Uuid32Generator.java Source code

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Here is the source code for Uuid32Generator.java

Source

// Copyright (c) 2003-2009, Jodd Team (jodd.org). All Rights Reserved.

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

/**
 * UUID generator of 32 bytes long values. It is builded from:
 * <ol>
 * <li> (0-7) IPAddress as HEX - 8 bytes
 * <li> (8-19) CurrentTimeMillis() as HEX - Display all 12 bytes
 * <li> (20-23) SecureRandom() as HEX - Keep only 4 significant bytes. Since this is "random" it doesn't really matter how many bytes you keep or eliminate
 * <li> (24-31) System.identityHashCode as Hex - 8 bytes
 * </ol>
 */
public class Uuid32Generator {

    public static String generateUUID() {
        return new Uuid32Generator().generate();
    }

    private static final String ZEROS = "000000000000"; // 12

    public String generate() {
        StringBuilder strRetVal = new StringBuilder();
        String strTemp;
        try {
            // IPAddress segment
            InetAddress addr = InetAddress.getLocalHost();
            byte[] ipaddr = addr.getAddress();
            for (byte anIpaddr : ipaddr) {
                Byte b = new Byte(anIpaddr);
                strTemp = Integer.toHexString(b.intValue() & 0x000000ff);
                strRetVal.append(ZEROS.substring(0, 2 - strTemp.length()));
                strRetVal.append(strTemp);
            }
            strRetVal.append(':');

            // CurrentTimeMillis() segment
            strTemp = Long.toHexString(System.currentTimeMillis());
            strRetVal.append(ZEROS.substring(0, 12 - strTemp.length()));
            strRetVal.append(strTemp).append(':');

            // random segment
            SecureRandom prng = SecureRandom.getInstance("SHA1PRNG");
            strTemp = Integer.toHexString(prng.nextInt());
            while (strTemp.length() < 8) {
                strTemp = '0' + strTemp;
            }
            strRetVal.append(strTemp.substring(4)).append(':');

            // IdentityHash() segment
            strTemp = Long.toHexString(System.identityHashCode(this));
            strRetVal.append(ZEROS.substring(0, 8 - strTemp.length()));
            strRetVal.append(strTemp);
        } catch (UnknownHostException uhex) {
            throw new RuntimeException("Unknown host.", uhex);
        } catch (NoSuchAlgorithmException nsaex) {
            throw new RuntimeException("Algorithm 'SHA1PRNG' is unavailiable.", nsaex);
        }
        return strRetVal.toString().toUpperCase();
    }

}