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 structures. 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 returned.

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 generating 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 *)
    	    (uio->uio_iov->iov_base - (uio->uio_offset - 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_reclen))
    	    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_reclen)) {
    	    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]
    attempt to read from an illegal offset in the directory

[EIO]
    a read error occurred while reading the directory

SEE ALSO
vnode(9)

AUTHORS
This man page was written by Doug Rabson.