A very old (ca. 1989) package including a document explaining various compression algorithms (LZSS, LZW, Huffman, LZARI, LZHUF) and the standard ANSI C source code to various (de)compression utilities implementing the described algorithms (LZARI, LZHUF, and LZSS).

Apparently the code in these utilities was used quite widely in Japan. If you come across what appears to be some kind of LZ/LZSS/etc. compressed data from old early 1990s Japanese-developed games, there’s a good chance the code in one of the utilities is exactly what you need, with only minimal changes to the source code required.