/*

 * 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);

    }

}