Cloak is a small node.js library for managing bitmasks for a set of values

I built it to allow me to send a large number of true/false values over a network without having more information than requred. Cloak takes your set of values and returns a bitmask value for each one, for example:

var values = ['apple', 'orange', 'banana', 'carrot', 'potato']

var cloak = new Cloak(values);

This gives each value a mask such that

apple = 1 orange = 2 banana = 4 carrot = 8 potato = 16

To get a subset of these values we can then add up the mask values and when required, cloak can turn those masks back into a set of values

So if we needed to pass a message to say 'apple', 'banana' and 'carrot' we would send 1 + 4 + 8 (13)

Then to get those values back from our number it would be

cloak.getValuesFromMask(13);

Which returns

=> ['apple', 'banana', 'carrot'];

Values can be added dynamically but not removed, remove and set value functionality may be added at a later date.

cloak.addValue('leak');

Which returns the mask value for that added value

=> 32

This also works with an array of values via addValues()

cloak.addValues(['onion', 'grape']);

Again this returns an array of masks

=> [64, 128]

You can fetch the key-value pair object to check what values are used

cloak.getMasks();

=> {
	1: 'apple',
	2: 'orange',
	4: 'banana',
	8: 'carrot',
	16: 'potato',
	32: 'leak',
	64: 'onion',
	128: 'grape'
}

Limitations

Due to the number limit of JS there's a limit of ~30 values which this can provide masks for. In the near future I aim to update this to use bignum.js to increase that, hoping that it won't cause too much of a slowdown when doing a large bitwise add.

It doesn't accept objects and arrays as values due to the way I've implemented it

Future work

• Finish tests
• Make the whole thing immutable
• Use bignum.js for dealing with larger numbers
• Make method names use proper language
• Allow all JS types to be used as array values