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    1   /*
    2    * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   package java.security.spec;
   26   
   27   import java.math.BigInteger;
   28   import java.util.Arrays;
   29   
   30   /**
   31    * This immutable class defines an elliptic curve (EC) prime
   32    * finite field.
   33    *
   34    * @see ECField
   35    *
   36    * @author Valerie Peng
   37    *
   38    * @since 1.5
   39    */
   40   public class ECFieldFp implements ECField {
   41   
   42       private BigInteger p;
   43   
   44       /**
   45        * Creates an elliptic curve prime finite field
   46        * with the specified prime <code>p</code>.
   47        * @param p the prime.
   48        * @exception NullPointerException if <code>p</code> is null.
   49        * @exception IllegalArgumentException if <code>p</code>
   50        * is not positive.
   51        */
   52       public ECFieldFp(BigInteger p) {
   53           if (p.signum() != 1) {
   54               throw new IllegalArgumentException("p is not positive");
   55           }
   56           this.p = p;
   57       }
   58   
   59       /**
   60        * Returns the field size in bits which is size of prime p
   61        * for this prime finite field.
   62        * @return the field size in bits.
   63        */
   64       public int getFieldSize() {
   65           return p.bitLength();
   66       };
   67   
   68       /**
   69        * Returns the prime <code>p</code> of this prime finite field.
   70        * @return the prime.
   71        */
   72       public BigInteger getP() {
   73           return p;
   74       }
   75   
   76       /**
   77        * Compares this prime finite field for equality with the
   78        * specified object.
   79        * @param obj the object to be compared.
   80        * @return true if <code>obj</code> is an instance
   81        * of ECFieldFp and the prime value match, false otherwise.
   82        */
   83       public boolean equals(Object obj) {
   84           if (this == obj)  return true;
   85           if (obj instanceof ECFieldFp) {
   86               return (p.equals(((ECFieldFp)obj).p));
   87           }
   88           return false;
   89       }
   90   
   91       /**
   92        * Returns a hash code value for this prime finite field.
   93        * @return a hash code value.
   94        */
   95       public int hashCode() {
   96           return p.hashCode();
   97       }
   98   }

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