Class FileSystem

java.lang.Object
   |
   +----FileSystem

A simulated file system.

FileSystem(String, String): Construct a FileSystem and open a FileSystem file.

allocateBlock(): Allocate a data block from the list of free blocks.
allocateIndexNode(): Allocate an index node for the file system.
close(): Close the backing file for this FileSystem, if any.
freeBlock(int): Mark a data block as being free in the free list.
getBlockSize(): Get the blockSize for this FileSystem.
getDataBlockOffset()
getFreeListBlockOffset()
getInodeBlockOffset()
getRootIndexNode(): Get the rootIndexNode for this FileSystem.
open(): Open a backing file for this FileSystem and read the superblock.
read(byte[], int): Read bytes into a buffer from the specified absolute block number of the file system.
readIndexNode(IndexNode, short): Reads an index node at the index node location specified.
write(byte[], int): Write bytes from a buffer to the specified absolute block number of the file system.
writeIndexNode(IndexNode, short): Writes an index node at the index node location specified.

ROOT_INDEX_NODE_NUMBER

 public static short ROOT_INDEX_NODE_NUMBER

NOT_A_BLOCK

 public static int NOT_A_BLOCK

FileSystem

 public FileSystem(String newFilename,
                   String newMode) throws IOException

Construct a FileSystem and open a FileSystem file.

Parameters:: newFilename - the name of the FileSystem file to open; newMode - the mode ("r" or "rw") to use when opening the file
Throws: IOException: if any IOExceptions are thrown during the open.

 public short getBlockSize()

Get the blockSize for this FileSystem.

 public int getFreeListBlockOffset()

 public int getInodeBlockOffset()

 public int getDataBlockOffset()

 public IndexNode getRootIndexNode()

Get the rootIndexNode for this FileSystem.

open

 public void open() throws IOException

Open a backing file for this FileSystem and read the superblock.

close

 public void close() throws IOException

Close the backing file for this FileSystem, if any.

Throws: IOException: if the closing the backing file causes any IOException to be thrown

read

 public void read(byte bytes[],
                  int blockNumber) throws IOException

Read bytes into a buffer from the specified absolute block number of the file system.

Parameters:: bytes - the byte buffer into which the block should be read; blockNumber - the absolute block number which should be read
Throws: IOException: if there are any exceptions during the read from the underlying "file system" file.

write

 public void write(byte bytes[],
                   int blockNumber) throws IOException

Write bytes from a buffer to the specified absolute block number of the file system.

Parameters:: bytes - the byte buffer from which the block should be written; blockNumber - the absolute block number which should be written
Throws: IOException: if there are any exceptions during the write to the underlying "file system" file.

 public void freeBlock(int dataBlockNumber) throws IOException

Mark a data block as being free in the free list.

Parameters:: dataBlockNumber - the data block which is to be marked free
Throws: IOException: if any exception occurs during an operation on the underlying "file system" file.

 public int allocateBlock() throws IOException

Allocate a data block from the list of free blocks.

Returns:: the data block number which was allocated; -1 if no blocks are available
Throws: IOException: if any exception occurs during an operation on the underlying "file system" file.

 public short allocateIndexNode() throws IOException

Allocate an index node for the file system.

Returns:: the inode number for the next available index node; -1 if there are no index nodes available.
Throws: IOException: if there is an exception during an operation on the underlying "file system" file.

 public void readIndexNode(IndexNode indexNode,
                           short indexNodeNumber) throws IOException

Reads an index node at the index node location specified.

 public void writeIndexNode(IndexNode indexNode,
                            short indexNodeNumber) throws IOException

Writes an index node at the index node location specified.