clownacy/clownnemesis

Compressor and decompressor for the Nemesis file format.

clownnemesis

A compressor and decompressor for the Nemesis format.

A description of the Nemesis format can be found here: https://segaretro.org/Nemesis_compression.

The compressor implements two prefix-code generation algorithms: Shannon-Fano and Huffman. Huffman produces the smallest files, while Shannon-Fano produces identical results to Sega's compressor.

Both an executable and library are provided. Both are written in ANSI C (C89).

To build this, use CMake.

clownnemesis's Issues

Sega-accurate compression should be padded to even length

Installing this compressor in my Sonic 2 disasm resulted in about a third of the Nemesis files not compressing identical to the original. I investigated a handful of the affected files, and the sole difference was that they were missing a single zero byte at the end. I would guess that Sega's original compressor inserted this extra byte if necessary to bring it to an even length.

Error with "decompression" by compressing specific file

Trying to compress a small file, it errors with "Could not decompress data", despite trying to compress the data. It works fine with other files I try, just this specific file doesn't work. It works fine with FW-KENSC, so I'm not sure why it doesn't work here.
index.zip