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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 }