| Author: | Lord Crass (guest: search) |
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| Date: | Wed, May 18th, 2011 @ 15:08 ( . ) |
Hopefully Nate or Pete has the original. I'm not sure how many instructions there are. When you look at the block of code that contains the compiled/interpreted program, you don't initially know which ones are opcodes and which are the operands. Once you start determining what each opcode does, you'll see how many operands it takes and the p-code starts falling into place. I see about 524 total bytes of p-code, which includes some data as well, such as the "COPY IS NOT PERMITTED" message. The Electronic Arts fat track loader is a svelte, efficient, specific-purpose interpreter compared to this thing. This one has stack, memory, and multiple registers. It occasionally makes calls into the C64's standard BASIC ROM as well as the kernel ROM (which actually makes it easier to determine the purpose of a given opcode). I can't find any distinguishing text about it, so I don't know if it's a generic compiler such as Blitz, or if it's a custom interpreter written for this title. I likely won't have to decode every instruction. Once I get enough of them figured out I should be able to see where it doing something with the values it reads in from the drive. Hopefully it's just a simple comparison and not some key for a decryption routine. I don't have a lot of spare time for this right now, so it might take some weeks to finish it off. |
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