187 lines
5.5 KiB
Java
187 lines
5.5 KiB
Java
/* ====================================================================
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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==================================================================== */
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package org.apache.poi.poifs.storage;
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import java.io.IOException;
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import java.io.OutputStream;
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import java.nio.ByteBuffer;
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import org.apache.poi.poifs.common.POIFSBigBlockSize;
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import org.apache.poi.poifs.common.POIFSConstants;
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import org.apache.poi.poifs.filesystem.BATManaged;
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import org.apache.poi.util.IntList;
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/**
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* This class manages and creates the Block Allocation Table, which is
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* basically a set of linked lists of block indices.
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* <P>
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* Each block of the filesystem has an index. The first block, the
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* header, is skipped; the first block after the header is index 0,
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* the next is index 1, and so on.
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* <P>
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* A block's index is also its index into the Block Allocation
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* Table. The entry that it finds in the Block Allocation Table is the
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* index of the next block in the linked list of blocks making up a
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* file, or it is set to -2: end of list.
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*
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* @author Marc Johnson (mjohnson at apache dot org)
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*/
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public final class BlockAllocationTableWriter implements BlockWritable, BATManaged {
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private IntList _entries;
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private BATBlock[] _blocks;
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private int _start_block;
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private POIFSBigBlockSize _bigBlockSize;
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/**
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* create a BlockAllocationTableWriter
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*/
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public BlockAllocationTableWriter(POIFSBigBlockSize bigBlockSize)
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{
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_bigBlockSize = bigBlockSize;
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_start_block = POIFSConstants.END_OF_CHAIN;
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_entries = new IntList();
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_blocks = new BATBlock[ 0 ];
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}
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/**
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* Create the BATBlocks we need
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*
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* @return start block index of BAT blocks
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*/
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public int createBlocks()
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{
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int xbat_blocks = 0;
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int bat_blocks = 0;
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while (true)
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{
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int calculated_bat_blocks =
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BATBlock.calculateStorageRequirements(_bigBlockSize,
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bat_blocks
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+ xbat_blocks
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+ _entries.size());
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int calculated_xbat_blocks =
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HeaderBlockWriter.calculateXBATStorageRequirements(
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_bigBlockSize, calculated_bat_blocks);
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if ((bat_blocks == calculated_bat_blocks)
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&& (xbat_blocks == calculated_xbat_blocks))
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{
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// stable ... we're OK
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break;
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}
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bat_blocks = calculated_bat_blocks;
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xbat_blocks = calculated_xbat_blocks;
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}
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int startBlock = allocateSpace(bat_blocks);
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allocateSpace(xbat_blocks);
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simpleCreateBlocks();
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return startBlock;
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}
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/**
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* Allocate space for a block of indices
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*
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* @param blockCount the number of blocks to allocate space for
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*
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* @return the starting index of the blocks
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*/
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public int allocateSpace(final int blockCount)
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{
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int startBlock = _entries.size();
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if (blockCount > 0)
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{
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int limit = blockCount - 1;
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int index = startBlock + 1;
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for (int k = 0; k < limit; k++)
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{
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_entries.add(index++);
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}
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_entries.add(POIFSConstants.END_OF_CHAIN);
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}
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return startBlock;
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}
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/**
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* get the starting block
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*
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* @return the starting block index
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*/
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public int getStartBlock()
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{
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return _start_block;
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}
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/**
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* create the BATBlocks
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*/
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void simpleCreateBlocks()
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{
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_blocks = BATBlock.createBATBlocks(_bigBlockSize, _entries.toArray());
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}
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/**
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* Write the storage to an OutputStream
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*
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* @param stream the OutputStream to which the stored data should
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* be written
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*
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* @exception IOException on problems writing to the specified
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* stream
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*/
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public void writeBlocks(final OutputStream stream)
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throws IOException
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{
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for (int j = 0; j < _blocks.length; j++)
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{
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_blocks[ j ].writeBlocks(stream);
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}
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}
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/**
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* Write the BAT into its associated block
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*/
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public static void writeBlock(final BATBlock bat, final ByteBuffer block)
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throws IOException
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{
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bat.writeData(block);
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}
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/**
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* Return the number of BigBlock's this instance uses
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*
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* @return count of BigBlock instances
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*/
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public int countBlocks()
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{
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return _blocks.length;
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}
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/**
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* Set the start block for this instance
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*/
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public void setStartBlock(int start_block)
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{
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_start_block = start_block;
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}
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}
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