source: Dev/trunk/src/client/dojox/math/random/Secure.js @ 501

// AMD-ID "dojox/math/random/Secure"
define(["dojo"], function(dojo) {

// Copyright (c) 2005  Tom Wu
// All Rights Reserved.
// See "LICENSE-BigInteger" for details.

// Random number generator - requires a PRNG backend, e.g. prng4.js

dojo.declare("dojox.math.random.Secure", null, {
        // summary:
        //              Super simple implementation of a random number generator,
        //              which relies on Math.random().

        constructor: function(prng, noEvents){
                // summary:
                //              Initializes an instance of a secure random generator.
                // prng: Function
                //              function that returns an instance of PRNG (pseudo random number generator)
                //              with two methods: init(array) and next(). It should have a property "size"
                //              to indicate the required pool size.
                // noEvents: Boolean?
                //              if false or absent, onclick and onkeypress event will be used to add
                //              "randomness", otherwise events will not be used.
                this.prng = prng;

                // Initialize the pool with junk if needed.
                var p = this.pool = new Array(prng.size);
                this.pptr = 0;
                for(var i = 0, len = prng.size; i < len;) {  // extract some randomness from Math.random()
                        var t = Math.floor(65536 * Math.random());
                        p[i++] = t >>> 8;
                        p[i++] = t & 255;
                }
                this.seedTime();

                if(!noEvents){
                        this.h = [
                                dojo.connect(dojo.body(), "onclick",    this, "seedTime"),
                                dojo.connect(dojo.body(), "onkeypress", this, "seedTime")
                        ];
                }
        },

        destroy: function(){
                // summary:
                //              Disconnects events, if any, preparing the object for GC.
                if(this.h){
                        dojo.forEach(this.h, dojo.disconnect);
                }
        },

        nextBytes: function(/* Array */ byteArray){
                // summary:
                //              Fills in an array of bytes with random numbers
                // byteArray: Array
                //              array to be filled in with random numbers, only existing
                //              elements will be filled.

                var state = this.state;

                if(!state){
                        this.seedTime();
                        state = this.state = this.prng();
                        state.init(this.pool);
                        for(var p = this.pool, i = 0, len = p.length; i < len; p[i++] = 0);
                        this.pptr = 0;
                        //this.pool = null;
                }

                for(var i = 0, len = byteArray.length; i < len; ++i){
                        byteArray[i] = state.next();
                }
        },

        seedTime: function() {
                // summary:
                //              Mix in the current time (w/milliseconds) into the pool
                this._seed_int(new Date().getTime());
        },

        _seed_int: function(x) {
                // summary:
                //              Mix in a 32-bit integer into the pool
                var p = this.pool, i = this.pptr;
                p[i++] ^= x & 255;
                p[i++] ^= (x >> 8) & 255;
                p[i++] ^= (x >> 16) & 255;
                p[i++] ^= (x >> 24) & 255;
                if(i >= this.prng.size){
                        i -= this.prng.size;
                }
                this.pptr = i;
        }
});

return dojox.math.random.Secure;
});