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Revision 1.5 by root, Sun Nov 29 15:53:48 2009 UTC vs.
Revision 1.16 by root, Tue Jul 5 17:05:54 2011 UTC

…		…
11	The newest version of this document is also available as an html-formatted	11	The newest version of this document is also available as an html-formatted
12	web page you might find easier to navigate when reading it for the first	12	web page you might find easier to navigate when reading it for the first
13	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libeio/eio.pod>.	13	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libeio/eio.pod>.
14		14
15	Note that this library is a by-product of the C<IO::AIO> perl	15	Note that this library is a by-product of the C<IO::AIO> perl
16	module, and many of the subtler points regarding requets lifetime	16	module, and many of the subtler points regarding requests lifetime
17	and so on are only documented in its documentation at the	17	and so on are only documented in its documentation at the
18	moment: L<http://pod.tst.eu/http://cvs.schmorp.de/IO-AIO/AIO.pm>.	18	moment: L<http://pod.tst.eu/http://cvs.schmorp.de/IO-AIO/AIO.pm>.
19		19
20	=head2 FEATURES	20	=head2 FEATURES
21		21
22	This library provides fully asynchronous versions of most POSIX functions	22	This library provides fully asynchronous versions of most POSIX functions
23	dealign with I/O. Unlike most asynchronous libraries, this not only	23	dealing with I/O. Unlike most asynchronous libraries, this not only
24	includes C<read> and C<write>, but also C<open>, C<stat>, C<unlink> and	24	includes C<read> and C<write>, but also C<open>, C<stat>, C<unlink> and
25	similar functions, as well as less rarely ones such as C<mknod>, C<futime>	25	similar functions, as well as less rarely ones such as C<mknod>, C<futime>
26	or C<readlink>.	26	or C<readlink>.
27		27
28	It also offers wrappers around C<sendfile> (Solaris, Linux, HP-UX and	28	It also offers wrappers around C<sendfile> (Solaris, Linux, HP-UX and
…		…
37	=head2 TIME REPRESENTATION	37	=head2 TIME REPRESENTATION
38		38
39	Libeio represents time as a single floating point number, representing the	39	Libeio represents time as a single floating point number, representing the
40	(fractional) number of seconds since the (POSIX) epoch (somewhere near	40	(fractional) number of seconds since the (POSIX) epoch (somewhere near
41	the beginning of 1970, details are complicated, don't ask). This type is	41	the beginning of 1970, details are complicated, don't ask). This type is
42	called C<eio_tstamp>, but it is guarenteed to be of type C<double> (or	42	called C<eio_tstamp>, but it is guaranteed to be of type C<double> (or
43	better), so you can freely use C<double> yourself.	43	better), so you can freely use C<double> yourself.
44		44
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
…		…
55	3. in the parent, continue business as usual, done	55	3. in the parent, continue business as usual, done
56	4. in the child, destroy all ready and pending requests and free the	56	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	57	memory used by the worker threads. This gives you a fully empty
58	libeio queue.	58	libeio queue.
59		59
		60	Note, however, since libeio does use threads, thr above guarantee doesn't
		61	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	the above might crash, and thus change.
		64
60	=head1 INITIALISATION/INTEGRATION	65	=head1 INITIALISATION/INTEGRATION
61		66
62	Before you can call any eio functions you first have to initialise the	67	Before you can call any eio functions you first have to initialise the
63	library. The library integrates into any event loop, but can also be used	68	library. The library integrates into any event loop, but can also be used
64	without one, including in polling mode.	69	without one, including in polling mode.
…		…
97	handled or C<done_poll> has been called, which signals the same.	102	handled or C<done_poll> has been called, which signals the same.
98		103
99	Note that C<eio_poll> might return after C<done_poll> and C<want_poll>	104	Note that C<eio_poll> might return after C<done_poll> and C<want_poll>
100	have been called again, so watch out for races in your code.	105	have been called again, so watch out for races in your code.
101		106
102	As with C<want_poll>, this callback is called while lcoks are being held,	107	As with C<want_poll>, this callback is called while locks are being held,
103	so you I<must not call any libeio functions form within this callback>.	108	so you I<must not call any libeio functions form within this callback>.
104		109
105	=item int eio_poll ()	110	=item int eio_poll ()
106		111
107	This function has to be called whenever there are pending requests that	112	This function has to be called whenever there are pending requests that
…		…
119	=back	124	=back
120		125
121	For libev, you would typically use an C<ev_async> watcher: the	126	For libev, you would typically use an C<ev_async> watcher: the
122	C<want_poll> callback would invoke C<ev_async_send> to wake up the event	127	C<want_poll> callback would invoke C<ev_async_send> to wake up the event
123	loop. Inside the callback set for the watcher, one would call C<eio_poll	128	loop. Inside the callback set for the watcher, one would call C<eio_poll
124	()> (followed by C<ev_async_send> again if C<eio_poll> indicates that not	129	()>.
125	all requests have been handled yet). The race is taken care of because	130
126	libev resets/rearms the async watcher before calling your callback,	131	If C<eio_poll ()> is configured to not handle all results in one go
127	and therefore, before calling C<eio_poll>. This might result in (some)	132	(i.e. it returns C<-1>) then you should start an idle watcher that calls
128	spurious wake-ups, but is generally harmless.	133	C<eio_poll> until it returns something C<!= -1>.
		134
		135	A full-featured conenctor between libeio and libev would look as follows
		136	(if C<eio_poll> is handling all requests, it can of course be simplified a
		137	lot by removing the idle watcher logic):
		138
		139	static struct ev_loop *loop;
		140	static ev_idle repeat_watcher;
		141	static ev_async ready_watcher;
		142
		143	/* idle watcher callback, only used when eio_poll */
		144	/* didn't handle all results in one call */
		145	static void
		146	repeat (EV_P_ ev_idle *w, int revents)
		147	{
		148	if (eio_poll () != -1)
		149	ev_idle_stop (EV_A_ w);
		150	}
		151
		152	/* eio has some results, process them */
		153	static void
		154	ready (EV_P_ ev_async *w, int revents)
		155	{
		156	if (eio_poll () == -1)
		157	ev_idle_start (EV_A_ &repeat_watcher);
		158	}
		159
		160	/* wake up the event loop */
		161	static void
		162	want_poll (void)
		163	{
		164	ev_async_send (loop, &ready_watcher)
		165	}
		166
		167	void
		168	my_init_eio ()
		169	{
		170	loop = EV_DEFAULT;
		171
		172	ev_idle_init (&repeat_watcher, repeat);
		173	ev_async_init (&ready_watcher, ready);
		174	ev_async_start (loop &watcher);
		175
		176	eio_init (want_poll, 0);
		177	}
129		178
130	For most other event loops, you would typically use a pipe - the event	179	For most other event loops, you would typically use a pipe - the event
131	loop should be told to wait for read readyness on the read end. In	180	loop should be told to wait for read readiness on the read end. In
132	C<want_poll> you would write a single byte, in C<done_poll> you would try	181	C<want_poll> you would write a single byte, in C<done_poll> you would try
133	to read that byte, and in the callback for the read end, you would call	182	to read that byte, and in the callback for the read end, you would call
134	C<eio_poll>. The race is avoided here because the event loop should invoke	183	C<eio_poll>.
135	your callback again and again until the byte has been read (as the pipe	184
136	read callback does not read it, only C<done_poll>).	185	You don't have to take special care in the case C<eio_poll> doesn't handle
		186	all requests, as the done callback will not be invoked, so the event loop
		187	will still signal readyness for the pipe until I<all> results have been
		188	processed.
		189
		190
		191	=head1 HIGH LEVEL REQUEST API
		192
		193	Libeio has both a high-level API, which consists of calling a request
		194	function with a callback to be called on completion, and a low-level API
		195	where you fill out request structures and submit them.
		196
		197	This section describes the high-level API.
		198
		199	=head2 REQUEST SUBMISSION AND RESULT PROCESSING
		200
		201	You submit a request by calling the relevant C<eio_TYPE> function with the
		202	required parameters, a callback of type C<int (eio_cb)(eio_req req)>
		203	(called C<eio_cb> below) and a freely usable C<void *data> argument.
		204
		205	The return value will either be 0, in case something went really wrong
		206	(which can basically only happen on very fatal errors, such as C<malloc>
		207	returning 0, which is rather unlikely), or a pointer to the newly-created
		208	and submitted C<eio_req *>.
		209
		210	The callback will be called with an C<eio_req *> which contains the
		211	results of the request. The members you can access inside that structure
		212	vary from request to request, except for:
		213
		214	=over 4
		215
		216	=item C<ssize_t result>
		217
		218	This contains the result value from the call (usually the same as the
		219	syscall of the same name).
		220
		221	=item C<int errorno>
		222
		223	This contains the value of C<errno> after the call.
		224
		225	=item C<void *data>
		226
		227	The C<void *data> member simply stores the value of the C<data> argument.
		228
		229	=back
		230
		231	The return value of the callback is normally C<0>, which tells libeio to
		232	continue normally. If a callback returns a nonzero value, libeio will
		233	stop processing results (in C<eio_poll>) and will return the value to its
		234	caller.
		235
		236	Memory areas passed to libeio must stay valid as long as a request
		237	executes, with the exception of paths, which are being copied
		238	internally. Any memory libeio itself allocates will be freed after the
		239	finish callback has been called. If you want to manage all memory passed
		240	to libeio yourself you can use the low-level API.
		241
		242	For example, to open a file, you could do this:
		243
		244	static int
		245	file_open_done (eio_req *req)
		246	{
		247	if (req->result < 0)
		248	{
		249	/* open() returned -1 */
		250	errno = req->errorno;
		251	perror ("open");
		252	}
		253	else
		254	{
		255	int fd = req->result;
		256	/* now we have the new fd in fd */
		257	}
		258
		259	return 0;
		260	}
		261
		262	/* the first three arguments are passed to open(2) */
		263	/* the remaining are priority, callback and data */
		264	if (!eio_open ("/etc/passwd", O_RDONLY, 0, 0, file_open_done, 0))
		265	abort (); /* something ent wrong, we will all die!!! */
		266
		267	Note that you additionally need to call C<eio_poll> when the C<want_cb>
		268	indicates that requests are ready to be processed.
		269
		270	=head2 AVAILABLE REQUESTS
		271
		272	The following request functions are available. I<All> of them return the
		273	C<eio_req *> on success and C<0> on failure, and I<all> of them have the
		274	same three trailing arguments: C<pri>, C<cb> and C<data>. The C<cb> is
		275	mandatory, but in most cases, you pass in C<0> as C<pri> and C<0> or some
		276	custom data value as C<data>.
		277
		278	=head3 POSIX API WRAPPERS
		279
		280	These requests simply wrap the POSIX call of the same name, with the same
		281	arguments. If a function is not implemented by the OS and cannot be emulated
		282	in some way, then all of these return C<-1> and set C<errorno> to C<ENOSYS>.
		283
		284	=over 4
		285
		286	=item eio_open (const char path, int flags, mode_t mode, int pri, eio_cb cb, void data)
		287
		288	=item eio_truncate (const char path, off_t offset, int pri, eio_cb cb, void data)
		289
		290	=item eio_chown (const char path, uid_t uid, gid_t gid, int pri, eio_cb cb, void data)
		291
		292	=item eio_chmod (const char path, mode_t mode, int pri, eio_cb cb, void data)
		293
		294	=item eio_mkdir (const char path, mode_t mode, int pri, eio_cb cb, void data)
		295
		296	=item eio_rmdir (const char path, int pri, eio_cb cb, void data)
		297
		298	=item eio_unlink (const char path, int pri, eio_cb cb, void data)
		299
		300	=item eio_utime (const char path, eio_tstamp atime, eio_tstamp mtime, int pri, eio_cb cb, void data)
		301
		302	=item eio_mknod (const char path, mode_t mode, dev_t dev, int pri, eio_cb cb, void data)
		303
		304	=item eio_link (const char path, const char new_path, int pri, eio_cb cb, void *data)
		305
		306	=item eio_symlink (const char path, const char new_path, int pri, eio_cb cb, void *data)
		307
		308	=item eio_rename (const char path, const char new_path, int pri, eio_cb cb, void *data)
		309
		310	=item eio_mlock (void addr, size_t length, int pri, eio_cb cb, void data)
		311
		312	=item eio_close (int fd, int pri, eio_cb cb, void *data)
		313
		314	=item eio_sync (int pri, eio_cb cb, void *data)
		315
		316	=item eio_fsync (int fd, int pri, eio_cb cb, void *data)
		317
		318	=item eio_fdatasync (int fd, int pri, eio_cb cb, void *data)
		319
		320	=item eio_futime (int fd, eio_tstamp atime, eio_tstamp mtime, int pri, eio_cb cb, void *data)
		321
		322	=item eio_ftruncate (int fd, off_t offset, int pri, eio_cb cb, void *data)
		323
		324	=item eio_fchmod (int fd, mode_t mode, int pri, eio_cb cb, void *data)
		325
		326	=item eio_fchown (int fd, uid_t uid, gid_t gid, int pri, eio_cb cb, void *data)
		327
		328	=item eio_dup2 (int fd, int fd2, int pri, eio_cb cb, void *data)
		329
		330	These have the same semantics as the syscall of the same name, their
		331	return value is available as C<< req->result >> later.
		332
		333	=item eio_read (int fd, void buf, size_t length, off_t offset, int pri, eio_cb cb, void data)
		334
		335	=item eio_write (int fd, void buf, size_t length, off_t offset, int pri, eio_cb cb, void data)
		336
		337	These two requests are called C<read> and C<write>, but actually wrap
		338	C<pread> and C<pwrite>. On systems that lack these calls (such as cygwin),
		339	libeio uses lseek/read_or_write/lseek and a mutex to serialise the
		340	requests, so all these requests run serially and do not disturb each
		341	other. However, they still disturb the file offset while they run, so it's
		342	not safe to call these functions concurrently with non-libeio functions on
		343	the same fd on these systems.
		344
		345	Not surprisingly, pread and pwrite are not thread-safe on Darwin (OS/X),
		346	so it is advised not to submit multiple requests on the same fd on this
		347	horrible pile of garbage.
		348
		349	=item eio_mlockall (int flags, int pri, eio_cb cb, void *data)
		350
		351	Like C<mlockall>, but the flag value constants are called
		352	C<EIO_MCL_CURRENT> and C<EIO_MCL_FUTURE>.
		353
		354	=item eio_msync (void addr, size_t length, int flags, int pri, eio_cb cb, void data)
		355
		356	Just like msync, except that the flag values are called C<EIO_MS_ASYNC>,
		357	C<EIO_MS_INVALIDATE> and C<EIO_MS_SYNC>.
		358
		359	=item eio_readlink (const char path, int pri, eio_cb cb, void data)
		360
		361	If successful, the path read by C<readlink(2)> can be accessed via C<<
		362	req->ptr2 >> and is I<NOT> null-terminated, with the length specified as
		363	C<< req->result >>.
		364
		365	if (req->result >= 0)
		366	{
		367	char target = strndup ((char )req->ptr2, req->result);
		368
		369	free (target);
		370	}
		371
		372	=item eio_realpath (const char path, int pri, eio_cb cb, void data)
		373
		374	Similar to the realpath libc function, but unlike that one, result is
		375	C<-1> on failure and the length of the returned path in C<ptr2> (which is
		376	not 0-terminated) - this is similar to readlink.
		377
		378	=item eio_stat (const char path, int pri, eio_cb cb, void data)
		379
		380	=item eio_lstat (const char path, int pri, eio_cb cb, void data)
		381
		382	=item eio_fstat (int fd, int pri, eio_cb cb, void *data)
		383
		384	Stats a file - if C<< req->result >> indicates success, then you can
		385	access the C<struct stat>-like structure via C<< req->ptr2 >>:
		386
		387	EIO_STRUCT_STAT statdata = (EIO_STRUCT_STAT )req->ptr2;
		388
		389	=item eio_statvfs (const char path, int pri, eio_cb cb, void data)
		390
		391	=item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data)
		392
		393	Stats a filesystem - if C<< req->result >> indicates success, then you can
		394	access the C<struct statvfs>-like structure via C<< req->ptr2 >>:
		395
		396	EIO_STRUCT_STATVFS statdata = (EIO_STRUCT_STATVFS )req->ptr2;
		397
		398	=back
		399
		400	=head3 READING DIRECTORIES
		401
		402	Reading directories sounds simple, but can be rather demanding, especially
		403	if you want to do stuff such as traversing a diretcory hierarchy or
		404	processing all files in a directory. Libeio can assist thess complex tasks
		405	with it's C<eio_readdir> call.
		406
		407	=over 4
		408
		409	=item eio_readdir (const char path, int flags, int pri, eio_cb cb, void data)
		410
		411	This is a very complex call. It basically reads through a whole directory
		412	(via the C<opendir>, C<readdir> and C<closedir> calls) and returns either
		413	the names or an array of C<struct eio_dirent>, depending on the C<flags>
		414	argument.
		415
		416	The C<< req->result >> indicates either the number of files found, or
		417	C<-1> on error. On success, null-terminated names can be found as C<< req->ptr2 >>,
		418	and C<struct eio_dirents>, if requested by C<flags>, can be found via C<<
		419	req->ptr1 >>.
		420
		421	Here is an example that prints all the names:
		422
		423	int i;
		424	char names = (char )req->ptr2;
		425
		426	for (i = 0; i < req->result; ++i)
		427	{
		428	printf ("name #%d: %s\n", i, names);
		429
		430	/* move to next name */
		431	names += strlen (names) + 1;
		432	}
		433
		434	Pseudo-entries such as F<.> and F<..> are never returned by C<eio_readdir>.
		435
		436	C<flags> can be any combination of:
		437
		438	=over 4
		439
		440	=item EIO_READDIR_DENTS
		441
		442	If this flag is specified, then, in addition to the names in C<ptr2>,
		443	also an array of C<struct eio_dirent> is returned, in C<ptr1>. A C<struct
		444	eio_dirent> looks like this:
		445
		446	struct eio_dirent
		447	{
		448	int nameofs; /* offset of null-terminated name string in (char )req->ptr2 /
		449	unsigned short namelen; /* size of filename without trailing 0 */
		450	unsigned char type; /* one of EIO_DT_* */
		451	signed char score; /* internal use */
		452	ino_t inode; /* the inode number, if available, otherwise unspecified */
		453	};
		454
		455	The only members you normally would access are C<nameofs>, which is the
		456	byte-offset from C<ptr2> to the start of the name, C<namelen> and C<type>.
		457
		458	C<type> can be one of:
		459
		460	C<EIO_DT_UNKNOWN> - if the type is not known (very common) and you have to C<stat>
		461	the name yourself if you need to know,
		462	one of the "standard" POSIX file types (C<EIO_DT_REG>, C<EIO_DT_DIR>, C<EIO_DT_LNK>,
		463	C<EIO_DT_FIFO>, C<EIO_DT_SOCK>, C<EIO_DT_CHR>, C<EIO_DT_BLK>)
		464	or some OS-specific type (currently
		465	C<EIO_DT_MPC> - multiplexed char device (v7+coherent),
		466	C<EIO_DT_NAM> - xenix special named file,
		467	C<EIO_DT_MPB> - multiplexed block device (v7+coherent),
		468	C<EIO_DT_NWK> - HP-UX network special,
		469	C<EIO_DT_CMP> - VxFS compressed,
		470	C<EIO_DT_DOOR> - solaris door, or
		471	C<EIO_DT_WHT>).
		472
		473	This example prints all names and their type:
		474
		475	int i;
		476	struct eio_dirent ents = (struct eio_dirent )req->ptr1;
		477	char names = (char )req->ptr2;
		478
		479	for (i = 0; i < req->result; ++i)
		480	{
		481	struct eio_dirent *ent = ents + i;
		482	char *name = names + ent->nameofs;
		483
		484	printf ("name #%d: %s (type %d)\n", i, name, ent->type);
		485	}
		486
		487	=item EIO_READDIR_DIRS_FIRST
		488
		489	When this flag is specified, then the names will be returned in an order
		490	where likely directories come first, in optimal C<stat> order. This is
		491	useful when you need to quickly find directories, or you want to find all
		492	directories while avoiding to stat() each entry.
		493
		494	If the system returns type information in readdir, then this is used
		495	to find directories directly. Otherwise, likely directories are names
		496	beginning with ".", or otherwise names with no dots, of which names with
		497	short names are tried first.
		498
		499	=item EIO_READDIR_STAT_ORDER
		500
		501	When this flag is specified, then the names will be returned in an order
		502	suitable for stat()'ing each one. That is, when you plan to stat()
		503	all files in the given directory, then the returned order will likely
		504	be fastest.
		505
		506	If both this flag and C<EIO_READDIR_DIRS_FIRST> are specified, then
		507	the likely dirs come first, resulting in a less optimal stat order.
		508
		509	=item EIO_READDIR_FOUND_UNKNOWN
		510
		511	This flag should not be specified when calling C<eio_readdir>. Instead,
		512	it is being set by C<eio_readdir> (you can access the C<flags> via C<<
		513	req->int1 >>, when any of the C<type>'s found were C<EIO_DT_UNKNOWN>. The
		514	absense of this flag therefore indicates that all C<type>'s are known,
		515	which can be used to speed up some algorithms.
		516
		517	A typical use case would be to identify all subdirectories within a
		518	directory - you would ask C<eio_readdir> for C<EIO_READDIR_DIRS_FIRST>. If
		519	then this flag is I<NOT> set, then all the entries at the beginning of the
		520	returned array of type C<EIO_DT_DIR> are the directories. Otherwise, you
		521	should start C<stat()>'ing the entries starting at the beginning of the
		522	array, stopping as soon as you found all directories (the count can be
		523	deduced by the link count of the directory).
		524
		525	=back
		526
		527	=back
		528
		529	=head3 OS-SPECIFIC CALL WRAPPERS
		530
		531	These wrap OS-specific calls (usually Linux ones), and might or might not
		532	be emulated on other operating systems. Calls that are not emulated will
		533	return C<-1> and set C<errno> to C<ENOSYS>.
		534
		535	=over 4
		536
		537	=item eio_sendfile (int out_fd, int in_fd, off_t in_offset, size_t length, int pri, eio_cb cb, void *data)
		538
		539	Wraps the C<sendfile> syscall. The arguments follow the Linux version, but
		540	libeio supports and will use similar calls on FreeBSD, HP/UX, Solaris and
		541	Darwin.
		542
		543	If the OS doesn't support some sendfile-like call, or the call fails,
		544	indicating support for the given file descriptor type (for example,
		545	Linux's sendfile might not support file to file copies), then libeio will
		546	emulate the call in userspace, so there are almost no limitations on its
		547	use.
		548
		549	=item eio_readahead (int fd, off_t offset, size_t length, int pri, eio_cb cb, void *data)
		550
		551	Calls C<readahead(2)>. If the syscall is missing, then the call is
		552	emulated by simply reading the data (currently in 64kiB chunks).
		553
		554	=item eio_sync_file_range (int fd, off_t offset, size_t nbytes, unsigned int flags, int pri, eio_cb cb, void *data)
		555
		556	Calls C<sync_file_range>. If the syscall is missing, then this is the same
		557	as calling C<fdatasync>.
		558
		559	Flags can be any combination of C<EIO_SYNC_FILE_RANGE_WAIT_BEFORE>,
		560	C<EIO_SYNC_FILE_RANGE_WRITE> and C<EIO_SYNC_FILE_RANGE_WAIT_AFTER>.
		561
		562	=back
		563
		564	=head3 LIBEIO-SPECIFIC REQUESTS
		565
		566	These requests are specific to libeio and do not correspond to any OS call.
		567
		568	=over 4
		569
		570	=item eio_mtouch (void addr, size_t length, int flags, int pri, eio_cb cb, void data)
		571
		572	Reads (C<flags == 0>) or modifies (C<flags == EIO_MT_MODIFY) the given
		573	memory area, page-wise, that is, it reads (or reads and writes back) the
		574	first octet of every page that spans the memory area.
		575
		576	This can be used to page in some mmapped file, or dirty some pages. Note
		577	that dirtying is an unlocked read-write access, so races can ensue when
		578	the some other thread modifies the data stored in that memory area.
		579
		580	=item eio_custom (void ()(eio_req ) execute, int pri, eio_cb cb, void *data)
		581
		582	Executes a custom request, i.e., a user-specified callback.
		583
		584	The callback gets the C<eio_req *> as parameter and is expected to read
		585	and modify any request-specific members. Specifically, it should set C<<
		586	req->result >> to the result value, just like other requests.
		587
		588	Here is an example that simply calls C<open>, like C<eio_open>, but it
		589	uses the C<data> member as filename and uses a hardcoded C<O_RDONLY>. If
		590	you want to pass more/other parameters, you either need to pass some
		591	struct or so via C<data> or provide your own wrapper using the low-level
		592	API.
		593
		594	static int
		595	my_open_done (eio_req *req)
		596	{
		597	int fd = req->result;
		598
		599	return 0;
		600	}
		601
		602	static void
		603	my_open (eio_req *req)
		604	{
		605	req->result = open (req->data, O_RDONLY);
		606	}
		607
		608	eio_custom (my_open, 0, my_open_done, "/etc/passwd");
		609
		610	=item eio_busy (eio_tstamp delay, int pri, eio_cb cb, void *data)
		611
		612	This is a a request that takes C<delay> seconds to execute, but otherwise
		613	does nothing - it simply puts one of the worker threads to sleep for this
		614	long.
		615
		616	This request can be used to artificially increase load, e.g. for debugging
		617	or benchmarking reasons.
		618
		619	=item eio_nop (int pri, eio_cb cb, void *data)
		620
		621	This request does nothing, except go through the whole request cycle. This
		622	can be used to measure latency or in some cases to simplify code, but is
		623	not really of much use.
		624
		625	=back
		626
		627	=head3 GROUPING AND LIMITING REQUESTS
		628
		629	There is one more rather special request, C<eio_grp>. It is a very special
		630	aio request: Instead of doing something, it is a container for other eio
		631	requests.
		632
		633	There are two primary use cases for this: a) bundle many requests into a
		634	single, composite, request with a definite callback and the ability to
		635	cancel the whole request with its subrequests and b) limiting the number
		636	of "active" requests.
		637
		638	Further below you will find more dicussion of these topics - first follows
		639	the reference section detailing the request generator and other methods.
		640
		641	=over 4
		642
		643	=item eio_grp (eio_cb cb, void *data)
		644
		645	Creates and submits a group request.
		646
		647	=back
		648
		649
		650
		651	#TODO
		652
		653	/*****************************************************************************/
		654	/* groups */
		655
		656	eio_req eio_grp (eio_cb cb, void data);
		657	void eio_grp_feed (eio_req grp, void (feed)(eio_req *req), int limit);
		658	void eio_grp_limit (eio_req *grp, int limit);
		659	void eio_grp_add (eio_req grp, eio_req req);
		660	void eio_grp_cancel (eio_req grp); / cancels all sub requests but not the group */
		661
		662
		663	=back
		664
		665
		666	=head1 LOW LEVEL REQUEST API
		667
		668	#TODO
		669
		670
		671	=head1 ANATOMY AND LIFETIME OF AN EIO REQUEST
		672
		673	A request is represented by a structure of type C<eio_req>. To initialise
		674	it, clear it to all zero bytes:
		675
		676	eio_req req;
		677
		678	memset (&req, 0, sizeof (req));
		679
		680	A more common way to initialise a new C<eio_req> is to use C<calloc>:
		681
		682	eio_req req = calloc (1, sizeof (req));
		683
		684	In either case, libeio neither allocates, initialises or frees the
		685	C<eio_req> structure for you - it merely uses it.
		686
		687	zero
		688
		689	#TODO
137		690
138	=head2 CONFIGURATION	691	=head2 CONFIGURATION
139		692
140	The functions in this section can sometimes be useful, but the default	693	The functions in this section can sometimes be useful, but the default
141	configuration will do in most case, so you should skip this section on	694	configuration will do in most case, so you should skip this section on
…		…
185	=item eio_set_max_idle (unsigned int nthreads)	738	=item eio_set_max_idle (unsigned int nthreads)
186		739
187	Libeio uses threads internally to handle most requests, and will start and stop threads on demand.	740	Libeio uses threads internally to handle most requests, and will start and stop threads on demand.
188		741
189	This call can be used to limit the number of idle threads (threads without	742	This call can be used to limit the number of idle threads (threads without
190	work to do): libeio will keep some threads idle in preperation for more	743	work to do): libeio will keep some threads idle in preparation for more
191	requests, but never longer than C<nthreads> threads.	744	requests, but never longer than C<nthreads> threads.
192		745
193	In addition to this, libeio will also stop threads when they are idle for	746	In addition to this, libeio will also stop threads when they are idle for
194	a few seconds, regardless of this setting.	747	a few seconds, regardless of this setting.
195		748
…		…
213	Returns the number of pending requests, i.e. requests that have been	766	Returns the number of pending requests, i.e. requests that have been
214	executed and have results, but have not been finished yet by a call to	767	executed and have results, but have not been finished yet by a call to
215	C<eio_poll>).	768	C<eio_poll>).
216		769
217	=back	770	=back
218
219
220	=head1 ANATOMY OF AN EIO REQUEST
221
222	#TODO
223
224
225	=head1 HIGH LEVEL REQUEST API
226
227	#TODO
228
229	=back
230
231
232	=head1 LOW LEVEL REQUEST API
233
234	#TODO
235		771
236	=head1 EMBEDDING	772	=head1 EMBEDDING
237		773
238	Libeio can be embedded directly into programs. This functionality is not	774	Libeio can be embedded directly into programs. This functionality is not
239	documented and not (yet) officially supported.	775	documented and not (yet) officially supported.

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Comparing libeio/eio.pod (file contents): Revision 1.5 by root, Sun Nov 29 15:53:48 2009 UTC vs. Revision 1.16 by root, Tue Jul 5 17:05:54 2011 UTC

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Comparing libeio/eio.pod (file contents):
Revision 1.5 by root, Sun Nov 29 15:53:48 2009 UTC vs.
Revision 1.16 by root, Tue Jul 5 17:05:54 2011 UTC