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363 lines
9.7 KiB
C
363 lines
9.7 KiB
C
/* fat.c - Read/write access to the FAT */
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/* Written 1993 by Werner Almesberger */
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/* FAT32, VFAT, Atari format support, and various fixes additions May 1998
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* by Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de> */
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#include "vfatlib.h"
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#define NDEBUG
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#include <debug.h>
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//#pragma warning(disable: 4018)
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static void get_fat(FAT_ENTRY *entry,void *fat,unsigned long cluster,DOS_FS *fs)
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{
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unsigned char *ptr;
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switch(fs->fat_bits) {
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case 12:
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ptr = &((unsigned char *) fat)[cluster*3/2];
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entry->value = 0xfff & (cluster & 1 ? (ptr[0] >> 4) | (ptr[1] << 4) :
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(ptr[0] | ptr[1] << 8));
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break;
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case 16:
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entry->value = CF_LE_W(((unsigned short *) fat)[cluster]);
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break;
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case 32:
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/* According to M$, the high 4 bits of a FAT32 entry are reserved and
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* are not part of the cluster number. So we cut them off. */
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{
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unsigned long e = CF_LE_L(((unsigned int *) fat)[cluster]);
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entry->value = e & 0xfffffff;
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entry->reserved = e >> 28;
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}
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break;
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default:
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die("Bad FAT entry size: %d bits.",fs->fat_bits);
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}
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entry->owner = NULL;
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}
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void read_fat(DOS_FS *fs)
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{
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int eff_size;
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unsigned long i;
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void *first,*second,*use;
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int first_ok,second_ok;
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eff_size = ((fs->clusters+2)*fs->fat_bits+7)/8;
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// TMN: Must round up to disk-sector boundary. For now, assume 512-byte disk.
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if (eff_size % 512) {
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eff_size += 512 - (eff_size % 512);
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}
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first = vfalloc(eff_size);
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fs_read(fs->fat_start,eff_size,first);
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use = first;
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if (fs->nfats > 1) {
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second = vfalloc(eff_size);
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fs_read(fs->fat_start+fs->fat_size,eff_size,second);
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}
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else
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second = NULL;
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if (second && memcmp(first,second,eff_size) != 0) {
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FAT_ENTRY first_media, second_media;
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memset (&first_media, 0, sizeof (first_media));
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memset (&second_media, 0, sizeof (second_media));
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get_fat(&first_media,first,0,fs);
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get_fat(&second_media,second,0,fs);
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first_ok = (first_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
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second_ok = (second_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
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if (first_ok && !second_ok) {
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VfatPrint("FATs differ - using first FAT.\n");
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fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
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}
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if (!first_ok && second_ok) {
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VfatPrint("FATs differ - using second FAT.\n");
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fs_write(fs->fat_start,eff_size,use = second);
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}
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if (first_ok && second_ok) {
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if (FsCheckFlags & FSCHECK_INTERACTIVE) {
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VfatPrint("FATs differ but appear to be intact. Use which FAT ?\n"
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"1) Use first FAT\n2) Use second FAT\n");
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if (get_key("12","?") == '1')
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fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
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else fs_write(fs->fat_start,eff_size,use = second);
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}
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else {
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VfatPrint("FATs differ but appear to be intact. Using first "
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"FAT.\n");
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fs_write(fs->fat_start+fs->fat_size,eff_size,use = first);
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}
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}
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if (!first_ok && !second_ok) {
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VfatPrint("Both FATs appear to be corrupt. Giving up.\n");
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//exit(1);
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}
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}
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fs->fat = qalloc(&FsCheckMemQueue,sizeof(FAT_ENTRY)*(fs->clusters+2));
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for (i = 2; i < fs->clusters+2; i++) get_fat(&fs->fat[i],use,i,fs);
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for (i = 2; i < fs->clusters+2; i++)
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if (fs->fat[i].value >= fs->clusters+2 &&
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(fs->fat[i].value < FAT_MIN_BAD(fs))) {
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VfatPrint("Cluster %ld out of range (%ld > %ld). Setting to EOF.\n",
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i-2,fs->fat[i].value,fs->clusters+2-1);
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set_fat(fs,i,-1);
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}
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vffree(first);
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if (second)
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vffree(second);
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}
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void set_fat(DOS_FS *fs,unsigned long cluster,unsigned long new)
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{
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unsigned char data[4];
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int size = 0;
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loff_t offs = 0LL;
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if ((long)new == -1)
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new = FAT_EOF(fs);
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else if ((long)new == -2)
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new = FAT_BAD(fs);
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switch( fs->fat_bits ) {
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case 12:
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offs = fs->fat_start+cluster*3/2;
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if (cluster & 1) {
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data[0] = ((new & 0xf) << 4) | (fs->fat[cluster-1].value >> 8);
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data[1] = new >> 4;
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}
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else {
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data[0] = new & 0xff;
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data[1] = (new >> 8) | (cluster == fs->clusters-1 ? 0 :
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(0xff & fs->fat[cluster+1].value) << 4);
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}
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size = 2;
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break;
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case 16:
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offs = fs->fat_start+cluster*2;
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*(unsigned short *) data = CT_LE_W(new);
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size = 2;
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break;
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case 32:
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offs = fs->fat_start+cluster*4;
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/* According to M$, the high 4 bits of a FAT32 entry are reserved and
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* are not part of the cluster number. So we never touch them. */
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*(unsigned long *) data = CT_LE_L( (new & 0xfffffff) |
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(fs->fat[cluster].reserved << 28) );
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size = 4;
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break;
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default:
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die("Bad FAT entry size: %d bits.",fs->fat_bits);
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}
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fs->fat[cluster].value = new;
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fs_write(offs,size,&data);
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fs_write(offs+fs->fat_size,size,&data);
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}
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int bad_cluster(DOS_FS *fs,unsigned long cluster)
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{
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return FAT_IS_BAD(fs,fs->fat[cluster].value);
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}
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unsigned long next_cluster(DOS_FS *fs,unsigned long cluster)
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{
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unsigned long value;
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value = fs->fat[cluster].value;
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if (FAT_IS_BAD(fs,value))
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die("Internal error: next_cluster on bad cluster");
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return FAT_IS_EOF(fs,value) ? -1 : value;
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}
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loff_t cluster_start(DOS_FS *fs,unsigned long cluster)
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{
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return fs->data_start+((loff_t)cluster-2)*fs->cluster_size;
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}
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void set_owner(DOS_FS *fs,unsigned long cluster,DOS_FILE *owner)
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{
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if (owner && fs->fat[cluster].owner)
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die("Internal error: attempt to change file owner");
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fs->fat[cluster].owner = owner;
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}
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DOS_FILE *get_owner(DOS_FS *fs,unsigned long cluster)
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{
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return fs->fat[cluster].owner;
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}
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void fix_bad(DOS_FS *fs)
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{
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unsigned long i;
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if (FsCheckFlags & FSCHECK_VERBOSE)
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VfatPrint("Checking for bad clusters.\n");
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for (i = 2; i < fs->clusters+2; i++)
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if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
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if (!fs_test(cluster_start(fs,i),fs->cluster_size)) {
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VfatPrint("Cluster %lu is unreadable.\n",i);
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set_fat(fs,i,-2);
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}
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}
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void reclaim_free(DOS_FS *fs)
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{
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int reclaimed;
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unsigned long i;
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if (FsCheckFlags & FSCHECK_VERBOSE)
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VfatPrint("Checking for unused clusters.\n");
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reclaimed = 0;
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for (i = 2; i < fs->clusters+2; i++)
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if (!get_owner(fs,i) && fs->fat[i].value &&
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!FAT_IS_BAD(fs,fs->fat[i].value)) {
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set_fat(fs,i,0);
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reclaimed++;
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}
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if (reclaimed)
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VfatPrint("Reclaimed %d unused cluster%s (%d bytes).\n",reclaimed,
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reclaimed == 1 ? "" : "s",reclaimed*fs->cluster_size);
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}
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static void tag_free(DOS_FS *fs,DOS_FILE *ptr)
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{
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DOS_FILE *owner;
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int prev;
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unsigned long i,walk;
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for (i = 2; i < fs->clusters+2; i++)
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if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
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!get_owner(fs,i) && !fs->fat[i].prev) {
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prev = 0;
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for (walk = i; walk > 0 && walk != -1;
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walk = next_cluster(fs,walk)) {
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if (!(owner = get_owner(fs,walk))) set_owner(fs,walk,ptr);
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else if (owner != ptr)
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die("Internal error: free chain collides with file");
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else {
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set_fat(fs,prev,-1);
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break;
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}
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prev = walk;
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}
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}
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}
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void reclaim_file(DOS_FS *fs)
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{
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DOS_FILE dummy;
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int reclaimed,files,changed;
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unsigned long i,next,walk;
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if (FsCheckFlags & FSCHECK_VERBOSE)
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VfatPrint("Reclaiming unconnected clusters.\n");
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for (i = 2; i < fs->clusters+2; i++) fs->fat[i].prev = 0;
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for (i = 2; i < fs->clusters+2; i++) {
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next = fs->fat[i].value;
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if (!get_owner(fs,i) && next && next < fs->clusters+2) {
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if (get_owner(fs,next) || !fs->fat[next].value ||
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FAT_IS_BAD(fs,fs->fat[next].value)) set_fat(fs,i,-1);
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else fs->fat[next].prev++;
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}
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}
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do {
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tag_free(fs,&dummy);
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changed = 0;
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for (i = 2; i < fs->clusters+2; i++)
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if (fs->fat[i].value && !FAT_IS_BAD(fs,fs->fat[i].value) &&
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!get_owner(fs, i)) {
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if (!fs->fat[fs->fat[i].value].prev--)
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die("Internal error: prev going below zero");
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set_fat(fs,i,-1);
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changed = 1;
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VfatPrint("Broke cycle at cluster %lu in free chain.\n",i);
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break;
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}
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}
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while (changed);
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files = reclaimed = 0;
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for (i = 2; i < fs->clusters+2; i++)
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if (get_owner(fs,i) == &dummy && !fs->fat[i].prev) {
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DIR_ENT de;
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loff_t offset;
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files++;
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offset = alloc_rootdir_entry(fs,&de,"FSCK%04dREC");
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de.start = CT_LE_W(i&0xffff);
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if (fs->fat_bits == 32)
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de.starthi = CT_LE_W(i>>16);
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for (walk = i; walk > 0 && walk != -1;
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walk = next_cluster(fs,walk)) {
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de.size = CT_LE_L(CF_LE_L(de.size)+fs->cluster_size);
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reclaimed++;
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}
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fs_write(offset,sizeof(DIR_ENT),&de);
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}
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if (reclaimed)
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VfatPrint("Reclaimed %d unused cluster%s (%d bytes) in %d chain%s.\n",
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reclaimed,reclaimed == 1 ? "" : "s",reclaimed*fs->cluster_size,files,
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files == 1 ? "" : "s");
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}
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unsigned long update_free(DOS_FS *fs)
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{
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unsigned long i;
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unsigned long free = 0;
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int do_set = 0;
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for (i = 2; i < fs->clusters+2; i++)
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if (!get_owner(fs,i) && !FAT_IS_BAD(fs,fs->fat[i].value))
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++free;
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if (!fs->fsinfo_start)
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return free;
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if (FsCheckFlags & FSCHECK_VERBOSE)
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VfatPrint("Checking free cluster summary.\n");
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if (fs->free_clusters >= 0) {
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if (free != fs->free_clusters) {
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VfatPrint( "Free cluster summary wrong (%ld vs. really %ld)\n",
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fs->free_clusters,free);
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if (FsCheckFlags & FSCHECK_INTERACTIVE)
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VfatPrint( "1) Correct\n2) Don't correct\n" );
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else VfatPrint( " Auto-correcting.\n" );
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if (!(FsCheckFlags & FSCHECK_INTERACTIVE) || get_key("12","?") == '1')
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do_set = 1;
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}
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}
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else {
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VfatPrint( "Free cluster summary uninitialized (should be %ld)\n", free );
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if (FsCheckFlags & FSCHECK_INTERACTIVE)
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VfatPrint( "1) Set it\n2) Leave it uninitialized\n" );
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else VfatPrint( " Auto-setting.\n" );
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if (!(FsCheckFlags & FSCHECK_INTERACTIVE) || get_key("12","?") == '1')
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do_set = 1;
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}
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if (do_set) {
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fs->free_clusters = free;
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free = CT_LE_L(free);
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fs_write(fs->fsinfo_start+offsetof(struct info_sector,free_clusters),
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sizeof(free),&free);
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}
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return free;
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}
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/* Local Variables: */
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/* tab-width: 8 */
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/* End: */
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