loop from blocking if lower-priority	724	of lower priority, but only once, using idle watchers to keep the event
697	coroutines exist, thus mapping low-priority coroutines to idle/background	725	loop from blocking if lower-priority coroutines are active, thus mapping
698	tasks).	726	low-priority coroutines to idle/background tasks).
699		727
700	=over 4	728	=over 4
701		729
702	=item ev_prepare_init (ev_prepare *, callback)	730	=item ev_prepare_init (ev_prepare *, callback)
703		731
…		…
718	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	746	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
719		747
720	This function combines a simple timer and an I/O watcher, calls your	748	This function combines a simple timer and an I/O watcher, calls your
721	callback on whichever event happens first and automatically stop both	749	callback on whichever event happens first and automatically stop both
722	watchers. This is useful if you want to wait for a single event on an fd	750	watchers. This is useful if you want to wait for a single event on an fd
723	or timeout without havign to allocate/configure/start/stop/free one or	751	or timeout without having to allocate/configure/start/stop/free one or
724	more watchers yourself.	752	more watchers yourself.
725		753
726	If C<fd> is less than 0, then no I/O watcher will be started and events	754	If C<fd> is less than 0, then no I/O watcher will be started and events
727	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	755	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
728	C<events> set will be craeted and started.	756	C<events> set will be craeted and started.
…		…
731	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	759	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
732	repeat = 0) will be started. While C<0> is a valid timeout, it is of	760	repeat = 0) will be started. While C<0> is a valid timeout, it is of
733	dubious value.	761	dubious value.
734		762
735	The callback has the type C<void (cb)(int revents, void arg)> and gets	763	The callback has the type C<void (cb)(int revents, void arg)> and gets
736	passed an events set like normal event callbacks (with a combination of	764	passed an C<revents> set like normal event callbacks (a combination of
737	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	765	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
738	value passed to C<ev_once>:	766	value passed to C<ev_once>:
739		767
740	static void stdin_ready (int revents, void *arg)	768	static void stdin_ready (int revents, void *arg)
741	{	769	{
…		…
762		790
763	Feed an event as if the given signal occured (loop must be the default loop!).	791	Feed an event as if the given signal occured (loop must be the default loop!).
764		792
765	=back	793	=back
766		794
		795	=head1 LIBEVENT EMULATION
		796
		797	Libev offers a compatibility emulation layer for libevent. It cannot
		798	emulate the internals of libevent, so here are some usage hints:
		799
		800	=over 4
		801
		802	=item * Use it by including <event.h>, as usual.
		803
		804	=item * The following members are fully supported: ev_base, ev_callback,
		805	ev_arg, ev_fd, ev_res, ev_events.
		806
		807	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		808	maintained by libev, it does not work exactly the same way as in libevent (consider
		809	it a private API).
		810
		811	=item * Priorities are not currently supported. Initialising priorities
		812	will fail and all watchers will have the same priority, even though there
		813	is an ev_pri field.
		814
		815	=item * Other members are not supported.
		816
		817	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		818	to use the libev header file and library.
		819
		820	=back
		821
		822	=head1 C++ SUPPORT
		823
		824	TBD.
		825
767	=head1 AUTHOR	826	=head1 AUTHOR
768		827
769	Marc Lehmann <libev@schmorp.de>.	828	Marc Lehmann <libev@schmorp.de>.
770		829

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Comparing libev/ev.pod (file contents): Revision 1.16 by root, Mon Nov 12 08:47:14 2007 UTC vs. Revision 1.27 by root, Wed Nov 14 05:02:07 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.16 by root, Mon Nov 12 08:47:14 2007 UTC vs.
Revision 1.27 by root, Wed Nov 14 05:02:07 2007 UTC