3 releases (1 stable)
1.0.0 | Sep 8, 2024 |
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0.1.1 | Sep 2, 2023 |
0.1.0 | Aug 20, 2023 |
#274 in Compression
Used in 2 crates
(via a2kit)
345KB
2.5K
SLoC
retrocompressor
The starting motivation for this project is to provide a library that aids in the handling of TD0 files (Teledisk-compatible disk images). It is envisioned that the scope will expand over time.
direct_ports::lzhuf
- nearly a direct port of the classicLZHUF
of Okumura et al.lzss_huff
- signficant rewrite ofLZHUF
with flexible parameterslzw
- LZW with fixed code width, other parameters flexibletd0
- convert normal Teledisk to advanced Teledisk, or vice-versa
Size Limits
This is not optimized for large files. Some 32-bit integers used to describe file sizes have been retained since they are part of the format. The maximum size, beyond which an error is returned, defaults to 3 MB for TD0 files, 1 GB otherwise.
Executable
The executable can be used to compress or expand files from the command line. For example, to compress or expand a file using LZSS with adaptive Huffman coding:
retrocompressor compress -m lzss_huff -i <big.txt> -o <small.lzh>
retrocompressor expand -m lzss_huff -i <small.lzh> -o <big.txt>
To get the general help
retrocompressor --help
Library
This crate can be used as a library. For an example of how to use the library see main.rs
(which calls into lib.rs
per the usual rust arrangement). Also see the crate documentation.
Teledisk
Teledisk images come in an "advanced" variety that uses LZW (v1.x) or LZSS/Huffman (v2.x) compression. Module lzw
handles the former case, while module lzss_huff
handles the latter. However, options need to be set correctly, and the Teledisk header needs to be modified whenever advanced compression is added or subtracted. As a convenience there is a module td0
that handles all known cases transparently. This can also be accessed from the command line:
retrocompressor compress -m td0 -i <normal.td0> -o <advanced.td0>
retrocompressor expand -m td0 -i <advanced.td0> -o <normal.td0>
Important
Advanced TD0 images in v2.x do not record the length of the expanded data. As a result, some decoders have trouble decoding the last symbol. The workaround is to pad the expanded TD0 with several disparate-valued bytes before compression. Teledisk evidently did this, so normally there is no problem, but if you are a creator of TD0 images, it is a good idea to include the padding.
Dependencies
~8–18MB
~256K SLoC