ZX02: 6502 size optimized compression

[dmsc]

Hi!

 

I made a modified version of the ZX0 compressor to make the decompressor smaller (and faster) in the 6502, by sacrificing about 0.5% compression ratio. The intended use is compressing data up to about 10kB, or where the decompressor size should be as small as possible.

 

Current 6502 code is 130 bytes for the small decompressor (this includes the initialization) and 175 bytes for the fast version.

 

Note that the compressor is only a slightly modified version of the original ZX0 compressor by Einar Saukas, but the decompressors (C and 6502 versions) are by me.

 

Code and documentation is here: https://github.com/dmsc/zx02 , go to the releases to download the compiled compressor for linux and windows.

 

EDIT: I added a third 6502 decompressor, with a trade off between size and speed, at 138 bytes it will probably be the best to use in most situations.

 

Current stats in the "conan.gfx" file are:

 

File	Size (bytes)	Speed (cycles/bytes)
zx02-fast.asm	175	48.1
zx02-optim.asm	138	58.0
zx02-small.asm	130	72.6

 

 

Have Fun!

 

Edited May 31, 2022 by dmsc
Adds new "optimal" decompresor code.