Bitmask.js

A small package to convert integers to bit arrays and back, with some utilities

Installation

Install with bower install bitmask, then add the bitmask.min.js script to your page. You can also require it if you're using requirejs.

If you're using NodeJS, you can install it using npm install bitmaskjs (note that the package name is bitmaskjs, not bitmask). You can then require it as usual.

Usage

Create a Bitmask object by passing either an integer value or a bit array to the constructor:

// Either
var myBitmask = new Bitmask(15);

// Or
var myBitmask = new Bitmask([1,1,1,1])

The constructor also accepts a second parameter that allows you to specifiy the padding (the length of the bit array). This value defaults to 8.

At any point you can retrieve the current value in its integer or array form, regardless of how you called the constructor, by using:

myBitmask.getInteger()  // 15
myBitmask.getBits()     // [1,1,1,1,0,0,0,0]

Instance Methods

• getInteger() - returns the integer value of the current instance
• getBits() - returns the bit array representation of the current instance
• hasBit(index) - returns true if the bit at the specified index is set
• setBit(index, value) - sets the bit at the specified index to value (true or false)
• toggleBit(index) - toggles the bit at the specified index
• lShift(n) - shifts the bit array to the left by n positions (default is 1)
• rShift(n) - shifts the bit array to the right by n positions (default is 1)

The following methods are chainable: setBit, toggleBit, lShift, rShift. The constructor is chainable as well.

new Bitmask(4).lShift(2).rShift(1).setBit(0, true).getInteger() // => 9

Contributing

You can edit the source in src/bitmask.js and build it using grunt. Remember to do an npm install beforehand to install all the dev dependencies!