This is LZ77-based compression code with a focus on small files, and simplicity of decompression. Packing (and depacking) code is done in C language, and depacking in 68000 assembly language is also provided.
As it is focused on small files, no fancy features like 32-bit offsets or chunk sizes. The packer will behave slightly better than lz4 on small files, but significantly worse on larger files.
The compressed file format is a succession of two types of chunks:
- Literal chunks : Chunks containing not packed data. They consist in one header byte containing the
number of bytes - 1 + 0xc0, then follows the corresponding number of bytes to be copied directly to the output byte stream. Such chunks contain between 1 and 64 uncompressed bytes. - Offset chunks : Chunks describing a repetition of previous data. They consist in one header byte containing the
number of bytes - 4, then an offset byte. Repetition size may vary between 4 and 195 bytes, and with offset values from -256 to -1.