From: Joel VanderWerf <vjoel@...>
Date: 2006-07-30T00:44:43+09:00
Subject: Re: How can I parse binary files?

Fabio Vitale wrote:
> This time I'm trying to write a binary file.
> 
> Q1: why does the structure MRKMessageFlags does not get the apropriate 
> values?

The problem is, unfortunately, not something that can easily be fixed in 
bit-struct's nested fields. When you do assignments like the following:

 >   msg.flags.flagSeen      = 1
 >   msg.flags.flagAnswered  = 0
 >   msg.flags.flagFlagged   = 1

you are operating on a *copy* of the flags structure. The reason is that 
msg.flags returns a copy of that structure. It doesn't return a 
reference to a subfield of msg. It might be possible to return an object 
that delegates back to the msg structure, but I think that might 
actually be more confusing than the way it is now.

Your best bet is, as Daniel suggested:

     flags = msg.flags
     flags.flagSeen      = 1
     flags.flagAnswered  = 0
     flags.flagFlagged   = 1
     msg.flags = flags

I will try to add a warning about this in the docs.

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