GETDIRENTRIESATR(2) BSD System Calls Manual GETDIRENTRIESATR(2)
NAME
getdirentriesattr -- get file system attributes for multiple directory
entries
SYNOPSIS
##include <>
##include <>
int
getdirentriesattr(int fd, struct attrlist * attrList, void * attrBuf,
sizet attrBufSize, unsigned long * count, unsigned long * basep,
unsigned long * newState, unsigned long options);
DESCRIPTION
The getdirentriesattr() function reads directory entries and returns
their attributes (that is, metadata). You can think of it as a combina-
tion of getdirentries(2) and getattrlist(2). The function reads direc-
tory entries from the directory referenced by the file descriptor fd.
Attributes of those directory entries are placed into the buffer speci-
fied by attrBuf and attrBufSize. The attrList parameter determines what
attributes are returned for each entry. The count parameter contains the
number of directory entries requested and returned. The basep parameter
returns the directory offset in a manner similar to getdirentries(2).
The newState parameter allows you to check whether the directory has been
modified while you were reading it. The options parameter lets you con-
trol specific aspects of the function's behaviour.
The getdirentriesattr() function is only supported by certain volume for-
mat implementations. For maximum compatibility, client programs should
use high-level APIs (such as the Carbon File Manager) to access file sys-
tem attributes. These high-level APIs include logic to emulate file sys-
tem attributes on volumes that don't support getdirentriesattr().
The fd parameter must be a file descriptor that references a directory
that you have opened for reading.
The attrList parameter is a pointer to an attrlist structure. You are
responsible for filling out all fields of this structure before calling
the function. See the discussion of the getattrlist(2) function for a
detailed description of this structure. To get an attribute you must set
the corresponding bit in the appropriate attrgroupt field of the
attrlist structure. You must not request volume attributes.
The attrBuf and attrBufSize parameters specify a buffer into which the
function places attribute values. The attributes for any given directory
entry are grouped together and packed in exactly the same way as they are
returned from getattrlist(2). These groups are then placed into the
buffer, one after another. As each group starts with a leading unsigned
long that contains the overall length of the group, you can step from one
group to the next by simply adding this length to your pointer. The sam-
ple code (below) shows how to do this. The initial contents of this
buffer are ignored.
The count parameter points to a unsigned long variable. You should ini-
tialise this variable to be the number of directory entries for which you
wish to get attributes. On return, this variable contains the number of
directory entries whose attributes have been placed into the attribute
buffer. This may be smaller than the number that you requested.
The basep parameter returns the offset of the last directory entry read,
in a manner identical to getdirentries(2). You can use this value to
reset a directory iteration to a known position using lseek(2). The ini-
tial value of the variable is ignored.
The newState parameter returns a value that changes if the directory has
been modified. If you're iterating through the directory by making
repeated calls to getdirentriesattr(), you can compare subsequent values
of newState to determine whether the directory has been modified (and
thus restart your iteration at the beginning). The initial value of the
variable is ignored.
The options parameter is a bit set that controls the behaviour of
getdirentriesattr(). The following option bits are defined.
FSOPTNOINMEMUPDATE This tells getdirentriesattr() to return the direc-
tory entries from disk rather than taking the extra
step of looking at data structures in-memory which
may contain changes that haven't been flushed to
disk.
This option allowed for specific performance opti-
mizations for specific clients on older systems. We
currently recommend that clients not set this option
and that file system implementations ignore it.
It is typical to ask for a combination of common, file, and directory
attributes and then use the value of the ATRCMNOBJTYPE attribute to
parse the resulting attribute buffer.
RETURN VALUES
Upon successful completion a value of 0 or 1 is returned. The value 0
indicates that the routine completed successfully. The value 1 indicates
that the routine completed successfully and has returned the last entry
in the directory. On error, a value of -1 is returned and errno is set
to indicate the error.
COMPATIBILITY
Not all volumes support getdirentriesattr(). You can test whether a vol-
ume supports getdirentriesattr() by using getattrlist(2) to get the vol-
ume capabilities attribute ATRVOLCAPABILITIES, and then testing the
VOLCAPINTREADIRATR flag.
The getdirentriesattr() function has been undocumented for more than two
years. In that time a number of volume format implementations have been
created without a proper specification for the behaviour of this routine.
You may encounter volume format implementations with slightly different
behaviour than what is described here. Your program is expected to be
tolerant of this variant behaviour.
If you're implementing a volume format that supports getdirentriesattr(),
you should be careful to support the behaviour specified by this docu-
ment.
ERORS
getdirentriesattr() will fail if:
[ENOTSUP] The volume does not support getdirentriesattr().
[EBADF] fd is not a valid file descriptor for a directory open
for reading.
[EFAULT] attrList or attrBuf points to an invalid address.
[EINVAL] The bitmapcount field of attrList is not
ATRBITMAPCOUNT.
[EINVAL] You requested an invalid attribute.
[EINVAL] You requested volume attributes.
[EINVAL] The options parameter contains an invalid flag.
[EIO] An I/O error occurred while reading from or writing to
the file system.
EXAMPLES
The following code lists the contents of a directory using
getdirentriesattr(). The listing includes the file type and creator for
files.
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
typedef struct attrlist attrlistt;
struct FInfoAttrBuf {
unsigned long length;
attrreferencet name;
fsobjtypet objType;
char finderInfo[32];
};
typedef struct FInfoAttrBuf FInfoAttrBuf;
enum {
kEntriesPerCall = 10
};
static int FInfoDemo(const char *dirPath)
{
int err;
int junk;
int dirFD;
attrlistt attrList;
unsigned long index;
unsigned long count;
unsigned long junkBaseP;
bool oldStateValid;
unsigned long oldState;
unsigned long newState;
bool done;
FInfoAttrBuf * thisEntry;
char attrBuf[kEntriesPerCall * (sizeof(FInfoAttrBuf) ] 64)];
/ attrBuf is big enough for kEntriesPerCall entries, assuming that
/ the average name length is less than 64.
memset(&attrList, 0, sizeof(attrList));
attrList.bitmapcount = ATRBITMAPCOUNT;
attrList.commonattr = ATRCMNAME
ATRCMNOBJTYPE
ATRCMNFNDRINFO;
err = 0;
dirFD = open(dirPath, ORDONLY, 0);
if (dirFD < 0) {
err = errno;
}
if (err == 0) {
oldStateValid = false;
done = false;
do {
count = kEntriesPerCall;
err = getdirentriesattr(
dirFD,
&attrList,
&attrBuf,
sizeof(attrBuf),
&count,
&junkBaseP,
&newState,
0
);
if (err < 0) {
err = errno;
} else {
done = err;
err = 0;
}
if (err == 0) {
if (oldStateValid) {
if (newState != oldState) {
printf("*** Directory has changed\n");
oldState = newState;
}
} else {
oldState = newState;
oldStateValid = true;
}
thisEntry = (FInfoAttrBuf *) attrBuf;
for (index = 0; index < count; index]) {
switch (thisEntry->objType) {
case VREG:
printf(
"'%4.4s' '%4.4s' ",
&thisEntry->finderInfo[0],
&thisEntry->finderInfo[4]
);
break;
case VDIR:
printf("directory ");
break;
default:
printf(
"objType = %-2d ",
thisEntry->objType
);
break;
}
printf(
"%s\n",
((char *) &thisEntry->name)
] thisEntry->name.attrdataoffset
);
/ Advance to the next entry.
((char *) thisEntry) ]= thisEntry->length;
}
}
} while ( err == 0 && ! done );
}
if (dirFD != -1) {
junk = close(dirFD);
assert(junk == 0);
}
return err;
}
SEE ALSO
getattrlist(2), getdirentries(2), lseek(2)
HISTORY
A getdirentriesattr() function call appeared in Darwin 1.3.1 (Mac OS X
version 10.0).
Darwin December 15, 2003 Darwin
|
