utility.java

解决了nat穿越的问题

/*
 * This file is part of JSTUN. 
 * 
 * Copyright (c) 2005 Thomas King <[e-mail]> - All rights
 * reserved.
 * 
 * This software is licensed under either the GNU Public License (GPL),
 * or the Apache 2.0 license. Copies of both license agreements are
 * included in this distribution.
 */

package de.javawi.jstun.util;

public class Utility {

	public static final byte IntegerToOneByte(int value) throws UtilityException {
		if ((value > Math.pow(2,15)) || (value < 0)) {
			throw new UtilityException("Integer value " + value + " is larger than 2^15");
		}
		return (byte)(value & 0xFF);
	}
	
	public static final byte[] IntegerToTwoBytes(int value) throws UtilityException {
		byte[] result = new byte[2];
		if ((value > Math.pow(2,31)) || (value < 0)) {
			throw new UtilityException("Integer value " + value + " is larger than 2^31");
		}
        result[0] = (byte)((value >>> 8) & 0xFF);
        result[1] = (byte)(value & 0xFF);
		return result; 
	}
	
	public static final byte[] IntegerToFourBytes(int value) throws UtilityException {
		byte[] result = new byte[4];
		if ((value > Math.pow(2,63)) || (value < 0)) {
			throw new UtilityException("Integer value " + value + " is larger than 2^63");
		}
        result[0] = (byte)((value >>> 24) & 0xFF);
		result[1] = (byte)((value >>> 16) & 0xFF);
		result[2] = (byte)((value >>> 8) & 0xFF);
        result[3] = (byte)(value & 0xFF);
		return result; 
	}
	
	public static final int OneByteToInteger(byte value) throws UtilityException {
		return (int)value & 0xFF;
	}
	
	public static final int TwoBytesToInteger(byte[] value) throws UtilityException {
		if (value.length < 2) {
			throw new UtilityException("Byte array too short!");
		}
        int temp0 = value[0] & 0xFF;
        int temp1 = value[1] & 0xFF;
        return ((temp0 << 8) + temp1);
	}
	
	public static final long FourBytesToLong(byte[] value) throws UtilityException {
		if (value.length < 4) {
			throw new UtilityException("Byte array too short!");
		}
        int temp0 = value[0] & 0xFF;
        int temp1 = value[1] & 0xFF;
		int temp2 = value[2] & 0xFF;
		int temp3 = value[3] & 0xFF;
        return (((long)temp0 << 24) + (temp1 << 16) + (temp2 << 8) + temp3);
	}	                                      
}