poi/src/java/org/apache/poi/poifs/storage/HeaderBlockWriter.java

/* ====================================================================
   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
==================================================================== */
        

package org.apache.poi.poifs.storage;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;

import org.apache.poi.poifs.common.POIFSBigBlockSize;
import org.apache.poi.poifs.common.POIFSConstants;

/**
 * The block containing the archive header
 *
 * @author Marc Johnson (mjohnson at apache dot org)
 */
public class HeaderBlockWriter implements HeaderBlockConstants, BlockWritable
{
   private final HeaderBlock _header_block;

    /**
     * Create a single instance initialized with default values
     */
    public HeaderBlockWriter(POIFSBigBlockSize bigBlockSize)
    {
       _header_block = new HeaderBlock(bigBlockSize);
    }

    /**
     * Create a single instance initialized with the specified 
     *  existing values
     */
    public HeaderBlockWriter(HeaderBlock headerBlock)
    {
       _header_block = headerBlock;
    }

    /**
     * Set BAT block parameters. Assumes that all BAT blocks are
     * contiguous. Will construct XBAT blocks if necessary and return
     * the array of newly constructed XBAT blocks.
     *
     * @param blockCount count of BAT blocks
     * @param startBlock index of first BAT block
     *
     * @return array of XBAT blocks; may be zero length, will not be
     *         null
     */

    public BATBlock [] setBATBlocks(final int blockCount,
                                    final int startBlock)
    {
        BATBlock[] rvalue;
        POIFSBigBlockSize bigBlockSize = _header_block.getBigBlockSize();

        _header_block.setBATCount(blockCount);

        // Set the BAT locations
        int limit  = Math.min(blockCount, _max_bats_in_header);
        int[] bat_blocks = new int[limit];
        for (int j = 0; j < limit; j++) {
           bat_blocks[j] = startBlock + j;
        }
        _header_block.setBATArray(bat_blocks);
        
        // Now do the XBATs
        if (blockCount > _max_bats_in_header)
        {
            int   excess_blocks      = blockCount - _max_bats_in_header;
            int[] excess_block_array = new int[ excess_blocks ];

            for (int j = 0; j < excess_blocks; j++)
            {
                excess_block_array[ j ] = startBlock + j
                                          + _max_bats_in_header;
            }
            rvalue = BATBlock.createXBATBlocks(bigBlockSize, excess_block_array,
                                               startBlock + blockCount);
            _header_block.setXBATStart(startBlock + blockCount);
        }
        else
        {
            rvalue = BATBlock.createXBATBlocks(bigBlockSize, new int[ 0 ], 0);
            _header_block.setXBATStart(POIFSConstants.END_OF_CHAIN);
        }
        _header_block.setXBATCount(rvalue.length);
        return rvalue;
    }

    /**
     * Set start of Property Table
     *
     * @param startBlock the index of the first block of the Property
     *                   Table
     */
    public void setPropertyStart(final int startBlock)
    {
       _header_block.setPropertyStart(startBlock);
    }

    /**
     * Set start of small block allocation table
     *
     * @param startBlock the index of the first big block of the small
     *                   block allocation table
     */
    public void setSBATStart(final int startBlock)
    {
        _header_block.setSBATStart(startBlock);
    }

    /**
     * Set count of SBAT blocks
     *
     * @param count the number of SBAT blocks
     */
    public void setSBATBlockCount(final int count)
    {
       _header_block.setSBATBlockCount(count);
    }

    /**
     * For a given number of BAT blocks, calculate how many XBAT
     * blocks will be needed
     *
     * @param blockCount number of BAT blocks
     *
     * @return number of XBAT blocks needed
     */

    static int calculateXBATStorageRequirements(POIFSBigBlockSize bigBlockSize, final int blockCount)
    {
        return (blockCount > _max_bats_in_header)
               ? BATBlock.calculateXBATStorageRequirements(
                     bigBlockSize, blockCount - _max_bats_in_header)
               : 0;
    }

    /* ********** START extension of BigBlock ********** */

    /**
     * Write the block's data to an OutputStream
     *
     * @param stream the OutputStream to which the stored data should
     *               be written
     *
     * @exception IOException on problems writing to the specified
     *            stream
     */
    public void writeBlocks(final OutputStream stream)
        throws IOException
    {
        _header_block.writeData(stream);
    }
    
    /**
     * Write the block's data to an existing block
     *
     * @param block the ByteBuffer of the block to which the 
     *               stored data should be written
     *
     * @exception IOException on problems writing to the block
     */
    public void writeBlock(ByteBuffer block)
        throws IOException
    {
       ByteArrayOutputStream baos = new ByteArrayOutputStream(
             _header_block.getBigBlockSize().getBigBlockSize()
       );
       _header_block.writeData(baos);
       
       block.put(baos.toByteArray());
    }

    /* **********  END  extension of BigBlock ********** */
}   // end public class HeaderBlockWriter