AOO410/main/xmerge/source/xmerge/java/org/openoffice/xmerge/util/EndianConverter.java

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 * Licensed to the Apache Software Foundation (ASF) under one
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 * 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
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package org.openoffice.xmerge.util;


/**
 * <p>Helper class providing static methods to convert data to/from 
 *    Network Byte Order (Big Endian).</p>
 *
 * <p>With the introduction of <code>java.nio.ByteOrder</code> and 
 *    <code>java.nio.ByteBuffer</code> in Java 1.4, it may no longer be
 *    necessary to use this class in the future.</p>
 *
 * @author  Mark Murnane
 * @version 1.1
 */
public class EndianConverter {
    
    /**
     * <p>Convert a <code>short</code> to a Little Endian representation.</p>
     *
     * @param   value   The <code>short</code> to be converted.
     *
     * @return  Two element <code>byte</code> array containing the converted 
     *          value.
     */
    public static byte[] writeShort (short value) {
        byte[] leShort = new byte[2];
        
        leShort[0] = (byte) value;
        leShort[1] = (byte) (value >>> 8);
        
        return leShort;
    }
    
    
    /**
     * <p>Convert an integer to a Little Endian representation.</p>
     *
     * @param   value   The <code>int</code> to be converted.
     *
     * @return  Four element <code>byte</code> array containing the converted 
     *          value.
     */
    public static byte[] writeInt (int value) {
        byte[] leInt = new byte[4];
        
        leInt[0] = (byte) value;
        leInt[1] = (byte) (value >>> 8);
        leInt[2] = (byte) (value >>> 16);
        leInt[3] = (byte) (value >>> 24);
        
        return leInt;
    }

    /**
     * <p>Converts a <code>double</code> to a Little Endian representation 
	 * of a float in IEEE-754 format. 
     *
     * <p>An array with more than eight elements can be used, but only the first 
     * eight elements will be read.</p>
     *
     * @param   value <code>double</code> containing the value to be converted   
     *
     * @return   <code>byte</code> array containing the LE representation of a IEEE-754 float
     */    
    public static byte[] writeDouble(double value) {

		long myDouble = Double.doubleToLongBits(value);
		byte[] leDouble = new byte[8];

		leDouble[0] = (byte) (myDouble >>> 0);
		leDouble[1] = (byte) (myDouble >>> 8);
		leDouble[2] = (byte) (myDouble >>> 16);
		leDouble[3] = (byte) (myDouble >>> 24);
		leDouble[4] = (byte) (myDouble >>> 32);
		leDouble[5] = (byte) (myDouble >>> 40);
		leDouble[6] = (byte) (myDouble >>> 48);
		leDouble[7] = (byte) (myDouble >>> 56);

		return leDouble; 
    }    
    
    /**
     * <p>Convert a Little Endian representation of a short to a Java 
     *    <code>short</code> (Network Byte Order).</p>
     *
     * <p>An array with more than two elements can be used, but only the first 
     *    two elements will be read.</p>
     *
     * @param   value   <code>byte</code> array containing the LE representation 
     *                  of the value.
     *
     * @return  <code>short</code> containing the converted value.
     */
    public static short readShort (byte[] value) {
        int high, low;
        
        high = value[1] & 0xFF;
        low  = value[0] & 0xFF;
        
        return (short)(high << 8 | low);
    }
    
    
    /**
     * <p>Convert a Little Endian representation of an integer to a Java 
     *    <code>int</code> (Network Byte Order).</p>
     *
     * <p>An array with more than four elements can be used, but only the first 
     * four elements will be read.</p>
     *
     * @param   value   <code>byte</code> array containing the LE representation 
     *                  of the value.
     *
     * @return  <code>int</code> containing the converted value.
     */    
    public static int readInt(byte[] value) {
        int number = 0;
        
        for (int i = 0; i < 4; i++) {
            number |= (value[i] & 0xFF) << ( i * 8);
        } 
        
        return number;
    }

    /**
     * <p>Convert a Little Endian representation of a float in IEEE-754 Little
	 * Endian to a Java <code>double</code> (Network Byte Order).</p>
     *
     * <p>An array with more than eight elements can be used, but only the first 
     * eight elements will be read.</p>
     *
     * @param   value   <code>byte</code> array containing the LE representation 
     *                  of a IEEE-754 float. 
     *
     * @return  <code>double</code> containing the converted value.
     */    
    public static double readDouble(byte[] value) {
		
		long lvalue = (	((long)(value[7]) 		<< 56)	+
						((long)(value[6]&0xFF)	<< 48)	+
						((long)(value[5]&0xFF)	<< 40)	+
						((long)(value[4]&0xFF)	<< 32)	+
						((long)(value[3]&0xFF)	<< 24)	+
						((long)(value[2]&0xFF)	<< 16)	+
						((long)(value[1]&0xFF)	<< 8)	+
					 	(long)(value[0]&0xFF));
										 
		return Double.longBitsToDouble(lvalue);
    }
}