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/*

 * Copyright (c) 1983 Regents of the University of California.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. All advertising materials mentioning features or use of this software

 *    must display the following acknowledgement:

 *      This product includes software developed by the University of

 *      California, Berkeley and its contributors.

 * 4. Neither the name of the University nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 */

#if defined(LIBC_SCCS) && !defined(lint)

static char sccsid[] = "@(#)telldir.c   5.9 (Berkeley) 2/23/91";

#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>

#include <dirent.h>

#include <stdlib.h>

#include <unistd.h>

/*

 * The option SINGLEUSE may be defined to say that a telldir

 * cookie may be used only once before it is freed. This option

 * is used to avoid having memory usage grow without bound.

 */

#define SINGLEUSE

/*

 * One of these structures is malloced to describe the current directory

 * position each time telldir is called. It records the current magic

 * cookie returned by getdirentries and the offset within the buffer

 * associated with that return value.

 */

struct ddloc {

        struct  ddloc *loc_next;/* next structure in list */

        long    loc_index;      /* key associated with structure */

        long    loc_seek;       /* magic cookie returned by getdirentries */

        long    loc_loc;        /* offset of entry in buffer */

};

#define NDIRHASH        32      /* Num of hash lists, must be a power of 2 */

#define LOCHASH(i)      ((i)&(NDIRHASH-1))

static long     dd_loccnt;      /* Index of entry for sequential readdir's */

static struct   ddloc *dd_hash[NDIRHASH];   /* Hash list heads for ddlocs */

/*

 * return a pointer into a directory

 */

long

telldir(dirp)

        const DIR *dirp;

{

        register int index;

        register struct ddloc *lp;

        if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL)

                return (-1);

        index = dd_loccnt++;

        lp->loc_index = index;

        lp->loc_seek = dirp->dd_seek;

        lp->loc_loc = dirp->dd_loc;

        lp->loc_next = dd_hash[LOCHASH(index)];

        dd_hash[LOCHASH(index)] = lp;

        return (index);

}

/*

 * seek to an entry in a directory.

 * Only values returned by "telldir" should be passed to seekdir.

 */

void

_seekdir(dirp, loc)

        register DIR *dirp;

        long loc;

{

        register struct ddloc *lp;

        register struct ddloc **prevlp;

        struct dirent *dp;

        extern long lseek();

        prevlp = &dd_hash[LOCHASH(loc)];

        lp = *prevlp;

        while (lp != NULL) {

                if (lp->loc_index == loc)

                        break;

                prevlp = &lp->loc_next;

                lp = lp->loc_next;

        }

        if (lp == NULL)

                return;

        if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek)

                goto found;

        (void) lseek(dirp->dd_fd, lp->loc_seek, 0);

        dirp->dd_seek = lp->loc_seek;

        dirp->dd_loc = 0;

        while (dirp->dd_loc < lp->loc_loc) {

                dp = readdir(dirp);

                if (dp == NULL)

                        break;

        }

found:

#ifdef SINGLEUSE

        *prevlp = lp->loc_next;

        free((caddr_t)lp);

#endif

}