Comments on: Using Bitmasks to Efficiently Store Data

By: atish

atish — Wed, 18 Jun 2008 21:11:57 +0000

http://www.racketmag.com/images/cookiecrisp.jpg

By: Matt Snider

Matt Snider — Tue, 17 Jun 2008 05:34:09 +0000

Thanks pawel. I thought that JavaScript supported binary operations, but when I setup a few test scripts, it didn’t work. I tried again today, and it worked just fine. I have upgraded the BitWriter script to properly use binary operators.

By: pawel

pawel — Mon, 16 Jun 2008 13:16:15 +0000

ouch, once ahgain:
hasBitmask : function(n){
return ( isValidBitmask(n) && n <= bit && ((bit & n) == n)) ? true : false
}

By: pawel

pawel — Mon, 16 Jun 2008 13:07:45 +0000

What’s the reason to “simulate ‘&’ (or ‘|’ or ‘^’) binary operator in other languages” instead of actually using binary operators?

/* will work for up to 256 stored values.
you can use any power of 2 if you need more/less “slots” */
isValidBitmask = function(n){
return (n>0) && !(256%n)
}

/* this is just an example of how I’d write hasBitmask function*/
hasBitmask : function(n){
return ( isValidBitmask(n) && n