package peersim.pastry;

import java.math.BigInteger;
import java.util.Random;

//_________________________________________________________________________________________________
/**
 * This initializator assign to the Nodes a nodeId (stored in the protocol
 * MSPastryProtocol) by using this 128-bit (32 byte) random generator.
 *
 * <b>Warning:</b> this implementation is not serialized and is not thread-safe
 * <p>Title: MSPASTRY</p>
 *
 * <p>Description: MsPastry implementation for PeerSim</p>
 *
 * <p>Copyright: Copyright (c) 2007</p>
 *
 * <p>Company: The Pastry Group</p>
 *
 * @author Elisa Bisoffi, Manuel Cortella
 * @version 1.0
 */
public final class UniformRandomGenerator {

    //______________________________________________________________________________________________
    private final Random rnd;
    private final int bits;


    //______________________________________________________________________________________________
    private final BigInteger nextRand() {
        return new BigInteger(bits, rnd);
    }


    //______________________________________________________________________________________________
    /**
     * initialized this random generator with the specified random seeder and the number of desider bits
     * to generate
     * @param aBits int
     * @param r Random
     */
    public UniformRandomGenerator(int aBits, Random r) {
        bits = aBits;
        rnd = r;
    }

    //______________________________________________________________________________________________
    /**
     * instanciate the random generator with the given seed
     * @param aSeed long
     * @param aBits number of bits of the number-to-be-generateed
     */
    public UniformRandomGenerator(int aBits, long aSeed) {
        this(aBits, new Random(aSeed));
    }


    //______________________________________________________________________________________________
    /**
     * Returns a unique 128-bit random number.
     * The number is also put into an internal store to check it will be never
     * returned again
     * @return BigInteger
     */
    public final BigInteger generate() {
        return nextRand();
    }
    //______________________________________________________________________________________________

} // End of class
//______________________________________________________________________________________________