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a few speed and/or compression ratio improvements

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Dennis Ranke
2021-11-24 22:35:24 +01:00
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# Upkr
Upkr is a simple general purpose lz packer designed to be used in the [MicroW8](https://github.com/exoticorn/microw8) platform.
The compressed format is base on [Shrinkler](https://github.com/askeksa/Shrinkler) with the main difference being that
Upkr doesn't differnetiate between literals at odd or even addresses.
The compressed format is losely based on [Shrinkler](https://github.com/askeksa/Shrinkler) with the main difference being that
Upkr doesn't differnetiate between literals at odd or even addresses and that I went with rANS/rABS instead of a range coder.
At this point, Upkr should be considered unstable - the exact format isn't finalized yet and still subject to change
and only a very simple (but also very fast) greedy compressor is implemented. The compression ratio will be improved
with a more thourough lz parse in the future, although even in the current state is is already similar to the
DEFLATE compression algorithm.
At this point, Upkr should still be considered unstable - the compressed format is not very likely to change but I still want
to keep that option open a little longer.
## Inspirations:
* Ferris' blog about his [C64 intro packer](https://yupferris.github.io/blog/2020/08/31/c64-4k-intro-packer-deep-dive.html)
* [Shrinkler](https://github.com/askeksa/Shrinkler)
* Ryg's [sample rANS implementation](https://github.com/rygorous/ryg_rans)