DragonFly On-Line Manual Pages

VOP_READDIR(9)        DragonFly Kernel Developer's Manual       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*)#
                     kmalloc(*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 *) kmalloc(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 direc-
                        tory

     [EIO]              a read error occurred while reading the directory

SEE ALSO
     vnode(9)

AUTHORS
     This man page was written by Doug Rabson.

DragonFly 3.5                    July 24, 1996                   DragonFly 3.5