uuidgen.java

服务器端源文件：btServer-20050819.zip

/**
 * Name: 		UUIDGen.java
 * Author: 		uk-dave (http://www.uk-dave.com)
 * Date: 		23th July 2003
 * Description:	Generates random-number based UUIDs
 *              This program should really use java.security.SecureRandom to ensure that random numbers are truly random (well, as near as),
 *              but becuase this program is to be used on TINI's and SNAP's plain old java.util.Random has to be used instead.
 * Useful Links:
 *              What is a UUID: http://www.dsps.net/uuid.html
 *              UUID Spec: http://www.opengroup.org/onlinepubs/9629399/apdxa.htm
 *              Proper Java UUID Generator: http://www.doomdark.org/doomdark/proj/jug/
 * 
 * Notes       : Modify by renyi to generate UUIDs without "-" sysmbol. JSR-82 only accepts UUID with
 * 				 no "-" symbol	
 */


package btServer;
import java.util.Random;
//import java.security.SecureRandom;

public class UUIDGen
{
	private static final String hexChars = "0123456789abcdef";
	private static final byte INDEX_TYPE = 6;
    private static final byte INDEX_VARIATION = 8;
    private static final byte TYPE_RANDOM_BASED = 4;

	private Random rnd;


	/**
	 * Constructor. Instantiates the rnd object to generate random numbers.
	 */
	public UUIDGen()
	{
		rnd = new Random(System.currentTimeMillis());
	}


	/**
	 * Generates a random UUID and returns the String representation of it.
	 * @returns a String representing a randomly generated UUID.
	 */
	public String generateUUID()
	{
		// Generate 128-bit random number
		byte[] uuid = new byte[16];
		nextRandomBytes(uuid);

		// Set various bits such as type
		uuid[INDEX_TYPE] &= (byte) 0x0F;
		uuid[INDEX_TYPE] |= (byte) (TYPE_RANDOM_BASED << 4);
		uuid[INDEX_VARIATION] &= (byte) 0x3F;
		uuid[INDEX_VARIATION] |= (byte) 0x80;

		// Convert byte array into a UUID formated string
		StringBuffer b = new StringBuffer(36);
		for (int i=0; i<16; i++)
		{
		    // Mod by renyi
			//if (i==4 || i==6 || i==8 || i==10) b.append('-');
			int hex = uuid[i] & 0xFF;
			b.append(hexChars.charAt(hex >> 4));
			b.append(hexChars.charAt(hex & 0x0F));
		}

		// Return UUID
		return b.toString();
	}


	/**
	 * Generates random bytes and places them into a user-supplied byte array.
	 * The number of random bytes produced is equal to the length of the byte array.
	 * Nicked from java.util.Random becuase the stupid SNAP board doesn't have this method!
	 * @param bytes the non-null byte array in which to put the random bytes.
	 */
	private void nextRandomBytes(byte[] bytes)
	{
		int numRequested = bytes.length;
		int numGot = 0, rand = 0;
		while (true)
		{
	    	for (int i=0; i<4; i++)
			{
				if (numGot == numRequested)
		    			return;
				rand = (i==0 ? rnd.nextInt() : rand>>8);
				bytes[numGot++] = (byte)rand;
	 		}
		}
    }


	/**
	 * Main. Only here for testing purposes.
	 */
	public static void main(String[] args)
	{
		UUIDGen uuidgen = new UUIDGen();
		System.out.println(uuidgen.generateUUID());
	}
}