Amiga Quarterback ADF file extractor
This python script is designed to accept the Central Coast Software's Quarterback backup disks as .ADF files, identify the CFM file markers within the file, and perform the LZW decompression algorithm on raw datastream, and write those decompressed files back into a qb_dump subdirectory of the current directory.
You must create a qb_dump folder!
This script uses standard Python3. There's nothing special or unique or exotic about the installation, and this script should function fine on Windows, OSX, and Linux. I developed it mostly using Jupyter Notebook, but tested it on Ubuntu 22.04.
You'll want to install PIP, if you've somehow used Python without it. And then install numpy and pandas using PIP.
This backup software was a popular HDD backup solution for the Commodore Amiga. The genesis of this project was that I had a couple corrupted disks within my backup set, and Quarterback, despite having SOME builtin protection against it, fails as soon as it encounters some corrupted data. QB also requires a catalog which is stored on the first and last floppy in the backup set, in order to extract the files. My tool works on standalone disks within the set without the catalog.
However, because there's no catalog support, there's a major limitation in the current, very beta, version. The original directory information IS NOT stored alongside the individual files, and so all files are simply written to the current directory.
There is support for a backup set spanning multiple disks. Once ADF'd, combine the ADF's into a single file, concatenating one disk after the others. The disk must be 901120 bytes long, and they should be in order. Once the ADF's are named properly, using cat within linux and redirecting the output is sufficient to build a massive disk file. Then, just execute this script against the file.
Because of the way LZW builds a new dictionary for every file, any corruption within a current file makes the rest of the file unreadable. The data prior to the corruption is safe.
I have not done much testing on it especially regarding the numerous different versions of quarterback, but more is planned. It's possible that some minor modifications are needed to support it, please email me the details and a sample ADF if possible, and I'll try my best to fix it.
QB tools uses fairly standard LZW compression on its files. It uses a code-size of 9 bits minimum, 16 bits maximum. The original C and ASM source code for quarterback is available publically, and I'll link it in the future. Because of the 16-bit maximum code-size, there's a drawback to compression performance on files over a couple hundred kilobytes. If there are repeated patterns not yet learned by the time all ~65k codes are filled, then the LZW dictionary will get no bigger. I have plans to have the script report the compression efficiency for each file as it's extracted.
#define FIRST_CODE 258 /* First free entry */
#define CLEAR_CODE 257 /* Table clear output code */
#define EOF_CODE 256 /* Last entry of file */