Geeking-out with Bitwise Operations

So, I was re-visiting some code the other day and thinking about how it could be optimized. I really wanted to focus on calculation speed/runtime execution and I remembered glancing at bitwise operators in the ActionScript Documentation back in the day but never really dug into what lies beneath…

As defined: A bitwise operation is one that affects 1 or 2 binary numbers on a bit level.

Background Binary Understanding:

Bits are like little containers for storing information and they can only contain one of two states.

Examples:

(3 bits) : 101
(8 bits or 1 byte) : 10110110

We know that a binary numerals are another way of referring to the “bit” unit of measurement. Binary is a base-2 system, which means that there are only 2 unique values allowed for a binary numeral — 0 or 1. We also know that binary numerals are made up of collections of our friend the “bit”.

The rules for incrementing binary numerics are as follows:

• Binary digits begin as ’0′ –> eg. to represent ’0′, the binary equivalent is ’0′
• Each time we increment beyond ’1′ the left most digit is incremented as well –> eg. to represent ’15′, the binary equivalent is ’1111′

I created a simple Flex app that handles a few of the more handy bitwise calculations. There’s not much to it but if anything it helps for experimenting to see what different values will produce real-time. Click the link to launch…

Get the Flash player…

Supported Bitwise operands and typical usages:

• & — AND (And — Useful when masking)
• ~ – NOT (Inverse — Useful when you need to switch all bits to their counterparts)
• | — OR (Or — Useful when setting flags)
• ^ — XOR (Exclusive Or)
• << — Shift Left
• >> — Shift Right
• >>> — Unsigned Shift Right
• <<< — Unsigned Shift Left

Further optimization:

• Avoid mixing data types.
• Use Signed Integers (int) for everything possible (e.g. counting variables, array access..).
• Use Number if you need precision.
• Use signed integers (int) only for ARGB color values.
• Avoid using uints for counting variables or arithmetic expressions.

Additional Reference:

http://www.gamedev.net/reference/articles/article1563.asp