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Game filesystem

Game files

These are all the files present in Super Scribblenauts's Nitro FS:

  • dwc/utility.bin: DWC utility data file, present in any DS games using Download Play

  • audio.sdat: SDAT sound data file (format used by most DS games)

  • audio.sadl: C header file with SDAT sound index values: likely left by mistake, just a regular header file included in the code when compiling

    Note: for quite a lot of DS games, these kind of intermediate-build files are mistakengly left in the Nitro FS

  • 1i and 1p: these files contain everything else in the game, in a custom filesystem format explained below.

Filesystem format

The files 1i and 1p (known as index and package files) together contain a filesystem, in a unique format used by this game (even the original Scribblenauts did it differently, storing files plainly in the Nitro FS).

Note: Scribblenauts Remix shares the exact same filesystem format, where the index and package files are the two OBB files found in the game data.

There is a total of 33383 files in the release game. Files contain no names, they are referred to by their index (file 0, file 1 ... up to file 33382), internally known as their file ID. There are several files where their file IDs are hardcoded in-game, while various other formats internally contain other sub-file IDs for further content.

The file 1i contains all the file offsets. It has the following binary format:

u32 file_count;
u32 file_offsets[file_count + 1];

There is an additional offset, which (at least in the release game) is just the repeated previous offset. This is likely done so that for the i-th file, the file size can always be computed as:

u32 file_size_i = file_offsets[i + 1] - file_offsets[i];

The game does indeed compute file sizes this way, expecting that intentional extra offset to be contained in 1i.

Various files are empty in the release game (the file offset is the same as the next file offset, thus the file has size 0).

File offsets found in 1i are absolute offsets of file 1p, which contains file data. Each file data is ended by a byte indicating whether it is compressed:

// ...

// current offset: file_offsets[i]
u8 file_i_data[file_size_i];
u8 file_i_comp_type; // 0 if plaintext, 1 if LZ77-compressed

// current offset: file_offsets[i+1]
u8 file_ip1_data[file_size_ip1];
u8 file_ip1_comp_type;

// ...

Note: unlike other file formats (from the SDK iself, and so on), binary formats specific to this game are not designed with any alignment/padding considerations, as can be seen by this filesystem data format (the final byte is always put after file data)

The release game has various different functions to read file data. Some functions read the entire data in an allocated buffer, while in other places, file reading is done "manually" by pretty much making raw reads to 1p.