/* fat.c  -  Read/write access to the FAT *//* Written 1993 by Werner Almesberger *//* 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,*use;    int first_ok,second_ok;    eff_size = ((fs->clusters+2)*fs->fat_bits+7)/8;    first = alloc(eff_size);    fs_read(fs->fat_start,eff_size,first);    use = first;    if (fs->nfats > 1) {	second = alloc(eff_size);	fs_read(fs->fat_start+fs->fat_size,eff_size,second);    }    else	second = NULL;    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,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);    if (second)	free(second);}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)*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 (%d bytes).\n",reclaimed,	  reclaimed == 1 ?  "" : "s",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 (%d bytes) in %d chain%s.\n",	  reclaimed,reclaimed == 1 ? "" : "s",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:             */