Date   : Tue, 20 Apr 2010 13:56:36 +0200
From   : rick@... (Rick Murray)
Subject: Unzipping metadata

On 20/04/2010 07:06, P. Van Ek wrote:

> I did look and as Rick says I am using a pc to unzip the files....
> Where does it say you must use a bbc unzip program to extract them !!!

Common sense! :-)

Ever got a generic Windows zip program to understand the difference 
between public and owner file permissions? Ever got a generic Windows 
zip program to understand RISC OS filetypes or BBC load/exec addresses? 
Heck, it's enough to a trial to get WinZip to put stuff in relative 
paths (it likes either no paths at all, or everything relative to root!).

I guess getting a generic Windows zip program to understand such 
extended features is akin to getting Windows to read an ADFS floppy. Or 
an ext# one, for that matter.


Interestingly enough, the RISC OS filetype (BBC load/exec) does not seem 
to be part of the official Zip specification. Was this an omission on 
the part of Acorn/RISC OS coders, or has it been forgotten?
    http://www.pkware.com/documents/casestudies/APPNOTE.TXT

Thanks to Kevin Bracey, this information is a documented part of the 
gzip format:
    http://www.gzip.org/format.txt
but, of course, this doesn't mean that:
    a. A PC gzip program will support Acorn extensions
&  b. It would know what to do with them even if it did...


Therefore, if you wish to extract metadata (load/exec/etc) with files in 
a zip file, it makes sense to use a system that is actually capable of 
handling such - namely a BBC itself or, for most cases, RISC OS (but 
note that RISC OS can't do load/exec *AND* datestamp, not that the 
datestamp matters in 99% of cases)...


Best wishes,

Rick.

-- 
Rick Murray, eeePC901 & ADSL WiFI'd into it, all ETLAs!
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
E01S FileStore, A3000/A5000/RiscPC/various PCs/blahblah...