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/* $OpenBSD: telldir.c,v 1.7 2005/08/08 08:05:34 espie Exp $ */
/*
* Copyright (c) 1983, 1993
* The 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. 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.
*/
#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 */
void __seekdir(DIR *, long);
/*
* return a pointer into a directory
*/
long
telldir(const DIR *dirp)
{
int index;
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(DIR *dirp, long loc)
{
struct ddloc *lp;
struct ddloc **prevlp;
struct dirent *dp;
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, (off_t)lp->loc_seek, SEEK_SET);
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
}
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