rossi.fstools.fs.fatfs
Class FatSuperBlock

java.lang.Object
  rossi.fstools.fs.fatfs.FatSuperBlock

All Implemented Interfaces:

DiskStructure, SuperBlock

public class FatSuperBlock

extends java.lang.Object

implements SuperBlock

Representation of FAT superblock.

  On disk the superblock looks like this:

        31        24        16       8       0
        --------------------------------------
  0000  |    Bootstrap               | SysID |
        --------------------------------------
  0004  |         System ID                  |
        --------------------------------------
  0008  |         System ID          |SectSze|
        --------------------------------------
  000C  |SectSze |SecPerClus| Reserved Sects |
        --------------------------------------
  0010  |NumFats | Root Dir Entries  |sectors|
        --------------------------------------
  0014  |sectors | Media    | Fat Length     |
        --------------------------------------
  0018  |Sectors per Track  | Heads          |
        --------------------------------------
  001C  |        Hidden Sectors              |
        --------------------------------------
  0020  |        Total Sectors               |
        --------------------------------------
  0024  |        Fat32 length                |
        --------------------------------------
  0028  | Flags             |  Version       |
        --------------------------------------
  002C  |        Root cluster                |
        --------------------------------------
  0030  | Info Sector       |  backup boot   |
        --------------------------------------
  0034  |        Reserved                    |
        --------------------------------------

 

Field Summary

protected int	backupBootSector
protected byte[]	bootStrap
protected long	fat32Length
protected int	fatLength
protected int	flags
protected int	heads
protected long	hiddenSectors
protected int	infoSector
static int	MAX_FAT12 Max number of clusters for FAT12.
static int	MAX_FAT16 Max number of clusters for FAT16.
static int	MAX_FAT32 Max number of clusters for FAT32.
protected byte	media
protected int	numFATs
protected int	reservedSectors
protected long	rootCluster
protected int	rootDirEntries
protected int	sectors
protected int	sectorSize
protected int	sectorsPerCluster
protected int	sectorsPerTrack
protected java.lang.String	systemId
protected long	totalSectors
protected int	version

Constructor Summary

FatSuperBlock()
Default constructor.

Method Summary

int	getBackupBootSector() Get the sector address of the backup boot sector.
byte[]	getBootStrap() Return the first 3 bytes of the filesystem.
int	getDataSize() Get the size in bytes of the structure.
long	getFat32Length() Get the length of the FAT in sectors for a FAT32 system.
int	getFatBits() Get the number bits per entry in the FAT.
int	getFatLength() FAT length in sectors.
int	getFirstDataSector() Get the sector address of the first data sector (cluster 2).
int	getFlags() Not sure what this is for.
int	getHeads() Number of heads.
long	getHiddenSectors() Number of hidden sectors.
int	getInfoSector() Get the sector address of the FAT32 info block.
byte	getMedia() Media descriptor byte.
long	getNumClusters() Get the number of clusters.
int	getNumFATs() Get the number of FAT tables.
long	getNumSectors() Get the number of sectors in the filesystem.
int	getReservedSectors() Get the number of reserved sectors.
long	getRootCluster() Get the first cluster of the root directory.
int	getRootDirEntries() Get the number of root directory entries.
int	getSectors() Get the count of sectors in the FS.
int	getSectorSize() Sector size.
int	getSectorsPerCluster() Get number of sectors per cluster.
int	getSectorsPerTrack() Number of sectors per track.
java.lang.String	getSystemId() Get the system identifier.
long	getTotalSectors() Total sectors in the filesystem.
int	getVersion() Get the filesystem version.
void	loadFromBuffer(byte[] buffer, int offset) Loads the object from a memory buffer
void	setBackupBootSector(int aBackupBootSector)
void	setBootStrap(byte[] aBootStrap)
void	setFat32Length(long aFat32Length)
void	setFatLength(int aFatLength)
void	setFlags(int aFlags)
void	setHeads(int aHeads)
void	setHiddenSectors(long aHiddenSectors)
void	setInfoSector(int aInfoSector)
void	setMedia(byte aMedia)
void	setNumFATs(int aNumFATs)
void	setReservedSectors(int aReservedSectors)
void	setRootCluster(long aRootCluster)
void	setRootDirEntries(int aRootDirEntries)
void	setSectors(int aSectors)
void	setSectorSize(int aSectorSize)
void	setSectorsPerCluster(int aSectorsPerCluster)
void	setSectorsPerTrack(int aSectorsPerTrack)
void	setSystemId(java.lang.String aSystemId)
void	setTotalSectors(long aTotalSectors)
void	setVersion(int aVersion)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

bootStrap

protected byte[] bootStrap

systemId

protected java.lang.String systemId

sectorSize

protected int sectorSize

sectorsPerCluster

protected int sectorsPerCluster

reservedSectors

protected int reservedSectors

numFATs

protected int numFATs

rootDirEntries

protected int rootDirEntries

sectors

protected int sectors

media

protected byte media

fatLength

protected int fatLength

sectorsPerTrack

protected int sectorsPerTrack

heads

protected int heads

hiddenSectors

protected long hiddenSectors

totalSectors

protected long totalSectors

fat32Length

protected long fat32Length

flags

protected int flags

version

protected int version

rootCluster

protected long rootCluster

infoSector

protected int infoSector

backupBootSector

protected int backupBootSector

MAX_FAT12

public static final int MAX_FAT12

Max number of clusters for FAT12.

See Also:

Constant Field Values

MAX_FAT16

public static final int MAX_FAT16

Max number of clusters for FAT16.

See Also:

Constant Field Values

MAX_FAT32

public static final int MAX_FAT32

Max number of clusters for FAT32.

See Also:

Constant Field Values

Constructor Detail

FatSuperBlock

public FatSuperBlock()

Default constructor.

Method Detail

getBootStrap

public byte[] getBootStrap()

Return the first 3 bytes of the filesystem. This typically contains a jump instruction to the bootstrap loader.

Returns:

bootStrap instruction.

setBootStrap

public void setBootStrap(byte[] aBootStrap)

getSystemId

public java.lang.String getSystemId()

Get the system identifier.

Returns:

system id

setSystemId

public void setSystemId(java.lang.String aSystemId)

getSectorSize

public int getSectorSize()

Sector size. Should be 512 bytes.

Returns:

sector size.

setSectorSize

public void setSectorSize(int aSectorSize)

getSectorsPerCluster

public int getSectorsPerCluster()

Get number of sectors per cluster. A cluster is the minimum allocation unit for files.

setSectorsPerCluster

public void setSectorsPerCluster(int aSectorsPerCluster)

getReservedSectors

public int getReservedSectors()

Get the number of reserved sectors. The FAT tables begin this many sectors into the filesystem.

Returns:

reservedSectors.

setReservedSectors

public void setReservedSectors(int aReservedSectors)

getNumFATs

public int getNumFATs()

Get the number of FAT tables. Usually 2.

Returns:

numFATs.

setNumFATs

public void setNumFATs(int aNumFATs)

getRootDirEntries

public int getRootDirEntries()

Get the number of root directory entries. This is only valid in FAT16 and FAT12, it will be zero in FAT32.

setRootDirEntries

public void setRootDirEntries(int aRootDirEntries)

getSectors

public int getSectors()

Get the count of sectors in the FS. Note that this is a 16 bit number and will be set to zero if the FS contains more than 65535 sectors. Unused in FAT32.

Returns:

numSectors.

See Also:

getTotalSectors()

setSectors

public void setSectors(int aSectors)

getMedia

public byte getMedia()

Media descriptor byte.

Returns:

media

setMedia

public void setMedia(byte aMedia)

getFatLength

public int getFatLength()

FAT length in sectors. Not used in FAT32.

Returns:

fat length

See Also:

getFat32Length()

setFatLength

public void setFatLength(int aFatLength)

getSectorsPerTrack

public int getSectorsPerTrack()

Number of sectors per track.

Returns:

sectors per track.

setSectorsPerTrack

public void setSectorsPerTrack(int aSectorsPerTrack)

getHeads

public int getHeads()

Number of heads.

Returns:

heads

setHeads

public void setHeads(int aHeads)

getHiddenSectors

public long getHiddenSectors()

Number of hidden sectors. Unused.

Returns:

hidden

setHiddenSectors

public void setHiddenSectors(long aHiddenSectors)

getTotalSectors

public long getTotalSectors()

Total sectors in the filesystem. This 32 bit value is only used if the 16 bit sectors value is zero.

Returns:

long

See Also:

getSectors()

setTotalSectors

public void setTotalSectors(long aTotalSectors)

getFat32Length

public long getFat32Length()

Get the length of the FAT in sectors for a FAT32 system. This overrides getFatLength() that is used in FAT12/16 systems.

Returns:

fat length in sectors;

See Also:

getFatLength()

setFat32Length

public void setFat32Length(long aFat32Length)

getFlags

public int getFlags()

Not sure what this is for. Unused here. Only valid for FAT32.

Returns:

flags.

setFlags

public void setFlags(int aFlags)

getVersion

public int getVersion()

Get the filesystem version. Only valid for FAT32.

Returns:

version

setVersion

public void setVersion(int aVersion)

getRootCluster

public long getRootCluster()

Get the first cluster of the root directory. This is only used for FAT32. In FAT12 and FAT16, the root directory isn't allocated via the FAT table. Rather it is of fixed size and resides between the end of the FAT tables and the start of the data area.

Returns:

root cluster

setRootCluster

public void setRootCluster(long aRootCluster)

getInfoSector

public int getInfoSector()

Get the sector address of the FAT32 info block.

Returns:

fat 32 info block location

setInfoSector

public void setInfoSector(int aInfoSector)

getBackupBootSector

public int getBackupBootSector()

Get the sector address of the backup boot sector. Only valid in FAT32.

Returns:

backup boot sector address.

setBackupBootSector

public void setBackupBootSector(int aBackupBootSector)

getNumSectors

public long getNumSectors()

Get the number of sectors in the filesystem. This handles figuring out which fields from the disk to use to arrive at the correct result.

Returns:

total number of sectors in the filesystem

getNumClusters

public long getNumClusters()

Get the number of clusters. The number of clusters is computed from the number of sectors less the reserved sectors, the root directory sectors (if any), and the FAT sectors.

Returns:

number of clusters.

getFatBits

public int getFatBits()

Get the number bits per entry in the FAT.

Returns:

number of fat bits.

getFirstDataSector

public int getFirstDataSector()

Get the sector address of the first data sector (cluster 2).

getDataSize

public int getDataSize()

Description copied from interface: DiskStructure

Get the size in bytes of the structure. For variable length sturctures this may represent the minimum length rather than the actual length.

Specified by:

getDataSize in interface DiskStructure

Returns:

the size of the structure.

loadFromBuffer

public void loadFromBuffer(byte[] buffer,
                           int offset)
                    throws FsException

Description copied from interface: DiskStructure

Loads the object from a memory buffer

Specified by:

loadFromBuffer in interface DiskStructure

Parameters:

buffer - a byte[] containing data to be read in populating the object

offset - a int indicating the offset within the buffer to start parsing.

Throws:

FsException - if a parse error occurs.