MediaWiki:Gadget-math.seedrandom.js

Note: After saving, you may have to bypass your browser's cache to see the changes.

• Firefox / Safari: Hold Shift while clicking Reload, or press either Ctrl-F5 or Ctrl-R (⌘-R on a Mac)
• Google Chrome: Press Ctrl-Shift-R (⌘-Shift-R on a Mac)
• Internet Explorer: Hold Ctrl while clicking Refresh, or press Ctrl-F5
• Opera: Go to Menu → Settings (Opera → Preferences on a Mac) and then to Privacy & security → Clear browsing data → Cached images and files.

// minified version of [[MediaWiki:SeedRandom.js]]

// From http://davidbau.com/archives/2010/01/30/random_seeds_coded_hints_and_quintillions.html
// Documentation at http://davidbau.com/archives/2010/01/30/random_seeds_coded_hints_and_quintillions.html
// Altered not to replace the Math.random but Math.seededrandom
// <nowiki>
 
// seedrandom.js version 2.0.
// Author: David Bau 4/2/2011
//
// Defines a method Math.seedrandom() that, when called, substitutes
// an explicitly seeded RC4-based algorithm for Math.random().  Also
// supports automatic seeding from local or network sources of entropy.
//
// Usage:
//
//   <script src=http://davidbau.com/encode/seedrandom-min.js></script>
//
//   Math.seedrandom('yipee'); Sets Math.seededrandom to a function that is
//                             initialized using the given explicit seed.
//
//   Math.seedrandom();        Sets Math.seededrandom to a function that is
//                             seeded using the current time, dom state,
//                             and other accumulated local entropy.
//                             The generated seed string is returned.
//
//   Math.seedrandom('yowza', true);
//                             Seeds using the given explicit seed mixed
//                             together with accumulated entropy.
//
//   <script src="http://bit.ly/srandom-512"></script>
//                             Seeds using physical random bits downloaded
//                             from random.org.
//
//   <script src="https://jsonlib.appspot.com/urandom?callback=Math.seedrandom">
//   </script>                 Seeds using urandom bits from call.jsonlib.com,
//                             which is faster than random.org.
//
// Examples:
//
//   Math.seedrandom("hello");            // Use "hello" as the seed.
//   document.write(Math.seededrandom());       // Always 0.5463663768140734
//   document.write(Math.seededrandom());       // Always 0.43973793770592234
//   var rng1 = Math.seededrandom;              // Remember the current prng.
//
//   var autoseed = Math.seedrandom();    // New prng with an automatic seed.
//   document.write(Math.seededrandom());       // Pretty much unpredictable.
//
//   Math.seededrandom = rng1;                  // Continue "hello" prng sequence.
//   document.write(Math.seededrandom());       // Always 0.554769432473455
//
//   Math.seedrandom(autoseed);           // Restart at the previous seed.
//   document.write(Math.seededrandom());       // Repeat the 'unpredictable' value.
//
// Notes:
//
// Each time seedrandom('arg') is called, entropy from the passed seed
// is accumulated in a pool to help generate future seeds for the
// zero-argument form of Math.seedrandom, so entropy can be injected over
// time by calling seedrandom with explicit data repeatedly.
//
// On speed - This javascript implementation of Math.random() is about
// 3-10x slower than the built-in Math.seededrandom() because it is not native
// code, but this is typically fast enough anyway.  Seeding is more expensive,
// especially if you use auto-seeding.  Some details (timings on Chrome 4):
//
// Our Math.seededrandom()      - avg less than 0.002 milliseconds per call
// seedrandom('explicit')       - avg less than 0.5 milliseconds per call
// seedrandom('explicit', true) - avg less than 2 milliseconds per call
// seedrandom()                 - avg about 38 milliseconds per call
//
// LICENSE (BSD):
//
// Copyright 2010 David Bau, all rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// 
//   1. Redistributions of source code must retain the above copyright
//      notice, this list of conditions and the following disclaimer.
//
//   2. Redistributions in binary form must reproduce the above copyright
//      notice, this list of conditions and the following disclaimer in the
//      documentation and/or other materials provided with the distribution.
// 
//   3. Neither the name of this module nor the names of its contributors may
//      be used to endorse or promote products derived from this software
//      without specific prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//

(function(j,i,g,m,k,n,o){function q(b){var e,f,a=this,c=b.length,d=0,h=a.i=a.j=a.m=0;a.S=[];a.c=[];for(c||(b=[c++]);d<g;)a.S[d]=d++;for(d=0;d<g;d++)e=a.S[d],h=h+e+b[d%c]&g-1,f=a.S[h],a.S[d]=f,a.S[h]=e;a.g=function(b){var c=a.S,d=a.i+1&g-1,e=c[d],f=a.j+e&g-1,h=c[f];c[d]=h;c[f]=e;for(var i=c[e+h&g-1];--b;)d=d+1&g-1,e=c[d],f=f+e&g-1,h=c[f],c[d]=h,c[f]=e,i=i*g+c[e+h&g-1];a.i=d;a.j=f;return i};a.g(g)}function p(b,e,f,a,c){f=[];c=typeof b;if(e&&c=="object")for(a in b)if(a.indexOf("S")<5)try{f.push(p(b[a],e-1))}catch(d){}return f.length?f:b+(c!="string"?"\0":"")}function l(b,e,f,a){b+="";for(a=f=0;a<b.length;a++){var c=e,d=a&g-1,h=(f^=e[a&g-1]*19)+b.charCodeAt(a);c[d]=h&g-1}b="";for(a in e)b+=String.fromCharCode(e[a]);return b}i.seedrandom=function(b,e){var f=[],a;b=l(p(e?[b,j]:arguments.length?b:[(new Date).getTime(),j,window],3),f);a=new q(f);l(a.S,j);i.seededrandom=function(){for(var c=a.g(m),d=o,b=0;c<k;)c=(c+b)*g,d*=g,b=a.g(1);for(;c>=n;)c/=2,d/=2,b>>>=1;return(c+b)/d};return b};o=i.pow(g,m);k=i.pow(2,k);n=k*2;l(i.random(),j)})([],Math,256,6,52);