JUST GOOD DESIGN | BLOG » Bitwise Operators

Bitwise Operators

March 2, 2007 at 11:28 pm · Filed under Flash, Actionscript

Bitwise operators are a very low level way to program and therefore not considered light reading, but lately I’ve been seeing enough interesting scenarios where they can be applied.

Since the basis for bitwise operators is to manipulate binary data, this is most suited for checking for 1 or 0.

Check to see if a number is odd ( 1 ) or even ( 0 ):

var x:Number = 3
var a:Number = x & 1
var x:Number = 2
var b:Number = x & 1

output( a, b ); // 1,0

var x:Number = 999999
var a:Number = x & 1

var x:Number = 222222
var b:Number = x & 1

output( a, b ); // 1,0

Use as a fast way to divide and floor:

function output ( )
{
      trace( arguments );
}

var x:Number = 100;
var a:Number = x >> 1
var b:Number = Math.floor( x / 2 );
output( a, b ); // 50, 50

var a:Number = x >> 2
var b:Number = Math.floor( x / 4 );
output( a, b ); // 25, 25

var a:Number = x >> 3
var b:Number = Math.floor( x / 8 );
output( a, b ); // 12, 12

var a:Number = x >> 4
var b:Number = Math.floor( x / 16 );
output( a, b ); // 6, 6

get/set flags:

// CONST
var A:int = (1< <0);
var B:int = (1<<1);
var C:int = (1<<2);
var D:int = (1<<3);
var E:int = (1<<4);

// VARS
var _1:int = (1<<0);
var _2:int = (0<<1);
var _3:int = (1<<2);
var _4:int = (1<<3);
var _5:int = (1<<4);

// VALS
var vals:int = _1 | _2 | _3 | _4 | _5;

// CHECK
_1 = ( vals & A );
_2 = ( vals & B );
_3 = ( vals & C );
_4 = ( vals & D );
_5 = ( vals & E );

BITWISE OPERATOR LINKS

Using Bitwise Operators to Manipulate Bits and Colors - Grant Skinner
Using bitwise operators in actionscript - Moock
Get a Speed Boost from the Bitwise Operator

Bitwise operators - Adobe

What are Bitwise operators and how/why do you use them?
Finding Odd/Even Values efficiently - Createage

BINARY LINKS

1001010001010001010001010001 - Createage

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8 Comments »

jgraup said,

March 3, 2007 @ 6:23 pm

http://pixeldepth.net/index.php?action=tutorials&category=1&id=1156254799
jgraup said,

March 3, 2007 @ 6:25 pm

http://vijayram.wordpress.com/2007/01/30/actionscript-code-tricks-3/
jgraup said,

March 14, 2007 @ 8:00 pm

Bitwise Color Creation
http://www.flash-creations.com/notes/asclass_color.php

example:
// three decimal numbers, one each for R-G-B
var nRed:Number = 101;
var nGreen:Number = 153;
var nBlue:Number = 204;
cCircle.setRGB(nRed< <16 | nGreen<<8 | nBlue);

see also
http://www.flash-creations.com/notes/actionscript_operators.php

jgraup said,

March 14, 2007 @ 8:14 pm

Simple way to get a gray color:

function getRandomGrayscaleColor ( ) :Number
{
var brightness = Math.round (Math.random() * 255 );
return getGrayscaleColor ( brightness );
}

function getGrayscaleColor ( brightness:Number )
{
return ( brightness <<16 | brightness <<8 | brightness )
}

for ( var i = 0; i < 100; i ++ )
{
// new ball
var ball = this.attachMovie( ‘ball’, ‘ball_’ + i, this.getNextHighestDepth() );
ball._x = Stage.width * Math.random();
ball._y = Stage.width * Math.random();

// set color
var colorObj:Color = new Color ( ball );
colorObj.setRGB ( getRandomGrayscaleColor ( ) );
}
jgraup said,

March 16, 2007 @ 6:07 pm

Bitwise XOR
Bytes that differ are 1, bytes that are the same are 0. Converted to 32-bit binary integers before the operation occurs and the fractional portion of an operand, if any, is discarded.

1 = 0
0 = 1

trace ( 1^1 ) // 0
trace ( 0^1 ) // 1
jgraup said,

March 16, 2007 @ 6:18 pm

One way to blindly toggle between a primary and secondary clip within an array.

var nINX = ( clips [ 0 ].isPrimary ) ? 1 : 0;
var oINX = ( nINX ^ 1 );

var primaryClip = clips[ oINX ];
var secondaryClip = clips[ nINX ];

secondaryClip.isPrimary = !( primaryClip.isPrimary = true )
jgraup said,

April 15, 2007 @ 4:40 pm

var a = false
trace( a ) // false
trace( a |= 0 ) // 0
trace( a |= true ) // 1
trace( a |= 99 ) // 99
trace( a |= true ) // 99
trace( a |= 0 ) // 99
jgraup said,

June 1, 2007 @ 1:19 am

http://lab.polygonal.de/2007/05/10/bitwise-gems-fast-integer-math/

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Bitwise Operators

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jgraup said,

jgraup said,

jgraup said,

jgraup said,

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