vop_readdir(9)

NAME

VOP_READDIR - read contents of a directory

SYNOPSIS

#include <sys/param.h>
#include <sys/dirent.h>
#include <sys/vnode.h>
int
VOP_READDIR(struct vnode *vp, struct uio *uio, struct  ucred
*cred,
        int *eofflag, int *ncookies, u_long **cookies);

DESCRIPTION

Read directory entries.

vp The vnode of the directory.

uio Where to read the directory contents.

cred The caller's credentials.

eofflag Return end of file status (NULL if not wanted).

ncookies Number of directory cookies generated for NFS

(NULL if not

wanted).

cookies Directory seek cookies generated for NFS (NULL if

not wanted).
The directory contents are read into struct dirent struc

tures. If the
on-disc data structures differ from this then they should be

translated.

LOCKS

The directory should be locked on entry and will still be

locked on exit.

RETURN VALUES

Zero is returned on success, otherwise an error code is re

turned.

If this is called from the NFS server, the extra arguments

eofflag,
ncookies and cookies are given. The value of *eofflag

should be set to
TRUE if the end of the directory is reached while reading.

The directory
seek cookies are returned to the NFS client and may be used

later to
restart a directory read part way through the directory.

There should be
one cookie returned per directory entry. The value of the

cookie should
be the offset within the directory where the on-disc version

of the
appropriate directory entry starts. Memory for the cookies

should be
allocated using:

...;
*ncookies = number of entries read;
*cookies = (u_int*)#

malloc(*ncookies * sizeof(u_int), M_TEMP,

M_WAITOK);

PSEUDOCODE

int
vop_readdir(struct vnode *vp, struct uio *uio, struct ucred

*cred,

int *eofflag, int *ncookies, u_int **cookies)

{

off_t off;
int error = 0;

/*

* Remember the original offset to use later in generat

ing cookies.
*/

off = uio->uio_offset;

/*

* Read directory contents starting at uio->uio_offset

into buffer
* pointed to by uio.
*/

...;

if (!error && ncookies != NULL) {

struct dirent *dpStart;
struct dirent *dpEnd;
struct dirent *dp;
int count;
u_int *cookiebuf;
u_int *cookiep;

if (uio->uio_segflg != UIO_SYSSPACE

uio->uio_iovcnt != 1)

panic("vop_readdir: unexpected uio from NFS

server");

/*

* Parse the stuff just read into the uio.
*/

dpStart = (struct dirent *)

((char *)uio->uio_iov->iov_base - (uio->uio_off

set - off));

dpEnd = (struct dirent *) uio->uio_iov->iov_base;

/*

* Count number of entries.
*/

for (dp = dpStart, count = 0;

dp < dpEnd;
dp = (struct dirent *)((caddr_t) dp + dp->d_re

clen))

count++;

cookiebuf = (u_int *) malloc(count * sizeof(u_int),

M_TEMP, M_WAITOK);
for (dp = dpStart; cookiep = cookiebuf;

dp < dpEnd;
dp = (struct dirent *)((caddr_t) dp + dp->d_re

clen)) {

off += dp->d_reclen;
*cookiep++ = (u_int) off;

}
*ncookies = count;
*cookies = cookiebuf;

}

if (eofflag && uio->uio_offset is past the end of the

directory) {

*eofflag = TRUE;

}

return error;

}

ERRORS

[EINVAL] An attempt was made to read from an ille

gal offset in

the directory.

[EIO] A read error occurred while reading the

directory.

SEE ALSO

vnode(9)

AUTHORS

This manual page was written by Doug Rabson.

BSD July 24, 1996

BSD