bitsetutils.java

基于人工免疫原理的入侵检测系统框架

/*=================
 * Copyright (C) 2001  Todd Kaplan
 *
 * Lisys is a program that monitors TCP SYN packets to detect network
 * traffic anomalies.
 *
 * Licensed under the GNU General Public License (GPL), version 2 or
 * higher.  Please see the COPYING and PATENT files included with the 
 * Lisys distribution, which can be found at:
 *
 *   http://www.cs.unm.edu/~judd/lisys/
 *
 * Also, the current text of the GPL can be found at: 
 *
 *   http://www.gnu.org/copyleft/gpl.html
 * 
 * Note that Lisys has NO WARRANTY!
 *=================*/

package edu.unm.cs.lisys.util;

import edu.unm.cs.lisys.debug.*;
import java.util.*;

/**==========
 * BitSetUtils.java
 *   This class adds a couple methods for making BitSets.
 *
 * Here are the people who have worked on this code in the order they
 * have worked on it:
 *   @author Todd Kaplan <[e-mail]>
 *   @author Justin Balthrop <[e-mail]>
 *==========*/

public class BitSetUtils
{
    /**==========
     * byteToBitSet:
     *   Makes a BitSet from a byte.
     *
     * @param b the byte to be converted
     * @return a BitSet
     *==========*/
    public static BitSet byteToBitSet(byte b)
    {
	BitSet bs = new BitSet(8);

	int num = (int) b;
	
	if (num < 0) num += 256;
	
	int divisor = 128;
	int msb = 7;
	
	for (int i = 0; i <= 7; i++) {
	    if ((num / divisor) > 0) {
		bs.set(i);
		num -= divisor;
	    }
	    divisor /= 2;
	}
	return bs;
    }

    /**==========
     * mergeBytes:
     *   Make a BitSet by merging an array of bytes.
     *
     * @param bytes an array of bytes
     * @return a BitSet
     *==========*/
    public static BitSet mergeBytes(byte[] bytes)
    {
	int numBytes = bytes.length;
	BitSet bs = new BitSet(numBytes);
	int bits = 8;
	BitSet tempBS;
	int index = 0;

	for (int i = 0; i < numBytes; i++) {
	    tempBS = byteToBitSet(bytes[i]);
	    for (int j = 0; j < bits; j++, index++) {
		if (tempBS.get(j) == true)
		    bs.set(index);
	    }
	}
	return bs;
    }
}