https://github.com/dfgordon/retrocompressor
compress and expand using retro formats
https://github.com/dfgordon/retrocompressor
Last synced: 6 months ago
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compress and expand using retro formats
- Host: GitHub
- URL: https://github.com/dfgordon/retrocompressor
- Owner: dfgordon
- License: other
- Created: 2023-08-13T18:57:51.000Z (almost 3 years ago)
- Default Branch: master
- Last Pushed: 2024-12-07T18:24:17.000Z (over 1 year ago)
- Last Synced: 2025-09-28T21:16:06.163Z (9 months ago)
- Language: Rust
- Size: 329 KB
- Stars: 6
- Watchers: 2
- Forks: 1
- Open Issues: 1
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Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
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README
# 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 classic `LZHUF` of Okumura et al.
* `lzss_huff` - signficant rewrite of `LZHUF` with flexible parameters
* `lzw` - LZW with fixed code width, other parameters flexible
* `td0` - 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 -o `
`retrocompressor expand -m lzss_huff -i -o `
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](https://docs.rs/retrocompressor/latest/retrocompressor).
## 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 -o `
`retrocompressor expand -m td0 -i -o `
### 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.