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+/* fat.c - Read/write access to the FAT
+
+ Copyright (C) 1993 Werner Almesberger <werner.almesberger@lrc.di.epfl.ch>
+ Copyright (C) 1998 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
+
+ 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 3 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, see <http://www.gnu.org/licenses/>.
+
+ On Debian systems, the complete text of the GNU General Public License
+ can be found in /usr/share/common-licenses/GPL-3 file.
+*/
+
+/* FAT32, VFAT, Atari format support, and various fixes additions May 1998
+ * by Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de> */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "common.h"
+#include "dosfsck.h"
+#include "io.h"
+#include "check.h"
+#include "fat.h"
+
+
+static void get_fat(FAT_ENTRY *entry,void *fat,unsigned long cluster,DOS_FS *fs)
+{
+ unsigned char *ptr;
+
+ switch(fs->fat_bits) {
+ case 12:
+ ptr = &((unsigned char *) fat)[cluster*3/2];
+ entry->value = 0xfff & (cluster & 1 ? (ptr[0] >> 4) | (ptr[1] << 4) :
+ (ptr[0] | ptr[1] << 8));
+ break;
+ case 16:
+ entry->value = CF_LE_W(((unsigned short *) fat)[cluster]);
+ break;
+ case 32:
+ /* According to M$, the high 4 bits of a FAT32 entry are reserved and
+ * are not part of the cluster number. So we cut them off. */
+ {
+ unsigned long e = CF_LE_L(((unsigned int *) fat)[cluster]);
+ entry->value = e & 0xfffffff;
+ entry->reserved = e >> 28;
+ }
+ break;
+ default:
+ die("Bad FAT entry size: %d bits.",fs->fat_bits);
+ }
+ entry->owner = NULL;
+}
+
+
+void read_fat(DOS_FS *fs)
+{
+ int eff_size;
+ unsigned long i;
+ void *first,*second = NULL;
+ int first_ok,second_ok;
+
+ eff_size = ((fs->clusters+2ULL)*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 = qalloc(&mem_queue,sizeof(FAT_ENTRY)*(fs->clusters+2ULL));
+ for (i = 2; i < fs->clusters+2; i++) get_fat(&fs->fat[i],first,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);
+}
+
+
+void set_fat(DOS_FS *fs,unsigned long cluster,unsigned long new)
+{
+ unsigned char data[4];
+ int size;
+ loff_t offs;
+
+ if ((long)new == -1)
+ new = FAT_EOF(fs);
+ else if ((long)new == -2)
+ new = FAT_BAD(fs);
+ switch( fs->fat_bits ) {
+ case 12:
+ offs = fs->fat_start+cluster*3/2;
+ if (cluster & 1) {
+ data[0] = ((new & 0xf) << 4) | (fs->fat[cluster-1].value >> 8);
+ data[1] = new >> 4;
+ }
+ else {
+ data[0] = new & 0xff;
+ data[1] = (new >> 8) | (cluster == fs->clusters-1 ? 0 :
+ (0xff & fs->fat[cluster+1].value) << 4);
+ }
+ size = 2;
+ break;
+ case 16:
+ offs = fs->fat_start+cluster*2;
+ *(unsigned short *) data = CT_LE_W(new);
+ size = 2;
+ break;
+ case 32:
+ offs = fs->fat_start+cluster*4;
+ /* According to M$, the high 4 bits of a FAT32 entry are reserved and
+ * are not part of the cluster number. So we never touch them. */
+ *(unsigned long *) data = CT_LE_L( (new & 0xfffffff) |
+ (fs->fat[cluster].reserved << 28) );
+ size = 4;
+ break;
+ default:
+ die("Bad FAT entry size: %d bits.",fs->fat_bits);
+ }
+ fs->fat[cluster].value = new;
+ fs_write(offs,size,&data);
+ fs_write(offs+fs->fat_size,size,&data);
+}
+
+
+int bad_cluster(DOS_FS *fs,unsigned long cluster)
+{
+ return FAT_IS_BAD(fs,fs->fat[cluster].value);
+}
+
+
+unsigned long next_cluster(DOS_FS *fs,unsigned long cluster)
+{
+ unsigned long value;
+
+ value = fs->fat[cluster].value;
+ if (FAT_IS_BAD(fs,value))
+ die("Internal error: next_cluster on bad cluster");
+ return FAT_IS_EOF(fs,value) ? -1 : value;
+}
+
+
+loff_t cluster_start(DOS_FS *fs,unsigned long cluster)
+{
+ return fs->data_start+((loff_t)cluster-2)*(unsigned long long)fs->cluster_size;
+}
+
+
+void set_owner(DOS_FS *fs,unsigned long cluster,DOS_FILE *owner)
+{
+ if (owner && fs->fat[cluster].owner)
+ die("Internal error: attempt to change file owner");
+ fs->fat[cluster].owner = owner;
+}
+
+
+DOS_FILE *get_owner(DOS_FS *fs,unsigned long cluster)
+{
+ return fs->fat[cluster].owner;
+}
+
+
+void fix_bad(DOS_FS *fs)
+{
+ unsigned long i;
+
+ if (verbose)
+ printf("Checking for bad clusters.\n");
+ for (i = 2; i < fs->clusters+2; i++)
+ if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
+ if (!fs_test(cluster_start(fs,i),fs->cluster_size)) {
+ printf("Cluster %lu is unreadable.\n",i);
+ set_fat(fs,i,-2);
+ }
+}
+
+
+void reclaim_free(DOS_FS *fs)
+{
+ int reclaimed;
+ unsigned long i;
+
+ if (verbose)
+ printf("Checking for unused clusters.\n");
+ reclaimed = 0;
+ for (i = 2; i < fs->clusters+2; i++)
+ if (!get_owner(fs,i) && fs->fat[i].value &&
+ !FAT_IS_BAD(fs,fs->fat[i].value)) {
+ set_fat(fs,i,0);
+ reclaimed++;
+ }
+ if (reclaimed)
+ printf("Reclaimed %d unused cluster%s (%llu bytes).\n",reclaimed,
+ reclaimed == 1 ? "" : "s",(unsigned long long)reclaimed*fs->cluster_size);
+}
+
+
+static void tag_free(DOS_FS *fs,DOS_FILE *ptr)
+{
+ DOS_FILE *owner;
+ int prev;
+ unsigned long i,walk;
+
+ for (i = 2; i < fs->clusters+2; i++)
+ if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
+ !get_owner(fs,i) && !fs->fat[i].prev) {
+ prev = 0;
+ for (walk = i; walk > 0 && walk != -1;
+ walk = next_cluster(fs,walk)) {
+ if (!(owner = get_owner(fs,walk))) set_owner(fs,walk,ptr);
+ else if (owner != ptr)
+ die("Internal error: free chain collides with file");
+ else {
+ set_fat(fs,prev,-1);
+ break;
+ }
+ prev = walk;
+ }
+ }
+}
+
+
+void reclaim_file(DOS_FS *fs)
+{
+ DOS_FILE dummy;
+ int reclaimed,files,changed;
+ unsigned long i,next,walk;
+
+ if (verbose)
+ printf("Reclaiming unconnected clusters.\n");
+ for (i = 2; i < fs->clusters+2; i++) fs->fat[i].prev = 0;
+ for (i = 2; i < fs->clusters+2; i++) {
+ next = fs->fat[i].value;
+ if (!get_owner(fs,i) && next && next < fs->clusters+2) {
+ if (get_owner(fs,next) || !fs->fat[next].value ||
+ FAT_IS_BAD(fs,fs->fat[next].value)) set_fat(fs,i,-1);
+ else fs->fat[next].prev++;
+ }
+ }
+ do {
+ tag_free(fs,&dummy);
+ changed = 0;
+ for (i = 2; i < fs->clusters+2; i++)
+ if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
+ !get_owner(fs, i)) {
+ if (!fs->fat[fs->fat[i].value].prev--)
+ die("Internal error: prev going below zero");
+ set_fat(fs,i,-1);
+ changed = 1;
+ printf("Broke cycle at cluster %lu in free chain.\n",i);
+ break;
+ }
+ }
+ while (changed);
+ files = reclaimed = 0;
+ for (i = 2; i < fs->clusters+2; i++)
+ if (get_owner(fs,i) == &dummy && !fs->fat[i].prev) {
+ DIR_ENT de;
+ loff_t offset;
+ files++;
+ offset = alloc_rootdir_entry(fs,&de,"FSCK%04dREC");
+ de.start = CT_LE_W(i&0xffff);
+ if (fs->fat_bits == 32)
+ de.starthi = CT_LE_W(i>>16);
+ for (walk = i; walk > 0 && walk != -1;
+ walk = next_cluster(fs,walk)) {
+ de.size = CT_LE_L(CF_LE_L(de.size)+fs->cluster_size);
+ reclaimed++;
+ }
+ fs_write(offset,sizeof(DIR_ENT),&de);
+ }
+ if (reclaimed)
+ printf("Reclaimed %d unused cluster%s (%llu bytes) in %d chain%s.\n",
+ reclaimed,reclaimed == 1 ? "" : "s",(unsigned long long)reclaimed*fs->cluster_size,files,
+ files == 1 ? "" : "s");
+}
+
+
+unsigned long update_free(DOS_FS *fs)
+{
+ unsigned long i;
+ unsigned long free = 0;
+ int do_set = 0;
+
+ for (i = 2; i < fs->clusters+2; i++)
+ if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
+ ++free;
+
+ if (!fs->fsinfo_start)
+ return free;
+
+ if (verbose)
+ printf("Checking free cluster summary.\n");
+ if (fs->free_clusters >= 0) {
+ if (free != fs->free_clusters) {
+ printf( "Free cluster summary wrong (%ld vs. really %ld)\n",
+ fs->free_clusters,free);
+ if (interactive)
+ printf( "1) Correct\n2) Don't correct\n" );
+ else printf( " Auto-correcting.\n" );
+ if (!interactive || get_key("12","?") == '1')
+ do_set = 1;
+ }
+ }
+ else {
+ printf( "Free cluster summary uninitialized (should be %ld)\n", free );
+ if (interactive)
+ printf( "1) Set it\n2) Leave it uninitialized\n" );
+ else printf( " Auto-setting.\n" );
+ if (!interactive || get_key("12","?") == '1')
+ do_set = 1;
+ }
+
+ if (do_set) {
+ fs->free_clusters = free;
+ free = CT_LE_L(free);
+ fs_write(fs->fsinfo_start+offsetof(struct info_sector,free_clusters),
+ sizeof(free),&free);
+ }
+
+ return free;
+}
+
+/* Local Variables: */
+/* tab-width: 8 */
+/* End: */
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