rawdatablock.java

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/* ====================================================================
   Copyright 2002-2004   Apache Software Foundation

   Licensed 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 org.apache.poi.poifs.common.POIFSConstants;
import org.apache.poi.util.IOUtils;

import java.io.*;

/**
 * A big block created from an InputStream, holding the raw data
 *
 * @author Marc Johnson (mjohnson at apache dot org
 */

public class RawDataBlock
    implements ListManagedBlock
{
    private byte[]  _data;
    private boolean _eof;

    /**
     * Constructor RawDataBlock
     *
     * @param stream the InputStream from which the data will be read
     *
     * @exception IOException on I/O errors, and if an insufficient
     *            amount of data is read
     */

    public RawDataBlock(final InputStream stream)
        throws IOException
    {
        _data = new byte[ POIFSConstants.BIG_BLOCK_SIZE ];
        int count = IOUtils.readFully(stream, _data);

        if (count == -1)
        {
            _eof = true;
        }
        else if (count != POIFSConstants.BIG_BLOCK_SIZE)
        {
            String type = " byte" + ((count == 1) ? ("")
                                                  : ("s"));

            throw new IOException("Unable to read entire block; " + count
                                  + type + " read; expected "
                                  + POIFSConstants.BIG_BLOCK_SIZE + " bytes");
        }
        else
        {
            _eof = false;
        }
    }

    /**
     * When we read the data, did we hit end of file?
     *
     * @return true if no data was read because we were at the end of
     *         the file, else false
     *
     * @exception IOException
     */

    public boolean eof()
        throws IOException
    {
        return _eof;
    }

    /* ********** START implementation of ListManagedBlock ********** */

    /**
     * Get the data from the block
     *
     * @return the block's data as a byte array
     *
     * @exception IOException if there is no data
     */

    public byte [] getData()
        throws IOException
    {
        if (eof())
        {
            throw new IOException("Cannot return empty data");
        }
        return _data;
    }

    /* **********  END  implementation of ListManagedBlock ********** */
}   // end public class RawDataBlock