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ScrambledKeyGenerator.javaAPI DocGlassfish v2 API4563Fri May 04 22:32:56 BST 2007com.sun.ejb.base.sfsb.util

ScrambledKeyGenerator

public class ScrambledKeyGenerator extends SimpleKeyGenerator
A utility class that generates stateful session keys using two longs The session id generated by this class is guarenteed to be unique as long as the system clock is never reset to a previous value The hashCode of the SessionKey generated by ScrambledKeyGenerator also allows uniform distribution of keys when hashed in a HashMap
author
Mahesh Kannan

Fields Summary
private SecureRandom
random
private int
cachedTime
Constructors Summary
public ScrambledKeyGenerator()


      
	init((int) System.currentTimeMillis(), System.identityHashCode(this));
public ScrambledKeyGenerator(byte[] ipAddress, int port)

	init(Utility.bytesToInt(ipAddress, 0), port);
public ScrambledKeyGenerator(long val)

	init((int) (val >>> 32), (int) ((val << 32) >>> 32));
Methods Summary
public java.lang.ObjectcreateSessionKey()
Create and return the sessionKey.

return
the sessionKey object

        int id = 0;
        synchronized (this) {
            id = ++idCounter;
            if (id < 0) {
                //idCounter wrapped around!!
                id = idCounter = 1;
	    }

	    if ((id & 0x000000FF) == 0) {
                cachedTime = (int) System.currentTimeMillis();
            }
        }
	
	return new SimpleSessionKey(
	    prefix + cachedTime,
	    //suffix + System.identityHashCode(new Object()), id
	    suffix + random.nextInt(), id
	);
private voidinit(int hi, int lo)

	byte[] hiBytes = new byte[4];
	Utility.intToBytes(hi, hiBytes, 0);
	byte[] loBytes = new byte[4];
	Utility.intToBytes(lo, loBytes, 0);

	swapBytes(hiBytes, loBytes, 2, 3);
	swapBytes(loBytes, loBytes, 2, 3);
	swapBytes(hiBytes, loBytes, 3, 0);
	swapBytes(hiBytes, hiBytes, 0, 3);
	swapBytes(hiBytes, loBytes, 1, 3);

	swapBytes(hiBytes, hiBytes, 0, 1);
	swapBytes(loBytes, loBytes, 2, 3);

        this.prefix = Utility.bytesToInt(hiBytes, 0);
	this.prefix <<= 32;
	
        this.suffix = Utility.bytesToInt(loBytes, 0);
	this.suffix <<= 32;

        //Inital isCounter value
        this.idCounter = 0;

        //Set the default time value
        this.cachedTime = (int) System.currentTimeMillis();
private static final voidswapBytes(byte[] a, byte[] b, int index1, int index2)

	byte temp = a[index1];
	a[index1] = b[index2];
	b[index2] = temp;