Re: IIgs and Mac

[dempson@actrix.gen.nz (David Empson)]

Daniel Webster <dwebster@monmouth.com> wrote:

> IS there a GS program that will allow the decoding of those Macintosh
> disk images?

It depends what disk images you are talking about.  There are two IIgs
programs that can copy an 800K "DiskCopy" disk image back to a floppy
disk: a freeware program called DISKCOPY, and Replicator by EGO Systems
(from the appropriate back issue of GS+ magazine).

Replicator might also work with 1.44MB disk images (assuming you have a
SuperDrive or similar), but I've never tried.
 
> I know that Apple has some of its ][ software stored as those types
> of images. 

The IIgs system software and HyperCard IIgs are stored as DiskCopy disk
images, but they are inside Macintosh self-extracting archives, which
can only be decoded on a Mac (they are a Mac application).  It should be
possible to extricate the compressed data from the SEA (stripping off
the application part), but the resulting file would be a StuffIt or
Compactor Pro file, neither of which can be decoded on the IIgs.

(ShrinkIt GS can decode files compressed with an old version of StuffIt,
but nothing recent.)

> Also, There are several Mac programs that allow the images to be mounted
> as disks on the desktop.  I figure that this would be tougher on a GS,
> having each volume assigned to a slot and all.

There is no need to assign it to a slot.  All that you need is a GS/OS
driver which provides access to the contents of the disk image.  It
could be used with any FST which supports a disk of the appropriate
size.

There is one major catch: it would be necessary to load the entire disk
image into memory while the disk was mounted.  If it was left on the
disk, then the disk image device driver would have to make GS/OS file
access calls to read and write the blocks of the disk image, and this
would mean making a call to GS/OS while a call is already active.  GS/OS
is not re-entrant, so this cannot be done.

If the device driver has a complete copy of the disk image in memory,
then there is no problem (except that you are using up 800K or more of
RAM just to mount the disk image).  All that is required is a utility
program, Finder Extension or NDA to mount and unmount the volumes.  It
would communicate with the device driver as required.  If the disk image
was modified, the file could even be written back out to disk when the
image was unmounted.

-- 
David Empson
dempson@actrix.gen.nz
Snail Mail: P.O. Box 27-103, Wellington, New Zealand