From: Guillaume Marcais <guslist@...>
Date: 2003-07-30T23:50:51+09:00
Subject: Re: Reading an integer out of 1..3 bytes

On Tue, 2003-07-29 at 22:30, gabriele renzi wrote:
> hi gurus and nubys,
> I'm working on a tiny dumb client for the Gnutella2/MP network, and I
> have packets like this:
> 
> [length of payload_length field][other stuff][payload_length field]
> ^^header
> 
> [payload]
> ^^data
> 
> now: payload_length can be 1..3 byte, encoded in little endian 
> (same of my platform), is there a rubysh way of reading 1,2 or 3 bytes
> on an integer from an IO?
> 
> PS 
> in the spec-draft I can read this example:
> 
> ReadBytes( (BYTE*)&nPacketLength, nLenLen ); 

Something like (untested):

l = packet[offset_to_payload_length_field].unpack("c#{len_len}")
payload_length = 0
l.each_with_index { |x, i| payload_length += x << i }


Guillaume.
> 
> the varname are obvious, but 
> I don't know what kind of code is this and what it actually does..
> 
>