simple-squiggle/node_modules/seedrandom/lib/alea.js

115 lines
3.2 KiB
JavaScript

// A port of an algorithm by Johannes Baagøe <baagoe@baagoe.com>, 2010
// http://baagoe.com/en/RandomMusings/javascript/
// https://github.com/nquinlan/better-random-numbers-for-javascript-mirror
// Original work is under MIT license -
// 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.
(function(global, module, define) {
function Alea(seed) {
var me = this, mash = Mash();
me.next = function() {
var t = 2091639 * me.s0 + me.c * 2.3283064365386963e-10; // 2^-32
me.s0 = me.s1;
me.s1 = me.s2;
return me.s2 = t - (me.c = t | 0);
};
// Apply the seeding algorithm from Baagoe.
me.c = 1;
me.s0 = mash(' ');
me.s1 = mash(' ');
me.s2 = mash(' ');
me.s0 -= mash(seed);
if (me.s0 < 0) { me.s0 += 1; }
me.s1 -= mash(seed);
if (me.s1 < 0) { me.s1 += 1; }
me.s2 -= mash(seed);
if (me.s2 < 0) { me.s2 += 1; }
mash = null;
}
function copy(f, t) {
t.c = f.c;
t.s0 = f.s0;
t.s1 = f.s1;
t.s2 = f.s2;
return t;
}
function impl(seed, opts) {
var xg = new Alea(seed),
state = opts && opts.state,
prng = xg.next;
prng.int32 = function() { return (xg.next() * 0x100000000) | 0; }
prng.double = function() {
return prng() + (prng() * 0x200000 | 0) * 1.1102230246251565e-16; // 2^-53
};
prng.quick = prng;
if (state) {
if (typeof(state) == 'object') copy(state, xg);
prng.state = function() { return copy(xg, {}); }
}
return prng;
}
function Mash() {
var n = 0xefc8249d;
var mash = function(data) {
data = String(data);
for (var i = 0; i < data.length; i++) {
n += data.charCodeAt(i);
var h = 0.02519603282416938 * n;
n = h >>> 0;
h -= n;
h *= n;
n = h >>> 0;
h -= n;
n += h * 0x100000000; // 2^32
}
return (n >>> 0) * 2.3283064365386963e-10; // 2^-32
};
return mash;
}
if (module && module.exports) {
module.exports = impl;
} else if (define && define.amd) {
define(function() { return impl; });
} else {
this.alea = impl;
}
})(
this,
(typeof module) == 'object' && module, // present in node.js
(typeof define) == 'function' && define // present with an AMD loader
);