[ViewVC] Diff of: cvs/libeio/eio.pod

Comparing libeio/eio.pod (file contents):
Revision 1.15 by root, Tue Jul 5 16:57:41 2011 UTC vs.
Revision 1.17 by root, Tue Jul 5 18:59:28 2011 UTC

…		…
45	Unlike the name component C<stamp> might indicate, it is also used for	45	Unlike the name component C<stamp> might indicate, it is also used for
46	time differences throughout libeio.	46	time differences throughout libeio.
47		47
48	=head2 FORK SUPPORT	48	=head2 FORK SUPPORT
49		49
50	Calling C<fork ()> is fully supported by this module. It is implemented in these steps:	50	Calling C<fork ()> is fully supported by this module - but you must not
		51	rely on this. It is currently implemented in these steps:
51		52
52	1. wait till all requests in "execute" state have been handled	53	1. wait till all requests in "execute" state have been handled
53	(basically requests that are already handed over to the kernel).	54	(basically requests that are already handed over to the kernel).
54	2. fork	55	2. fork
55	3. in the parent, continue business as usual, done	56	3. in the parent, continue business as usual, done
56	4. in the child, destroy all ready and pending requests and free the	57	4. in the child, destroy all ready and pending requests and free the
57	memory used by the worker threads. This gives you a fully empty	58	memory used by the worker threads. This gives you a fully empty
58	libeio queue.	59	libeio queue.
59		60
60	Note, however, since libeio does use threads, thr above guarantee doesn't	61	Note, however, since libeio does use threads, the above guarantee doesn't
61	cover your libc, for example, malloc and other libc functions are not	62	cover your libc, for example, malloc and other libc functions are not
62	fork-safe, so there is very little you can do after a fork, and in fatc,	63	fork-safe, so there is very little you can do after a fork, and in fact,
63	the above might crash, and thus change.	64	the above might crash, and thus change.
64		65
65	=head1 INITIALISATION/INTEGRATION	66	=head1 INITIALISATION/INTEGRATION
66		67
67	Before you can call any eio functions you first have to initialise the	68	Before you can call any eio functions you first have to initialise the
…		…
130		131
131	If C<eio_poll ()> is configured to not handle all results in one go	132	If C<eio_poll ()> is configured to not handle all results in one go
132	(i.e. it returns C<-1>) then you should start an idle watcher that calls	133	(i.e. it returns C<-1>) then you should start an idle watcher that calls
133	C<eio_poll> until it returns something C<!= -1>.	134	C<eio_poll> until it returns something C<!= -1>.
134		135
135	A full-featured wrapper would look as follows (if C<eio_poll> is handling	136	A full-featured conenctor between libeio and libev would look as follows
136	all requests, it can of course be simplified a lot by removing the idle	137	(if C<eio_poll> is handling all requests, it can of course be simplified a
137	watcher logic):	138	lot by removing the idle watcher logic):
138		139
139	static struct ev_loop *loop;	140	static struct ev_loop *loop;
140	static ev_idle repeat_watcher;	141	static ev_idle repeat_watcher;
141	static ev_async ready_watcher;	142	static ev_async ready_watcher;
142		143
143	/* idle watcher callback, only used when eio_poll */	144	/* idle watcher callback, only used when eio_poll */
144	/* didn't handle all results in one call */	145	/* didn't handle all results in one call */
145	static void	146	static void
146	repeat (EV_P_ ev_idle *w, int revents)	147	repeat (EV_P_ ev_idle *w, int revents)
147	{	148	{
148	if (eio_poll () != -1)	149	if (eio_poll () != -1)
149	ev_idle_stop (EV_A_ w);	150	ev_idle_stop (EV_A_ w);
150	}	151	}
151		152
152	/* eio has some results, process them */	153	/* eio has some results, process them */
153	static void	154	static void
154	ready (EV_P_ ev_async *w, int revents)	155	ready (EV_P_ ev_async *w, int revents)
155	{	156	{
156	if (eio_poll () == -1)	157	if (eio_poll () == -1)
157	ev_idle_start (EV_A_ &repeat_watcher);	158	ev_idle_start (EV_A_ &repeat_watcher);
158	}	159	}
159		160
160	/* wake up the event loop */	161	/* wake up the event loop */
161	static void	162	static void
162	want_poll (void)	163	want_poll (void)
163	{	164	{
164	ev_async_send (loop, &ready_watcher)	165	ev_async_send (loop, &ready_watcher)
165	}	166	}
166		167
167	void	168	void
168	my_init_eio ()	169	my_init_eio ()
169	{	170	{
170	loop = EV_DEFAULT;	171	loop = EV_DEFAULT;
171		172
172	ev_idle_init (&repeat_watcher, repeat);	173	ev_idle_init (&repeat_watcher, repeat);
173	ev_async_init (&ready_watcher, ready);	174	ev_async_init (&ready_watcher, ready);
174	ev_async_start (loop &watcher);	175	ev_async_start (loop &watcher);
175		176
176	eio_init (want_poll, 0);	177	eio_init (want_poll, 0);
177	}	178	}
178		179
179	For most other event loops, you would typically use a pipe - the event	180	For most other event loops, you would typically use a pipe - the event
180	loop should be told to wait for read readiness on the read end. In	181	loop should be told to wait for read readiness on the read end. In
181	C<want_poll> you would write a single byte, in C<done_poll> you would try	182	C<want_poll> you would write a single byte, in C<done_poll> you would try
182	to read that byte, and in the callback for the read end, you would call	183	to read that byte, and in the callback for the read end, you would call
183	C<eio_poll>. The race is avoided here because the event loop should invoke	184	C<eio_poll>.
184	your callback again and again until the byte has been read (as the pipe	185
185	read callback does not read it, only C<done_poll>).	186	You don't have to take special care in the case C<eio_poll> doesn't handle
		187	all requests, as the done callback will not be invoked, so the event loop
		188	will still signal readyness for the pipe until I<all> results have been
		189	processed.
186		190
187		191
188	=head1 HIGH LEVEL REQUEST API	192	=head1 HIGH LEVEL REQUEST API
189		193
190	Libeio has both a high-level API, which consists of calling a request	194	Libeio has both a high-level API, which consists of calling a request
…		…
262	abort (); /* something ent wrong, we will all die!!! */	266	abort (); /* something ent wrong, we will all die!!! */
263		267
264	Note that you additionally need to call C<eio_poll> when the C<want_cb>	268	Note that you additionally need to call C<eio_poll> when the C<want_cb>
265	indicates that requests are ready to be processed.	269	indicates that requests are ready to be processed.
266		270
		271	=head2 CANCELLING REQUESTS
		272
		273	Sometimes the need for a request goes away before the request is
		274	finished. In that case, one can cancel the reqiest by a call to
		275	C<eio_cancel>:
		276
		277	=over 4
		278
		279	=item eio_cancel (eio_req *req)
		280
		281	Cancel the request. If the request is currently executing it might still
		282	continue to execute, and in other cases it might still take a while till
		283	the request is cancelled.
		284
		285	Even if cancelled, the finish callback will still be invoked - the
		286	callbacks of all cancellable requests need to check whether the request
		287	has been cancelled by calling C<EIO_CANCELLED (req)>:
		288
		289	static int
		290	my_eio_cb (eio_req *req)
		291	{
		292	if (EIO_CANCELLED (req))
		293	return 0;
		294	}
		295
		296	In addition, cancelled requests will either have C<< req->result >> set to
		297	C<-1> and C<errno> to C<ECANCELED>, or otherwise they were successfully
		298	executed despite being cancelled (e.g. when they have already been
		299	executed at the time they were cancelled).
		300
		301	=back
		302
267	=head2 AVAILABLE REQUESTS	303	=head2 AVAILABLE REQUESTS
268		304
269	The following request functions are available. I<All> of them return the	305	The following request functions are available. I<All> of them return the
270	C<eio_req *> on success and C<0> on failure, and I<all> of them have the	306	C<eio_req *> on success and C<0> on failure, and I<all> of them have the
271	same three trailing arguments: C<pri>, C<cb> and C<data>. The C<cb> is	307	same three trailing arguments: C<pri>, C<cb> and C<data>. The C<cb> is
…		…
379	=item eio_fstat (int fd, int pri, eio_cb cb, void *data)	415	=item eio_fstat (int fd, int pri, eio_cb cb, void *data)
380		416
381	Stats a file - if C<< req->result >> indicates success, then you can	417	Stats a file - if C<< req->result >> indicates success, then you can
382	access the C<struct stat>-like structure via C<< req->ptr2 >>:	418	access the C<struct stat>-like structure via C<< req->ptr2 >>:
383		419
384	EIO_STRUCT_STAT statdata = (EIO_STRUCT_STAT )req->ptr2;	420	EIO_STRUCT_STAT statdata = (EIO_STRUCT_STAT )req->ptr2;
385		421
386	=item eio_statvfs (const char path, int pri, eio_cb cb, void data)	422	=item eio_statvfs (const char path, int pri, eio_cb cb, void data)
387		423
388	=item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data)	424	=item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data)
389		425
390	Stats a filesystem - if C<< req->result >> indicates success, then you can	426	Stats a filesystem - if C<< req->result >> indicates success, then you can
391	access the C<struct statvfs>-like structure via C<< req->ptr2 >>:	427	access the C<struct statvfs>-like structure via C<< req->ptr2 >>:
392		428
393	EIO_STRUCT_STATVFS statdata = (EIO_STRUCT_STATVFS )req->ptr2;	429	EIO_STRUCT_STATVFS statdata = (EIO_STRUCT_STATVFS )req->ptr2;
394		430
395	=back	431	=back
396		432
397	=head3 READING DIRECTORIES	433	=head3 READING DIRECTORIES
398		434
…		…
438		474
439	If this flag is specified, then, in addition to the names in C<ptr2>,	475	If this flag is specified, then, in addition to the names in C<ptr2>,
440	also an array of C<struct eio_dirent> is returned, in C<ptr1>. A C<struct	476	also an array of C<struct eio_dirent> is returned, in C<ptr1>. A C<struct
441	eio_dirent> looks like this:	477	eio_dirent> looks like this:
442		478
443	struct eio_dirent	479	struct eio_dirent
444	{	480	{
445	int nameofs; /* offset of null-terminated name string in (char )req->ptr2 /	481	int nameofs; /* offset of null-terminated name string in (char )req->ptr2 /
446	unsigned short namelen; /* size of filename without trailing 0 */	482	unsigned short namelen; /* size of filename without trailing 0 */
447	unsigned char type; /* one of EIO_DT_* */	483	unsigned char type; /* one of EIO_DT_* */
448	signed char score; /* internal use */	484	signed char score; /* internal use */
449	ino_t inode; /* the inode number, if available, otherwise unspecified */	485	ino_t inode; /* the inode number, if available, otherwise unspecified */
450	};	486	};
451		487
452	The only members you normally would access are C<nameofs>, which is the	488	The only members you normally would access are C<nameofs>, which is the
453	byte-offset from C<ptr2> to the start of the name, C<namelen> and C<type>.	489	byte-offset from C<ptr2> to the start of the name, C<namelen> and C<type>.
454		490
455	C<type> can be one of:	491	C<type> can be one of:
…		…
635	Further below you will find more dicussion of these topics - first follows	671	Further below you will find more dicussion of these topics - first follows
636	the reference section detailing the request generator and other methods.	672	the reference section detailing the request generator and other methods.
637		673
638	=over 4	674	=over 4
639		675
640	=item eio_grp (eio_cb cb, void *data)	676	=item eio_req grp = eio_grp (eio_cb cb, void data)
641		677
642	Creates and submits a group request.	678	Creates, submits and returns a group request.
		679
		680	=item eio_grp_add (eio_req grp, eio_req req)
		681
		682	Adds a request to the request group.
		683
		684	=item eio_grp_cancel (eio_req *grp)
		685
		686	Cancels all requests I<in> the group, but I<not> the group request
		687	itself. You can cancel the group request via a normal C<eio_cancel> call.
		688
		689
643		690
644	=back	691	=back
645		692
646		693
647		694
…		…
651	/* groups */	698	/* groups */
652		699
653	eio_req eio_grp (eio_cb cb, void data);	700	eio_req eio_grp (eio_cb cb, void data);
654	void eio_grp_feed (eio_req grp, void (feed)(eio_req *req), int limit);	701	void eio_grp_feed (eio_req grp, void (feed)(eio_req *req), int limit);
655	void eio_grp_limit (eio_req *grp, int limit);	702	void eio_grp_limit (eio_req *grp, int limit);
656	void eio_grp_add (eio_req grp, eio_req req);
657	void eio_grp_cancel (eio_req grp); / cancels all sub requests but not the group */	703	void eio_grp_cancel (eio_req grp); / cancels all sub requests but not the group */
658		704
659		705
660	=back	706	=back
661		707
…		…
668	=head1 ANATOMY AND LIFETIME OF AN EIO REQUEST	714	=head1 ANATOMY AND LIFETIME OF AN EIO REQUEST
669		715
670	A request is represented by a structure of type C<eio_req>. To initialise	716	A request is represented by a structure of type C<eio_req>. To initialise
671	it, clear it to all zero bytes:	717	it, clear it to all zero bytes:
672		718
673	eio_req req;	719	eio_req req;
674		720
675	memset (&req, 0, sizeof (req));	721	memset (&req, 0, sizeof (req));
676		722
677	A more common way to initialise a new C<eio_req> is to use C<calloc>:	723	A more common way to initialise a new C<eio_req> is to use C<calloc>:
678		724
679	eio_req req = calloc (1, sizeof (req));	725	eio_req req = calloc (1, sizeof (req));
680		726
681	In either case, libeio neither allocates, initialises or frees the	727	In either case, libeio neither allocates, initialises or frees the
682	C<eio_req> structure for you - it merely uses it.	728	C<eio_req> structure for you - it merely uses it.
683		729
684	zero	730	zero

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Comparing libeio/eio.pod (file contents): Revision 1.15 by root, Tue Jul 5 16:57:41 2011 UTC vs. Revision 1.17 by root, Tue Jul 5 18:59:28 2011 UTC

Diff Legend

Comparing libeio/eio.pod (file contents):
Revision 1.15 by root, Tue Jul 5 16:57:41 2011 UTC vs.
Revision 1.17 by root, Tue Jul 5 18:59:28 2011 UTC