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From: Justin Mclean <justin@classsoftware.com>
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Subject: UID performance
Date: Fri, 18 Oct 2013 12:17:53 +1100
Message-Id: <AACC94DD-8DC8-4FC8-BEDF-A4178EAA3DB4@classsoftware.com>
To: dev@flex.apache.org
Mime-Version: 1.0 (Apple Message framework v1283)

Hi,

This is about 2/3rds to twice as fast by my measurements (in Scout). Any =
one confirm?

Changes include.
- Use a string to store hex digits and charAt rather than array of ascii
- Use Array.join rather than String.fromCharCode
- Remove Math.floor as they are not required
- Set up static array and reuse that rather than creating new array each =
time

The timeString could probably be improved to remove the string =
manipulation but put the digits directly into the correct place into the =
array to save another 5% or so.

BYW any see where Number.toString is being called in there?

Any feedback?

Thanks,
Justin

diff --git a/frameworks/projects/framework/src/mx/utils/UIDUtil.as =
b/frameworks/projects/framework/src/mx/utils/UIDUtil.as
index 4993563..576b598 100644
--- a/frameworks/projects/framework/src/mx/utils/UIDUtil.as
+++ b/frameworks/projects/framework/src/mx/utils/UIDUtil.as
@@ -61,10 +61,16 @@ public class UIDUtil
=20
     /**
      *  @private
-     *  Char codes for 0123456789ABCDEF
      */
-    private static const ALPHA_CHAR_CODES:Array =3D [48, 49, 50, 51, =
52, 53, 54,=20
-        55, 56, 57, 65, 66, 67, 68, 69, 70];
+	private static const CHAR_CODES:String =3D "0123456789ABCDEF";
+=09
+	private static var EMPTYUID:Array =3D [
+		'0','0','0','0','0','0','0','0',
+		'-','0','0','0','0',
+		'-','0','0','0','0',
+		'-','0','0','0','0',
+		'0','0','0','0','0','0','0','0','0','0','0','0'
+	];
=20
     =
//------------------------------------------------------------------------=
--
     //
@@ -106,53 +112,53 @@ public class UIDUtil
      *  @playerversion AIR 1.1
      *  @productversion Flex 3
      */
-    public static function createUID():String
-    {
-        var uid:Array =3D new Array(36);
-        var index:int =3D 0;
-       =20
-        var i:int;
-        var j:int;
-       =20
-        for (i =3D 0; i < 8; i++)
-        {
-            uid[index++] =3D ALPHA_CHAR_CODES[Math.floor(Math.random() =
*  16)];
-        }
-
-        for (i =3D 0; i < 3; i++)
-        {
-            uid[index++] =3D 45; // charCode for "-"
-           =20
-            for (j =3D 0; j < 4; j++)
-            {
-                uid[index++] =3D =
ALPHA_CHAR_CODES[Math.floor(Math.random() *  16)];
-            }
-        }
-       =20
-        uid[index++] =3D 45; // charCode for "-"
-
-        var time:Number =3D new Date().getTime();
-        // Note: time is the number of milliseconds since 1970,
-        // which is currently more than one trillion.
-        // We use the low 8 hex digits of this number in the UID.
-        // Just in case the system clock has been reset to
-        // Jan 1-4, 1970 (in which case this number could have only
-        // 1-7 hex digits), we pad on the left with 7 zeros
-        // before taking the low digits.
-        var timeString:String =3D ("0000000" + =
time.toString(16).toUpperCase()).substr(-8);
-       =20
-        for (i =3D 0; i < 8; i++)
-        {
-            uid[index++] =3D timeString.charCodeAt(i);
-        }
-       =20
-        for (i =3D 0; i < 4; i++)
-        {
-            uid[index++] =3D ALPHA_CHAR_CODES[Math.floor(Math.random() =
*  16)];
-        }
-       =20
-        return String.fromCharCode.apply(null, uid);
-    }
+	public static function createUID():String
+	{
+		var uid:Array =3D EMPTYUID;
+		var index:int =3D 0;
+	=09
+		var i:int;
+		var j:int;
+	=09
+		for (i =3D 0; i < 8; i++)
+		{
+			uid[index++] =3D CHAR_CODES.charAt(Math.random() =
* 16);
+		}
+	=09
+		for (i =3D 0; i < 3; i++)
+		{
+			index++; // skip "-"
+		=09
+			for (j =3D 0; j < 4; j++)
+			{
+				uid[index++] =3D =
CHAR_CODES.charAt(Math.random() * 16);
+			}
+		}
+	=09
+		index++; // skip "-"
+	=09
+		var time:Number =3D new Date().getTime();
+		// Note: time is the number of milliseconds since 1970,
+		// which is currently more than one trillion.
+		// We use the low 8 hex digits of this number in the =
UID.
+		// Just in case the system clock has been reset to
+		// Jan 1-4, 1970 (in which case this number could have =
only
+		// 1-7 hex digits), we pad on the left with 7 zeros
+		// before taking the low digits.
+		var timeString:String =3D ("0000000" + =
time.toString(16).toUpperCase()).substr(-8);
+	=09
+		for (i =3D 0; i < 8; i++)
+		{
+			uid[index++] =3D timeString.charAt(i);
+		}
+	=09
+		for (i =3D 0; i < 4; i++)
+		{
+			uid[index++] =3D CHAR_CODES.charAt(Math.random() =
* 16);
+		}
+	=09
+		return uid.join("");
+	}