conversion.java

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/**
 * JDBM LICENSE v1.00
 *
 * Redistribution and use of this software and associated documentation
 * ("Software"), with or without modification, are permitted provided
 * that the following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright
 *    statements and notices.  Redistributions must also contain a
 *    copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the
 *    above copyright notice, this list of conditions and the
 *    following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. The name "JDBM" must not be used to endorse or promote
 *    products derived from this Software without prior written
 *    permission of Cees de Groot.  For written permission,
 *    please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "JDBM"
 *    nor may "JDBM" appear in their names without prior written
 *    permission of Cees de Groot.
 *
 * 5. Due credit should be given to the JDBM Project
 *    (http://jdbm.sourceforge.net/).
 *
 * THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 2001 (C) Alex Boisvert. All Rights Reserved.
 * Contributions are Copyright (C) 2001 by their associated contributors.
 *
 */

package jdbm.helper;


/**
 * Miscelaneous conversion utility methods.
 *
 * @author <a href="mailto:[e-mail]">Alex Boisvert</a>
 * @version $Id: Conversion.java,v 1.3 2002/05/31 06:33:20 boisvert Exp $
 */
public class Conversion
{

    /**
     * Convert a string into a byte array.
     */
    public static byte[] convertToByteArray( String s )
    {
        try {
            // see the following page for character encoding
            // http://java.sun.com/products/jdk/1.1/docs/guide/intl/encoding.doc.html
            return s.getBytes( "UTF8" );
        } catch ( java.io.UnsupportedEncodingException uee ) {
            uee.printStackTrace();
            throw new Error( "Platform doesn't support UTF8 encoding" );
        }
    }


    /**
     * Convert a byte into a byte array.
     */
    public static byte[] convertToByteArray( byte n )
    {
        n = (byte)( n ^ ( (byte) 0x80 ) ); // flip MSB because "byte" is signed
        return new byte[] { n };
    }


    /**
     * Convert a short into a byte array.
     */
    public static byte[] convertToByteArray( short n )
    {
        n = (short) ( n ^ ( (short) 0x8000 ) ); // flip MSB because "short" is signed
        byte[] key = new byte[ 2 ];
        pack2( key, 0, n );
        return key;
    }


    /**
     * Convert an int into a byte array.
     */
    public static byte[] convertToByteArray( int n )
    {
        n = (n ^ 0x80000000); // flip MSB because "int" is signed
        byte[] key = new byte[4];
        pack4(key, 0, n);
        return key;
    }


    /**
     * Convert a long into a byte array.
     */
    public static byte[] convertToByteArray( long n )
    {
        n = (n ^ 0x8000000000000000L); // flip MSB because "long" is signed
        byte[] key = new byte[8];
        pack8( key, 0, n );
        return key;
    }


    /**
     * Convert a byte array (encoded as UTF-8) into a String
     */
    public static String convertToString( byte[] buf )
    {
        try {
            // see the following page for character encoding
            // http://java.sun.com/products/jdk/1.1/docs/guide/intl/encoding.doc.html
            return new String( buf, "UTF8" );
        } catch ( java.io.UnsupportedEncodingException uee ) {
            uee.printStackTrace();
            throw new Error( "Platform doesn't support UTF8 encoding" );
        }
    }


    /**
     * Convert a byte array into an integer (signed 32-bit) value.
     */
    public static int convertToInt( byte[] buf )
    {
        int value = unpack4( buf, 0 );
        value = ( value ^ 0x80000000 ); // flip MSB because "int" is signed
        return value;
    }


    /**
     * Convert a byte array into a long (signed 64-bit) value.
     */
    public static long convertToLong( byte[] buf )
    {
        long value = ( (long) unpack4( buf, 0 ) << 32  )
                     + ( unpack4( buf, 4 ) & 0xFFFFFFFFL );
        value = ( value ^ 0x8000000000000000L ); // flip MSB because "long" is signed
        return value;
    }




    static int unpack4( byte[] buf, int offset )
    {
        int value = ( buf[ offset ] << 24 )
            | ( ( buf[ offset+1 ] << 16 ) & 0x00FF0000 )
            | ( ( buf[ offset+2 ] << 8 ) & 0x0000FF00 )
            | ( ( buf[ offset+3 ] << 0 ) & 0x000000FF );

        return value;
    }


    static final void pack2( byte[] data, int offs, int val )
    {
        data[offs++] = (byte) ( val >> 8 );
        data[offs++] = (byte) val;
    }


    static final void pack4( byte[] data, int offs, int val )
    {
        data[offs++] = (byte) ( val >> 24 );
        data[offs++] = (byte) ( val >> 16 );
        data[offs++] = (byte) ( val >> 8 );
        data[offs++] = (byte) val;
    }


    static final void pack8( byte[] data, int offs, long val )
    {
        pack4( data, 0, (int) ( val >> 32 ) );
        pack4( data, 4, (int) val );
    }


    /**
     * Test static methods
     */
    public static void main( String[] args )
    {
        byte[] buf;

        buf = convertToByteArray( (int) 5 );
        System.out.println( "int value of 5 is: " + convertToInt( buf ) );

        buf = convertToByteArray( (int) -1 );
        System.out.println( "int value of -1 is: " + convertToInt( buf ) );

        buf = convertToByteArray( (int) 22111000 );
        System.out.println( "int value of 22111000 is: " + convertToInt( buf ) );


        buf = convertToByteArray( (long) 5L );
        System.out.println( "long value of 5 is: " + convertToLong( buf ) );

        buf = convertToByteArray( (long) -1L );
        System.out.println( "long value of -1 is: " + convertToLong( buf ) );

        buf = convertToByteArray( (long) 1112223334445556667L );
        System.out.println( "long value of 1112223334445556667 is: " + convertToLong( buf ) );
    }

}