[sebhc] H8D files and labels

Jack Rubin jack.rubin at ameritech.net
Mon Mar 27 21:32:43 CST 2006

A minor quibble and/or request - if all image files are a fixed size,
it's easy to make a quick visual check of a directory and (if file sizes
are constant) be fairly sure that they have been
created/saved/transferred correctly. The value of incorporating
"metadata" into the record seems to far outweigh this convenience. In
that case, it would be nice to have a verify mode in IMD or an
associated utility that could operate on an arbitrary list of files to
report back on the integrity of the included images.


> -----Original Message-----
> From: sebhc-bounces at sebhc.org 
> [mailto:sebhc-bounces at sebhc.org] On Behalf Of Dave Dunfield
> Sent: Monday, March 27, 2006 8:24 PM
> To: sebhc at sebhc.org
> Subject: [sebhc] H8D files and labels
> I seem to have deleted it, but someone was just talking about 
> keeping labels for H8D files...
> What I did when I defined the ImageDisk file format, was that 
> I make everything from the beginning of the file up to a 0x1A 
> (^Z) character a "comment". IMD puts in it's "IMD" signature, 
> as well as the version and timestamp as the first line, then 
> the user-supplied comment can go "on forever".
> Because 0x1A (^Z) is the DOS text-EOF character, you can TYPE 
> these files to see the comment - TYPE stops output when it 
> hits the ^Z. IMD simply scans for the ^Z before it starts 
> processing track data.
> We could easily modify the H8D definition to do the same 
> thing. It would be very easy to add support for this to the 
> simulator(s). Just check the file size - if < disk image, 
> error (as now), if == disk image size, no comment. If > disk 
> image size, scan for the ^Z and check the remaining size == 
> disk image. Record the offset to ^Z and add this to all seeks 
> within the file.
> With this scheme, you can put plenty of information right in 
> the file, where you don't need to worry about it getting 
> separated from the image. When I record an image with IMD, I 
> usually type any label on the disk into the comment so that 
> it is preserved along with the data content.
> Dave
> --
> dave06a (at)    Dave Dunfield
> dunfield (dot)  Firmware development services & tools: 
com             Collector of vintage computing equipment:

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