/*
* Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code 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. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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 in the LICENSE file that
* accompanied this code).
*
* 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package sun.security.util;
import java.io.ByteArrayOutputStream;
import java.util.Arrays;
/**
* A packed array of booleans.
*
* @author Joshua Bloch
* @author Douglas Hoover
*/
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 << (BITS_PER_UNIT - 1 - (idx % BITS_PER_UNIT));
}
/**
* 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 <= 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 << unusedBits);
/*
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 = 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 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());
}
public BitArray truncate() {
for (int i=length-1; i>=0; i--) {
if (get(i)) {
return new BitArray(i+1, Arrays.copyOf(repn, (i + BITS_PER_UNIT)/BITS_PER_UNIT));
}
}
return new BitArray(1);
}
}