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	/*
	* 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 {@code 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,
	* {@code 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);
	}

	}

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