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
26package 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
47class 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}
136