Package org.apache.poi.poifs.filesystem

Class BlockStore

java.lang.Object

org.apache.poi.poifs.filesystem.BlockStore

Direct Known Subclasses:

POIFSFileSystem, POIFSMiniStore

public abstract class BlockStore
extends Object

This abstract class describes a way to read, store, chain and free a series of blocks (be they Big or Small ones)

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected class	BlockStore.ChainLoopDetector	Used to detect if a chain has a loop in it, so we can bail out with an error rather than spinning away for ever...

Constructor Summary

Constructors

Constructor	Description
BlockStore()

Method Summary

Modifier and Type	Method	Description
protected abstract ByteBuffer	createBlockIfNeeded(int offset)	Extends the file if required to hold blocks up to the specified offset, and return the block from there.
protected abstract BATBlock.BATBlockAndIndex	getBATBlockAndIndex(int offset)	Returns the BATBlock that handles the specified offset, and the relative index within it
protected abstract ByteBuffer	getBlockAt(int offset)	Load the block at the given offset.
protected abstract int	getBlockStoreBlockSize()	Returns the size of the blocks managed through the block store.
protected abstract BlockStore.ChainLoopDetector	getChainLoopDetector()	Creates a Detector for loops in the chain
protected abstract int	getFreeBlock()	Finds a free block, and returns its offset.
protected abstract int	getNextBlock(int offset)	Works out what block follows the specified one.
protected abstract void	releaseBuffer(ByteBuffer buffer)	Releases a mmap-ed buffer, which you are sure won't be used again
protected abstract void	setNextBlock(int offset, int nextBlock)	Changes the record of what block follows the specified one.

Methods inherited from class java.lang.Object

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

Constructor Detail

BlockStore

public BlockStore()

Method Detail

getBlockStoreBlockSize

protected abstract int getBlockStoreBlockSize()

Returns the size of the blocks managed through the block store.

getBlockAt

protected abstract ByteBuffer getBlockAt(int offset)
                                  throws IOException

Load the block at the given offset.

Throws:

IOException

createBlockIfNeeded

protected abstract ByteBuffer createBlockIfNeeded(int offset)
                                           throws IOException

Extends the file if required to hold blocks up to the specified offset, and return the block from there.

Throws:

IOException

releaseBuffer

protected abstract void releaseBuffer(ByteBuffer buffer)

Releases a mmap-ed buffer, which you are sure won't be used again

Parameters:

buffer - the buffer

getBATBlockAndIndex

protected abstract BATBlock.BATBlockAndIndex getBATBlockAndIndex(int offset)

Returns the BATBlock that handles the specified offset, and the relative index within it

getNextBlock

protected abstract int getNextBlock(int offset)

Works out what block follows the specified one.

setNextBlock

protected abstract void setNextBlock(int offset,
                                     int nextBlock)

Changes the record of what block follows the specified one.

getFreeBlock

protected abstract int getFreeBlock()
                             throws IOException

Finds a free block, and returns its offset. This method will extend the file/stream if needed, and if doing so, allocate new FAT blocks to address the extra space.

Throws:

IOException

getChainLoopDetector

protected abstract BlockStore.ChainLoopDetector getChainLoopDetector()
                                                              throws IOException

Creates a Detector for loops in the chain

Throws:

IOException