reactos/lib/fslib/vfatlib/check/fat.c

   1 /* fat.c  -  Read/write access to the FAT */
   2
   3 /* Written 1993 by Werner Almesberger */
   4
   5 /* FAT32, VFAT, Atari format support, and various fixes additions May 1998
   6  * by Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de> */
   7
   8
   9 #include "vfatlib.h"
  10
  11 #define NDEBUG
  12 #include <debug.h>
  13
  14
  15 //#pragma warning(disable: 4018)
  16
  17 static void get_fat(FAT_ENTRY *entry,void *fat,unsigned long cluster,DOS_FS *fs)
  18 {
  19     unsigned char *ptr;
  20
  21     switch(fs->fat_bits) {
  22       case 12:
  23         ptr = &((unsigned char *) fat)[cluster*3/2];
  24         entry->value = 0xfff & (cluster & 1 ? (ptr[0] >> 4) | (ptr[1] << 4) :
  25           (ptr[0] | ptr[1] << 8));
  26         break;
  27       case 16:
  28         entry->value = CF_LE_W(((unsigned short *) fat)[cluster]);
  29         break;
  30       case 32:
  31         /* According to M$, the high 4 bits of a FAT32 entry are reserved and
  32          * are not part of the cluster number. So we cut them off. */
  33         {
  34             unsigned long e = CF_LE_L(((unsigned int *) fat)[cluster]);
  35             entry->value = e & 0xfffffff;
  36             entry->reserved = e >> 28;
  37         }
  38         break;
  39       default:
  40         die("Bad FAT entry size: %d bits.",fs->fat_bits);
  41     }
  42     entry->owner = NULL;
  43 }
  44
  45
  46 void read_fat(DOS_FS *fs)
  47 {
  48     int eff_size;
  49     unsigned long i;
  50     void *first,*second,*use;
  51     int first_ok,second_ok;
  52
  53     eff_size = ((fs->clusters+2)*fs->fat_bits+7)/8;
  54         // TMN: Must round up to disk-sector boundary. For now, assume 512-byte disk.
  55         if (eff_size % 512) {
  56                 eff_size += 512 - (eff_size % 512);
  57         }
  58     first = vfalloc(eff_size);
  59     fs_read(fs->fat_start,eff_size,first);
  60     use = first;
  61     if (fs->nfats > 1) {
  62         second = vfalloc(eff_size);
  63         fs_read(fs->fat_start+fs->fat_size,eff_size,second);
  64     }
  65     else
  66         second = NULL;
  67     if (second && memcmp(first,second,eff_size) != 0) {
  68         FAT_ENTRY first_media, second_media;
  69     memset (&first_media, 0, sizeof (first_media));
  70     memset (&second_media, 0, sizeof (second_media));
  71         get_fat(&first_media,first,0,fs);
  72         get_fat(&second_media,second,0,fs);
  73         first_ok = (first_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
  74         second_ok = (second_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
  75         if (first_ok && !second_ok) {
  76             VfatPrint("FATs differ - using first FAT.\n");
  77             fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
  78         }
  79         if (!first_ok && second_ok) {
  80             VfatPrint("FATs differ - using second FAT.\n");
  81             fs_write(fs->fat_start,eff_size,use = second);
  82         }
  83         if (first_ok && second_ok) {
  84             if (FsCheckFlags & FSCHECK_INTERACTIVE) {
  85                 VfatPrint("FATs differ but appear to be intact. Use which FAT ?\n"
  86                   "1) Use first FAT\n2) Use second FAT\n");
  87                 if (get_key("12","?") == '1')
  88                     fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
  89                 else fs_write(fs->fat_start,eff_size,use = second);
  90             }
  91             else {
  92                 VfatPrint("FATs differ but appear to be intact. Using first "
  93                   "FAT.\n");
  94                 fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
  95             }
  96         }
  97         if (!first_ok && !second_ok) {
  98             VfatPrint("Both FATs appear to be corrupt. Giving up.\n");
  99             //exit(1);
 100         }
 101     }
 102     fs->fat = qalloc(&FsCheckMemQueue,sizeof(FAT_ENTRY)*(fs->clusters+2));
 103     for (i = 2; i < fs->clusters+2; i++) get_fat(&fs->fat[i],use,i,fs);
 104     for (i = 2; i < fs->clusters+2; i++)
 105         if (fs->fat[i].value >= fs->clusters+2 &&
 106             (fs->fat[i].value < FAT_MIN_BAD(fs))) {
 107             VfatPrint("Cluster %ld out of range (%ld > %ld). Setting to EOF.\n",
 108                    i-2,fs->fat[i].value,fs->clusters+2-1);
 109             set_fat(fs,i,-1);
 110         }
 111     vffree(first);
 112     if (second)
 113         vffree(second);
 114 }
 115
 116
 117 void set_fat(DOS_FS *fs,unsigned long cluster,unsigned long new)
 118 {
 119     unsigned char data[4];
 120     int size = 0;
 121     loff_t offs = 0LL;
 122
 123     if ((long)new == -1)
 124         new = FAT_EOF(fs);
 125     else if ((long)new == -2)
 126         new = FAT_BAD(fs);
 127     switch( fs->fat_bits ) {
 128       case 12:
 129         offs = fs->fat_start+cluster*3/2;
 130         if (cluster & 1) {
 131             data[0] = ((new & 0xf) << 4) | (fs->fat[cluster-1].value >> 8);
 132             data[1] = new >> 4;
 133         }
 134         else {
 135             data[0] = new & 0xff;
 136             data[1] = (new >> 8) | (cluster == fs->clusters-1 ? 0 :
 137               (0xff & fs->fat[cluster+1].value) << 4);
 138         }
 139         size = 2;
 140         break;
 141       case 16:
 142         offs = fs->fat_start+cluster*2;
 143         *(unsigned short *) data = CT_LE_W(new);
 144         size = 2;
 145         break;
 146       case 32:
 147         offs = fs->fat_start+cluster*4;
 148         /* According to M$, the high 4 bits of a FAT32 entry are reserved and
 149          * are not part of the cluster number. So we never touch them. */
 150         *(unsigned long *) data = CT_LE_L( (new & 0xfffffff) |
 151                                            (fs->fat[cluster].reserved << 28) );
 152         size = 4;
 153         break;
 154       default:
 155         die("Bad FAT entry size: %d bits.",fs->fat_bits);
 156     }
 157     fs->fat[cluster].value = new;
 158     fs_write(offs,size,&data);
 159     fs_write(offs+fs->fat_size,size,&data);
 160 }
 161
 162
 163 int bad_cluster(DOS_FS *fs,unsigned long cluster)
 164 {
 165     return FAT_IS_BAD(fs,fs->fat[cluster].value);
 166 }
 167
 168
 169 unsigned long next_cluster(DOS_FS *fs,unsigned long cluster)
 170 {
 171     unsigned long value;
 172
 173     value = fs->fat[cluster].value;
 174     if (FAT_IS_BAD(fs,value))
 175         die("Internal error: next_cluster on bad cluster");
 176     return FAT_IS_EOF(fs,value) ? -1 : value;
 177 }
 178
 179
 180 loff_t cluster_start(DOS_FS *fs,unsigned long cluster)
 181 {
 182     return fs->data_start+((loff_t)cluster-2)*fs->cluster_size;
 183 }
 184
 185
 186 void set_owner(DOS_FS *fs,unsigned long cluster,DOS_FILE *owner)
 187 {
 188     if (owner && fs->fat[cluster].owner)
 189         die("Internal error: attempt to change file owner");
 190     fs->fat[cluster].owner = owner;
 191 }
 192
 193
 194 DOS_FILE *get_owner(DOS_FS *fs,unsigned long cluster)
 195 {
 196     return fs->fat[cluster].owner;
 197 }
 198
 199
 200 void fix_bad(DOS_FS *fs)
 201 {
 202     unsigned long i;
 203
 204     if (FsCheckFlags & FSCHECK_VERBOSE)
 205         VfatPrint("Checking for bad clusters.\n");
 206     for (i = 2; i < fs->clusters+2; i++)
 207         if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
 208             if (!fs_test(cluster_start(fs,i),fs->cluster_size)) {
 209                 VfatPrint("Cluster %lu is unreadable.\n",i);
 210                 set_fat(fs,i,-2);
 211             }
 212 }
 213
 214
 215 void reclaim_free(DOS_FS *fs)
 216 {
 217     int reclaimed;
 218     unsigned long i;
 219
 220     if (FsCheckFlags & FSCHECK_VERBOSE)
 221         VfatPrint("Checking for unused clusters.\n");
 222     reclaimed = 0;
 223     for (i = 2; i < fs->clusters+2; i++)
 224         if (!get_owner(fs,i) && fs->fat[i].value &&
 225             !FAT_IS_BAD(fs,fs->fat[i].value)) {
 226             set_fat(fs,i,0);
 227             reclaimed++;
 228         }
 229     if (reclaimed)
 230         VfatPrint("Reclaimed %d unused cluster%s (%d bytes).\n",reclaimed,
 231           reclaimed == 1 ?  "" : "s",reclaimed*fs->cluster_size);
 232 }
 233
 234
 235 static void tag_free(DOS_FS *fs,DOS_FILE *ptr)
 236 {
 237     DOS_FILE *owner;
 238     int prev;
 239     unsigned long i,walk;
 240
 241     for (i = 2; i < fs->clusters+2; i++)
 242         if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
 243             !get_owner(fs,i) && !fs->fat[i].prev) {
 244             prev = 0;
 245             for (walk = i; walk > 0 && walk != -1;
 246                  walk = next_cluster(fs,walk)) {
 247                 if (!(owner = get_owner(fs,walk))) set_owner(fs,walk,ptr);
 248                 else if (owner != ptr)
 249                         die("Internal error: free chain collides with file");
 250                     else {
 251                         set_fat(fs,prev,-1);
 252                         break;
 253                     }
 254                 prev = walk;
 255             }
 256         }
 257 }
 258
 259
 260 void reclaim_file(DOS_FS *fs)
 261 {
 262     DOS_FILE dummy;
 263     int reclaimed,files,changed;
 264     unsigned long i,next,walk;
 265
 266     if (FsCheckFlags & FSCHECK_VERBOSE)
 267         VfatPrint("Reclaiming unconnected clusters.\n");
 268     for (i = 2; i < fs->clusters+2; i++) fs->fat[i].prev = 0;
 269     for (i = 2; i < fs->clusters+2; i++) {
 270         next = fs->fat[i].value;
 271         if (!get_owner(fs,i) && next && next < fs->clusters+2) {
 272             if (get_owner(fs,next) || !fs->fat[next].value ||
 273                 FAT_IS_BAD(fs,fs->fat[next].value)) set_fat(fs,i,-1);
 274             else fs->fat[next].prev++;
 275         }
 276     }
 277     do {
 278         tag_free(fs,&dummy);
 279         changed = 0;
 280         for (i = 2; i < fs->clusters+2; i++)
 281             if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
 282                 !get_owner(fs, i)) {
 283                 if (!fs->fat[fs->fat[i].value].prev--)
 284                     die("Internal error: prev going below zero");
 285                 set_fat(fs,i,-1);
 286                 changed = 1;
 287                 VfatPrint("Broke cycle at cluster %lu in free chain.\n",i);
 288                 break;
 289             }
 290     }
 291     while (changed);
 292     files = reclaimed = 0;
 293     for (i = 2; i < fs->clusters+2; i++)
 294         if (get_owner(fs,i) == &dummy && !fs->fat[i].prev) {
 295             DIR_ENT de;
 296             loff_t offset;
 297             files++;
 298             offset = alloc_rootdir_entry(fs,&de,"FSCK%04dREC");
 299             de.start = CT_LE_W(i&0xffff);
 300             if (fs->fat_bits == 32)
 301                 de.starthi = CT_LE_W(i>>16);
 302             for (walk = i; walk > 0 && walk != -1;
 303                  walk = next_cluster(fs,walk)) {
 304                 de.size = CT_LE_L(CF_LE_L(de.size)+fs->cluster_size);
 305                 reclaimed++;
 306             }
 307             fs_write(offset,sizeof(DIR_ENT),&de);
 308         }
 309     if (reclaimed)
 310         VfatPrint("Reclaimed %d unused cluster%s (%d bytes) in %d chain%s.\n",
 311           reclaimed,reclaimed == 1 ? "" : "s",reclaimed*fs->cluster_size,files,
 312           files == 1 ? "" : "s");
 313 }
 314
 315
 316 unsigned long update_free(DOS_FS *fs)
 317 {
 318     unsigned long i;
 319     unsigned long free = 0;
 320     int do_set = 0;
 321
 322     for (i = 2; i < fs->clusters+2; i++)
 323         if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
 324             ++free;
 325
 326     if (!fs->fsinfo_start)
 327         return free;
 328
 329     if (FsCheckFlags & FSCHECK_VERBOSE)
 330         VfatPrint("Checking free cluster summary.\n");
 331     if (fs->free_clusters >= 0) {
 332         if (free != fs->free_clusters) {
 333             VfatPrint( "Free cluster summary wrong (%ld vs. really %ld)\n",
 334                     fs->free_clusters,free);
 335             if (FsCheckFlags & FSCHECK_INTERACTIVE)
 336                 VfatPrint( "1) Correct\n2) Don't correct\n" );
 337             else VfatPrint( "  Auto-correcting.\n" );
 338             if (!(FsCheckFlags & FSCHECK_INTERACTIVE) || get_key("12","?") == '1')
 339                 do_set = 1;
 340         }
 341     }
 342     else {
 343         VfatPrint( "Free cluster summary uninitialized (should be %ld)\n", free );
 344         if (FsCheckFlags & FSCHECK_INTERACTIVE)
 345             VfatPrint( "1) Set it\n2) Leave it uninitialized\n" );
 346         else VfatPrint( "  Auto-setting.\n" );
 347         if (!(FsCheckFlags & FSCHECK_INTERACTIVE) || get_key("12","?") == '1')
 348             do_set = 1;
 349     }
 350
 351     if (do_set) {
 352         fs->free_clusters = free;
 353         free = CT_LE_L(free);
 354         fs_write(fs->fsinfo_start+offsetof(struct info_sector,free_clusters),
 355                  sizeof(free),&free);
 356     }
 357
 358     return free;
 359 }
 360
 361 /* Local Variables: */
 362 /* tab-width: 8     */
 363 /* End:             */