Rob Northen compression
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Rob Northen compression (RNC) is a multi-platform compression format created by Rob Northen in 1991. It is a variant of LZSS and Huffman. Decompression libraries have been written for the PC, Mega Drive, Game Boy, SNES and Atari Lynx. RNC is used in a number of games by UK developers (notably Bullfrog and Traveller's Tales), including Sonic 3D: Flickies' Island, Dungeon Keeper 2, Magic Carpet, Syndicate and Syndicate Wars.
Header Format
Most RNC compressed files come in a standard 18 byte header:
| Data Type | Description | Size (in Bytes) |
|---|---|---|
| Signature | ASCII "RNC" | 3 |
| Compression Method | 1 or 2 (In binary) | 1 |
| Uncompressed Size | Size of the original file | 4 |
| Compressed Size | Size of the RNC data (excluding header) | 4 |
| Uncompressed CRC | Checksum of the original file | 2 |
| Compressed CRC | Checksum of the RNC data | 2 |
| Leeway | Difference between compressed and uncompressed data in largest pack chunk (if larger than compressed data) | 1 |
| Pack Chunks | Amount of pack chunks | 1 |
Each multi-byte portion of the header is big endian.