// 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();
}
}
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