1/*
2 * Copyright (c) 1997, 2006, 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 sun.security.util;
27
28import java.io.ByteArrayOutputStream;
29import java.util.Arrays;
30
31/**
32 * A packed array of booleans.
33 *
34 * @author Joshua Bloch
35 * @author Douglas Hoover
36 */
37
38public class BitArray {
39
40    private byte[] repn;
41    private int length;
42
43    private static final int BITS_PER_UNIT = 8;
44
45    private static int subscript(int idx) {
46        return idx / BITS_PER_UNIT;
47    }
48
49    private static int position(int idx) { // bits big-endian in each unit
50        return 1 << (BITS_PER_UNIT - 1 - (idx % BITS_PER_UNIT));
51    }
52
53    /**
54     * Creates a BitArray of the specified size, initialized to zeros.
55     */
56    public BitArray(int length) throws IllegalArgumentException {
57        if (length < 0) {
58            throw new IllegalArgumentException("Negative length for BitArray");
59        }
60
61        this.length = length;
62
63        repn = new byte[(length + BITS_PER_UNIT - 1)/BITS_PER_UNIT];
64    }
65
66
67    /**
68     * Creates a BitArray of the specified size, initialized from the
69     * specified byte array.  The most significant bit of {@code a[0]} gets
70     * index zero in the BitArray.  The array a must be large enough
71     * to specify a value for every bit in the BitArray.  In other words,
72     * {@code 8*a.length <= length}.
73     */
74    public BitArray(int length, byte[] a) throws IllegalArgumentException {
75
76        if (length < 0) {
77            throw new IllegalArgumentException("Negative length for BitArray");
78        }
79        if (a.length * BITS_PER_UNIT < length) {
80            throw new IllegalArgumentException("Byte array too short to represent " +
81                                               "bit array of given length");
82        }
83
84        this.length = length;
85
86        int repLength = ((length + BITS_PER_UNIT - 1)/BITS_PER_UNIT);
87        int unusedBits = repLength*BITS_PER_UNIT - length;
88        byte bitMask = (byte) (0xFF << unusedBits);
89
90        /*
91         normalize the representation:
92          1. discard extra bytes
93          2. zero out extra bits in the last byte
94         */
95        repn = new byte[repLength];
96        System.arraycopy(a, 0, repn, 0, repLength);
97        if (repLength > 0) {
98            repn[repLength - 1] &= bitMask;
99        }
100    }
101
102    /**
103     * Create a BitArray whose bits are those of the given array
104     * of Booleans.
105     */
106    public BitArray(boolean[] bits) {
107        length = bits.length;
108        repn = new byte[(length + 7)/8];
109
110        for (int i=0; i < length; i++) {
111            set(i, bits[i]);
112        }
113    }
114
115
116    /**
117     *  Copy constructor (for cloning).
118     */
119    private BitArray(BitArray ba) {
120        length = ba.length;
121        repn = ba.repn.clone();
122    }
123
124    /**
125     *  Returns the indexed bit in this BitArray.
126     */
127    public boolean get(int index) throws ArrayIndexOutOfBoundsException {
128        if (index < 0 || index >= length) {
129            throw new ArrayIndexOutOfBoundsException(Integer.toString(index));
130        }
131
132        return (repn[subscript(index)] & position(index)) != 0;
133    }
134
135    /**
136     *  Sets the indexed bit in this BitArray.
137     */
138    public void set(int index, boolean value)
139    throws ArrayIndexOutOfBoundsException {
140        if (index < 0 || index >= length) {
141            throw new ArrayIndexOutOfBoundsException(Integer.toString(index));
142        }
143        int idx = subscript(index);
144        int bit = position(index);
145
146        if (value) {
147            repn[idx] |= bit;
148        } else {
149            repn[idx] &= ~bit;
150        }
151    }
152
153    /**
154     * Returns the length of this BitArray.
155     */
156    public int length() {
157        return length;
158    }
159
160    /**
161     * Returns a Byte array containing the contents of this BitArray.
162     * The bit stored at index zero in this BitArray will be copied
163     * into the most significant bit of the zeroth element of the
164     * returned byte array.  The last byte of the returned byte array
165     * will be contain zeros in any bits that do not have corresponding
166     * bits in the BitArray.  (This matters only if the BitArray's size
167     * is not a multiple of 8.)
168     */
169    public byte[] toByteArray() {
170        return repn.clone();
171    }
172
173    public boolean equals(Object obj) {
174        if (obj == this) return true;
175        if (obj == null || !(obj instanceof BitArray)) return false;
176
177        BitArray ba = (BitArray) obj;
178
179        if (ba.length != length) return false;
180
181        for (int i = 0; i < repn.length; i += 1) {
182            if (repn[i] != ba.repn[i]) return false;
183        }
184        return true;
185    }
186
187    /**
188     * Return a boolean array with the same bit values a this BitArray.
189     */
190    public boolean[] toBooleanArray() {
191        boolean[] bits = new boolean[length];
192
193        for (int i=0; i < length; i++) {
194            bits[i] = get(i);
195        }
196        return bits;
197    }
198
199    /**
200     * Returns a hash code value for this bit array.
201     *
202     * @return  a hash code value for this bit array.
203     */
204    public int hashCode() {
205        int hashCode = 0;
206
207        for (int i = 0; i < repn.length; i++)
208            hashCode = 31*hashCode + repn[i];
209
210        return hashCode ^ length;
211    }
212
213
214    public Object clone() {
215        return new BitArray(this);
216    }
217
218
219    private static final byte[][] NYBBLE = {
220        { (byte)'0',(byte)'0',(byte)'0',(byte)'0'},
221        { (byte)'0',(byte)'0',(byte)'0',(byte)'1'},
222        { (byte)'0',(byte)'0',(byte)'1',(byte)'0'},
223        { (byte)'0',(byte)'0',(byte)'1',(byte)'1'},
224        { (byte)'0',(byte)'1',(byte)'0',(byte)'0'},
225        { (byte)'0',(byte)'1',(byte)'0',(byte)'1'},
226        { (byte)'0',(byte)'1',(byte)'1',(byte)'0'},
227        { (byte)'0',(byte)'1',(byte)'1',(byte)'1'},
228        { (byte)'1',(byte)'0',(byte)'0',(byte)'0'},
229        { (byte)'1',(byte)'0',(byte)'0',(byte)'1'},
230        { (byte)'1',(byte)'0',(byte)'1',(byte)'0'},
231        { (byte)'1',(byte)'0',(byte)'1',(byte)'1'},
232        { (byte)'1',(byte)'1',(byte)'0',(byte)'0'},
233        { (byte)'1',(byte)'1',(byte)'0',(byte)'1'},
234        { (byte)'1',(byte)'1',(byte)'1',(byte)'0'},
235        { (byte)'1',(byte)'1',(byte)'1',(byte)'1'}
236    };
237
238    private static final int BYTES_PER_LINE = 8;
239
240    /**
241     *  Returns a string representation of this BitArray.
242     */
243    public String toString() {
244        ByteArrayOutputStream out = new ByteArrayOutputStream();
245
246        for (int i = 0; i < repn.length - 1; i++) {
247            out.write(NYBBLE[(repn[i] >> 4) & 0x0F], 0, 4);
248            out.write(NYBBLE[repn[i] & 0x0F], 0, 4);
249
250            if (i % BYTES_PER_LINE == BYTES_PER_LINE - 1) {
251                out.write('\n');
252            } else {
253                out.write(' ');
254            }
255        }
256
257        // in last byte of repn, use only the valid bits
258        for (int i = BITS_PER_UNIT * (repn.length - 1); i < length; i++) {
259            out.write(get(i) ? '1' : '0');
260        }
261
262        return new String(out.toByteArray());
263
264    }
265
266    public BitArray truncate() {
267        for (int i=length-1; i>=0; i--) {
268            if (get(i)) {
269                return new BitArray(i+1, Arrays.copyOf(repn, (i + BITS_PER_UNIT)/BITS_PER_UNIT));
270            }
271        }
272        return new BitArray(1);
273    }
274
275}
276