Modifying Sonic and Gens to end after an Act is complete.

I was wondering weather to put this in technical discussion or here. Move this if you need to (though please PM me so I'm not confused).

Basically, what I wanted to do was have an RPG, but rather than having standard RPG battles, you complete an Act. I suppose it wouldn't be too difficult to start Sonic 1 ingame, and to reorder the level progression so that the first Act listed in the list is the one started (I have 149 Gigabytes on my external harddrive. 20 or so different ROMs is of no concern to me ;D). However, I wanted to know if it was possible to have Gens write 0 or 1 to a file (let's say Results.txt) and exit when you lose all your lives (0) or beat the Act (1). I was thinking about changing 2 invalid opcodes to write 0/1 and exit. Then I'd call those opcodes in the DisASM when needed.

3 things:
1.) What is Gens compiled in? I couldn't get it to compile in Visual Studio 2005. Would Visual Studio 6 work?
2.) Where is Gens are the opcodes (and, if it's not immedeatly obvious, how wouls I add 2 new ones?)
3.) How would I call a raw opcode in the Sonic 1 DisASM? I'm using the SVN build. What's the format? I hope they aren't completely inaccessible.

 

I'd use Kega Fusion, but it's not open source, so I can't put in new opcodes without doing some pd/YR style ASM hacking of the Kega executable. Since Gens is open source, I decided to use that. As I'm using the Acts as a replacement for RPG battles in my Sonic RPG, I don't really care about it working on real hardware.

Anyway, what should I use to compile Gens?

EDIT: I still don't know, but I remembered to end questions with a question mark. Thus the term "question mark". ;D

 

That's what I thought to. Nearly had an ameurism getting it to compile in VS2005. I actually found one of the files I needed in my VS6 install. Of course, it would have been a lot easier if I had VC7.

POINT IS: I got the blasted thing to compile. I gutted the NetPlay, ConsoleClassix, and (probably) screwed up the Game Genie code, but it works now. Though the changing from 32-bit mode to 32-bit mode doesn't quite make sense to me. That, or it starts in fullscreen then goes to a window. I don't quite know. Again, I use Kega. I've managed to modify the emulator's menus so that you can't select a file or load a savestate (the main game will boot up the emulator and rom when needed. I swear I would have gone insane if it turned out you couldn't specify the file to open in Gens via the command line).

The current problem: First, I'm not able to type very well at the moment due to my mental exhaustion (I don't know how the people who write these things don't go insane). Second, tomarow's a school day. Third, and [/offtopic], I can't figure out where the opcodes are. It's not that I don't have hunches, it's just I don't know much about Gens' inner workings or 68k ASM.

SH2.c has an opcode table. I need some help with this. My idea is to make 2 copies of nop, and change their affects. The first part of that would be to figure out why nop is filled out in that table the way it is:

Code (Text):

1.     { IFMT_0,   0x0009, SH2I_NOP      },

later in the same file:

Code (Text):

1.     { IFMT_0,   0x0009, SH2I_NOP_DS      },

In SH2.h (listing this particular one mainly for my own purposes):

Code (Text):

1. void SH2I_NOP();

Later:

Code (Text):

1. void SH2I_NOP_DS();

SH2a.asm:

Code (Text):

1. ALIGN32
2.  
3. DECLF SH2I_NOP
4.  
5.     RET 1, 1, 1

Later:

Code (ASM):

1. DECLF SH2I_NOP_DS
2.  
3.     RET_DS 1, 1, 1

Apparently, _DS means delay slot:

Code (Text):

1. // Delay-slot instruction function definition

What is a delay slot or whatever?

Let me get this straight: SH2.h is predefining the ASM functions in SH2a.asm? Crazy.

So I want to know the following:
First, take this:

Code (Text):

1.     { IFMT_0,   0x0009, SH2I_NOP      },

What is IFMT_0?
Why does it use 0x0009? Is it like the raw opcode or something? If I were to put this in place of nop in the Sonic 1 disasm, would it work as nop or would the compiler explode?
SH2I_NOP is the name of a procedure. Is it calling the procedure or a constant?

And in this:

Code (Text):

1. ALIGN32
2.  
3. DECLF SH2I_NOP
4.  
5.     RET 1, 1, 1

I saw a lot of things going RET 1, 1, 1. If I'm just exiting Gens, does this really matter?

Finally, how would I go about accessing Gens from these Opcodes? I saw a lot of references to ebp, and I think that's where the Genesis's memory starts. Could I use a C procedure instead of an ASM procedure and just tell Gens to exit?

Thanks in advance.

P.S. Gens appears to be coded in C and ASM. Might be C++, not sure.

EDIT: Is there anyway to get the SVN's default assembler to recognize 0xED00 and 0xED01 as valid opcodes. I was lucky enough to figure out it knows they're opcodes, but not what kind. They take no arguments, by the way. I can't really test if my idea's working until someone does this.

Actually, it seems it's 78 and 79. Lol. Talk to you guys later.

Update: I haven't got it to write to a file, but I got Gens to recognize 78 and 79 as opcodes. To verify this, I used nop and rts in the same places in my ASM hack, and compared where they were. I replaced 71 (nop) with 78 (my 1st custom opcode). In my modified Gens, it does nothing unusual after you hit the spikes (where the opcode is), but in Kega, it screws up completely. Unless Gens by default handles invalid opcodes more gracefully, then that is proof my opcode at least doesb't break the world in half. But I really need a 68k assembler with support for opcodes 78 and 79 (win and lose, maybe?)

 

That requires more knowledge of Gens than I will probably ever have and I could potentially use these opcodes whenever I want.

Because I'm using them inplace of battles in my "RPG" (at this point, it really stopped being an RPG). The whole point is that there's only 1 level.

I'm not leet enough to do any of that.

My project sort of shifted in focus. I was thinking of using a modified version of my own battle system, but eventually decided to have the classic platforming segments instead of RPG battles.
Also, RPG Maker crashes my system.

Now for the progress update. I've got to where I can run C++ code in those two opcodes. The problem is none of the procedures I call seem to be in scope or whatever it's called. I will update later.

 

Wait, wasn't SRAM the stuff games use to save the game?

Anyway, could someone help me? I'm in main68kgen.c, and I can't figure our how to call any procedures. I'm, oddly enough, better at ASM than C. Which means I have no clue how to get Gens to close. If someone could look through the source for me and see what code you'd have use to exit Gens, that would be great. I'm pretty sure I can get the file stuff to work (my main program deletes the file after loading it, so it will always create a new file. Wait, didn't a new file being made require some more code or something? Urgh, forgot about that for a moment.) Anyway, if you want to help, paste this under i_nop(void). It doesn't have to be a valid opcode, it just needs to compile. If it compiles, you've figured it out.

Code (Text):

1. static void i_custom1(void)
2. {    //BOOKMARK
3. //    Open results.txt
4. //    Append "1" to file
5. //    Close file
6. //    Exit
7.     ret_timing(4);
8. }

Thanks in advance.

EDIT: Rereading x64's idea, that actually does seem like a good idea. I'll look into it.