Re: Brutal Deluxe's holidays project 1: IIgs mount virtual disk image

["ict@ccess" <gids.rs@sasktel.net>]

On Aug 19, 4:32 am, "Peter Watson" <paw77@N_O_hotmail_S_P_A_M.com>
wrote:
> "Toinet" <antoine.vig...@laposte.net> wrote in message
>
> 8f27b9af-c978-4b5e-b447-30cc6d76420c@o6g2000yqj.googlegroups.com">news:8f27b9af-c978-4b5e-b447-30cc6d76420c@o6g2000yqj.googlegroups.com...
>
> > It is not possible to mount a HFS partition nor a DOS 3.x or RDOS 3.x
> > partition, it is limited to ProDOS files only (140 KB or 800KB). Note
> > that the files are loaded into memory in one shot. There are no ways
> > to open files larger than available RAM or >800 KB.
>
> I understand the size limitation due to loading everything into memory, but
> I'm curious to know why you couldn't support other disk sizes such as a 1.44
> MB ProDOS file image?
> --
> Peter Watson
> -- Write to MS-DOS disks on the Apple IIgs?
> -- Impossible!  ;-)


Exactly!  I think it was gone about the wrong way.  You don't need to
load the entire disk image into memory.  You just have to load the
directory and then load files from there.  That way, there are a few
utilities that can read a dos 3.3 catalog from Prodos.  Really, all
that is needed is a driver that calculates the offset to a hard drive
block.  Since it is known that the Prodos catalog starts on block #2
on any drive, then just add 2 to the starting directory block of the
disk image.  Any file can also be loaded by adding the files block
number to the theoretical starting block zero of the disk image.  This
sounds and is much easier than loading the entire image into memory.

Rob