Re: CP/M .com & .arc files to apple II?

[Andy McFadden <fadden@fadden.com>]

Paul Schlyter <pausch@saaf.se> wrote:
> You already have code which reads CP/M files, right?  Writing isn't that
> much more complex really.  And CP/M allocated new blocks in a quite
> simpleminded way: whenever a new block was needed, the first free block
> from the beginning of the disk was allocated.  I think it's OK to only
> write non-sparse new files to a CP/M disk --- even CP/M's own PIP utility
> isn't able to transfer a sparse file from one unit to another....

Writing is more complex because, if you do it wrong, you destroy the
disk image. :-)

If CiderPress can't open a disk image or displays a file incorrectly, I
can fix it.  If it subtly corrupts files in ways that don't get discovered
until much later, I can't.

Adding write capability to a filesystem raises some other issues as well.
When DOS became writable I had to deal with conversion of text files
from ProDOS format to DOS format.  The actual conversion is trivial,
but deciding when it should and shouldn't be done, making sure it got
done everywhere it needed to be, and adding UI to deal with edge cases,
took some doing.  CP/M has potential issues with text files from other
filesystems (do they need to end in Ctrl-Z?  If I find a Ctrl-Z in a
DOS text file, do I need to remove/escape it?).  At the very least it
needs to be better about preserving CP/M volume numbers on copied and
extracted/added files.  Should the "edit attributes" dialog morph to
allow you to change the volume number?

None of this is brain surgery, but there are a lot of little things to
get right, and a lot of testing to be done.

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