/*
* Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.security.spec;
import java.math.BigInteger;
/**
* This immutable class represents a point on an elliptic curve (EC)
* in affine coordinates. Other coordinate systems can
* extend this class to represent this point in other
* coordinates.
*
* @author Valerie Peng
*
* @since 1.5
*/
public class ECPoint {
private final BigInteger x;
private final BigInteger y;
/**
* This defines the point at infinity.
*/
public static final ECPoint POINT_INFINITY = new ECPoint();
// private constructor for constructing point at infinity
private ECPoint() {
this.x = null;
this.y = null;
}
/**
* Creates an ECPoint from the specified affine x-coordinate
* <code>x</code> and affine y-coordinate <code>y</code>.
* @param x the affine x-coordinate.
* @param y the affine y-coordinate.
* @exception NullPointerException if <code>x</code> or
* <code>y</code> is null.
*/
public ECPoint(BigInteger x, BigInteger y) {
if ((x==null) || (y==null)) {
throw new NullPointerException("affine coordinate x or y is null");
}
this.x = x;
this.y = y;
}
/**
* Returns the affine x-coordinate <code>x</code>.
* Note: POINT_INFINITY has a null affine x-coordinate.
* @return the affine x-coordinate.
*/
public BigInteger getAffineX() {
return x;
}
/**
* Returns the affine y-coordinate <code>y</code>.
* Note: POINT_INFINITY has a null affine y-coordinate.
* @return the affine y-coordinate.
*/
public BigInteger getAffineY() {
return y;
}
/**
* Compares this elliptic curve point for equality with
* the specified object.
* @param obj the object to be compared.
* @return true if <code>obj</code> is an instance of
* ECPoint and the affine coordinates match, false otherwise.
*/
public boolean equals(Object obj) {
if (this == obj) return true;
if (this == POINT_INFINITY) return false;
if (obj instanceof ECPoint) {
return ((x.equals(((ECPoint)obj).x)) &&
(y.equals(((ECPoint)obj).y)));
}
return false;
}
/**
* Returns a hash code value for this elliptic curve point.
* @return a hash code value.
*/
public int hashCode() {
if (this == POINT_INFINITY) return 0;
return x.hashCode() << 5 + y.hashCode();
}
}