package sort;

/** Maps elements to buckets using a subset of the digits of each element. */
public class RadixBucketizer implements Bucketizer {

    // Offset of digits to use (in multiples of digits, from LSD).
    private int rad = 0;

    // Number of digits to use.
    private int digits;

    /** Creates a <b><tt>RadixBucketizer</b></tt> that uses the given 
     *  number of digits at a time.
     *  @param digits the number of digits used at a time
     */
    public RadixBucketizer(int digits) {
	this.digits = digits;
    }

    /** Creates a <b><tt>RadixBucketizer</b></tt> that uses 4 digits at 
     *  a time. 
     */
    public RadixBucketizer() {
	this(4);
    }

    /** Sets the offset of digits to use.
     *  @param rad the new offset
     */
    public void setRad(int rad) {
	this.rad = rad;
    }

    /** Computes the bucket into which the given element should be placed. */
    public int getPos(int x) {
	return (x >> (digits * rad)) & (0xffffffff >>> (32 - digits));
    }

}