xethya-random-bbs/dist/index.es6.js

An implementation of the Blum Blum Shub PRNG.

import _Object$assign from 'babel-runtime/core-js/object/assign';
import _classCallCheck from 'babel-runtime/helpers/classCallCheck';
import _createClass from 'babel-runtime/helpers/createClass';

/**
 * xethya-random-bbs
 *
 * Copyright © 2016 Joel A. Villarreal Bertoldi. All rights reserved.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE.txt file in the root directory of this source tree.
 */

/**
 * Default constant value for setting up the BBS PRNG.
 * P must be a prime number.
 * @type {Number}
 */
var P = 87566873;

/**
 * Default constant value for setting up the BBS PRNG.
 * Q must be a prime number.
 * @type {Number}
 */
var Q = 5631179;

/**
 * A list of default seed values, tested to be evenly distributed.
 * @see  http://wiki.fib.upc.es/sim/index.php/Blum_Blum_Shub#Tests
 * @type {Array.<Number>}
 */
var DefaultSeeds = [193945, 740191, 191];

/**
 * Instantiates a Blum Blum Shub PRNG.
 */

var BlumBlumShub = function () {

  /**
   * Initializes the generator.
   *
   * @param  {Number} p    A prime value (defaults to P).
   * @param  {Number} q    A prime value (defaults to Q).
   * @param  {Number} seedNumber A seed number to feed the generator (defaults to any value
   *                       in DefaultSeeds).
   * @constructor
   */
  function BlumBlumShub(settings) {
    _classCallCheck(this, BlumBlumShub);

    var defaults = {
      p: P,
      q: Q,
      seedNumber: null
    };

    this.settings = _Object$assign({}, defaults, settings);

    var seedNumber = this.settings.seedNumber;
    var _settings = this.settings;
    var p = _settings.p;
    var q = _settings.q;


    if (seedNumber) {
      seedNumber = Math.abs(seedNumber);
    } else {
      seedNumber = DefaultSeeds[Math.floor(Math.random() * DefaultSeeds.length)];
    }

    this.seedNumber = seedNumber;
    this.randomIndex = seedNumber;
    this.M = p * q;
    this.P = p;
    this.Q = q;
  }

  /**
   * Determines if the generator works better by being reinstantiated after
   * every generated number.
   *
   * @return {Boolean}
   * @static
   */


  _createClass(BlumBlumShub, [{
    key: 'generateRandom',


    /**
     * Generates a pseudo-random number and updates the seed for a next roll.
     * Number is always between 0 and 1.
     *
     * @return {Number}
     */
    value: function generateRandom() {
      var r = this.randomIndex * this.randomIndex % this.M;
      this.randomIndex = r;
      return Math.abs(r / this.M);
    }

    /**
     * Same as `generateRandom()`, but converts the number to an Integer.
     *
     * @return {Number}
     */

  }, {
    key: 'generateRandomInteger',
    value: function generateRandomInteger() {
      return Number(this.generateRandom().toString().replace(/\./, ''));
    }
  }], [{
    key: 'recommendsToReinstantiate',
    value: function recommendsToReinstantiate() {
      return false;
    }
  }]);

  return BlumBlumShub;
}();

export { P, Q, DefaultSeeds, BlumBlumShub };
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