From: Joel VanderWerf <vjoel@...>
Date: 2006-07-10T12:42:48+09:00
Subject: Re: Marshal's handling of floats

Brian Palmer wrote:
> Actually, I'm not terribly concerned with precision, but rather with 
> speed and size. The application I'm building needs to communicate data 
> over a wireless network every 100 milliseconds, and it needs to use as 
> little bandwidth as possible. I was considering just using the Marshal 
> methods, but Marshal's floating-point representation killed that idea, 
> though for other Ruby built-in data types it seems to be quite good, 
> even truncating small integers to bytes and shorts. I've decided that I 
> only need a couple decimal places of accuracy, though, so I'm just going 
> to multiply each float by 100 and then convert it to an int.

If you don't need to send arbitrary (marshallable) ruby objects, but 
only fairly well-defined struct-like packets, the you might find this 
helpful. It's built on top of pack/unpack, but it has a "dsl" flavor and 
makes it easier to work with odd-length bit fields, for example:

http://redshift.sourceforge.net/bit-struct/

(I wrote this for purposes like yours: to send data over a constrained 
wireless network, and also to communicate easily with non-ruby code, so 
Marshal was not an option.)

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407