Package org.apache.poi.poifs.filesystem
Class BlockStore
java.lang.Object
org.apache.poi.poifs.filesystem.BlockStore
- Direct Known Subclasses:
POIFSFileSystem
,POIFSMiniStore
This abstract class describes a way to read, store, chain
and free a series of blocks (be they Big or Small ones)
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprotected class
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 -
Method Summary
Modifier and TypeMethodDescriptionprotected 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 itprotected abstract ByteBuffer
getBlockAt
(int offset) Load the block at the given offset.protected abstract int
Returns the size of the blocks managed through the block store.protected abstract BlockStore.ChainLoopDetector
Creates a Detector for loops in the chainprotected abstract int
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
setNextBlock
(int offset, int nextBlock) Changes the record of what block follows the specified one.
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Constructor Details
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BlockStore
public BlockStore()
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Method Details
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getBlockStoreBlockSize
protected abstract int getBlockStoreBlockSize()Returns the size of the blocks managed through the block store. -
getBlockAt
Load the block at the given offset.- Throws:
IOException
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createBlockIfNeeded
Extends the file if required to hold blocks up to the specified offset, and return the block from there.- Throws:
IOException
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getBATBlockAndIndex
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
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
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getChainLoopDetector
Creates a Detector for loops in the chain- Throws:
IOException
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