Re: CiderPress Bug

[Andy McFadden <fadden@fadden.com>]

Andy McFadden <fadden@fadden.com> wrote:
> Jayson Smith <nospamratguyspambegone@nospamplease.bellsouth.ihatespam.net> wrote:
>>                              Even on a freshly formatted DOS 3.3 disk,
>> formatted from within CiderPress, some files aren't copying properly, some
>> just have 1 sector, and a few use less sectors than they do on the original
>> disk.
> 
> Make sure you're using the latest version (2.1).  There were some problems
> with cut & paste to DOS 3.3 disk in v2.0, notably failure to set the aux
> type correctly on BIN files, and incorrect handling of empty files.  I'm
> not aware of a problem that would leave a partially-created file behind
> though -- CiderPress is pretty good about cleaning up after itself, e.g.
> when the disk fills up.

I should probably explain one thing about DOS 'B' files.  They have an
embedded length that determines how much of the file is loaded on a BLOAD
or BSAVE.  Some cracked games use this feature to put a small "loader"
program at the front of the file.  When you BRUN the file, only the loader
is read into memory and executed; the loader then reads the rest of the
sectors of the file.

DOS copy programs will copy all of the sectors in the file, regardless of
the length.  CiderPress obeys the length.  If you try to copy & paste one
of these files, the copy will be incomplete.

DDD 2.1 files have a similar problem, because compressed disk images are
often larger than 64K, and there's no way to specify the length.  CiderPress
attempts to recognize DDD images and "fixes" their length, so that the
"open as disk image" feature doesn't think it's a zero-length file.

Fixing the situation for files with "loader" segments isn't as easy,
because they essentially have *two* lengths.  If CiderPress just uses the
length of the entire file, based on the sector count, then the length
value in the new file will be incorrect, and the program still won't work.

There is one fairly straightforward way around this: change the file
type to something other than 'B' (e.g. 'S').  These files have no length
value, so all sectors must be copied as they are.  The current version
of CiderPress doesn't allow changing DOS types, because the "right" way
to change them requires rewriting the file.  I think I'm going to allow
changing them the "wrong" way, so you can do this type-changing trick
to copy the files.  (It's also sort of handy when you get the file type
wrong when extracting stuff from tape.)

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