From: Charles Mills <cmills@...>
Date: 2005-01-09T09:51:25+09:00
Subject: Re: file io question


Mark Firestone wrote:
> I'm writing a fido mail tosser for my ruby bbs.  (A thankless task
that
> is far worse than I ever imagined when I started.) and I have a
problem
> I don't understand.
>
> To read the packets (the header in this case, I have to do the
> following, is it is stored in an odd way.  Here's a snippet of the
file
> header...
>
> PP�
>  (and lots of other low ascii characters...)
>
> So, I read it like this, suck in a bunch of it in a buffer...
>
> buffer   = happy.read(0x3a)
>
> orgnode	= (buffer[0x01] << 8) + buffer[0x00]
> destnode  	= (buffer[0x03] << 8) + buffer[0x02]
> orgnet	= (buffer[0x15] << 8) + buffer[0x14]
> destnet	= (buffer[0x17] << 8) + buffer[0x16]
> orgzone	= (buffer[0x23] << 8) + buffer[0x22]
> destzone	= (buffer[0x25] << 8) + buffer[0x24]
>
> and so on.  This works great, we get the right answer...
>
> if I try to reverse this and write stuff, it doesn't work.  For
> example...
>
> happy = File.new("#{path}", File::CREAT|File::APPEND|File::RDWR,
0644)
>
> buffer = []

should this be:
buffer = ''

>
>    buffer[0x00] = (f_hdr.orgnode & 0x00ff)
>    buffer[0x01] = ((f_hdr.orgnode & 0xff00) >> 8)
>    buffer[0x02] = (f_hdr.destnode & 0x00ff).chr
>    buffer[0x03] = ((f_hdr.destnode & 0xff00) >> 8)
>    buffer[0x04] = ((f_hdr.year + 1900) & 0x00ff)
>    buffer[0x05] = (((f_hdr.year + 1900) & 0xff00) >> 8)
>    buffer[0x06] = f_hdr.month
>    buffer[0x08] = f_hdr.day
>    buffer[0x0a] = f_hdr.hour
>
> and so on and then...
>
> happy.write buffer
(...)
Sounds like you should be using String#unpack and Array#pack.

-Charlie