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package com.sun.ejb.base.sfsb.util;
import com.sun.ejb.spi.sfsb.util.SFSBUUIDUtil;
import com.sun.enterprise.util.Utility;
/**
* 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 SimpleKeyGenerator
* also allows uniform distribution of keys when hashed in a HashMap
*
* @author Mahesh Kannan
*/
public class SimpleKeyGenerator
implements SFSBUUIDUtil
{
protected long prefix;
protected long suffix;
protected int idCounter;
public SimpleKeyGenerator() {
long now = System.currentTimeMillis();
now = ((int) (now >>> 32)) + ((int) now);
scramble((int) now, System.identityHashCode(this));
}
public SimpleKeyGenerator(byte[] ipAddress, int port) {
scramble(Utility.bytesToInt(ipAddress, 0), port);
}
public SimpleKeyGenerator(long uniquePrefix) {
this.prefix = uniquePrefix;
//Initial suffix
this.suffix = System.currentTimeMillis();
//Inital isCounter value
this.idCounter = 0;
}
/**
* Create and return the sessionKey.
* @return the sessionKey object
*/
public Object createSessionKey() {
int id = 0;
synchronized (this) {
id = idCounter++;
if (id < 0) {
//idCounter wrapped around!!
id = idCounter = 0;
suffix = System.currentTimeMillis();
}
}
return new SimpleSessionKey(prefix, suffix, id);
}
/**
* Called from the Container before publishing an IOR.
* The method must convert the sessionKey into a byte[]
* @return A byte[] representation of the key. The byte[]
* could be created using serialization.
*/
public byte[] keyToByteArray(Object sessionKey) {
SimpleSessionKey key = (SimpleSessionKey) sessionKey;
byte[] array = new byte[20];
Utility.longToBytes(key.prefix, array, 0);
Utility.longToBytes(key.suffix, array, 8);
Utility.intToBytes(key.id, array, 16);
return array;
}
/**
* Return the sessionKey that represents the sessionKey.
* This has to be super efficient as the container calls this
* method on every invocation. Two objects obtained from identical
* byte[] must satisfy both o1.equals(o2) and
* o1.hashCode() == o2.hashCode()
* @return the sessionKey object
*/
public Object byteArrayToKey(byte[] array, int startIndex, int len) {
long myPrefix = Utility.bytesToLong(array, startIndex);
long mySuffix = Utility.bytesToLong(array, startIndex+8);
int myId = Utility.bytesToInt(array, startIndex+16);
return new SimpleSessionKey(myPrefix, mySuffix, myId);
}
private void scramble(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(hiBytes, loBytes, 3, 0);
swapBytes(hiBytes, loBytes, 1, 3);
swapBytes(hiBytes, hiBytes, 0, 3);
swapBytes(loBytes, loBytes, 2, 3);
this.prefix = Utility.bytesToInt(hiBytes, 0);
this.prefix =
(this.prefix << 32) + Utility.bytesToInt(loBytes, 0);
//Inital isCounter value
this.idCounter = 0;
//Set the default suffix value
this.suffix = (int) System.currentTimeMillis();
}
private static final void swapBytes(byte[] a, byte[] b,
int index1, int index2)
{
byte temp = a[index1];
a[index1] = b[index2];
b[index2] = temp;
}
protected static class SimpleSessionKey
implements java.io.Serializable
{
long prefix;
long suffix;
int id;
public SimpleSessionKey(long prefix, long suffix, int id) {
this.prefix = prefix;
this.suffix = suffix;
this.id = id;
}
public int hashCode() {
return (int) id;
}
public boolean equals(Object otherObj) {
if (otherObj instanceof SimpleSessionKey) {
SimpleSessionKey other = (SimpleSessionKey) otherObj;
return (
(id == other.id) && (prefix == other.prefix)
&& (suffix == other.suffix)
);
}
return false;
}
public String toString() {
StringBuffer sbuf = new StringBuffer();
sbuf.append(Long.toHexString(prefix)).append("-")
.append(Long.toHexString(suffix)).append("-")
.append(Integer.toHexString(id));
return sbuf.toString();
}
}
}
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