From Retrosoftware

Revision as of 08:40, 1 July 2011

Epic Database format

This is a simple description of some reverse engineering performed on the Epic Adventures database format. It is a work in progress, so mistakes may exist.

All work has so far only been performed on Castle Frankenstein, although patterns have been noticed in some of the other games.

Files

All game data and code is stored in the file $.FRANK2. Once loaded, the file is relocated down to &0C00. All offsets used below are offsets from the start of the file. Unless noted otherwise, memory pointers will be to locations in the BBC memory, so will need &0C00 deducted to get the file offset.

Text Encoding

Verbs, nouns and the dictionary are trivial obfuscated by a single roll left to prevent dumping the game file to give clues.

Strings, such as system messages, messages and room descriptions are stored as a stream of &00 terminated bytes. Each byte is an index to an entry in the dictionary, which are then concatenated together to form the string.

Colour is defined by the a byte of greater than &F8 (which returns a dictionary entry of &01 to &08. The mapping has been completely resolved yet.

Note: there are some grey areas around the creation of strings as some words seem to lack space around the edge of the screen. It is possible that some form of wordwrap is in place which has been discovered yet.

Data Chunks

The following chunks have been identified:

Header

The header has the following known fields:

Save Game Data

All data is initially set to &00; it will be update during the game. The filename use is stored at &57 and potentially could be used as a magic number for the game.

Known fields in the memory area are:

Room Exits

This chunk comprises of 6 bytes for each room; each byte holds the destination room for the direction. The order of bytes is NSEWUD.

So to get the destination room for South from room 10, the formula is: &0700+(room*6)+1