3 * Stäubli Faverges - <www.staubli.com>
4 * Pierre AUBERT p.aubert@staubli.com
6 * See file CREDITS for list of people who contributed to this
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License as
11 * published by the Free Software Foundation; either version 2 of
12 * the License, or (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
33 /*-----------------------------------------------------------------------------
35 *-----------------------------------------------------------------------------
37 unsigned int fat_decode (Fs_t *fs, unsigned int num)
39 unsigned int start = num * 3 / 2;
40 unsigned char *address = fs -> fat_buf + start;
42 if (num < 2 || start + 1 > (fs -> fat_len * SZ_STD_SECTOR))
46 return ((address [1] & 0xff) << 4) | ((address [0] & 0xf0 ) >> 4);
48 return ((address [1] & 0xf) << 8) | (address [0] & 0xff );
50 /*-----------------------------------------------------------------------------
52 *-----------------------------------------------------------------------------
54 static int check_fat (Fs_t *fs)
58 /* Cluster verification */
59 for (i = 3 ; i < fs -> num_clus; i++){
60 f = fat_decode (fs, i);
61 if (f < FAT12_LAST && f > fs -> num_clus){
62 /* Wrong cluster number detected */
68 /*-----------------------------------------------------------------------------
70 *-----------------------------------------------------------------------------
72 static int read_one_fat (BootSector_t *boot, Fs_t *fs, int nfat)
74 if (dev_read (fs -> fat_buf,
75 (fs -> fat_start + nfat * fs -> fat_len),
80 if (fs -> fat_buf [0] || fs -> fat_buf [1] || fs -> fat_buf [2]) {
81 if ((fs -> fat_buf [0] != boot -> descr &&
82 (fs -> fat_buf [0] != 0xf9 || boot -> descr != MEDIA_STD)) ||
83 fs -> fat_buf [0] < MEDIA_STD){
87 if (fs -> fat_buf [1] != 0xff || fs -> fat_buf [2] != 0xff){
88 /* FAT doesn't start with good values */
93 if (fs -> num_clus >= FAT12_MAX_NB) {
94 /* Too much clusters */
98 return check_fat (fs);
100 /*-----------------------------------------------------------------------------
102 *-----------------------------------------------------------------------------
104 int read_fat (BootSector_t *boot, Fs_t *fs)
109 /* Allocate Fat Buffer */
110 buflen = fs -> fat_len * SZ_STD_SECTOR;
112 free (fs -> fat_buf);
115 if ((fs -> fat_buf = malloc (buflen)) == NULL) {
119 /* Try to read each Fat */
120 for (i = 0; i< fs -> nb_fat; i++){
121 if (read_one_fat (boot, fs, i) == 0) {
128 if (i == fs -> nb_fat){
132 if (fs -> fat_len > (((fs -> num_clus + 2) *
133 (FAT_BITS / 4) -1 ) / 2 /
134 SZ_STD_SECTOR + 1)) {