1 /*
   2  * Copyright (c) 1999, 2007, 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 
  26 package java.math;
  27 
  28 /**
  29  * A class used to represent multiprecision integers that makes efficient
  30  * use of allocated space by allowing a number to occupy only part of
  31  * an array so that the arrays do not have to be reallocated as often.
  32  * When performing an operation with many iterations the array used to
  33  * hold a number is only increased when necessary and does not have to
  34  * be the same size as the number it represents. A mutable number allows
  35  * calculations to occur on the same number without having to create
  36  * a new number for every step of the calculation as occurs with
  37  * BigIntegers.
  38  *
  39  * Note that SignedMutableBigIntegers only support signed addition and
  40  * subtraction. All other operations occur as with MutableBigIntegers.
  41  *
  42  * @see     BigInteger
  43  * @author  Michael McCloskey
  44  * @since   1.3
  45  */
  46 
  47 class SignedMutableBigInteger extends MutableBigInteger {
  48 
  49    /**
  50      * The sign of this MutableBigInteger.
  51      */
  52     int sign = 1;
  53 
  54     // Constructors
  55 
  56     /**
  57      * The default constructor. An empty MutableBigInteger is created with
  58      * a one word capacity.
  59      */
  60     SignedMutableBigInteger() {
  61         super();
  62     }
  63 
  64     /**
  65      * Construct a new MutableBigInteger with a magnitude specified by
  66      * the int val.
  67      */
  68     SignedMutableBigInteger(int val) {
  69         super(val);
  70     }
  71 
  72     /**
  73      * Construct a new MutableBigInteger with a magnitude equal to the
  74      * specified MutableBigInteger.
  75      */
  76     SignedMutableBigInteger(MutableBigInteger val) {
  77         super(val);
  78     }
  79 
  80    // Arithmetic Operations
  81 
  82    /**
  83      * Signed addition built upon unsigned add and subtract.
  84      */
  85     void signedAdd(SignedMutableBigInteger addend) {
  86         if (sign == addend.sign)
  87             add(addend);
  88         else
  89             sign = sign * subtract(addend);
  90 
  91     }
  92 
  93    /**
  94      * Signed addition built upon unsigned add and subtract.
  95      */
  96     void signedAdd(MutableBigInteger addend) {
  97         if (sign == 1)
  98             add(addend);
  99         else
 100             sign = sign * subtract(addend);
 101 
 102     }
 103 
 104    /**
 105      * Signed subtraction built upon unsigned add and subtract.
 106      */
 107     void signedSubtract(SignedMutableBigInteger addend) {
 108         if (sign == addend.sign)
 109             sign = sign * subtract(addend);
 110         else
 111             add(addend);
 112 
 113     }
 114 
 115    /**
 116      * Signed subtraction built upon unsigned add and subtract.
 117      */
 118     void signedSubtract(MutableBigInteger addend) {
 119         if (sign == 1)
 120             sign = sign * subtract(addend);
 121         else
 122             add(addend);
 123         if (intLen == 0)
 124              sign = 1;
 125     }
 126 
 127     /**
 128      * Print out the first intLen ints of this MutableBigInteger's value
 129      * array starting at offset.
 130      */
 131     public String toString() {
 132         return this.toBigInteger(sign).toString();
 133     }
 134 
 135 }