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Bug fixes for random #306

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Bug fixes for random #306

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d7987e0
Fixed random when range>2**31
Sc00bz Dec 1, 2016
d6a9555
Fixed off by one bug
Sc00bz Dec 1, 2016
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10 changes: 5 additions & 5 deletions app/js/diceware.js
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Original file line number Diff line number Diff line change
Expand Up @@ -58,14 +58,14 @@ Diceware.prototype.getWords = function(words) {

Diceware.prototype.random = function (min, max) {
var rval = 0;
var range = max - min;
var range = max - min + 1;

var bits_needed = Math.ceil(Math.log2(range));
if (bits_needed > 53) {
throw new Exception("We cannot generate numbers larger than 53 bits.");
}
var bytes_needed = Math.ceil(bits_needed / 8);
var mask = Math.pow(2, bits_needed) - 1;
var mod = Math.pow(2, bits_needed);
// 7776 -> (2^13 = 8192) -1 == 8191 or 0x00001111 11111111

// Create byte array and fill with N random numbers
Expand All @@ -78,8 +78,8 @@ Diceware.prototype.random = function (min, max) {
p -= 8;
}

// Use & to apply the mask and reduce the number of recursive lookups
rval = rval & mask;
// Use % to reduce the number of recursive lookups
rval = rval % mod;

if (rval >= range) {
// Integer out of acceptable range
Expand All @@ -93,6 +93,6 @@ Diceware.prototype.getSingleWord = function() {
if (!window.crypto || !window.crypto.getRandomValues) {
return null;
}
var index = this.random(0, this.wordlist.length);
var index = this.random(0, this.wordlist.length - 1);
return this.wordlist[index];
};