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/** \file
* \brief Random number generator
*
* A port of an algorithm by Johannes Baagøe <baagoe@baagoe.com>, 2010 and
* Tommy Ettinger (tommy.ettinger@gmail.com)
*
* Original code is available at
* http://baagoe.com/en/RandomMusings/javascript/
* https://github.com/nquinlan/better-random-numbers-for-javascript-mirror
* https://gist.github.com/tommyettinger/46a874533244883189143505d203312c
*
* SPDX-License-Identifier: GPL-3.0-or-later
* SPDX-License-Identifier: MIT
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*
* \license Original work is under MIT license and in public domain, the derived code is under GPL-3.0-or-later
*/
//
// Copyright (C) 2010 by Johannes Baagøe <baagoe@baagoe.org>
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
/**
* alea creates a function that is functionally equivalent to Math.random.
*
* That is, successive calls of the returned function return Number values
* with positive sign, greater than or equal to 0 but less than 1, chosen
* pseudo-randomly with approximately uniform distribution over that range.
*
* The internal state of random, and hence the sequence of pseudo-random
* numbers it returns, is determined by the arguments to alea. Two functions
* returned by calls to alea with the same argument values will return exactly
* the same sequence of pseudo-random numbers. String and Number arguments
* should provide repeatable output across platforms. Object arguments[3]
* provide repeatable output on the same platform, but not necessarily on others.
*
* Please call alea() with at least one argument, the implementation with
* nno arguments described by Baagøe was not implemented here. This provides
* easy means to provide somewhat unpredictable numbers, like Math.random does.
*
* Example usage: let module_prng = alea(domainHash, "MyModuleName"); module_prng();
*
* See more details in the README.md at
* https://github.com/nquinlan/better-random-numbers-for-javascript-mirror
*/
var alea =`
function Alea(...args) {
var mash = new Mash();
// Apply the seeding algorithm from Baagoe.
mash.addData(' ');
for (var i = 0; i < args.length; i++) {
mash.addData(args[i]);
}
this.seed = mash.n | 0; // Create a 32-bit UInt
mash = null;
this.xoring = [];
for (let i = 0; i < 64; i += 8) {
this.xoring.push(parseInt(domainHash.slice(i, i+8), 16) >>> 0); // Store 32-bit unsigned integers
}
}
Alea.prototype = {
current: 0,
stored_random: 0,
random_bits: 0,
next: function() {
this.seed += 0x6D2B79F5;
var t = this.seed;
this.current = (this.current + t) & 7;
t = Math.imul(t ^ t >>> 15, t | 1);
t ^= t + Math.imul(t ^ t >>> 7, t | 61);
return (((t ^ t >>> 14) ^ this.xoring[this.current]) >>> 0); // '>>> 0' casts to unsigned
},
normalized: function() {
return this.next() / 4294967296;
},
get_bits: function(count) {// 0 < count <= 32
if (count === 32) {
return this.next();
}
else if (count <= this.random_bits) {
let mask = ((1 << count) >>> 0) - 1;
let ret = this.stored_random & mask;
this.stored_random = this.stored_random >>> count;
this.random_bits -= count;
return ret;
}
else {
let needed = count - this.random_bits;
let ret = this.stored_random << needed;
this.random_bits = 32;
this.stored_random = this.next();
return ret | this.get_bits(needed);
}
}
}
function impl(...seed) {
var xg = new Alea(...seed);
var prng = xg.normalized.bind(xg);
prng.uint32 = xg.next.bind(xg);
prng.fract53 = function() {
return prng() + (prng() * 0x200000 | 0) * 1.1102230246251565e-16; // 2^-53
};
prng.get_bits = xg.get_bits.bind(xg);
return prng;
}
// Original at https://github.com/nquinlan/better-random-numbers-for-javascript-mirror/blob/master/support/js/Mash.js
function Mash()
{
this.n = 0xefc8249d;
}
Mash.prototype = {
addData: function(data) {
data = String(data);
for (var i = 0; i < data.length; i++) {
this.addNumber(data.charCodeAt(i));
}
return this;
},
addNumber: function(num) {
this.n += num;
var h = 0.02519603282416938 * this.n;
this.n = h >>> 0;
h -= this.n;
h *= this.n;
this.n = h >>> 0;
h -= this.n;
this.n += h * 0x100000000; // 2^32
return this;
},
finalize: function() {
return (this.n >>> 0) * 2.3283064365386963e-10; // 2^-32
}
}
var alea = impl;
`
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