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The Apache Commons Codec package contains simple encoder and decoders for various formats such as Base64 and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities.
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/* ====================================================================
   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.util;

import org.apache.poi.util.LittleEndian.BufferUnderrunException;

import java.io.*;

/**
 * representation of an integer (32-bit) field at a fixed location
 * within a byte array
 *
 * @author Marc Johnson (mjohnson at apache dot org
 */

public class IntegerField
    implements FixedField
{
    private int       _value;
    private final int _offset;

    /**
     * construct the IntegerField with its offset into its containing
     * byte array
     *
     * @param offset of the field within its byte array
     *
     * @exception ArrayIndexOutOfBoundsException if the offset is
     *            negative
     */

    public IntegerField(final int offset)
        throws ArrayIndexOutOfBoundsException
    {
        if (offset < 0)
        {
            throw new ArrayIndexOutOfBoundsException("negative offset");
        }
        _offset = offset;
    }

    /**
     * construct the IntegerField with its offset into its containing
     * byte array and initialize its value
     *
     * @param offset of the field within its byte array
     * @param value the initial value
     *
     * @exception ArrayIndexOutOfBoundsException if the offset is
     *            negative
     */

    public IntegerField(final int offset, final int value)
        throws ArrayIndexOutOfBoundsException
    {
        this(offset);
        set(value);
    }

    /**
     * Construct the IntegerField with its offset into its containing
     * byte array and initialize its value from its byte array
     *
     * @param offset of the field within its byte array
     * @param data the byte array to read the value from
     *
     * @exception ArrayIndexOutOfBoundsException if the offset is not
     *            within the range of 0..(data.length - 1)
     */

    public IntegerField(final int offset, final byte [] data)
        throws ArrayIndexOutOfBoundsException
    {
        this(offset);
        readFromBytes(data);
    }

    /**
     * construct the IntegerField with its offset into its containing
     * byte array, initialize its value, and write the value to a byte
     * array
     *
     * @param offset of the field within its byte array
     * @param value the initial value
     * @param data the byte array to write the value to
     *
     * @exception ArrayIndexOutOfBoundsException if the offset is
     *            negative or too large
     */

    public IntegerField(final int offset, final int value, final byte [] data)
        throws ArrayIndexOutOfBoundsException
    {
        this(offset);
        set(value, data);
    }

    /**
     * get the IntegerField's current value
     *
     * @return current value
     */

    public int get()
    {
        return _value;
    }

    /**
     * set the IntegerField's current value
     *
     * @param value to be set
     */

    public void set(final int value)
    {
        _value = value;
    }

    /**
     * set the IntegerField's current value and write it to a byte
     * array
     *
     * @param value to be set
     * @param data the byte array to write the value to
     *
     * @exception ArrayIndexOutOfBoundsException if the offset is too
     *            large
     */

    public void set(final int value, final byte [] data)
        throws ArrayIndexOutOfBoundsException
    {
        _value = value;
        writeToBytes(data);
    }

    /* ********** START implementation of FixedField ********** */

    /**
     * set the value from its offset into an array of bytes
     *
     * @param data the byte array from which the value is to be read
     *
     * @exception ArrayIndexOutOfBoundsException if the offset is too
     *            large
     */

    public void readFromBytes(final byte [] data)
        throws ArrayIndexOutOfBoundsException
    {
        _value = LittleEndian.getInt(data, _offset);
    }

    /**
     * set the value from an InputStream
     *
     * @param stream the InputStream from which the value is to be
     *               read
     *
     * @exception BufferUnderrunException if there is not enough data
     *            available from the InputStream
     * @exception IOException if an IOException is thrown from reading
     *            the InputStream
     */

    public void readFromStream(final InputStream stream)
        throws IOException
    {
        _value = LittleEndian.readInt(stream);
    }

    /**
     * write the value out to an array of bytes at the appropriate
     * offset
     *
     * @param data the array of bytes to which the value is to be
     *             written
     *
     * @exception ArrayIndexOutOfBoundsException if the offset is too
     *            large
     */

    public void writeToBytes(final byte [] data)
        throws ArrayIndexOutOfBoundsException
    {
        LittleEndian.putInt(data, _offset, _value);
    }

    /**
     * return the value as a String
     *
     * @return the value as a String
     */

    public String toString()
    {
        return String.valueOf(_value);
    }

    /* **********  END  implementation of FixedField ********** */
}   // end public class IntegerField