/*

 * 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 com.sun.tools.javac.util;

/** A class for extensible, mutable bit sets.

 *

 *  <p><b>This is NOT part of any supported API.

 *  If you write code that depends on this, you do so at your own risk.

 *  This code and its internal interfaces are subject to change or

 *  deletion without notice.</b>

 */

public class Bits {

    private final static int wordlen = 32;

    private final static int wordshift = 5;

    private final static int wordmask = wordlen - 1;

    private int[] bits;

    /** Construct an initially empty set.

     */

    public Bits() {

        this(new int[1]);

    }

    /** Construct a set consisting initially of given bit vector.

     */

    public Bits(int[] bits) {

        this.bits = bits;

    }

    /** Construct a set consisting initially of given range.

     */

    public Bits(int start, int limit) {

        this();

        inclRange(start, limit);

    }

    private void sizeTo(int len) {

        if (bits.length < len) {

            int[] newbits = new int[len];

            System.arraycopy(bits, 0, newbits, 0, bits.length);

            bits = newbits;

        }

    }

    /** This set = {}.

     */

    public void clear() {

        for (int i = 0; i < bits.length; i++) bits[i] = 0;

    }

    /** Return a copy of this set.

     */

    public Bits dup() {

        int[] newbits = new int[bits.length];

        System.arraycopy(bits, 0, newbits, 0, bits.length);

        return new Bits(newbits);

    }

    /** Include x in this set.

     */

    public void incl(int x) {

        Assert.check(x >= 0);

        sizeTo((x >>> wordshift) + 1);

        bits[x >>> wordshift] = bits[x >>> wordshift] |

            (1 << (x & wordmask));

    }

    /** Include [start..limit) in this set.

     */

    public void inclRange(int start, int limit) {

        sizeTo((limit >>> wordshift) + 1);

        for (int x = start; x < limit; x++)

            bits[x >>> wordshift] = bits[x >>> wordshift] |

                (1 << (x & wordmask));

    }

    /** Exclude [start...end] from this set.

     */

    public void excludeFrom(int start) {

        Bits temp = new Bits();

        temp.sizeTo(bits.length);

        temp.inclRange(0, start);

        andSet(temp);

    }

    /** Exclude x from this set.

     */

    public void excl(int x) {

        Assert.check(x >= 0);

        sizeTo((x >>> wordshift) + 1);

        bits[x >>> wordshift] = bits[x >>> wordshift] &

            ~(1 << (x & wordmask));

    }

    /** Is x an element of this set?

     */

    public boolean isMember(int x) {

        return

            0 <= x && x < (bits.length << wordshift) &&

            (bits[x >>> wordshift] & (1 << (x & wordmask))) != 0;

    }

     */

    public Bits andSet(Bits xs) {

        sizeTo(xs.bits.length);

        for (int i = 0; i < xs.bits.length; i++)

            bits[i] = bits[i] & xs.bits[i];

        return this;

    }

    /** this set = this set | xs.

     */

    public Bits orSet(Bits xs) {

        sizeTo(xs.bits.length);

        for (int i = 0; i < xs.bits.length; i++)

            bits[i] = bits[i] | xs.bits[i];

        return this;

    }

    /** this set = this set \ xs.

     */

    public Bits diffSet(Bits xs) {

        for (int i = 0; i < bits.length; i++) {

            if (i < xs.bits.length) {

                bits[i] = bits[i] & ~xs.bits[i];

            }

        }

        return this;

    }

    /** this set = this set ^ xs.

     */

    public Bits xorSet(Bits xs) {

        sizeTo(xs.bits.length);

        for (int i = 0; i < xs.bits.length; i++)

            bits[i] = bits[i] ^ xs.bits[i];

        return this;

    }

    /** Count trailing zero bits in an int. Algorithm from "Hacker's

     *  Delight" by Henry S. Warren Jr. (figure 5-13)

     */

    private static int trailingZeroBits(int x) {

        Assert.check(wordlen == 32);

        if (x == 0) return 32;

        int n = 1;

        if ((x & 0xffff) == 0) { n += 16; x >>>= 16; }

        if ((x & 0x00ff) == 0) { n +=  8; x >>>=  8; }

        if ((x & 0x000f) == 0) { n +=  4; x >>>=  4; }

        if ((x & 0x0003) == 0) { n +=  2; x >>>=  2; }

        return n - (x&1);

    }

     *  If none are set, returns -1.  This provides a nice way to iterate

     *  over the members of a bit set:

     *  for (int i = bits.nextBit(0); i>=0; i = bits.nextBit(i+1)) ...

     */

    public int nextBit(int x) {

        int windex = x >>> wordshift;

        if (windex >= bits.length) return -1;

        int word = bits[windex] & ~((1 << (x & wordmask))-1);

        while (true) {

            if (word != 0)

                return (windex << wordshift) + trailingZeroBits(word);

            windex++;

            if (windex >= bits.length) return -1;

            word = bits[windex];

        }

    }

    /** a string representation of this set.

     */

    public String toString() {

        char[] digits = new char[bits.length * wordlen];

        for (int i = 0; i < bits.length * wordlen; i++)

            digits[i] = isMember(i) ? '1' : '0';

        return new String(digits);

    }

    /** Test Bits.nextBit(int). */

    public static void main(String[] args) {

        java.util.Random r = new java.util.Random();

        Bits bits = new Bits();

        int dupCount = 0;

        for (int i=0; i<125; i++) {

            int k;

            do {

                k = r.nextInt(250);

            } while (bits.isMember(k));

            System.out.println("adding " + k);

            bits.incl(k);

        }

        int count = 0;

        for (int i = bits.nextBit(0); i >= 0; i = bits.nextBit(i+1)) {

            System.out.println("found " + i);

            count ++;

        }

        if (count != 125) throw new Error();

    }

}