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/*
* (C) Copyright 2002
* Stäubli Faverges - <www.staubli.com>
* Pierre AUBERT p.aubert@staubli.com
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <common.h>
#include <config.h>
#include <malloc.h>
#include "dos.h"
#include "fdos.h"
/*-----------------------------------------------------------------------------
* fat_decode --
*-----------------------------------------------------------------------------
*/
unsigned int fat_decode (Fs_t *fs, unsigned int num)
{
unsigned int start = num * 3 / 2;
unsigned char *address = fs -> fat_buf + start;
if (num < 2 || start + 1 > (fs -> fat_len * SZ_STD_SECTOR))
return 1;
if (num & 1)
return ((address [1] & 0xff) << 4) | ((address [0] & 0xf0 ) >> 4);
else
return ((address [1] & 0xf) << 8) | (address [0] & 0xff );
}
/*-----------------------------------------------------------------------------
* check_fat --
*-----------------------------------------------------------------------------
*/
static int check_fat (Fs_t *fs)
{
int i, f;
/* Cluster verification */
for (i = 3 ; i < fs -> num_clus; i++){
f = fat_decode (fs, i);
if (f < FAT12_LAST && f > fs -> num_clus){
/* Wrong cluster number detected */
return (-1);
}
}
return (0);
}
/*-----------------------------------------------------------------------------
* read_one_fat --
*-----------------------------------------------------------------------------
*/
static int read_one_fat (BootSector_t *boot, Fs_t *fs, int nfat)
{
if (dev_read (fs -> fat_buf,
(fs -> fat_start + nfat * fs -> fat_len),
fs -> fat_len) < 0) {
return (-1);
}
if (fs -> fat_buf [0] || fs -> fat_buf [1] || fs -> fat_buf [2]) {
if ((fs -> fat_buf [0] != boot -> descr &&
(fs -> fat_buf [0] != 0xf9 || boot -> descr != MEDIA_STD)) ||
fs -> fat_buf [0] < MEDIA_STD){
/* Unknown Media */
return (-1);
}
if (fs -> fat_buf [1] != 0xff || fs -> fat_buf [2] != 0xff){
/* FAT doesn't start with good values */
return (-1);
}
}
if (fs -> num_clus >= FAT12_MAX_NB) {
/* Too much clusters */
return (-1);
}
return check_fat (fs);
}
/*-----------------------------------------------------------------------------
* read_fat --
*-----------------------------------------------------------------------------
*/
int read_fat (BootSector_t *boot, Fs_t *fs)
{
unsigned int buflen;
int i;
/* Allocate Fat Buffer */
buflen = fs -> fat_len * SZ_STD_SECTOR;
if (fs -> fat_buf) {
free (fs -> fat_buf);
}
if ((fs -> fat_buf = malloc (buflen)) == NULL) {
return (-1);
}
/* Try to read each Fat */
for (i = 0; i< fs -> nb_fat; i++){
if (read_one_fat (boot, fs, i) == 0) {
/* Fat is OK */
fs -> num_fat = i;
break;
}
}
if (i == fs -> nb_fat){
return (-1);
}
if (fs -> fat_len > (((fs -> num_clus + 2) *
(FAT_BITS / 4) -1 ) / 2 /
SZ_STD_SECTOR + 1)) {
return (-1);
}
return (0);
}
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