290 lines
8.6 KiB
Java
290 lines
8.6 KiB
Java
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/*
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* Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.security.util;
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import java.io.ByteArrayOutputStream;
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import java.util.Arrays;
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/**
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* A packed array of booleans.
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*
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* @author Joshua Bloch
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* @author Douglas Hoover
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*/
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public class BitArray {
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private byte[] repn;
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private int length;
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private static final int BITS_PER_UNIT = 8;
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private static int subscript(int idx) {
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return idx / BITS_PER_UNIT;
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}
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private static int position(int idx) { // bits big-endian in each unit
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return 1 << (BITS_PER_UNIT - 1 - (idx % BITS_PER_UNIT));
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}
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/**
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* Creates a BitArray of the specified size, initialized to zeros.
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*/
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public BitArray(int length) throws IllegalArgumentException {
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if (length < 0) {
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throw new IllegalArgumentException("Negative length for BitArray");
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}
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this.length = length;
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repn = new byte[(length + BITS_PER_UNIT - 1)/BITS_PER_UNIT];
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}
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/**
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* Creates a BitArray of the specified size, initialized from the
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* specified byte array. The most significant bit of {@code a[0]} gets
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* index zero in the BitArray. The array must be large enough to specify
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* a value for every bit of the BitArray. i.e. {@code 8*a.length <= length}.
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*/
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public BitArray(int length, byte[] a) throws IllegalArgumentException {
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this(length, a, 0);
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}
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/**
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* Creates a BitArray of the specified size, initialized from the
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* specified byte array starting at the specified offset. The most
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* significant bit of {@code a[ofs]} gets index zero in the BitArray.
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* The array must be large enough to specify a value for every bit of
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* the BitArray, i.e. {@code 8*(a.length - ofs) <= length}.
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*/
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public BitArray(int length, byte[] a, int ofs)
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throws IllegalArgumentException {
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if (length < 0) {
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throw new IllegalArgumentException("Negative length for BitArray");
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}
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if ((a.length - ofs) * BITS_PER_UNIT < length) {
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throw new IllegalArgumentException
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("Byte array too short to represent " + length + "-bit array");
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}
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this.length = length;
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int repLength = ((length + BITS_PER_UNIT - 1)/BITS_PER_UNIT);
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int unusedBits = repLength*BITS_PER_UNIT - length;
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byte bitMask = (byte) (0xFF << unusedBits);
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/*
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normalize the representation:
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1. discard extra bytes
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2. zero out extra bits in the last byte
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*/
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repn = new byte[repLength];
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System.arraycopy(a, ofs, repn, 0, repLength);
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if (repLength > 0) {
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repn[repLength - 1] &= bitMask;
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}
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}
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/**
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* Create a BitArray whose bits are those of the given array
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* of Booleans.
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*/
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public BitArray(boolean[] bits) {
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length = bits.length;
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repn = new byte[(length + 7)/8];
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for (int i=0; i < length; i++) {
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set(i, bits[i]);
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}
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}
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/**
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* Copy constructor (for cloning).
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*/
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private BitArray(BitArray ba) {
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length = ba.length;
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repn = ba.repn.clone();
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}
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/**
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* Returns the indexed bit in this BitArray.
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*/
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public boolean get(int index) throws ArrayIndexOutOfBoundsException {
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if (index < 0 || index >= length) {
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throw new ArrayIndexOutOfBoundsException(Integer.toString(index));
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}
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return (repn[subscript(index)] & position(index)) != 0;
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}
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/**
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* Sets the indexed bit in this BitArray.
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*/
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public void set(int index, boolean value)
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throws ArrayIndexOutOfBoundsException {
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if (index < 0 || index >= length) {
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throw new ArrayIndexOutOfBoundsException(Integer.toString(index));
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}
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int idx = subscript(index);
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int bit = position(index);
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if (value) {
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repn[idx] |= bit;
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} else {
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repn[idx] &= ~bit;
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}
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}
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/**
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* Returns the length of this BitArray.
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*/
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public int length() {
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return length;
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}
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/**
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* Returns a Byte array containing the contents of this BitArray.
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* The bit stored at index zero in this BitArray will be copied
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* into the most significant bit of the zeroth element of the
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* returned byte array. The last byte of the returned byte array
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* will be contain zeros in any bits that do not have corresponding
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* bits in the BitArray. (This matters only if the BitArray's size
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* is not a multiple of 8.)
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*/
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public byte[] toByteArray() {
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return repn.clone();
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}
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public boolean equals(Object obj) {
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if (obj == this) return true;
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if (obj == null || !(obj instanceof BitArray)) return false;
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BitArray ba = (BitArray) obj;
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if (ba.length != length) return false;
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for (int i = 0; i < repn.length; i += 1) {
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if (repn[i] != ba.repn[i]) return false;
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}
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return true;
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}
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/**
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* Return a boolean array with the same bit values a this BitArray.
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*/
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public boolean[] toBooleanArray() {
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boolean[] bits = new boolean[length];
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for (int i=0; i < length; i++) {
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bits[i] = get(i);
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}
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return bits;
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}
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/**
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* Returns a hash code value for this bit array.
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*
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* @return a hash code value for this bit array.
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*/
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public int hashCode() {
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int hashCode = 0;
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for (int i = 0; i < repn.length; i++)
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hashCode = 31*hashCode + repn[i];
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return hashCode ^ length;
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}
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public Object clone() {
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return new BitArray(this);
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}
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private static final byte[][] NYBBLE = {
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{ (byte)'0',(byte)'0',(byte)'0',(byte)'0'},
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{ (byte)'0',(byte)'0',(byte)'0',(byte)'1'},
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{ (byte)'0',(byte)'0',(byte)'1',(byte)'0'},
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{ (byte)'0',(byte)'0',(byte)'1',(byte)'1'},
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{ (byte)'0',(byte)'1',(byte)'0',(byte)'0'},
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{ (byte)'0',(byte)'1',(byte)'0',(byte)'1'},
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{ (byte)'0',(byte)'1',(byte)'1',(byte)'0'},
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{ (byte)'0',(byte)'1',(byte)'1',(byte)'1'},
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{ (byte)'1',(byte)'0',(byte)'0',(byte)'0'},
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{ (byte)'1',(byte)'0',(byte)'0',(byte)'1'},
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{ (byte)'1',(byte)'0',(byte)'1',(byte)'0'},
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{ (byte)'1',(byte)'0',(byte)'1',(byte)'1'},
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{ (byte)'1',(byte)'1',(byte)'0',(byte)'0'},
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{ (byte)'1',(byte)'1',(byte)'0',(byte)'1'},
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{ (byte)'1',(byte)'1',(byte)'1',(byte)'0'},
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{ (byte)'1',(byte)'1',(byte)'1',(byte)'1'}
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};
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private static final int BYTES_PER_LINE = 8;
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/**
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* Returns a string representation of this BitArray.
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*/
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public String toString() {
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if (length == 0) {
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return "";
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}
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ByteArrayOutputStream out = new ByteArrayOutputStream();
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for (int i = 0; i < repn.length - 1; i++) {
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out.write(NYBBLE[(repn[i] >> 4) & 0x0F], 0, 4);
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out.write(NYBBLE[repn[i] & 0x0F], 0, 4);
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if (i % BYTES_PER_LINE == BYTES_PER_LINE - 1) {
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out.write('\n');
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} else {
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out.write(' ');
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}
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}
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// in last byte of repn, use only the valid bits
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for (int i = BITS_PER_UNIT * (repn.length - 1); i < length; i++) {
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out.write(get(i) ? '1' : '0');
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}
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return new String(out.toByteArray());
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}
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public BitArray truncate() {
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for (int i=length-1; i>=0; i--) {
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if (get(i)) {
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return new BitArray(i+1, repn, 0);
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}
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}
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return new BitArray(1);
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}
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}
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