143 lines
4.1 KiB
C
143 lines
4.1 KiB
C
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/*
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* (C) Copyright 2002
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* St<EFBFBD>ubli Faverges - <www.staubli.com>
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* Pierre AUBERT p.aubert@staubli.com
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*/
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#include <common.h>
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#include <config.h>
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#include <malloc.h>
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#if (CONFIG_COMMANDS & CFG_CMD_FDOS)
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#include "dos.h"
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#include "fdos.h"
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/*-----------------------------------------------------------------------------
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* fat_decode --
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*-----------------------------------------------------------------------------
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*/
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unsigned int fat_decode (Fs_t *fs, unsigned int num)
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{
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unsigned int start = num * 3 / 2;
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unsigned char *address = fs -> fat_buf + start;
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if (num < 2 || start + 1 > (fs -> fat_len * SZ_STD_SECTOR))
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return 1;
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if (num & 1)
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return ((address [1] & 0xff) << 4) | ((address [0] & 0xf0 ) >> 4);
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else
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return ((address [1] & 0xf) << 8) | (address [0] & 0xff );
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}
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/*-----------------------------------------------------------------------------
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* check_fat --
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*-----------------------------------------------------------------------------
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*/
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static int check_fat (Fs_t *fs)
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{
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int i, f;
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/* Cluster verification */
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for (i = 3 ; i < fs -> num_clus; i++){
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f = fat_decode (fs, i);
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if (f < FAT12_LAST && f > fs -> num_clus){
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/* Wrong cluster number detected */
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return (-1);
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}
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}
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return (0);
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}
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/*-----------------------------------------------------------------------------
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* read_one_fat --
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*-----------------------------------------------------------------------------
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*/
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static int read_one_fat (BootSector_t *boot, Fs_t *fs, int nfat)
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{
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if (dev_read (fs -> fat_buf,
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(fs -> fat_start + nfat * fs -> fat_len),
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fs -> fat_len) < 0) {
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return (-1);
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}
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if (fs -> fat_buf [0] || fs -> fat_buf [1] || fs -> fat_buf [2]) {
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if ((fs -> fat_buf [0] != boot -> descr &&
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(fs -> fat_buf [0] != 0xf9 || boot -> descr != MEDIA_STD)) ||
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fs -> fat_buf [0] < MEDIA_STD){
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/* Unknown Media */
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return (-1);
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}
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if (fs -> fat_buf [1] != 0xff || fs -> fat_buf [2] != 0xff){
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/* FAT doesn't start with good values */
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return (-1);
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}
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}
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if (fs -> num_clus >= FAT12_MAX_NB) {
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/* Too much clusters */
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return (-1);
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}
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return check_fat (fs);
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}
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/*-----------------------------------------------------------------------------
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* read_fat --
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*-----------------------------------------------------------------------------
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*/
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int read_fat (BootSector_t *boot, Fs_t *fs)
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{
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unsigned int buflen;
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int i;
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/* Allocate Fat Buffer */
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buflen = fs -> fat_len * SZ_STD_SECTOR;
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if (fs -> fat_buf) {
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free (fs -> fat_buf);
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}
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if ((fs -> fat_buf = malloc (buflen)) == NULL) {
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return (-1);
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}
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/* Try to read each Fat */
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for (i = 0; i< fs -> nb_fat; i++){
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if (read_one_fat (boot, fs, i) == 0) {
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/* Fat is OK */
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fs -> num_fat = i;
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break;
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}
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}
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if (i == fs -> nb_fat){
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return (-1);
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}
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if (fs -> fat_len > (((fs -> num_clus + 2) *
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(FAT_BITS / 4) -1 ) / 2 /
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SZ_STD_SECTOR + 1)) {
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return (-1);
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}
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return (0);
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}
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#endif
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