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

87 lines
1.9 KiB
JavaScript

// A Javascript implementaion of the "xorwow" prng algorithm by
// George Marsaglia. See http://www.jstatsoft.org/v08/i14/paper
(function(global, module, define) {
function XorGen(seed) {
var me = this, strseed = '';
// Set up generator function.
me.next = function() {
var t = (me.x ^ (me.x >>> 2));
me.x = me.y; me.y = me.z; me.z = me.w; me.w = me.v;
return (me.d = (me.d + 362437 | 0)) +
(me.v = (me.v ^ (me.v << 4)) ^ (t ^ (t << 1))) | 0;
};
me.x = 0;
me.y = 0;
me.z = 0;
me.w = 0;
me.v = 0;
if (seed === (seed | 0)) {
// Integer seed.
me.x = seed;
} else {
// String seed.
strseed += seed;
}
// Mix in string seed, then discard an initial batch of 64 values.
for (var k = 0; k < strseed.length + 64; k++) {
me.x ^= strseed.charCodeAt(k) | 0;
if (k == strseed.length) {
me.d = me.x << 10 ^ me.x >>> 4;
}
me.next();
}
}
function copy(f, t) {
t.x = f.x;
t.y = f.y;
t.z = f.z;
t.w = f.w;
t.v = f.v;
t.d = f.d;
return t;
}
function impl(seed, opts) {
var xg = new XorGen(seed),
state = opts && opts.state,
prng = function() { return (xg.next() >>> 0) / 0x100000000; };
prng.double = function() {
do {
var top = xg.next() >>> 11,
bot = (xg.next() >>> 0) / 0x100000000,
result = (top + bot) / (1 << 21);
} while (result === 0);
return result;
};
prng.int32 = xg.next;
prng.quick = prng;
if (state) {
if (typeof(state) == 'object') copy(state, xg);
prng.state = function() { return copy(xg, {}); }
}
return prng;
}
if (module && module.exports) {
module.exports = impl;
} else if (define && define.amd) {
define(function() { return impl; });
} else {
this.xorwow = impl;
}
})(
this,
(typeof module) == 'object' && module, // present in node.js
(typeof define) == 'function' && define // present with an AMD loader
);