/* * @(#)BitArray.java 1.14 06/10/10 * * Copyright 1990-2008 Sun Microsystems, Inc. All Rights Reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License version * 2 only, as published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License version 2 for more details (a copy is * included at /legal/license.txt). * * You should have received a copy of the GNU General Public License * version 2 along with this work; if not, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA * 02110-1301 USA * * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa * Clara, CA 95054 or visit www.sun.com if you need additional * information or have any questions. * */ package sun.security.util; import java.io.ByteArrayOutputStream; /** * A packed array of booleans. * * @author Joshua Bloch * @author Douglas Hoover * @version 1.7 02/02/00 */ public class BitArray { private byte[] repn; private int length; private static final int BITS_PER_UNIT = 8; private static int subscript(int idx) { return idx / BITS_PER_UNIT; } private static int position(int idx) { // bits big-endian in each unit return 1 } /** * Creates a BitArray of the specified size, initialized to zeros. */ public BitArray(int length) throws IllegalArgumentException { if (length < 0) { throw new IllegalArgumentException("Negative length for BitArray"); } this.length = length; repn = new byte[(length + BITS_PER_UNIT - 1)/BITS_PER_UNIT]; } /** * Creates a BitArray of the specified size, initialized from the * specified byte array. The most significant bit of a[0] gets * index zero in the BitArray. The array a must be large enough * to specify a value for every bit in the BitArray. In other words, * 8*a.length */ public BitArray(int length, byte[] a) throws IllegalArgumentException { if (length < 0) { throw new IllegalArgumentException("Negative length for BitArray"); } if (a.length * BITS_PER_UNIT < length) { throw new IllegalArgumentException("Byte array too short to represent " + "bit array of given length"); } this.length = length; int repLength = ((length + BITS_PER_UNIT - 1)/BITS_PER_UNIT); int unusedBits = repLength*BITS_PER_UNIT - length; byte bitMask = (byte) (0xFF /* normalize the representation: 1. discard extra bytes 2. zero out extra bits in the last byte */ repn = new byte[repLength]; System.arraycopy(a, 0, repn, 0, repLength); if (repLength > 0) { repn[repLength - 1] &= bitMask; } } /** * Create a BitArray whose bits are those of the given array * of Booleans. */ public BitArray(boolean[] bits) { length = bits.length; repn = new byte[(length + 7)/8]; for (int i=0; i < length; i++) { set(i, bits[i]); } } /** * Copy constructor (for cloning). */ private BitArray(BitArray ba) { length = ba.length; repn = (byte[]) ba.repn.clone(); } /** * Returns the indexed bit in this BitArray. */ public boolean get(int index) throws ArrayIndexOutOfBoundsException { if (index < 0 || index >= length) { throw new ArrayIndexOutOfBoundsException(Integer.toString(index)); } return (repn[subscript(index)] & position(index)) != 0; } /** * Sets the indexed bit in this BitArray. */ public void set(int index, boolean value) throws ArrayIndexOutOfBoundsException { if (index < 0 || index >= length) { throw new ArrayIndexOutOfBoundsException(Integer.toString(index)); } int idx = subscript(index); int bit = position(index); if (value) { repn[idx] |= bit; } else { repn[idx] &= ~bit; } } /** * Returns the length of this BitArray. */ public int length() { return length; } /** * Returns a Byte array containing the contents of this BitArray. * The bit stored at index zero in this BitArray will be copied * into the most significant bit of the zeroth element of the * returned byte array. The last byte of the returned byte array * will be contain zeros in any bits that do not have corresponding * bits in the BitArray. (This matters only if the BitArray's size * is not a multiple of 8.) */ public byte[] toByteArray() { return (byte[]) repn.clone(); } public boolean equals(Object obj) { if (obj == this) return true; if (obj == null || !(obj instanceof BitArray)) return false; BitArray ba = (BitArray) obj; if (ba.length != length) return false; for (int i = 0; i < repn.length; i += 1) { if (repn[i] != ba.repn[i]) return false; } return true; } /** * Return a boolean array with the same bit values a this BitArray. */ public boolean[] toBooleanArray() { boolean[] bits = new boolean[length]; for (int i=0; i < length; i++) { bits[i] = get(i); } return bits; } /** * Returns a hash code value for this bit array. * * @return a hash code value for this bit array. */ public int hashCode() { int hashCode = 0; for (int i = 0; i < repn.length; i++) hashCode = 31*hashCode + repn[i]; return hashCode ^ length; } public Object clone() { return new BitArray(this); } private static final byte[][] NYBBLE = { { (byte)'0',(byte)'0',(byte)'0',(byte)'0'}, { (byte)'0',(byte)'0',(byte)'0',(byte)'1'}, { (byte)'0',(byte)'0',(byte)'1',(byte)'0'}, { (byte)'0',(byte)'0',(byte)'1',(byte)'1'}, { (byte)'0',(byte)'1',(byte)'0',(byte)'0'}, { (byte)'0',(byte)'1',(byte)'0',(byte)'1'}, { (byte)'0',(byte)'1',(byte)'1',(byte)'0'}, { (byte)'0',(byte)'1',(byte)'1',(byte)'1'}, { (byte)'1',(byte)'0',(byte)'0',(byte)'0'}, { (byte)'1',(byte)'0',(byte)'0',(byte)'1'}, { (byte)'1',(byte)'0',(byte)'1',(byte)'0'}, { (byte)'1',(byte)'0',(byte)'1',(byte)'1'}, { (byte)'1',(byte)'1',(byte)'0',(byte)'0'}, { (byte)'1',(byte)'1',(byte)'0',(byte)'1'}, { (byte)'1',(byte)'1',(byte)'1',(byte)'0'}, { (byte)'1',(byte)'1',(byte)'1',(byte)'1'} }; private static final int BYTES_PER_LINE = 8; /** * Returns a string representation of this BitArray. */ public String toString() { ByteArrayOutputStream out = new ByteArrayOutputStream(); for (int i = 0; i < repn.length - 1; i++) { out.write(NYBBLE[(repn[i] >> 4) & 0x0F], 0, 4); out.write(NYBBLE[repn[i] & 0x0F], 0, 4); if (i % BYTES_PER_LINE == BYTES_PER_LINE - 1) { out.write('\n'); } else { out.write(' '); } } // in last byte of repn, use only the valid bits for (int i = BITS_PER_UNIT * (repn.length - 1); i < length; i++) { out.write(get(i) ? '1' : '0'); } return new String(out.toByteArray()); } }
