SRAM and status saves can be confused with other cartridges

[micahcowan]

The problem

SRAM and "status" saves are currently registered according to the app's title, which is derived from the ROM file's filename. However, this can lead to confusion when different cartridges wind up being given the same title.

For instance, I have Family BASIC in multiple versions. Two of the filenames I have are Family BASIC (Japan) (v3.0).nes, and Family BASIC (Japan) (v2.0a).nes. Both of these, when dropped onto Nesemu, will be given the title "Family Basic"; however, their memory is not compatible. The automatic writing of the sram of one, is liable to corrupt the sram of the other. If I choose the "Save status" menu item in one of them, that save state becomes available via "Load status" in the other; but they are not compatible (Family BASIC v2 will throw an exception if loading the status saved by v3, and emulation for all open apps will cease. The window manager functions will remain responsive, however.)

Similar issues exist for other titles; I often have different ROM editions for the same game, perhaps for two different countries. The countries will appear in the filename in parenthesis (and therefore will be removed from the app title). Usually the two ROMs will be very similar, but it is still very possible for sram corruption (and, especially, save state corruption) to occur.

Proposed fix

I'd like to move away from using the title in the StorageUtil keys, and instead use the value of cartridge.calcHashValue() to derive a key. This is expected to drastically decrease the chances of differing cartridges from sharing the same data.

(I'm happy to do the work on this myself; but I wanted to get your thoughts first.)

[tyfkda]

I would prefer to use the file name as the key for the save data.
If you plan to change the key, could you please make it so that older save data can still be referenced as a fallback?
It would be helpful if, when older save data exists, it could be re-saved using the new key.

[micahcowan]

Right, I absolutely meant to include that in my original post's description: honor old save-key scheme, and convert them to the new keys.

I'm concerned that file names aren't unique enough keys - even if we were to use the full original filename, it could be easy for different games to have the same title and get the incompatible save states. Do you prefer the file name keys primarily for reasons of readability when you, as the developer, are looking through the set of keys presently in localStorage?

[tyfkda]

I think it's unlikely that file names will be the same, so it can probably be ignored.