xref: /aosp_15_r20/external/mtools/fat.c (revision d5c9a868b113e0ec0db2f27bc2ce8a253e77c4b0)

/*  Copyright 1996-2006,2008,2009 Alain Knaff.
 *  This file is part of mtools.
 *
 *  Mtools 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.
 *
 *  Mtools 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 Mtools.  If not, see <http://www.gnu.org/licenses/>.
 */


#include "sysincludes.h"
#include "msdos.h"
#include "stream.h"
#include "mtools.h"
#include "fsP.h"
#include "file_name.h"

#ifdef HAVE_LONG_LONG
typedef long long fatBitMask;
#else
typedef long fatBitMask;
#endif

typedef struct FatMap_t {
	unsigned char *data;
	fatBitMask dirty;
	fatBitMask valid;
} FatMap_t;

#define SECT_PER_ENTRY (sizeof(fatBitMask)*8)
#define ONE ((fatBitMask) 1)

static __inline__ ssize_t readSector(Fs_t *This, char *buf, unsigned int off,
				     size_t size)
{
	return PREADS(This->head.Next, buf, sectorsToBytes(This, off),
		      size << This->sectorShift);
}


static __inline__ ssize_t forceReadSector(Fs_t *This, char *buf,
					  unsigned int off, size_t size)
{
	return force_pread(This->head.Next, buf, sectorsToBytes(This, off),
			   size << This->sectorShift);
}


static __inline__ ssize_t forceWriteSector(Fs_t *This, char *buf, unsigned int off,
					   size_t size)
{
	return force_pwrite(This->head.Next, buf, sectorsToBytes(This, off),
			    size << This->sectorShift);
}


static FatMap_t *GetFatMap(Fs_t *Stream)
{
	size_t nr_entries;
	size_t i;
	FatMap_t *map;

	Stream->fat_error = 0;
	nr_entries = (Stream->fat_len + SECT_PER_ENTRY - 1) / SECT_PER_ENTRY;
	map = NewArray(nr_entries, FatMap_t);
	if(!map)
		return 0;

	for(i=0; i< nr_entries; i++) {
		map[i].data = 0;
		map[i].valid = 0;
		map[i].dirty = 0;
	}

	return map;
}

static __inline__ int locate(Fs_t *Stream, uint32_t offset,
			     uint32_t *slot, uint32_t *bit)
{
	if(offset >= Stream->fat_len)
		return -1;
	*slot = offset / SECT_PER_ENTRY;
	*bit = offset % SECT_PER_ENTRY;
	return 0;
}

static __inline__ ssize_t fatReadSector(Fs_t *This,
					unsigned int sector,
					unsigned int slot,
					unsigned int bit, unsigned int dupe,
					fatBitMask bitmap)
{
	unsigned int fat_start;
	ssize_t ret;
	unsigned int nr_sectors;

	dupe = (dupe + This->primaryFat) % This->num_fat;
	fat_start = This->fat_start + This->fat_len * dupe;

	if(bitmap == 0) {
	    nr_sectors = SECT_PER_ENTRY - bit%SECT_PER_ENTRY;
	} else {
	    nr_sectors = 1;
	}

	/* first, read as much as the buffer can give us */
	ret = readSector(This,
			 (char *)(This->FatMap[slot].data+(bit<<This->sectorShift)),
			 fat_start+sector,
			 nr_sectors);
	if(ret < 0)
		return 0;

	if((size_t) ret < This->sector_size) {
		/* if we got less than one sector's worth, insist to get at
		 * least one sector */
		ret = forceReadSector(This,
				      (char *) (This->FatMap[slot].data +
						(bit << This->sectorShift)),
				      fat_start+sector, 1);
		if(ret < (int) This->sector_size)
			return 0;
		return 1;
	}

	return ret >> This->sectorShift;
}


static ssize_t fatWriteSector(Fs_t *This,
			      unsigned int sector,
			      unsigned int slot,
			      unsigned int bit,
			      unsigned int dupe)
{
	unsigned int fat_start;

	dupe = (dupe + This->primaryFat) % This->num_fat;
	if(dupe && !This->writeAllFats)
		return This->sector_size;

	fat_start = This->fat_start + This->fat_len * dupe;

	return forceWriteSector(This,
				(char *)
				(This->FatMap[slot].data + bit * This->sector_size),
				fat_start+sector, 1);
}

static unsigned char *loadSector(Fs_t *This,
				 unsigned int sector, fatAccessMode_t mode,
				 int recurs)
{
	uint32_t slot, bit;
	ssize_t ret;

	if(locate(This,sector, &slot, &bit) < 0)
		return 0;
#if 0
        if (((This->fat_len + SECT_PER_ENTRY - 1) / SECT_PER_ENTRY) <= slot) {
		fprintf(stderr,"This should not happen\n");
		fprintf(stderr, "fat_len = %d\n", This->fat_len);
		fprintf(stderr, "SECT_PER_ENTRY=%d\n", (int)SECT_PER_ENTRY);
		fprintf(stderr, "sector = %d slot = %d bit=%d\n",
			sector, slot, bit);
		fprintf(stderr, "left = %d",(int)
			((This->fat_len+SECT_PER_ENTRY-1) / SECT_PER_ENTRY));
                return 0;
	}
#endif
	if(!This->FatMap[slot].data) {
		/* allocate the storage space */
		This->FatMap[slot].data =
			malloc(This->sector_size * SECT_PER_ENTRY);
		if(!This->FatMap[slot].data)
			return 0;
		memset(This->FatMap[slot].data, 0xee,
		       This->sector_size * SECT_PER_ENTRY);
	}

	if(! (This->FatMap[slot].valid & (ONE << bit))) {
		unsigned int i;
		ret = -1;
		for(i=0; i< This->num_fat; i++) {
			/* read the sector */
			ret = fatReadSector(This, sector, slot, bit, i,
					    This->FatMap[slot].valid);

			if(ret == 0) {
				fprintf(stderr,
					"Error reading fat number %d\n", i);
				continue;
			}
			if(This->FatMap[slot].valid)
			    /* Set recurs if there have already been
			     * sectors loaded in this bitmap long
			     */
			    recurs = 1;
			break;
		}

		/* all copies bad.  Return error */
		if(ret == 0)
			return 0;

		for(i=0; (int) i < ret; i++)
			This->FatMap[slot].valid |= ONE << (bit + i);

		if(!recurs && ret == 1)
			/* do some prefetching, if we happened to only
			 * get one sector */
			loadSector(This, sector+1, mode, 1);
		if(!recurs && batchmode)
			for(i=0; i < 1024; i++)
				loadSector(This, sector+i, mode, 1);
	}

	if(mode == FAT_ACCESS_WRITE) {
		This->FatMap[slot].dirty |= ONE << bit;
		This->fat_dirty = 1;
	}
	return This->FatMap[slot].data + (bit << This->sectorShift);
}


static unsigned char *getAddress(Fs_t *Stream,
				 unsigned int num, fatAccessMode_t mode)
{
	unsigned char *ret;
	unsigned int sector;
	unsigned int offset;

	sector = num >> Stream->sectorShift;
	ret = 0;
	if(sector == Stream->lastFatSectorNr &&
	   Stream->lastFatAccessMode >= mode)
		ret = Stream->lastFatSectorData;
	if(!ret) {
		ret = loadSector(Stream, sector, mode, 0);
		if(!ret)
			return 0;
		Stream->lastFatSectorNr = sector;
		Stream->lastFatSectorData = ret;
		Stream->lastFatAccessMode = mode;
	}
	offset = num & Stream->sectorMask;
	return ret+offset;
}


static int readByte(Fs_t *Stream, unsigned int start)
{
	unsigned char *address;

	address = getAddress(Stream, start, FAT_ACCESS_READ);
	if(!address)
		return -1;
	return *address;
}


/*
 * Fat 12 encoding:
 *	|    byte n     |   byte n+1    |   byte n+2    |
 *	|7|6|5|4|3|2|1|0|7|6|5|4|3|2|1|0|7|6|5|4|3|2|1|0|
 *	| | | | | | | | | | | | | | | | | | | | | | | | |
 *	| n+0.0 | n+0.5 | n+1.0 | n+1.5 | n+2.0 | n+2.5 |
 *	    \_____  \____   \______/________/_____   /
 *	      ____\______\________/   _____/  ____\_/
 *	     /     \      \          /       /     \
 *	| n+1.5 | n+0.0 | n+0.5 | n+2.0 | n+2.5 | n+1.0 |
 *	|      FAT entry k      |    FAT entry k+1      |
 */

 /*
 * Get and decode a FAT (file allocation table) entry.  Returns the cluster
 * number on success or 1 on failure.
 */

static unsigned int fat12_decode(Fs_t *Stream, unsigned int num)
{
	unsigned int start = num * 3 / 2;
	int byte0 = readByte(Stream, start);
	int byte1 = readByte(Stream, start+1);

	if (num < 2 || byte0 < 0 || byte1 < 0 || num > Stream->num_clus+1) {
		fprintf(stderr,"[1] Bad address %d\n", num);
		return 1;
	}

	if (num & 1)
		return ((uint32_t)byte1 << 4) | (((uint32_t)byte0 & 0xf0)>>4);
	else
		return (((uint32_t)byte1 & 0xf) << 8) | (uint32_t)byte0;
}


/*
 * Puts a code into the FAT table.  Is the opposite of fat_decode().  No
 * sanity checking is done on the code.  Returns a 1 on error.
 */
static void fat12_encode(Fs_t *Stream, unsigned int num, unsigned int code)
{
	unsigned int start = num * 3 / 2;
	unsigned char *address0 = getAddress(Stream, start, FAT_ACCESS_WRITE);
	unsigned char *address1 = getAddress(Stream, start+1, FAT_ACCESS_WRITE);

	if (num & 1) {
		/* (odd) not on byte boundary */
		*address0 = (*address0 & 0x0f) | ((code << 4) & 0xf0);
		*address1 = (code >> 4) & 0xff;
	} else {
		/* (even) on byte boundary */
		*address0 = code & 0xff;
		*address1 = (*address1 & 0xf0) | ((code >> 8) & 0x0f);
	}
}


/*
 * Fat 16 encoding:
 *	|    byte n     |   byte n+1    |
 *	|7|6|5|4|3|2|1|0|7|6|5|4|3|2|1|0|
 *	| | | | | | | | | | | | | | | | |
 *	|         FAT entry k           |
 */

static unsigned int fat16_decode(Fs_t *Stream, unsigned int num)
{
	unsigned char *address = getAddress(Stream, num << 1, FAT_ACCESS_READ);
	if(!address)
		return 1;
	return _WORD(address);
}

static void fat16_encode(Fs_t *Stream, unsigned int num, unsigned int code)
{
	if(code > UINT16_MAX) {
		fprintf(stderr, "FAT16 code %x too big\n", code);
		exit(1);
	}
	unsigned char *address = getAddress(Stream, num << 1, FAT_ACCESS_WRITE);
	set_word(address, (uint16_t) code);
}


#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
/* Ignore alignment warnings about casting to type with higher
 * alignment requirement. Requirement is met, as initial pointer is an
 * even offset into a buffer allocated by malloc, which according to
 * manpage is "suitably aligned for any built-in type */
static unsigned int fast_fat16_decode(Fs_t *Stream, unsigned int num)
{
	unsigned short *address =
		(unsigned short *) getAddress(Stream, num << 1,
					      FAT_ACCESS_READ);
	if(!address)
		return 1;
	return *address;
}

static void fast_fat16_encode(Fs_t *Stream, unsigned int num, unsigned int code)
{
	unsigned short *address =
		(unsigned short *) getAddress(Stream, num << 1,
					      FAT_ACCESS_WRITE);
	if(code > UINT16_MAX) {
		fprintf(stderr, "FAT16 code %x too big\n", code);
		exit(1);
	}
	*address = (uint16_t) code;
}
#pragma GCC diagnostic pop



/*
 * Fat 32 encoding
 */
#define FAT32_HIGH 0xf0000000
#define FAT32_ADDR 0x0fffffff

static unsigned int fat32_decode(Fs_t *Stream, unsigned int num)
{
	unsigned char *address = getAddress(Stream, num << 2, FAT_ACCESS_READ);
	if(!address)
		return 1;
	return _DWORD(address) & FAT32_ADDR;
}

static void fat32_encode(Fs_t *Stream, unsigned int num, unsigned int code)
{
	unsigned char *address = getAddress(Stream, num << 2, FAT_ACCESS_WRITE);
	set_dword(address,(code&FAT32_ADDR) | (_DWORD(address)&FAT32_HIGH));
}

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
static unsigned int fast_fat32_decode(Fs_t *Stream, unsigned int num)
{
	unsigned int *address =
		(unsigned int *) getAddress(Stream, num << 2,
					    FAT_ACCESS_READ);
	if(!address)
		return 1;
	return (*address) & FAT32_ADDR;
}

static void fast_fat32_encode(Fs_t *Stream, unsigned int num, unsigned int code)
{
	unsigned int *address =
		(unsigned int *) getAddress(Stream, num << 2,
					    FAT_ACCESS_WRITE);
	*address = (*address & FAT32_HIGH) | (code & FAT32_ADDR);
}
#pragma GCC diagnostic pop

/*
 * Write the FAT table to the disk.  Up to now the FAT manipulation has
 * been done in memory.  All errors are fatal.  (Might not be too smart
 * to wait till the end of the program to write the table.  Oh well...)
 */

void fat_write(Fs_t *This)
{
	unsigned int i, j, dups, bit, slot;
	ssize_t ret;

	/*fprintf(stderr, "Fat write\n");*/

	if (!This->fat_dirty)
		return;

	dups = This->num_fat;
	if (This->fat_error)
		dups = 1;


	for(i=0; i<dups; i++){
		j = 0;
		for(slot=0;j<This->fat_len;slot++) {
			if(!This->FatMap[slot].dirty) {
				j += SECT_PER_ENTRY;
				continue;
			}
			for(bit=0;
			    bit < SECT_PER_ENTRY && j<This->fat_len;
			    bit++,j++) {
				if(!(This->FatMap[slot].dirty & (ONE << bit)))
					continue;
				ret = fatWriteSector(This,j,slot, bit, i);
				if (ret < (int) This->sector_size){
					if (ret < 0 ){
						perror("error in fat_write");
						exit(1);
					} else {
						fprintf(stderr,
							"end of file in fat_write\n");
						exit(1);
					}
				}
				/* if last dupe, zero it out */
				if(i==dups-1)
					This->FatMap[slot].dirty &= ~(ONE<<bit);
			}
		}
	}
	/* write the info sector, if any */
	if(This->infoSectorLoc && This->infoSectorLoc != MAX32) {
		/* initialize info sector */
		InfoSector_t *infoSector;
		infoSector = (InfoSector_t *) safe_malloc(This->sector_size);
		if(forceReadSector(This, (char *)infoSector,
				   This->infoSectorLoc, 1) !=
		   (signed int) This->sector_size) {
			fprintf(stderr,"Trouble reading the info sector\n");
			memset(infoSector->filler1, 0, sizeof(infoSector->filler1));
			memset(infoSector->filler2, 0, sizeof(infoSector->filler2));
		}
		set_dword(infoSector->signature1, INFOSECT_SIGNATURE1);
		set_dword(infoSector->signature2, INFOSECT_SIGNATURE2);
		set_dword(infoSector->pos, This->last);
		set_dword(infoSector->count, This->freeSpace);
		set_word(infoSector->signature3, 0xaa55);
		if(forceWriteSector(This, (char *)infoSector, This->infoSectorLoc, 1) !=
		   (signed int) This->sector_size)
			fprintf(stderr,"Trouble writing the info sector\n");
		free(infoSector);
	}
	This->fat_dirty = 0;
	This->lastFatAccessMode = FAT_ACCESS_READ;
}



/*
 * Zero-Fat
 * Used by mformat.
 */
int zero_fat(Fs_t *Stream, uint8_t media_descriptor)
{
	unsigned int i, j;
	unsigned int fat_start;
	unsigned char *buf;

	buf = malloc(Stream->sector_size);
	if(!buf) {
		perror("alloc fat sector buffer");
		return -1;
	}
	for(i=0; i< Stream->num_fat; i++) {
		fat_start = Stream->fat_start + i*Stream->fat_len;
		for(j = 0; j < Stream->fat_len; j++) {
			if(j <= 1)
				memset(buf, 0, Stream->sector_size);
			if(!j) {
				buf[0] = media_descriptor;
				buf[2] = buf[1] = 0xff;
				if(Stream->fat_bits > 12)
					buf[3] = 0xff;
				if(Stream->fat_bits > 16) {
					buf[4] = 0xff;
					buf[5] = 0xff;
					buf[6] = 0xff;
					buf[7] = 0x0f;
				}
			}

			if(forceWriteSector(Stream, (char *)buf,
					    fat_start + j, 1) !=
			   (signed int) Stream->sector_size) {
				fprintf(stderr,
					"Trouble initializing a FAT sector\n");
				free(buf);
				return -1;
			}
		}
	}

	free(buf);
	Stream->FatMap = GetFatMap(Stream);
	if (Stream->FatMap == NULL) {
		perror("alloc fat map");
		return -1;
	}
	return 0;
}


static void set_fat12(Fs_t *This)
{
	This->fat_bits = 12;
	This->end_fat = 0xfff;
	This->last_fat = 0xff6;
	This->fat_decode = fat12_decode;
	This->fat_encode = fat12_encode;
}

static uint16_t word_endian_test = 0x1234;

static void set_fat16(Fs_t *This)
{
	uint8_t *t = (uint8_t *) &word_endian_test;
	This->fat_bits = 16;
	This->end_fat = 0xffff;
	This->last_fat = 0xfff6;

	if(t[0] == 0x34 && t[1] == 0x12) {
		This->fat_decode = fast_fat16_decode;
		This->fat_encode = fast_fat16_encode;
	} else {
		This->fat_decode = fat16_decode;
		This->fat_encode = fat16_encode;
	}
}

static uint32_t dword_endian_test = 0x12345678;

static void set_fat32(Fs_t *This)
{
	uint8_t *t = (uint8_t *) &dword_endian_test;
	This->fat_bits = 32;
	This->end_fat = 0xfffffff;
	This->last_fat = 0xffffff6;

	if(t[0] == 0x78 && t[1] == 0x56 && t[2] == 0x34 && t[3] == 0x12) {
		This->fat_decode = fast_fat32_decode;
		This->fat_encode = fast_fat32_encode;
	} else {
		This->fat_decode = fat32_decode;
		This->fat_encode = fat32_encode;
	}
}

void set_fat(Fs_t *This) {
	if(This->num_clus < FAT12)
		set_fat12(This);
	else if(This->num_clus < FAT16)
		set_fat16(This);
	else
		set_fat32(This);
}

static int check_fat(Fs_t *This)
{
	/*
	 * This is only a sanity check.  For disks with really big FATs,
	 * there is no point in checking the whole FAT.
	 */

	unsigned int i, f;
	unsigned int tocheck;
	if(mtools_skip_check)
		return 0;

	/* too few sectors in the FAT */
	if(This->fat_len < NEEDED_FAT_SIZE(This)) {
		fprintf(stderr, "Too few sectors in FAT\n");
		return -1;
	}
	/* we do not warn about too much sectors in FAT, which may
	 * happen when a partition has been shrunk using FIPS, or on
	 * other occurrences */

	tocheck = This->num_clus;
	if (tocheck + 1 >= This->last_fat) {
		fprintf(stderr, "Too many clusters in FAT\n");
		return -1;
	}

	if(tocheck > 4096)
		tocheck = 4096;

	for ( i= 3 ; i < tocheck; i++){
		f = This->fat_decode(This,i);
		if (f == 1 || (f < This->last_fat && f > This->num_clus)){
			fprintf(stderr,
				"Cluster # at %d too big(%#x)\n", i,f);
			fprintf(stderr,"Probably non MS-DOS disk\n");
			return -1;
		}
	}
	return 0;
}


/*
 * Read the first sector of FAT table into memory.  Crude error detection on
 * wrong FAT encoding scheme.
 */
static int check_media_type(Fs_t *This, union bootsector *boot)
{
	unsigned char *address;

	This->FatMap = GetFatMap(This);
	if (This->FatMap == NULL) {
		perror("alloc fat map");
		return -1;
	}

	address = getAddress(This, 0, FAT_ACCESS_READ);
	if(!address) {
		fprintf(stderr,
			"Could not read first FAT sector\n");
		return -1;
	}

	if(mtools_skip_check)
		return 0;

	if(!address[0] && !address[1] && !address[2])
		/* Some Atari disks have zeroes where Dos has media descriptor
		 * and 0xff.  Do not consider this as an error */
		return 0;

	if((address[0] != boot->boot.descr && boot->boot.descr >= 0xf0 &&
	    ((address[0] != 0xf9 && address[0] != 0xf7)
	     || boot->boot.descr != 0xf0)) || address[0] < 0xf0) {
		fprintf(stderr,
			"Bad media types %02x/%02x, probably non-MSDOS disk\n",
				address[0],
				boot->boot.descr);
		return -1;
	}

	if(address[1] != 0xff || address[2] != 0xff){
		fprintf(stderr,"Initial bytes of fat is not 0xff\n");
		return -1;
	}

	return 0;
}

static int fat_32_read(Fs_t *This, union bootsector *boot)
{
	size_t size;

	This->fat_len = DWORD(ext.fat32.bigFat);
	This->writeAllFats = !(boot->boot.ext.fat32.extFlags[0] & 0x80);
	This->primaryFat = boot->boot.ext.fat32.extFlags[0] & 0xf;
	This->rootCluster = DWORD(ext.fat32.rootCluster);
	This->clus_start = This->fat_start + This->num_fat * This->fat_len;

	/* read the info sector */
	size = This->sector_size;
	This->infoSectorLoc = WORD(ext.fat32.infoSector);
	if(This->sector_size >= 512 &&
	   This->infoSectorLoc && This->infoSectorLoc != MAX32) {
		InfoSector_t *infoSector;
		infoSector = (InfoSector_t *) safe_malloc(size);
		if(forceReadSector(This, (char *)infoSector,
				   This->infoSectorLoc, 1) ==
		   (signed int) This->sector_size &&
		   _DWORD(infoSector->signature1) == INFOSECT_SIGNATURE1 &&
		   _DWORD(infoSector->signature2) == INFOSECT_SIGNATURE2) {
			This->freeSpace = _DWORD(infoSector->count);
			This->last = _DWORD(infoSector->pos);
		}
		free(infoSector);
	}

	return(check_media_type(This, boot) || check_fat(This));
}


static int old_fat_read(Fs_t *This, union bootsector *boot, int nodups)
{
	This->writeAllFats = 1;
	This->primaryFat = 0;
	This->dir_start = This->fat_start + This->num_fat * This->fat_len;
	This->infoSectorLoc = MAX32;

	if(nodups)
		This->num_fat = 1;

	if(check_media_type(This, boot))
		return -1;

	if(This->num_clus >= FAT12)
		/* third FAT byte must be 0xff */
		if(!mtools_skip_check && readByte(This, 3) != 0xff)
			return -1;

	return check_fat(This);
}

/*
 * Read the first sector of the  FAT table into memory and initialize
 * structures.
 */
int fat_read(Fs_t *This, union bootsector *boot, int nodups)
{
	This->fat_error = 0;
	This->fat_dirty = 0;
	This->last = MAX32;
	This->freeSpace = MAX32;
	This->lastFatSectorNr = 0;
	This->lastFatSectorData = 0;

	if(This->num_clus < FAT16)
		return old_fat_read(This, boot, nodups);
	else
		return fat_32_read(This, boot);
}


unsigned int fatDecode(Fs_t *This, unsigned int pos)
{
	unsigned int ret;

	ret = This->fat_decode(This, pos);
	if(ret && (ret < 2 || ret > This->num_clus+1) && ret < This->last_fat) {
		fprintf(stderr, "Bad FAT entry %d at %d\n", ret, pos);
		This->fat_error++;
	}
	return ret;
}

/* append a new cluster */
void fatAppend(Fs_t *This, unsigned int pos, unsigned int newpos)
{
	This->fat_encode(This, pos, newpos);
	This->fat_encode(This, newpos, This->end_fat);
	if(This->freeSpace != MAX32)
		This->freeSpace--;
}

/* de-allocates the given cluster */
void fatDeallocate(Fs_t *This, unsigned int pos)
{
	This->fat_encode(This, pos, 0);
	if(This->freeSpace != MAX32)
		This->freeSpace++;
}

/* allocate a new cluster */
void fatAllocate(Fs_t *This, unsigned int pos, unsigned int value)
{
	This->fat_encode(This, pos, value);
	if(This->freeSpace != MAX32)
		This->freeSpace--;
}

void fatEncode(Fs_t *This, unsigned int pos, unsigned int value)
{
	unsigned int oldvalue = This->fat_decode(This, pos);
	This->fat_encode(This, pos, value);
	if(This->freeSpace != MAX32) {
		if(oldvalue)
			This->freeSpace++;
		if(value)
			This->freeSpace--;
	}
}

unsigned int get_next_free_cluster(Fs_t *This, unsigned int last)
{
	unsigned int i;

	if(This->last != MAX32)
		last = This->last;

	if (last < 2 ||
	    last >= This->num_clus+1)
		last = 1;

	for (i=last+1; i< This->num_clus+2; i++) {
		unsigned int r = fatDecode(This, i);
		if(r == 1)
			goto exit_0;
		if (!r) {
			This->last = i;
			return i;
		}
	}

	for(i=2; i < last+1; i++) {
		unsigned int r = fatDecode(This, i);
		if(r == 1)
			goto exit_0;
		if (!r) {
			This->last = i;
			return i;
		}
	}


	fprintf(stderr,"No free cluster %d %d\n", This->preallocatedClusters,
		This->last);
	return 1;
 exit_0:
	fprintf(stderr, "FAT error\n");
	return 1;
}

bool getSerialized(Fs_t *Fs) {
	return Fs->serialized;
}

unsigned long getSerialNumber(Fs_t *Fs) {
	return Fs->serial_number;
}

uint32_t getClusterBytes(Fs_t *Fs) {
	return Fs->cluster_size * Fs->sector_size;
}

int fat_error(Stream_t *Dir)
{
	Stream_t *Stream = GetFs(Dir);
	DeclareThis(Fs_t);

	if(This->fat_error)
		fprintf(stderr,"Fat error detected\n");

	return This->fat_error;
}

uint32_t fat32RootCluster(Stream_t *Dir)
{
	Stream_t *Stream = GetFs(Dir);
	DeclareThis(Fs_t);

	if(This->fat_bits == 32)
		return This->rootCluster;
	else
		return 0;
}


/*
 * Get the amount of free space on the diskette
 */
mt_off_t getfree(Stream_t *Dir)
{
	Stream_t *Stream = GetFs(Dir);
	DeclareThis(Fs_t);

	if(This->freeSpace == MAX32 || This->freeSpace == 0) {
		register unsigned int i;
		uint32_t total;

		total = 0L;
		for (i = 2; i < This->num_clus + 2; i++) {
			unsigned int r = fatDecode(This,i);
			if(r == 1) {
				return -1;
			}
			if (!r)
				total++;
		}
		This->freeSpace = total;
	}
	return sectorsToBytes(This,
			      This->freeSpace * This->cluster_size);
}


/*
 * Ensure that there is a minimum of total sectors free
 */
int getfreeMinClusters(Stream_t *Dir, uint32_t size)
{
	Stream_t *Stream = GetFs(Dir);
	DeclareThis(Fs_t);
	register unsigned int i, last;
	size_t total;

	if(batchmode && This->freeSpace == MAX32)
		getfree(Stream);

	if(This->freeSpace != MAX32) {
		if(This->freeSpace >= size)
			return 1;
		else {
			fprintf(stderr, "Disk full\n");
			got_signal = 1;
			return 0;
		}
	}

	total = 0L;

	/* we start at the same place where we'll start later to actually
	 * allocate the sectors.  That way, the same sectors of the FAT, which
	 * are already loaded during getfreeMin will be able to be reused
	 * during get_next_free_cluster */
	last = This->last;

	if ( last < 2 || last >= This->num_clus + 2)
		last = 1;
	for (i=last+1; i< This->num_clus+2; i++){
		unsigned int r = fatDecode(This, i);
		if(r == 1) {
			goto exit_0;
		}
		if (!r)
			total++;
		if(total >= size)
			return 1;
	}
	for(i=2; i < last+1; i++){
		unsigned int r = fatDecode(This, i);
		if(r == 1) {
			goto exit_0;
		}
		if (!r)
			total++;
		if(total >= size)
			return 1;
	}
	fprintf(stderr, "Disk full\n");
	got_signal = 1;
	return 0;
 exit_0:
	fprintf(stderr, "FAT error\n");
	return 0;
}


int getfreeMinBytes(Stream_t *Dir, mt_off_t size)
{
	Stream_t *Stream = GetFs(Dir);
	DeclareThis(Fs_t);
	mt_off_t size2;

	size2 = size  / (This->sector_size * This->cluster_size);
	if(size % (This->sector_size * This->cluster_size))
		size2++;
	if((smt_off_t)size2 > UINT32_MAX) {
		fprintf(stderr, "Requested size too big\n");
		exit(1);
	}
	return getfreeMinClusters(Dir, (uint32_t) size2);
}


uint32_t getStart(Stream_t *Dir, struct directory *dir)
{
	Stream_t *Stream = GetFs(Dir);
	uint32_t first;

	first = START(dir);
	if(fat32RootCluster(Stream)) {
		first |=  (uint32_t) STARTHI(dir) << 16;
	}
	return first;
}

int fs_free(Stream_t *Stream)
{
	DeclareThis(Fs_t);

	if(This->FatMap) {
		int i, nr_entries;
		nr_entries = (This->fat_len + SECT_PER_ENTRY - 1) /
			SECT_PER_ENTRY;
		for(i=0; i< nr_entries; i++)
			if(This->FatMap[i].data)
				free(This->FatMap[i].data);
		free(This->FatMap);
	}
	if(This->cp)
		cp_close(This->cp);
	return 0;
}