From e6c3273e4ea4f5ee63eb2b6b44b159b34677104b Mon Sep 17 00:00:00 2001
From: Fomafix <fomafix@googlemail.com>
Date: Sat, 14 Feb 2015 10:24:15 +0000
Subject: [PATCH] mediawiki.user: Simplify mw.user.generateRandomSessionId

* Remove lookup table for hex strings.
* Convert 32 bit instead of 8 bit to hex at once.

Change-Id: I6e6ac9e0813c4ba540e0a53b8e6667162cb60bf7
---
 resources/src/mediawiki/mediawiki.user.js | 44 +++++++++--------------
 1 file changed, 16 insertions(+), 28 deletions(-)

diff --git a/resources/src/mediawiki/mediawiki.user.js b/resources/src/mediawiki/mediawiki.user.js
index 240d1bd1b1..c4c91f95b1 100644
--- a/resources/src/mediawiki/mediawiki.user.js
+++ b/resources/src/mediawiki/mediawiki.user.js
@@ -2,11 +2,9 @@
  * @class mw.user
  * @singleton
  */
-/* global Uint8Array */
+/* global Uint32Array */
 ( function ( mw, $ ) {
-	var i,
-		userInfoPromise,
-		byteToHex = [];
+	var userInfoPromise;
 
 	/**
 	 * Get the current user's groups or rights
@@ -21,12 +19,6 @@
 		return userInfoPromise;
 	}
 
-	// Map from numbers 0-255 to a hex string (with padding)
-	for ( i = 0; i < 256; i++ ) {
-		// Padding: Add a full byte (0x100, 256) and strip the extra character
-		byteToHex[ i ] = ( i + 256 ).toString( 16 ).slice( 1 );
-	}
-
 	// mw.user with the properties options and tokens gets defined in mediawiki.js.
 	$.extend( mw.user, {
 
@@ -51,36 +43,32 @@
 		 * @return {string} 64 bit integer in hex format, padded
 		 */
 		generateRandomSessionId: function () {
-			/* eslint-disable no-bitwise */
-			var rnds, i, r,
-				hexRnds = new Array( 8 ),
+			var rnds, i,
+				hexRnds = new Array( 2 ),
 				// Support: IE 11
 				crypto = window.crypto || window.msCrypto;
 
-			// Based on https://github.com/broofa/node-uuid/blob/bfd9f96127/uuid.js
 			if ( crypto && crypto.getRandomValues ) {
-				// Fill an array with 8 random values, each of which is 8 bits.
-				// Note that Uint8Array is array-like but does not implement Array.
-				rnds = new Uint8Array( 8 );
+				// Fill an array with 2 random values, each of which is 32 bits.
+				// Note that Uint32Array is array-like but does not implement Array.
+				rnds = new Uint32Array( 2 );
 				crypto.getRandomValues( rnds );
 			} else {
-				rnds = new Array( 8 );
-				for ( i = 0; i < 8; i++ ) {
-					if ( ( i & 3 ) === 0 ) {
-						r = Math.random() * 0x100000000;
-					}
-					rnds[ i ] = r >>> ( ( i & 3 ) << 3 ) & 255;
-				}
+				rnds = [
+					Math.floor( Math.random() * 0x100000000 ),
+					Math.floor( Math.random() * 0x100000000 )
+				];
 			}
-			// Convert from number to hex
-			for ( i = 0; i < 8; i++ ) {
-				hexRnds[ i ] = byteToHex[ rnds[ i ] ];
+			// Convert number to a string with 16 hex characters
+			for ( i = 0; i < 2; i++ ) {
+				// Add 0x100000000 before converting to hex and strip the extra character
+				// after converting to keep the leading zeros.
+				hexRnds[ i ] = ( rnds[ i ] + 0x100000000 ).toString( 16 ).slice( 1 );
 			}
 
 			// Concatenation of two random integers with entropy n and m
 			// returns a string with entropy n+m if those strings are independent
 			return hexRnds.join( '' );
-			/* eslint-enable no-bitwise */
 		},
 
 		/**
-- 
2.20.1