void read_fat(DOS_FS *fs)
{
int eff_size;
unsigned long i;
void *first,*second,*use;
int first_ok,second_ok;
eff_size = ((fs->clusters+2)*fs->fat_bits+7)/8;
first = alloc(eff_size);
second = alloc(eff_size);
fs_read(fs->fat_start,eff_size,first);
fs_read(fs->fat_start+fs->fat_size,eff_size,second);
use = first;
if (memcmp(first,second,eff_size) != 0) {
FAT_ENTRY first_media, second_media;
get_fat(&first_media,first,0,fs);
get_fat(&second_media,second,0,fs);
first_ok = (first_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
second_ok = (second_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
if (first_ok && !second_ok) {
printf("FATs differ - using first FAT.\n");
fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
}
if (!first_ok && second_ok) {
printf("FATs differ - using second FAT.\n");
fs_write(fs->fat_start,eff_size,use = second);
}
if (first_ok && second_ok) {
if (interactive) {
printf("FATs differ but appear to be intact. Use which FAT ?\n"
"1) Use first FAT\n2) Use second FAT\n");
if (get_key("12","?") == '1')
fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
else fs_write(fs->fat_start,eff_size,use = second);
}
else {
printf("FATs differ but appear to be intact. Using first "
"FAT.\n");
fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
}
}
if (!first_ok && !second_ok) {
printf("Both FATs appear to be corrupt. Giving up.\n");
exit(1);
}
}
fs->fat = qalloc(&mem_queue,sizeof(FAT_ENTRY)*(fs->clusters+2));
for (i = 2; i < fs->clusters+2; i++) get_fat(&fs->fat[i],use,i,fs);
for (i = 2; i < fs->clusters+2; i++)
if (fs->fat[i].value >= fs->clusters+2 &&
(fs->fat[i].value < FAT_MIN_BAD(fs))) {
printf("Cluster %ld out of range (%ld > %ld). Setting to EOF.\n",
i-2,fs->fat[i].value,fs->clusters+2-1);
set_fat(fs,i,-1);
}
free(first);
free(second);
}
/**
* Build a bookkeeping structure from the partition's FAT table.
* If the partition has multiple FATs and they don't agree, try to pick a winner,
* and queue a command to overwrite the loser.
* One error that is fixed here is a cluster that links to something out of range.
*
* @param[inout] fs Information about the filesystem
*/
void read_fat(DOS_FS * fs)
{
int eff_size;
unsigned long i;
void *first, *second = NULL;
int first_ok, second_ok;
unsigned long total_num_clusters;
/* Clean up from previous pass */
if (fs->fat)
free(fs->fat);
if (fs->cluster_owner)
free(fs->cluster_owner);
fs->fat = NULL;
fs->cluster_owner = NULL;
total_num_clusters = fs->clusters + 2UL;
eff_size = (total_num_clusters * fs->fat_bits + 7) / 8ULL;
first = alloc(eff_size);
fs_read(fs->fat_start, eff_size, first);
if (fs->nfats > 1) {
second = alloc(eff_size);
fs_read(fs->fat_start + fs->fat_size, eff_size, second);
}
if (second && memcmp(first, second, eff_size) != 0) {
FAT_ENTRY first_media, second_media;
get_fat(&first_media, first, 0, fs);
get_fat(&second_media, second, 0, fs);
first_ok = (first_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
second_ok = (second_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
if (first_ok && !second_ok) {
printf("FATs differ - using first FAT.\n");
fs_write(fs->fat_start + fs->fat_size, eff_size, first);
}
if (!first_ok && second_ok) {
printf("FATs differ - using second FAT.\n");
fs_write(fs->fat_start, eff_size, second);
memcpy(first, second, eff_size);
}
if (first_ok && second_ok) {
if (interactive) {
printf("FATs differ but appear to be intact. Use which FAT ?\n"
"1) Use first FAT\n2) Use second FAT\n");
if (get_key("12", "?") == '1') {
fs_write(fs->fat_start + fs->fat_size, eff_size, first);
} else {
fs_write(fs->fat_start, eff_size, second);
memcpy(first, second, eff_size);
}
} else {
printf("FATs differ but appear to be intact. Using first "
"FAT.\n");
fs_write(fs->fat_start + fs->fat_size, eff_size, first);
}
}
if (!first_ok && !second_ok) {
printf("Both FATs appear to be corrupt. Giving up.\n");
exit(1);
}
}
if (second) {
free(second);
}
fs->fat = (unsigned char *)first;
fs->cluster_owner = alloc(total_num_clusters * sizeof(DOS_FILE *));
memset(fs->cluster_owner, 0, (total_num_clusters * sizeof(DOS_FILE *)));
/* Truncate any cluster chains that link to something out of range */
for (i = 2; i < fs->clusters + 2; i++) {
FAT_ENTRY curEntry;
get_fat(&curEntry, fs->fat, i, fs);
if (curEntry.value == 1) {
printf("Cluster %ld out of range (1). Setting to EOF.\n", i - 2);
set_fat(fs, i, -1);
}
if (curEntry.value >= fs->clusters + 2 &&
(curEntry.value < FAT_MIN_BAD(fs))) {
printf("Cluster %ld out of range (%ld > %ld). Setting to EOF.\n",
i - 2, curEntry.value, fs->clusters + 2 - 1);
set_fat(fs, i, -1);
}
}
}
