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

Comparing libev/ev.pod (file contents):
Revision 1.354 by root, Tue Jan 11 01:40:25 2011 UTC vs.
Revision 1.366 by sf-exg, Thu Feb 3 16:21:08 2011 UTC

…		…
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_run (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
441	when you want to receive them.	441	when you want to receive them.
442		442
443	This behaviour is useful when you want to do your own signal handling, or	443	This behaviour is useful when you want to do your own signal handling, or
444	want to handle signals only in specific threads and want to avoid libev	444	want to handle signals only in specific threads and want to avoid libev
445	unblocking the signals.	445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
446		449
447	This flag's behaviour will become the default in future versions of libev.	450	This flag's behaviour will become the default in future versions of libev.
448		451
449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
450		453
…		…
865	anymore.	868	anymore.
866		869
867	... queue jobs here, make sure they register event watchers as long	870	... queue jobs here, make sure they register event watchers as long
868	... as they still have work to do (even an idle watcher will do..)	871	... as they still have work to do (even an idle watcher will do..)
869	ev_run (my_loop, 0);	872	ev_run (my_loop, 0);
870	... jobs done or somebody called unloop. yeah!	873	... jobs done or somebody called break. yeah!
871		874
872	=item ev_break (loop, how)	875	=item ev_break (loop, how)
873		876
874	Can be used to make a call to C<ev_run> return early (but only after it	877	Can be used to make a call to C<ev_run> return early (but only after it
875	has processed all outstanding events). The C<how> argument must be either	878	has processed all outstanding events). The C<how> argument must be either
…		…
1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1360	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1358	functions that do not need a watcher.	1361	functions that do not need a watcher.
1359		1362
1360	=back	1363	=back
1361		1364
1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
1363		1366	OWN COMPOSITE WATCHERS> idioms.
1364	Each watcher has, by default, a member C<void *data> that you can change
1365	and read at any time: libev will completely ignore it. This can be used
1366	to associate arbitrary data with your watcher. If you need more data and
1367	don't want to allocate memory and store a pointer to it in that data
1368	member, you can also "subclass" the watcher type and provide your own
1369	data:
1370
1371	struct my_io
1372	{
1373	ev_io io;
1374	int otherfd;
1375	void *somedata;
1376	struct whatever *mostinteresting;
1377	};
1378
1379	...
1380	struct my_io w;
1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
1382
1383	And since your callback will be called with a pointer to the watcher, you
1384	can cast it back to your own type:
1385
1386	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1387	{
1388	struct my_io w = (struct my_io )w_;
1389	...
1390	}
1391
1392	More interesting and less C-conformant ways of casting your callback type
1393	instead have been omitted.
1394
1395	Another common scenario is to use some data structure with multiple
1396	embedded watchers:
1397
1398	struct my_biggy
1399	{
1400	int some_data;
1401	ev_timer t1;
1402	ev_timer t2;
1403	}
1404
1405	In this case getting the pointer to C<my_biggy> is a bit more
1406	complicated: Either you store the address of your C<my_biggy> struct
1407	in the C<data> member of the watcher (for woozies), or you need to use
1408	some pointer arithmetic using C<offsetof> inside your watchers (for real
1409	programmers):
1410
1411	#include <stddef.h>
1412
1413	static void
1414	t1_cb (EV_P_ ev_timer *w, int revents)
1415	{
1416	struct my_biggy big = (struct my_biggy *)
1417	(((char *)w) - offsetof (struct my_biggy, t1));
1418	}
1419
1420	static void
1421	t2_cb (EV_P_ ev_timer *w, int revents)
1422	{
1423	struct my_biggy big = (struct my_biggy *)
1424	(((char *)w) - offsetof (struct my_biggy, t2));
1425	}
1426		1367
1427	=head2 WATCHER STATES	1368	=head2 WATCHER STATES
1428		1369
1429	There are various watcher states mentioned throughout this manual -	1370	There are various watcher states mentioned throughout this manual -
1430	active, pending and so on. In this section these states and the rules to	1371	active, pending and so on. In this section these states and the rules to
…		…
1437		1378
1438	Before a watcher can be registered with the event looop it has to be	1379	Before a watcher can be registered with the event looop it has to be
1439	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1380	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1440	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1381	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1441		1382
1442	In this state it is simply some block of memory that is suitable for use	1383	In this state it is simply some block of memory that is suitable for
1443	in an event loop. It can be moved around, freed, reused etc. at will.	1384	use in an event loop. It can be moved around, freed, reused etc. at
		1385	will - as long as you either keep the memory contents intact, or call
		1386	C<ev_TYPE_init> again.
1444		1387
1445	=item started/running/active	1388	=item started/running/active
1446		1389
1447	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1390	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1448	property of the event loop, and is actively waiting for events. While in	1391	property of the event loop, and is actively waiting for events. While in
…		…
1476	latter will clear any pending state the watcher might be in, regardless	1419	latter will clear any pending state the watcher might be in, regardless
1477	of whether it was active or not, so stopping a watcher explicitly before	1420	of whether it was active or not, so stopping a watcher explicitly before
1478	freeing it is often a good idea.	1421	freeing it is often a good idea.
1479		1422
1480	While stopped (and not pending) the watcher is essentially in the	1423	While stopped (and not pending) the watcher is essentially in the
1481	initialised state, that is it can be reused, moved, modified in any way	1424	initialised state, that is, it can be reused, moved, modified in any way
1482	you wish.	1425	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1426	it again).
1483		1427
1484	=back	1428	=back
1485		1429
1486	=head2 WATCHER PRIORITY MODELS	1430	=head2 WATCHER PRIORITY MODELS
1487		1431
…		…
1680	always get a readiness notification instantly, and your read (or possibly	1624	always get a readiness notification instantly, and your read (or possibly
1681	write) will still block on the disk I/O.	1625	write) will still block on the disk I/O.
1682		1626
1683	Another way to view it is that in the case of sockets, pipes, character	1627	Another way to view it is that in the case of sockets, pipes, character
1684	devices and so on, there is another party (the sender) that delivers data	1628	devices and so on, there is another party (the sender) that delivers data
1685	on it's own, but in the case of files, there is no such thing: the disk	1629	on its own, but in the case of files, there is no such thing: the disk
1686	will not send data on it's own, simply because it doesn't know what you	1630	will not send data on its own, simply because it doesn't know what you
1687	wish to read - you would first have to request some data.	1631	wish to read - you would first have to request some data.
1688		1632
1689	Since files are typically not-so-well supported by advanced notification	1633	Since files are typically not-so-well supported by advanced notification
1690	mechanism, libev tries hard to emulate POSIX behaviour with respect	1634	mechanism, libev tries hard to emulate POSIX behaviour with respect
1691	to files, even though you should not use it. The reason for this is	1635	to files, even though you should not use it. The reason for this is
…		…
2362	=head3 The special problem of inheritance over fork/execve/pthread_create	2306	=head3 The special problem of inheritance over fork/execve/pthread_create
2363		2307
2364	Both the signal mask (C<sigprocmask>) and the signal disposition	2308	Both the signal mask (C<sigprocmask>) and the signal disposition
2365	(C<sigaction>) are unspecified after starting a signal watcher (and after	2309	(C<sigaction>) are unspecified after starting a signal watcher (and after
2366	stopping it again), that is, libev might or might not block the signal,	2310	stopping it again), that is, libev might or might not block the signal,
2367	and might or might not set or restore the installed signal handler.	2311	and might or might not set or restore the installed signal handler (but
		2312	see C<EVFLAG_NOSIGMASK>).
2368		2313
2369	While this does not matter for the signal disposition (libev never	2314	While this does not matter for the signal disposition (libev never
2370	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2315	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2371	C<execve>), this matters for the signal mask: many programs do not expect	2316	C<execve>), this matters for the signal mask: many programs do not expect
2372	certain signals to be blocked.	2317	certain signals to be blocked.
…		…
3243	atexit (program_exits);	3188	atexit (program_exits);
3244		3189
3245		3190
3246	=head2 C<ev_async> - how to wake up an event loop	3191	=head2 C<ev_async> - how to wake up an event loop
3247		3192
3248	In general, you cannot use an C<ev_run> from multiple threads or other	3193	In general, you cannot use an C<ev_loop> from multiple threads or other
3249	asynchronous sources such as signal handlers (as opposed to multiple event	3194	asynchronous sources such as signal handlers (as opposed to multiple event
3250	loops - those are of course safe to use in different threads).	3195	loops - those are of course safe to use in different threads).
3251		3196
3252	Sometimes, however, you need to wake up an event loop you do not control,	3197	Sometimes, however, you need to wake up an event loop you do not control,
3253	for example because it belongs to another thread. This is what C<ev_async>	3198	for example because it belongs to another thread. This is what C<ev_async>
…		…
3363	trust me.	3308	trust me.
3364		3309
3365	=item ev_async_send (loop, ev_async *)	3310	=item ev_async_send (loop, ev_async *)
3366		3311
3367	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3312	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3368	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3313	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3314	returns.
		3315
3369	C<ev_feed_event>, this call is safe to do from other threads, signal or	3316	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3370	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3317	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3371	section below on what exactly this means).	3318	embedding section below on what exactly this means).
3372		3319
3373	Note that, as with other watchers in libev, multiple events might get	3320	Note that, as with other watchers in libev, multiple events might get
3374	compressed into a single callback invocation (another way to look at this	3321	compressed into a single callback invocation (another way to look at this
3375	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3322	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3376	reset when the event loop detects that).	3323	reset when the event loop detects that).
…		…
3456		3403
3457	This section explains some common idioms that are not immediately	3404	This section explains some common idioms that are not immediately
3458	obvious. Note that examples are sprinkled over the whole manual, and this	3405	obvious. Note that examples are sprinkled over the whole manual, and this
3459	section only contains stuff that wouldn't fit anywhere else.	3406	section only contains stuff that wouldn't fit anywhere else.
3460		3407
3461	=over 4	3408	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
3462		3409
3463	=item Model/nested event loop invocations and exit conditions.	3410	Each watcher has, by default, a C<void *data> member that you can read
		3411	or modify at any time: libev will completely ignore it. This can be used
		3412	to associate arbitrary data with your watcher. If you need more data and
		3413	don't want to allocate memory separately and store a pointer to it in that
		3414	data member, you can also "subclass" the watcher type and provide your own
		3415	data:
		3416
		3417	struct my_io
		3418	{
		3419	ev_io io;
		3420	int otherfd;
		3421	void *somedata;
		3422	struct whatever *mostinteresting;
		3423	};
		3424
		3425	...
		3426	struct my_io w;
		3427	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3428
		3429	And since your callback will be called with a pointer to the watcher, you
		3430	can cast it back to your own type:
		3431
		3432	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
		3433	{
		3434	struct my_io w = (struct my_io )w_;
		3435	...
		3436	}
		3437
		3438	More interesting and less C-conformant ways of casting your callback
		3439	function type instead have been omitted.
		3440
		3441	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3442
		3443	Another common scenario is to use some data structure with multiple
		3444	embedded watchers, in effect creating your own watcher that combines
		3445	multiple libev event sources into one "super-watcher":
		3446
		3447	struct my_biggy
		3448	{
		3449	int some_data;
		3450	ev_timer t1;
		3451	ev_timer t2;
		3452	}
		3453
		3454	In this case getting the pointer to C<my_biggy> is a bit more
		3455	complicated: Either you store the address of your C<my_biggy> struct in
		3456	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3457	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3458	real programmers):
		3459
		3460	#include <stddef.h>
		3461
		3462	static void
		3463	t1_cb (EV_P_ ev_timer *w, int revents)
		3464	{
		3465	struct my_biggy big = (struct my_biggy *)
		3466	(((char *)w) - offsetof (struct my_biggy, t1));
		3467	}
		3468
		3469	static void
		3470	t2_cb (EV_P_ ev_timer *w, int revents)
		3471	{
		3472	struct my_biggy big = (struct my_biggy *)
		3473	(((char *)w) - offsetof (struct my_biggy, t2));
		3474	}
		3475
		3476	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
3464		3477
3465	Often (especially in GUI toolkits) there are places where you have	3478	Often (especially in GUI toolkits) there are places where you have
3466	I<modal> interaction, which is most easily implemented by recursively	3479	I<modal> interaction, which is most easily implemented by recursively
3467	invoking C<ev_run>.	3480	invoking C<ev_run>.
3468		3481
…		…
3497	exit_main_loop = 1;	3510	exit_main_loop = 1;
3498		3511
3499	// exit both	3512	// exit both
3500	exit_main_loop = exit_nested_loop = 1;	3513	exit_main_loop = exit_nested_loop = 1;
3501		3514
3502	=item Thread locking example	3515	=head2 THREAD LOCKING EXAMPLE
3503		3516
3504	Here is a fictitious example of how to run an event loop in a different	3517	Here is a fictitious example of how to run an event loop in a different
3505	thread than where callbacks are being invoked and watchers are	3518	thread from where callbacks are being invoked and watchers are
3506	created/added/removed.	3519	created/added/removed.
3507		3520
3508	For a real-world example, see the C<EV::Loop::Async> perl module,	3521	For a real-world example, see the C<EV::Loop::Async> perl module,
3509	which uses exactly this technique (which is suited for many high-level	3522	which uses exactly this technique (which is suited for many high-level
3510	languages).	3523	languages).
…		…
3536	// now associate this with the loop	3549	// now associate this with the loop
3537	ev_set_userdata (EV_A_ u);	3550	ev_set_userdata (EV_A_ u);
3538	ev_set_invoke_pending_cb (EV_A_ l_invoke);	3551	ev_set_invoke_pending_cb (EV_A_ l_invoke);
3539	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);	3552	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3540		3553
3541	// then create the thread running ev_loop	3554	// then create the thread running ev_run
3542	pthread_create (&u->tid, 0, l_run, EV_A);	3555	pthread_create (&u->tid, 0, l_run, EV_A);
3543	}	3556	}
3544		3557
3545	The callback for the C<ev_async> watcher does nothing: the watcher is used	3558	The callback for the C<ev_async> watcher does nothing: the watcher is used
3546	solely to wake up the event loop so it takes notice of any new watchers	3559	solely to wake up the event loop so it takes notice of any new watchers
…		…
3635	Note that sending the C<ev_async> watcher is required because otherwise	3648	Note that sending the C<ev_async> watcher is required because otherwise
3636	an event loop currently blocking in the kernel will have no knowledge	3649	an event loop currently blocking in the kernel will have no knowledge
3637	about the newly added timer. By waking up the loop it will pick up any new	3650	about the newly added timer. By waking up the loop it will pick up any new
3638	watchers in the next event loop iteration.	3651	watchers in the next event loop iteration.
3639		3652
3640	=back	3653	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3654
		3655	While the overhead of a callback that e.g. schedules a thread is small, it
		3656	is still an overhead. If you embed libev, and your main usage is with some
		3657	kind of threads or coroutines, you might want to customise libev so that
		3658	doesn't need callbacks anymore.
		3659
		3660	Imagine you have coroutines that you can switch to using a function
		3661	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3662	and that due to some magic, the currently active coroutine is stored in a
		3663	global called C<current_coro>. Then you can build your own "wait for libev
		3664	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3665	the differing C<;> conventions):
		3666
		3667	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3668	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3669
		3670	That means instead of having a C callback function, you store the
		3671	coroutine to switch to in each watcher, and instead of having libev call
		3672	your callback, you instead have it switch to that coroutine.
		3673
		3674	A coroutine might now wait for an event with a function called
		3675	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3676	matter when, or whether the watcher is active or not when this function is
		3677	called):
		3678
		3679	void
		3680	wait_for_event (ev_watcher *w)
		3681	{
		3682	ev_cb_set (w) = current_coro;
		3683	switch_to (libev_coro);
		3684	}
		3685
		3686	That basically suspends the coroutine inside C<wait_for_event> and
		3687	continues the libev coroutine, which, when appropriate, switches back to
		3688	this or any other coroutine. I am sure if you sue this your own :)
		3689
		3690	You can do similar tricks if you have, say, threads with an event queue -
		3691	instead of storing a coroutine, you store the queue object and instead of
		3692	switching to a coroutine, you push the watcher onto the queue and notify
		3693	any waiters.
		3694
		3695	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3696	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3697
		3698	// my_ev.h
		3699	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3700	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3701	#include "../libev/ev.h"
		3702
		3703	// my_ev.c
		3704	#define EV_H "my_ev.h"
		3705	#include "../libev/ev.c"
		3706
		3707	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3708	F<my_ev.c> into your project. When properly specifying include paths, you
		3709	can even use F<ev.h> as header file name directly.
3641		3710
3642		3711
3643	=head1 LIBEVENT EMULATION	3712	=head1 LIBEVENT EMULATION
3644		3713
3645	Libev offers a compatibility emulation layer for libevent. It cannot	3714	Libev offers a compatibility emulation layer for libevent. It cannot
…		…
4575	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4644	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4576		4645
4577	#include "ev_cpp.h"	4646	#include "ev_cpp.h"
4578	#include "ev.c"	4647	#include "ev.c"
4579		4648
4580	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4649	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4581		4650
4582	=head2 THREADS AND COROUTINES	4651	=head2 THREADS AND COROUTINES
4583		4652
4584	=head3 THREADS	4653	=head3 THREADS
4585		4654
…		…
4636	default loop and triggering an C<ev_async> watcher from the default loop	4705	default loop and triggering an C<ev_async> watcher from the default loop
4637	watcher callback into the event loop interested in the signal.	4706	watcher callback into the event loop interested in the signal.
4638		4707
4639	=back	4708	=back
4640		4709
4641	See also L<Thread locking example>.	4710	See also L<THREAD LOCKING EXAMPLE>.
4642		4711
4643	=head3 COROUTINES	4712	=head3 COROUTINES
4644		4713
4645	Libev is very accommodating to coroutines ("cooperative threads"):	4714	Libev is very accommodating to coroutines ("cooperative threads"):
4646	libev fully supports nesting calls to its functions from different	4715	libev fully supports nesting calls to its functions from different
…		…
5155	The physical time that is observed. It is apparently strictly monotonic :)	5224	The physical time that is observed. It is apparently strictly monotonic :)
5156		5225
5157	=item wall-clock time	5226	=item wall-clock time
5158		5227
5159	The time and date as shown on clocks. Unlike real time, it can actually	5228	The time and date as shown on clocks. Unlike real time, it can actually
5160	be wrong and jump forwards and backwards, e.g. when the you adjust your	5229	be wrong and jump forwards and backwards, e.g. when you adjust your
5161	clock.	5230	clock.
5162		5231
5163	=item watcher	5232	=item watcher
5164		5233
5165	A data structure that describes interest in certain events. Watchers need	5234	A data structure that describes interest in certain events. Watchers need
…		…
5168	=back	5237	=back
5169		5238
5170	=head1 AUTHOR	5239	=head1 AUTHOR
5171		5240
5172	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael	5241	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
5173	Magnusson and Emanuele Giaquinta.	5242	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
5174		5243

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Comparing libev/ev.pod (file contents): Revision 1.354 by root, Tue Jan 11 01:40:25 2011 UTC vs. Revision 1.366 by sf-exg, Thu Feb 3 16:21:08 2011 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.354 by root, Tue Jan 11 01:40:25 2011 UTC vs.
Revision 1.366 by sf-exg, Thu Feb 3 16:21:08 2011 UTC