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build/node_modules/seedrandom/lib/xor128.js

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+// A Javascript implementaion of the "xor128" prng algorithm by
+// George Marsaglia.  See http://www.jstatsoft.org/v08/i14/paper
+
+(function(global, module, define) {
+
+function XorGen(seed) {
+  var me = this, strseed = '';
+
+  me.x = 0;
+  me.y = 0;
+  me.z = 0;
+  me.w = 0;
+
+  // Set up generator function.
+  me.next = function() {
+    var t = me.x ^ (me.x << 11);
+    me.x = me.y;
+    me.y = me.z;
+    me.z = me.w;
+    return me.w ^= (me.w >>> 19) ^ t ^ (t >>> 8);
+  };
+
+  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;
+    me.next();
+  }
+}
+
+function copy(f, t) {
+  t.x = f.x;
+  t.y = f.y;
+  t.z = f.z;
+  t.w = f.w;
+  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.xor128 = impl;
+}
+
+})(
+  this,
+  (typeof module) == 'object' && module,    // present in node.js
+  (typeof define) == 'function' && define   // present with an AMD loader
+);
+
+