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/* Copyright (C) 1994, 1995, 1996, 1997, 1999 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <stddef.h>
#include <dirent.h>
#include <unistd.h>
#include <sys/types.h>
#include <stdlib.h>
#include "dirstream.h"
/* Internal data structure for telldir and seekdir. */
struct record
{
struct record *next; /* Link in chain. */
off_t cookie; /* Value returned by `telldir'. */
off_t pos;
size_t offset;
};
#define NBUCKETS 32
static struct record *records[32];
static off_t lastpos;
__libc_lock_define_initialized(static, lock) /* Locks above data. */
/* Return the current position of DIRP. */
long int
telldir (dirp)
DIR *dirp;
{
struct record *new;
long int pos;
new = malloc (sizeof *new);
if (new == NULL)
return -1l;
__libc_lock_lock (lock);
new->pos = dirp->filepos;
new->offset = dirp->offset;
new->cookie = ++lastpos;
new->next = records[new->cookie % NBUCKETS];
records[new->cookie % NBUCKETS] = new;
pos = new->cookie;
__libc_lock_unlock (lock);
return pos;
}
/* Seek to position POS in DIRP. */
void
seekdir (dirp, pos)
DIR *dirp;
long int pos;
{
struct record *r, **prevr;
__libc_lock_lock (lock);
for (prevr = &records[pos % NBUCKETS], r = *prevr;
r != NULL;
prevr = &r->next, r = r->next)
if (r->cookie == pos)
{
__libc_lock_lock (dirp->__lock);
if (dirp->filepos != r->pos || dirp->offset != r->offset)
{
dirp->size = 0; /* Must read a fresh buffer. */
/* Move to the saved position. */
__lseek (dirp->fd, r->pos, SEEK_SET);
dirp->filepos = r->pos;
dirp->offset = 0;
/* Read entries until we reach the saved offset. */
while (dirp->offset < r->offset)
{
struct dirent *scan;
__libc_lock_unlock (dirp->__lock);
scan = readdir (dirp);
__libc_lock_lock (dirp->__lock);
if (! scan)
break;
}
}
__libc_lock_unlock (dirp->__lock);
/* To prevent leaking memory, cookies returned from telldir
can only be used once. So free this one's record now. */
*prevr = r->next;
free (r);
break;
}
__libc_lock_unlock (lock);
/* If we lost there is no way to indicate it. Oh well. */
}
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