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UUIDGenerator.javaAPI DocApache Tomcat 6.0.142936Fri Jul 20 04:20:36 BST 2007org.apache.catalina.tribes.util

UUIDGenerator

public class UUIDGenerator extends Object
simple generation of a UUID
author
Filip Hanik
version
1.0

Fields Summary
public static final int
UUID_LENGTH
public static final int
UUID_VERSION
public static final int
BYTES_PER_INT
public static final int
BITS_PER_BYTE
protected static SecureRandom
secrand
protected static Random
rand
Constructors Summary
Methods Summary
public static voidnextBytes(byte[] into, int offset, int length, java.util.Random r)
Same as java.util.Random.nextBytes except this one we dont have to allocate a new byte array

param
into byte[]
param
offset int
param
length int
param
r Random

        int numRequested = length;
        int numGot = 0, rnd = 0;
        while (true) {
            for (int i = 0; i < BYTES_PER_INT; i++) {
                if (numGot == numRequested) return;
                rnd = (i == 0 ? r.nextInt() : rnd >> BITS_PER_BYTE);
                into[offset+numGot] = (byte) rnd;
                numGot++;
            }
        }
public static byte[]randomUUID(boolean secure)

     
        secrand = new SecureRandom();
        secrand.setSeed(rand.nextLong());
    
        byte[] result = new byte[UUID_LENGTH];
        return randomUUID(secure,result,0);
public static byte[]randomUUID(boolean secure, byte[] into, int offset)

        if ( (offset+UUID_LENGTH)>into.length )
            throw new ArrayIndexOutOfBoundsException("Unable to fit "+UUID_LENGTH+" bytes into the array. length:"+into.length+" required length:"+(offset+UUID_LENGTH));
        Random r = (secure&&(secrand!=null))?secrand:rand;
        nextBytes(into,offset,UUID_LENGTH,r);
        into[6+offset] &= 0x0F;
        into[6+offset] |= (UUID_VERSION << 4);
        into[8+offset] &= 0x3F; //0011 1111
        into[8+offset] |= 0x80; //1000 0000
        return into;