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-rw-r--r--fs/fdos/fat.c145
1 files changed, 145 insertions, 0 deletions
diff --git a/fs/fdos/fat.c b/fs/fdos/fat.c
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+++ b/fs/fdos/fat.c
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+/*
+ * (C) Copyright 2002
+ * Stubli Faverges - <www.staubli.com>
+ * Pierre AUBERT p.aubert@staubli.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <config.h>
+#include <malloc.h>
+
+#if (CONFIG_COMMANDS & CFG_CMD_FDOS)
+
+#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);
+}
+
+
+
+
+#endif
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