Re: More thoughts about Lode Runner & other multiload games...

[Steve Nickolas <usotsuki@buric.co>]

http://1.buric.co/lrrbcd.zip

Given a sector containing a level from Lode Runner, these tools will 
convert between the 256-byte (only 224 used) raw sector form and a 
196-byte format made through what I call "reverse binary-coded decimal 
packing".

Basically, each nibble contains a value from 0-9 (where they could take a 
value up to 15).  This means each byte has only 100 options, instead of 
256.  A range of 100 will fit in 7 bits (which have a range of 128). 
Therefore by taking the converted values, and packing 8 bytes in 7 by 
discarding the top bits, the file is reduced from 224 used bytes to 196.

lrrbcd.c is a tool to encode levels using this scheme.
lrunrbcd.c is a tool to decode levels using this scheme.

I haven't translated the UNRBCD algo to 6502 yet.  Also, it breaks in 
Watcom C, so you'll probably need to use GNU C (e.g., MinGW).

-uso.