bitset.js

/**
 * @license BitSet.js v1.0.0 05/03/2014
 * http://www.xarg.org/2014/03/javascript-bit-array/
 *
 * Copyright (c) 2014, Robert Eisele (robert@xarg.org)
 * Dual licensed under the MIT or GPL Version 2 licenses.
 **/


/**
 * BitSet Class
 * 
 * @param {number|String=} alloc The number of bits to use at max, or a bit-string to copy
 * @param {number=} value The default value for the bits
 * @constructor
 **/
function BitSet(alloc, value) {

    if (alloc === undefined) {
        alloc = 31;
    } else if (typeof alloc === 'string') {
        alloc = alloc['length'];
    }
    
    if (value !== 1) {
        value = 0;
    } else {
        value = 2147483647;
    }

    /**
     * @const
     * @type {number}
     */
    var size = 31;

    /**
     * 
     * @type {number}
     */
    var length = Math.ceil(alloc / size);

    for (var i = length; i--; ) {
        this[i] = value;
    }

    if (typeof alloc === 'string') {

        for (i = alloc['length']; i--; ) {
            this['set'](i, alloc.charAt(i));
        }
    }

    var transformRange = function(obj, from, to, mode) {

        // determine param type
        if (to === undefined) {

            if (from === undefined) {
                from = 0;
                to = length * size - 1;
            } else {
                to = from;
            }
        }

        // check range
        if (from < 0 || to < from || size * length <= to) {
            return null;
        }

        for (var i = length; i--; ) {

            // determine local start and end
            var s = Math.max(from, i * size);
            var e = Math.min(to, size - 1 + size * i);

            if (s <= e) {

                /**
                 * @type {number}
                 Original derivated formula: ~(((1 << (e % size - s % size + 1)) - 1) << s % size)
                 Simplified: */
                var mask = ~(1 << (1 + e % size)) + (1 << s % size);

                if (mode === 0)
                    obj[i] &= mask;
                else
                    obj[i] ^= ~mask;
            }
        }
        return obj;
    };

    this['size'] = size * length;
    this['length'] = length;


    /**
     * Creates the bitwise AND of two sets. The result is stored in-place.
     *
     * Ex:
     * bs1 = new BitSet(10);
     * bs2 = new BitSet(10);
     *
     * bs1.and(bs2);
     * 
     * @param {BitSet} obj A bitset object
     * @returns {BitSet} this
     */
    this['and'] = function(obj) {

        if (obj instanceof BitSet) {

            for (var i = length; i--; ) {
                this[i] &= obj[i] || 0;
            }
        }
        return this;
    };


    /**
     * Creates the bitwise OR of two sets. The result is stored in-place.
     *
     * Ex:
     * bs1 = new BitSet(10);
     * bs2 = new BitSet(10);
     *
     * bs1.or(bs2);
     * 
     * @param {BitSet} obj A bitset object
     * @returns {BitSet} this
     */
    this['or'] = function(obj) {

        if (obj instanceof BitSet) {

            for (var i = length; i--; ) {
                this[i] |= obj[i] || 0;
            }
        }
        return this;
    };


    /**
     * Creates the bitwise NAND of two sets. The result is stored in-place.
     *
     * Ex:
     * bs1 = new BitSet(10);
     * bs2 = new BitSet(10);
     *
     * bs1.nand(bs2);
     * 
     * @param {BitSet} obj A bitset object
     * @returns {BitSet} this
     */
    this['nand'] = function(obj) {

        if (obj instanceof BitSet) {

            for (var i = length; i--; ) {
                this[i] = ~(this[i] & (obj[i] || 0));
            }
        }
        return this;
    };


    /**
     * Creates the bitwise NOR of two sets. The result is stored in-place.
     *
     * Ex:
     * bs1 = new BitSet(10);
     * bs2 = new BitSet(10);
     *
     * bs1.or(bs2);
     * 
     * @param {BitSet} obj A bitset object
     * @returns {BitSet} this
     */
    this['nor'] = function(obj) {

        if (obj instanceof BitSet) {

            for (var i = length; i--; ) {
                this[i] = ~(this[i] | (obj[i] || 0));
            }
        }
        return this;
    };


    /**
     * Creates the bitwise NOT of a set. The result is stored in-place.
     *
     * Ex:
     * bs1 = new BitSet(10);
     *
     * bs1.not();
     * 
     * @returns {BitSet} this
     */
    this['not'] = function() {

        for (var i = length; i--; ) {
            this[i] = ~this[i];
        }
        return this;
    };

    /**
     * Creates the bitwise XOR of two sets. The result is stored in-place.
     *
     * Ex:
     * bs1 = new BitSet(10);
     * bs2 = new BitSet(10);
     *
     * bs1.xor(bs2);
     * 
     * @param {BitSet} obj A bitset object
     * @returns {BitSet} this
     */
    this['xor'] = function(obj) {

        if (obj instanceof BitSet) {

            for (var i = length; i--; ) {
                this[i] = (this[i] ^ (obj[i] || 0));
            }
        }
        return this;
    };


    /**
     * Compares two BitSet objects
     * 
     * Ex:
     * bs1 = new BitSet(10);
     * bs2 = new BitSet(10);
     * 
     * bs1.equals(bs2) ? 'yes' : 'no'
     *
     * @param {BitSet} obj A bitset object
     * @returns {boolean} Whether the two BitSets are similar
     */
    this['equals'] = function(obj) {

        if (obj instanceof BitSet) {

            if (obj['length'] !== length) {
                return false;
            }

            for (var i = length; i--; ) {

                if (obj[i] !== this[i])
                    return false;
            }

        } else {
            return false;
        }
        return true;
    };


    /**
     * Clones the actual object
     * 
     * Ex:
     * bs1 = new BitSet(10);
     * bs2 = bs1.clone();
     *
     * @returns {BitSet} A new BitSet object, containing a copy of the actual object
     */
    this['clone'] = function() {

        /**
         * 
         * @type {BitSet}
         */
        var tmp = new BitSet(this['size']);

        for (var i = length; i--; ) {
            tmp[i] = this[i];
        }
        return tmp;
    };

    /**
     * Check if the BitSet is empty, means all bits are unset
     * 
     * Ex:
     * bs1 = new BitSet(10);
     * 
     * bs1.isEmpty() ? 'yes' : 'no'
     *
     * @returns {boolean} Whether the bitset is empty
     */
    this['isEmpty'] = function() {

        for (var i = length; i--; ) {
            if (0 !== this[i])
                return false;
        }
        return true;
    };

    /**
     * Overrides the toString method to get a binary representation of the BitSet
     *
     * @returns string A binary string
     */
    this['toString'] = function(sep) {

        var str = "";
        for (var i = length; i--; ) {

            if (i + 1 < length && sep !== undefined)
                str += String(sep);

            var tmp = this[i].toString(2);
            str += (new Array(1 + size - tmp['length']).join("0"));
            str += tmp;
        }
        return str;
    };

    /**
     * Calculates the number of bits set
     * 
     * Ex:
     * bs1 = new BitSet(10);
     * 
     * var num = bs1.cardinality();
     *
     * @returns {number} The number of bits set
     */
    this['cardinality'] = function() {

        for (var n, num = 0, i = length; i--; ) {

            for (n = this[i]; n; n &= n - 1, num++) {
            }
        }
        return num;
    };


    /**
     * Calculates the Most Significant Bit / log base two
     * 
     * Ex:
     * bs1 = new BitSet(10);
     * 
     * var logbase2 = bs1.msb();
     * 
     * var truncatedTwo = Math.pow(2, logbase2); // May overflow!
     *
     * @returns {number} The index of the highest bit set
     */
    this['msb'] = function() {

        for (var i = length; i--; ) {

            var v = this[i];
            var c = 0;

            if (v) {

                for (; (v >>= 1); c++) {

                }
                return size * i + c;
            }
        }
        return 0;
    };


    /**
     * Set a single bit flag
     * 
     * Ex:
     * bs1 = new BitSet(10);
     * 
     * bs1.set(3, 1);
     *
     * @param {number} ndx The index of the bit to be set
     * @param {number=} value Optional value that should be set on the index (0 or 1)
     * @returns {BitSet} this
     */
    this['set'] = function(ndx, value) {

        if (value === undefined) {
            value = 1;
        }

        if (0 <= ndx && ndx < size * length) {

            var slot = ndx / size | 0;

            this[slot] ^= (1 << ndx % size) & (-(value & 1) ^ this[slot]);

            return this;
        }
        return null;
    };

    /**
     * Set a range of bits
     * 
     * Ex:
     * bs1 = new BitSet();
     * 
     * bs1.setRange(0, 5, "01011");
     * bs1.setRange(10, 15, 1);
     *
     * @param {number} from The start index of the range to be set
     * @param {number} to The end index of the range to be set
     * @param {number|String=} value Optional value that should be set on the index (0 or 1), or a bit string of the length of the window
     * @returns {BitSet} this
     */
    this['setRange'] = function(from, to, value) {

        if (from <= to && 0 <= from && to < size * length) {

            if (typeof value === "string") {

                // If window size is != string length, abort
                if (to - from !== value.length) {
                    return null;
                }

                for (var i = 0; i < value.length; i++) {
                    this['set'](i + from, value.charAt(value.length - i - 1));
                }

            } else {

                if (undefined === value) {
                    value = 1;
                }

                for (var i = from; i <= to; i++) {
                    this['set'](i, value);
                }
            }

            return this;
        }
        return null;
    };

    /**
     * Get a single bit flag of a certain bit position
     * 
     * Ex:
     * bs1 = new BitSet();
     * var isValid = bs1.get(12);
     * 
     * @param {number} ndx the index to be fetched
     * @returns {number|null} The binary flag
     */
    this['get'] = function(ndx) {

        if (0 <= ndx && ndx < size * length) {

            return (this[ndx / size | 0] >> (ndx % size)) & 1;
        }
        return null;
    };

    /**
     * Gets an entire range as a new bitset object
     * 
     * Ex:
     * bs1 = new BitSet();
     * bs1.getRange(4, 8);
     * 
     * @param {number} from The start index of the range to be get
     * @param {number} to The end index of the range to be get
     * @returns {BitSet} A new smaller bitset object, containing the extracted range 
     */
    this['getRange'] = function(from, to) {

        if (from <= to && 0 <= from && to < size * length) {

            var tmp = new BitSet(to - from + 1);

            // Quite okay for a first naive implementation, needs improvement
            for (var i = from; i <= to; i++) {
                tmp['set'](i - from, this['get'](i));
            }
            return tmp;
        }
        return null;
    };

    /**
     * Clear a range of bits by setting it to 0
     * 
     * Ex:
     * bs1 = new BitSet();
     * bs1.clear(); // Clear entire set
     * bs1.clear(5); // Clear single bit
     * bs1.clar(3,10); // Clear a bit range
     * 
     * @param {number=} from The start index of the range to be cleared
     * @param {number=} to The end index of the range to be cleared
     * @returns {BitSet} this
     */
    this['clear'] = function(from, to) {

        return transformRange(this, from, to, 0);
    };

    /**
     * Flip/Invert a range of bits by setting
     * 
     * Ex:
     * bs1 = new BitSet();
     * bs1.flip(); // Flip entire set
     * bs1.flip(5); // Flip single bit
     * bs1.flip(3,10); // Flip a bit range
     * 
     * @param {number=} from The start index of the range to be flipped
     * @param {number=} to The end index of the range to be flipped
     * @returns {BitSet} this
     */
    this['flip'] = function(from, to) {

        return transformRange(this, from, to, 1);
    };
}

if (typeof module !== 'undefined' && module['exports']) {
    module['exports']['BitSet'] = BitSet;
}

var bs = new BitSet(2, 1); // Set default value to 1
console.log(bs.toString())