254 lines
8.4 KiB
JavaScript
254 lines
8.4 KiB
JavaScript
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/*
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Copyright 2019 David Bau.
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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(function (global, pool, math) {
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//
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// The following constants are related to IEEE 754 limits.
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//
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var width = 256, // each RC4 output is 0 <= x < 256
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chunks = 6, // at least six RC4 outputs for each double
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digits = 52, // there are 52 significant digits in a double
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rngname = 'random', // rngname: name for Math.random and Math.seedrandom
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startdenom = math.pow(width, chunks),
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significance = math.pow(2, digits),
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overflow = significance * 2,
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mask = width - 1,
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nodecrypto; // node.js crypto module, initialized at the bottom.
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//
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// seedrandom()
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// This is the seedrandom function described above.
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//
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function seedrandom(seed, options, callback) {
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var key = [];
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options = (options == true) ? { entropy: true } : (options || {});
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// Flatten the seed string or build one from local entropy if needed.
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var shortseed = mixkey(flatten(
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options.entropy ? [seed, tostring(pool)] :
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(seed == null) ? autoseed() : seed, 3), key);
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// Use the seed to initialize an ARC4 generator.
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var arc4 = new ARC4(key);
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// This function returns a random double in [0, 1) that contains
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// randomness in every bit of the mantissa of the IEEE 754 value.
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var prng = function() {
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var n = arc4.g(chunks), // Start with a numerator n < 2 ^ 48
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d = startdenom, // and denominator d = 2 ^ 48.
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x = 0; // and no 'extra last byte'.
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while (n < significance) { // Fill up all significant digits by
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n = (n + x) * width; // shifting numerator and
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d *= width; // denominator and generating a
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x = arc4.g(1); // new least-significant-byte.
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}
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while (n >= overflow) { // To avoid rounding up, before adding
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n /= 2; // last byte, shift everything
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d /= 2; // right using integer math until
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x >>>= 1; // we have exactly the desired bits.
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}
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return (n + x) / d; // Form the number within [0, 1).
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};
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prng.int32 = function() { return arc4.g(4) | 0; }
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prng.quick = function() { return arc4.g(4) / 0x100000000; }
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prng.double = prng;
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// Mix the randomness into accumulated entropy.
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mixkey(tostring(arc4.S), pool);
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// Calling convention: what to return as a function of prng, seed, is_math.
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return (options.pass || callback ||
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function(prng, seed, is_math_call, state) {
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if (state) {
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// Load the arc4 state from the given state if it has an S array.
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if (state.S) { copy(state, arc4); }
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// Only provide the .state method if requested via options.state.
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prng.state = function() { return copy(arc4, {}); }
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}
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// If called as a method of Math (Math.seedrandom()), mutate
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// Math.random because that is how seedrandom.js has worked since v1.0.
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if (is_math_call) { math[rngname] = prng; return seed; }
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// Otherwise, it is a newer calling convention, so return the
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// prng directly.
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else return prng;
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})(
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prng,
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shortseed,
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'global' in options ? options.global : (this == math),
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options.state);
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}
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//
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// ARC4
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//
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// An ARC4 implementation. The constructor takes a key in the form of
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// an array of at most (width) integers that should be 0 <= x < (width).
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//
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// The g(count) method returns a pseudorandom integer that concatenates
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// the next (count) outputs from ARC4. Its return value is a number x
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// that is in the range 0 <= x < (width ^ count).
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//
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function ARC4(key) {
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var t, keylen = key.length,
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me = this, i = 0, j = me.i = me.j = 0, s = me.S = [];
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// The empty key [] is treated as [0].
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if (!keylen) { key = [keylen++]; }
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// Set up S using the standard key scheduling algorithm.
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while (i < width) {
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s[i] = i++;
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}
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for (i = 0; i < width; i++) {
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s[i] = s[j = mask & (j + key[i % keylen] + (t = s[i]))];
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s[j] = t;
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}
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// The "g" method returns the next (count) outputs as one number.
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(me.g = function(count) {
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// Using instance members instead of closure state nearly doubles speed.
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var t, r = 0,
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i = me.i, j = me.j, s = me.S;
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while (count--) {
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t = s[i = mask & (i + 1)];
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r = r * width + s[mask & ((s[i] = s[j = mask & (j + t)]) + (s[j] = t))];
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}
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me.i = i; me.j = j;
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return r;
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// For robust unpredictability, the function call below automatically
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// discards an initial batch of values. This is called RC4-drop[256].
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// See http://google.com/search?q=rsa+fluhrer+response&btnI
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})(width);
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}
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//
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// copy()
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// Copies internal state of ARC4 to or from a plain object.
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//
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function copy(f, t) {
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t.i = f.i;
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t.j = f.j;
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t.S = f.S.slice();
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return t;
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};
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//
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// flatten()
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// Converts an object tree to nested arrays of strings.
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//
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function flatten(obj, depth) {
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var result = [], typ = (typeof obj), prop;
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if (depth && typ == 'object') {
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for (prop in obj) {
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try { result.push(flatten(obj[prop], depth - 1)); } catch (e) {}
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}
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}
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return (result.length ? result : typ == 'string' ? obj : obj + '\0');
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}
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//
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// mixkey()
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// Mixes a string seed into a key that is an array of integers, and
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// returns a shortened string seed that is equivalent to the result key.
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//
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function mixkey(seed, key) {
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var stringseed = seed + '', smear, j = 0;
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while (j < stringseed.length) {
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key[mask & j] =
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mask & ((smear ^= key[mask & j] * 19) + stringseed.charCodeAt(j++));
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}
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return tostring(key);
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}
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//
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// autoseed()
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// Returns an object for autoseeding, using window.crypto and Node crypto
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// module if available.
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//
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function autoseed() {
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try {
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var out;
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if (nodecrypto && (out = nodecrypto.randomBytes)) {
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// The use of 'out' to remember randomBytes makes tight minified code.
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out = out(width);
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} else {
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out = new Uint8Array(width);
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(global.crypto || global.msCrypto).getRandomValues(out);
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}
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return tostring(out);
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} catch (e) {
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var browser = global.navigator,
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plugins = browser && browser.plugins;
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return [+new Date, global, plugins, global.screen, tostring(pool)];
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}
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}
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//
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// tostring()
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// Converts an array of charcodes to a string
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//
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function tostring(a) {
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return String.fromCharCode.apply(0, a);
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}
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//
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// When seedrandom.js is loaded, we immediately mix a few bits
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// from the built-in RNG into the entropy pool. Because we do
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// not want to interfere with deterministic PRNG state later,
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// seedrandom will not call math.random on its own again after
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// initialization.
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//
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mixkey(math.random(), pool);
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//
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// Nodejs and AMD support: export the implementation as a module using
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// either convention.
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//
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if ((typeof module) == 'object' && module.exports) {
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module.exports = seedrandom;
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// When in node.js, try using crypto package for autoseeding.
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try {
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nodecrypto = require('crypto');
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} catch (ex) {}
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} else if ((typeof define) == 'function' && define.amd) {
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define(function() { return seedrandom; });
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} else {
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// When included as a plain script, set up Math.seedrandom global.
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math['seed' + rngname] = seedrandom;
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}
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// End anonymous scope, and pass initial values.
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})(
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// global: `self` in browsers (including strict mode and web workers),
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// otherwise `this` in Node and other environments
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(typeof self !== 'undefined') ? self : this,
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[], // pool: entropy pool starts empty
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Math // math: package containing random, pow, and seedrandom
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);
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