From: Mark Hubbart <discordantus@...>
Date: 2004-10-09T03:27:21+09:00
Subject: Re: parsing data and displaying hex

On Fri, 8 Oct 2004 23:04:44 +0900, Ray Pendergraph
<raymondpendergraph@yahoo.com> wrote:
> I am sort of a novice to Ruby so I will just start out with a
> simplified example what I want to do. I have an array with two bytes
> in it [0x03,0x9A] and depending on what the byte order of the file
> (not the architecture) is want to display these bytes as 922 or 39427
> (both unsigned shorts). I want to do this without reversing the index
> on the array or anything goofy like that. Whats the most proper way to
> do this in Ruby? I suspect my solution lies somewhere in pack... I
> toyed with it briefly but decided to ask.

unpack is easier than it first looks...
Assuming unsigned integers:

# pack the bytes
bytes = [0x03,0x9A].pack('cc')
# unpack in big-endian
big = bytes.unpack('n')
# unpack small-endian
small = bytes.unpack('v')

I'm not sure if there's a way to use pack for this using signed
integers. I didn't see anything in the reference that offers unpacking
two bytes as signed little-endian integers. If you need signed
integers, you might have to resort to tricks.

reference for string.unpack:
http://www.rubycentral.com/ref/ref_c_string.html#unpack

hth,
Mark