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82 lines
1.7 KiB
82 lines
1.7 KiB
// A Javascript implementaion of the "xor128" prng algorithm by
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// George Marsaglia. See http://www.jstatsoft.org/v08/i14/paper
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(function(global, module, define) {
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function XorGen(seed) {
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var me = this, strseed = '';
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me.x = 0;
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me.y = 0;
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me.z = 0;
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me.w = 0;
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// Set up generator function.
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me.next = function() {
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var t = me.x ^ (me.x << 11);
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me.x = me.y;
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me.y = me.z;
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me.z = me.w;
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return me.w ^= (me.w >>> 19) ^ t ^ (t >>> 8);
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};
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if (seed === (seed | 0)) {
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// Integer seed.
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me.x = seed;
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} else {
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// String seed.
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strseed += seed;
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}
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// Mix in string seed, then discard an initial batch of 64 values.
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for (var k = 0; k < strseed.length + 64; k++) {
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me.x ^= strseed.charCodeAt(k) | 0;
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me.next();
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}
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}
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function copy(f, t) {
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t.x = f.x;
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t.y = f.y;
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t.z = f.z;
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t.w = f.w;
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return t;
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}
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function impl(seed, opts) {
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var xg = new XorGen(seed),
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state = opts && opts.state,
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prng = function() { return (xg.next() >>> 0) / 0x100000000; };
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prng.double = function() {
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do {
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var top = xg.next() >>> 11,
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bot = (xg.next() >>> 0) / 0x100000000,
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result = (top + bot) / (1 << 21);
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} while (result === 0);
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return result;
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};
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prng.int32 = xg.next;
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prng.quick = prng;
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if (state) {
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if (typeof(state) == 'object') copy(state, xg);
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prng.state = function() { return copy(xg, {}); }
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}
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return prng;
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}
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if (module && module.exports) {
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module.exports = impl;
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} else if (define && define.amd) {
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define(function() { return impl; });
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} else {
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this.xor128 = impl;
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}
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})(
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this,
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(typeof module) == 'object' && module, // present in node.js
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(typeof define) == 'function' && define // present with an AMD loader
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);
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