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Thread: [GCN] Animal Crossing: Checksum help

  1. #1

    Default [GCN] Animal Crossing: Checksum help

    Since I have nothing better to do currently, I was going to try my hand at making a save game editor for Animal Crossing for the Gamecube; Problem is that I can't seem to find/figure out how the checksum is calculated (though I do know it actually saves the game data twice and the checksum is right after the magic "GAFE" for both times). Anyone interested in helping/informing me of said checksum calculation?

    As for what I actually plan in the editor: Everything I can find, if I have the time to.

  2. #2

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    A little history:
    A long time ago there was some interest in backporting the core AC:WW editor features to the AC:GC game.
    Someone actually made progress, but AFAIK never released a program to the public.

    The problem: getting AC:GC gamesaves to a PC (and back again) was a pain with the GameCube hardware.
    This is much easier today with WiiBrew (and/or USB Gecko). But it is still a pain ;->

    The .GCI file is exactly 467,008 bytes (0x72040 bytes)
    They look like they contain 3 copies of data, each 0x26000 bytes long (after the 0x40 byte header)
    First copy? starts at 0x00040, next copy at 0x26040, last copy at 0x4C040. The first copy has something weird about it.

    NOTE: in AC:WW there are 2 copies of gamesave data. In AC:CF/Wii there is only one copy/version. The extra copies made sense because the gamesave data was on a cartridge that a user could easily unplug during save.

    I'll see if I can dig up some old notes on the format (very minimal). If interested, you may have to do a lot of trial-and-error to figure out item codes and terrain codes.

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  4. #3

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    > The .GCI file is exactly 467,008 bytes (0x72040 bytes)
    > They look like they contain 3 copies of data, each 0x26000 bytes long (after the 0x40 byte header)
    > First copy? starts at 0x00040, next copy at 0x26040, last copy at 0x4C040. The first copy has something weird about it.

    I always just assumed the first 0x26000 bytes were for Resetti's uses (or travel uses), since it lacks a lot of info that the later two have (such as house data, player names, etc)

    > NOTE: in AC:WW there are 2 copies of gamesave data. In AC:CF/Wii there is only one copy/version. The extra copies made sense because the gamesave data was on a cartridge that a user could easily unplug during save.

    Don't get why they would think they would need three for the Gamecube version; No matter how they would save the data on it, it would only take two to make sure that either old data is preserved as a backup or that new data is saved correctly.

    > I'll see if I can dig up some old notes on the format (very minimal). If interested, you may have to do a lot of trial-and-error to figure out item codes and terrain codes.

    Thanks for the help, I've actually already found all the item codes, and have been working on the terrain codes as of late. I've also figured out where a lot of data is in the save, the only real problem I've had is the checksum.

  5. #4

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    I dont have this game, but could try to make guesses by using several typical checksum algorithms.
    So, do you think you could share several copies of savegame file (saved at various times)?
    And how many bytes actually the checksum number?

    If those guesses fail, then we may need to do open surgery.

  6. #5

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    Quote Originally Posted by conanac View Post
    I dont have this game, but could try to make guesses by using several typical checksum algorithms.
    So, do you think you could share several copies of savegame file (saved at various times)?
    And how many bytes actually the checksum number?

    If those guesses fail, then we may need to do open surgery.
    http://rapidshare.com/files/33180515..._Saves.7z.html (Contains four saves that were done in short succession)

    As for how many bytes, I believe the checksum starts at 0x2604B and ends at either 0x26054 or 0x26060

  7. #6

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    I have checked them, and looks like we need to use some kind of open surgery approach (and i have sent a PM to you).

  8. #7
    Chris (Administrator) Vash's Avatar
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    Hehe, I see Virus lurking around on this one...

    I'll be waiting patiently in the corner...
    Animal Crossing: City Folk
    ACToolkit - NPC_Tool - PattView

  9. #8

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    Has everyone giving up on this?? I think it would be fun to custom this game since a saw a U-Tube Video of someone customized town.
    (I'm jealous)

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