org.deckfour.xes.nikefs2
Class NikeFS2BlockProvider

java.lang.Object
  org.deckfour.xes.nikefs2.NikeFS2BlockProvider

public class NikeFS2BlockProvider
extends Object

This class implements a block provider for the NikeFS2 virtual file system. It is backed by an OS-level random-access file, which stores the actual contents of the blocks. Also, this class contains static facilities for managing the current set of open files, thereby reducing the number of concurrently open and used file handles to a sensible minimum.

Author:

Christian W. Guenther (christian@deckfour.org)

Field Summary

protected BitSet	blockAllocationMap Bit set indicating which blocks served by this provider are still free, i.e.
protected int	blockSize Size (in bytes) of each block in this block provider.
protected File	file Backing file for this block provider.
protected boolean	mapped Flag indicating whether this block provider is using memory mapping for faster access to its contents (default and recommended is true).
protected int	numberOfBlocks Number of blocks provided by this block provider.
protected RandomAccessFile	rafile Random-access file wrapper, if non-mapped
protected int	size Size (in bytes) of this block provider, i.e.

Constructor Summary

NikeFS2BlockProvider(File storage, int size, int blockSize, boolean mapped)
Creates a new block provider.

Method Summary

NikeFS2Block	allocateBlock() Allocates a new block from this block provider.
int	blockSize() Returns the size of blocks provided by this instance.
void	freeBlock(NikeFS2Block block) De-allocates the specified block in this provider.
int	getBlockOffset(int blockNumber) Returns the internal offset of the specified block in the backing file (in bytes).
File	getFile() Provides direct access to the backing file.
int	numberOfBlocks() Returns the number of blocks provided by this instance.
int	numberOfFreeBlocks() Returns the number of non-allocated blocks in this instance.
int	read(int blockNumber, int blockOffset) Reads from the specified block.
int	read(int blockNumber, int blockOffset, byte[] buffer) Reads from the specified block.
int	read(int blockNumber, int blockOffset, byte[] buffer, int bufferOffset, int length) Reads from the specified block.
int	size() Returns the size, in bytes, of this block provider in total.
void	write(int blockNumber, int blockOffset, byte[] buffer) Writes to this block.
void	write(int blockNumber, int blockOffset, byte[] buffer, int bufferOffset, int length) Writes to this block.
void	write(int blockNumber, int blockOffset, int value) Writes to this block.

Methods inherited from class java.lang.Object

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

Field Detail

mapped

protected final boolean mapped

Flag indicating whether this block provider is using memory mapping for faster access to its contents (default and recommended is true).

file

protected final File file

Backing file for this block provider.

rafile

protected final RandomAccessFile rafile

Random-access file wrapper, if non-mapped

size

protected final int size

Size (in bytes) of this block provider, i.e. of its backing file.

blockSize

protected final int blockSize

Size (in bytes) of each block in this block provider.

numberOfBlocks

protected final int numberOfBlocks

Number of blocks provided by this block provider.

blockAllocationMap

protected final BitSet blockAllocationMap

Bit set indicating which blocks served by this provider are still free, i.e. not yet allocated. Every block is addressed by its unique index within this provider. For each block, a bit set to true, at the block's index in this bit set, indicates that the block is free. Blocks whose index's bit is set to false are currently allocated.

Constructor Detail

NikeFS2BlockProvider

public NikeFS2BlockProvider(File storage,
                            int size,
                            int blockSize,
                            boolean mapped)
                     throws IOException

Creates a new block provider.

Parameters:

storage - Backing file to store actual contents in.

size - Size of the backing file in bytes.

blockSize - Size of blocks in bytes.

mapped - Whether to use memory mapping for this block provider (it is recommended to set this flag to true).

Throws:

IOException

Method Detail

getFile

public File getFile()

Provides direct access to the backing file.

Returns:

The random access file backing this block provider.

size

public int size()

Returns the size, in bytes, of this block provider in total.

Returns:

Number of bytes totally provided by this instance.

numberOfBlocks

public int numberOfBlocks()

Returns the number of blocks provided by this instance.

Returns:

The number of blocks provided by this instance.

numberOfFreeBlocks

public int numberOfFreeBlocks()

Returns the number of non-allocated blocks in this instance.

Returns:

The number of non-allocated blocks in this instance.

blockSize

public int blockSize()

Returns the size of blocks provided by this instance.

Returns:

The size of blocks (in bytes) provided by this instance.

allocateBlock

public NikeFS2Block allocateBlock()

Allocates a new block from this block provider.

Returns:

A newly allocated block from this provider. May return null, if no free blocks are currently available.

freeBlock

public void freeBlock(NikeFS2Block block)

De-allocates the specified block in this provider.

Parameters:

block - The block to be freed.

getBlockOffset

public int getBlockOffset(int blockNumber)

Returns the internal offset of the specified block in the backing file (in bytes).

Parameters:

blockNumber - The internal number of the block in question.

Returns:

Internal offset of the block, in bytes, in the backing file.

read

public int read(int blockNumber,
                int blockOffset,
                byte[] buffer)
         throws IOException

Reads from the specified block.

Parameters:

blockNumber - Internal number of the block in question.

blockOffset - Offset, in bytes, within this block.

buffer - Buffer to store read data in.

Returns:

The number of read bytes.

Throws:

IOException

read

public int read(int blockNumber,
                int blockOffset,
                byte[] buffer,
                int bufferOffset,
                int length)
         throws IOException

Reads from the specified block.

Parameters:

blockNumber - Internal number of the block in question.

blockOffset - Offset, in bytes, within this block.

buffer - Buffer to store read data in.

bufferOffset - Offset in the given buffer to start writing at.

length - Number of bytes to be read.

Returns:

The number of read bytes.

Throws:

IOException

read

public int read(int blockNumber,
                int blockOffset)
         throws IOException

Reads from the specified block.

Parameters:

blockNumber - Internal number of the block in question.

blockOffset - Offset, in bytes, within this block.

Returns:

The read byte.

Throws:

IOException

write

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

Writes to this block.

Parameters:

blockNumber - Internal number of the block in question.

blockOffset - Offset within the block to commence writing at.

buffer - Buffer storing the data to be written.

Throws:

IOException

write

public void write(int blockNumber,
                  int blockOffset,
                  byte[] buffer,
                  int bufferOffset,
                  int length)
           throws IOException

Writes to this block.

Parameters:

blockNumber - Internal number of the block in question.

blockOffset - Offset within the block to commence writing at.

buffer - Buffer storing the data to be written.

bufferOffset - Offset within the buffer from where to read.

length - Number of bytes to be written.

Throws:

IOException

write

public void write(int blockNumber,
                  int blockOffset,
                  int value)
           throws IOException

Writes to this block.

Parameters:

blockNumber - Internal number of the block in question.

blockOffset - Offset within the block to commence writing at.

value - Byte value to be written.

Throws:

IOException