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## org.apache.poi.poifs.storage
Class BlockAllocationTableWriter

    java.lang.Object
      org.apache.poi.poifs.storage.BlockAllocationTableWriter

All Implemented Interfaces:
  BATManaged, BlockWritable

    public final class BlockAllocationTableWriter

extends java.lang.Object
implements BlockWritable, BATManaged

This class manages and creates the Block Allocation Table, which is basically a set of linked lists of block indices.

Each block of the filesystem has an index. The first block, the header, is skipped; the first block after the header is index 0, the next is index 1, and so on.

A block's index is also its index into the Block Allocation Table. The entry that it finds in the Block Allocation Table is the index of the next block in the linked list of blocks making up a file, or it is set to -2: end of list.

Author:
  Marc Johnson (mjohnson at apache dot org)

Constructor Summary
`BlockAllocationTableWriter(POIFSBigBlockSize bigBlockSize)` create a BlockAllocationTableWriter

Method Summary
`int` | `allocateSpace(int blockCount)` Allocate space for a block of indices
`int` | `countBlocks()` Return the number of BigBlock's this instance uses
`int` | `createBlocks()` Create the BATBlocks we need
`int` | `getStartBlock()` get the starting block
`void` | `setStartBlock(int start_block)` Set the start block for this instance
`static void` | `writeBlock(BATBlock bat, java.nio.ByteBuffer block)` Write the BAT into its associated block
`void` | `writeBlocks(java.io.OutputStream stream)` Write the storage to an OutputStream

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### BlockAllocationTableWriter

    public BlockAllocationTableWriter(POIFSBigBlockSize bigBlockSize)

  create a BlockAllocationTableWriter

Method Detail

### createBlocks

    public int createBlocks()

  Create the BATBlocks we need

  Returns:
    start block index of BAT blocks

### allocateSpace

    public int allocateSpace(int blockCount)

  Allocate space for a block of indices

  Parameters:
    `blockCount` - the number of blocks to allocate space for
  Returns:
    the starting index of the blocks

### getStartBlock

    public int getStartBlock()

  get the starting block

  Returns:
    the starting block index

### writeBlocks

    public void writeBlocks(java.io.OutputStream stream)
                     throws java.io.IOException

  Write the storage to an OutputStream

  Specified by:
    `writeBlocks` in interface `BlockWritable`
  Parameters:
    `stream` - the OutputStream to which the stored data should be written
  Throws:
    `java.io.IOException` - on problems writing to the specified stream

### writeBlock

    public static void writeBlock(BATBlock bat,
                                  java.nio.ByteBuffer block)
                           throws java.io.IOException

  Write the BAT into its associated block

  Throws:
    `java.io.IOException`

### countBlocks

    public int countBlocks()

  Return the number of BigBlock's this instance uses

  Specified by:
    `countBlocks` in interface `BATManaged`
  Returns:
    count of BigBlock instances

### setStartBlock

    public void setStartBlock(int start_block)

  Set the start block for this instance

  Specified by:
    `setStartBlock` in interface `BATManaged`
  Parameters:
    `start_block` - index into the array of BigBlock instances making up the the filesystem

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Copyright 2017 The Apache Software Foundation or its licensors, as applicable.