Hello,
when i run trid on some old DOS backup files like BACKUPID*.@@@ these
are misidentified as "MP3 audio", "MacBinary 1 header", "Adobe PhotoShop Brush",
"DEGAS med-res bitmap", "Sybase iAnywhere database files" or others ( see
appended @@@-old.txt )
A good starting point for such files is archiveteam org website
So i add to new trid definition files this URL as reference by line
<RefURL>
http://fileformats.archiveteam.org/wiki/BACKUP_(MS-DOS)</RefURL>
The format of such files is described in BACKUP & RESTORE document for
the Free DOS project found for example at
http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/dos/restore/brtecdoc.htm
According to Free DOS documentation test for padding 121 nul bytes by XML
construct like
<Pattern>
<Bytes>0000000000000000000000000000000000000000</Bytes>
<Pos>7</Pos>
</Pattern>
Unfortunately this file format has no characteristic magic pattern. The backup
sequence id is stored offset 1, year at offset 3, day at 5 and month at 6.
Real world examples are dated about 1983 and little later according to
https://en.wikipedia.org/wiki/Timeline_of_DOS_operating_systems.
So it is sufficient to test year in range from 1792 till 2047 (0700h-07FFh) or
expressed as XML construct:
<Pattern>
<Bytes>07</Bytes>
<Pos>4</Pos>
</Pattern>
At the beginning a flag byte is stored, where FFh means last file of backup
process and 00h means not last. So i create 2 variant definition file.
The first is @@@.trid.xml with XML construct
<Pattern>
<Bytes>00</Bytes>
<Pos>0</Pos>
</Pattern>
The second is @@@-last.trid.xml with lines
<Pattern>
<Bytes>FF</Bytes>
<Pos>0</Pos>
</Pattern>
According to Free Dos documentation Microsoft and IBM use different backup file
format in different DOS versions. The format described by above patterns is used
in version 2.0 till 3.2. So such files are described as "DOS 2.0-3.2 backup
control file"
With these 2 new definition files finally all my BACKUPID.@@@ files
are now recognized ( see appended output @@@-new.txt ).
trid definitions and output are stored in archive backupid.zip.
I hope that my XML files can be used in future version of triddefs.
With best wishes
J?rg Jenderek
