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Adapted from SmileBASIC source’s page. here’s some credits blah

• SmileBASIC file format (this one)
• 12Me21 (& co.) - JavaScript file parser / writer (online)
• SmileBASIC API Team - TypeScript file parser / writer
• third item

SmileBASIC File Format

Overview

Note from Record

Quick note: I didn’t figure out most of the format of SB files. Trinitro21 did most of the work figuring out the file structure, and the footer was thanks to code plutooo had for smilehax. I just wrote this document, which sums everything we know.
DISCLAIMER: This is not 100% correct and may change at any time.
By the way, me (Record) and Trinitro21 (triangle) wrote an API to download programs from the SmileBASIC servers. It can also display GRPs as PNGs. It’s available at http://sbapi.me/

Note from V360

I made the table formatting worse and probably added some incorrect info; lots of love

hmmmmmmm the tables aren’t 100% right – the data offsets aren’t right maybe? I also need to add End of Header to a lot more things.

(Modified some of this to be nice and Markdown; Offset is no longer abbreviated to Ofs.; Size (in bytes is abbreviated to Bytes)

(Also added a “type” section which is mostly redundant. It uses the same types as like… rust or something so i16 is signed int 16 bits, u16 is unsigned int 16 bits etc. Stolen from sbfile.js from 12’s sbtools)

SmileBASIC, being a complete technical overhaul of Petit Computer, has its own format for storing files. There are 2 main types of files: TXT and DAT. Both include the common header and footer, but DAT files have a secondary header after the common header to store metadata.

All files are stored in SmileBASIC’s ExtData archive stored on the SD card. The default folder is stored as ### in the ExtData, and filenames are prefixed with T or B, for Text (TXT) and Binary (DAT), respectively.

Common Header

The shared part of every SB file is the common header. This contains information such as the username of who wrote it, how large the data stored is, and when it was last modified. The common header is 80 bytes long on the 3DS and 112 bytes on Switch. All values are little-endian.

Any files with a file version of 0 loaded will become files with a file version of 1 when saved. This is obvious – it’s a round trip from SYS to an array to a user project, of course it’s the same.

In SB4, uploader information is slightly longer, to accomodate longer NNIDs. Due to this, the header lengths vary between platforms.

3DS Uploader Information

Switch Uploader Information

The header ends at &h50 on 3DS and &h70 on Switch. Note that there’s empty space.

DAT Secondary Header

Fun Fact! The constant string “PCBN” at the beginning stands for Petit Computer BiNary!

TXT and PRG files just place the UTF-8 text after the footer. However, the DAT and GRP files need more information – the data type, the dimensions, etc.. To store this, they employ a secondary header, stored immediately after the end of the first header. This secondary header stores information for SB to parse the file properly.

The offset is relative to the end of the common header, so it will change position depending on the version of SmileBASIC in use.

Afterward, the data is stored in row-major order (left-to-right wrapping from top-to-bottom, instead of top-to-bottom wrapping from left-to-right).

(Example: Say we have a 9x9 grid of numbers)
┌─┬─┬─┐
│A│D│G│
├─┼─┼─┤
│H│B│E│
├─┼─┼─┤
│F│I│C│
└─┴─┴─┘

Row-Major:    A D G H B E F I C
Column-Major: A H F D B I G E C

META Project file (Petit Computer Project Metadata)

META files are used in projects to store metadata about a project, including icon, name, and description.

(offset is the offset after the header, which changes depending on the version of SmileBASIC in use.)

The data following is the icon’s pixel data, encoded in BGRA8888. Icons are always square, so you can find the length of the icon data by squaring the icon width and multiplying by 4, the number of bytes per pixel.

Projects

File type 2 in SB3 and file type 3 on SB4 are reserved for project files that are used for uploading/downloading projects from the server. When downloaded, SmileBASIC automatically unpacks them into the proper file structure. As such, this file format should never be encountered unless you’re talking to the SB servers yourself. If you’re doing that, figuring out project file format is left as an exercise for you :)

Common Footer

The footer is a 20 byte HMAC-SHA1 hash of the header and data using this HMAC key:

nqmby+e9S?{%U*-V]51n%^xZMk8>b{?x]&?(NmmV[,g85:%6Sqd"'U")/8u77UL2

The footer must be valid in order to download/upload a file. The absence of a valid footer will cause an error when doing either of these.

Adapted from SmileBASIC source’s page. here’s some credits blah

• SmileBASIC file format (this one)
• 12Me21 (& co.) - JavaScript file parser / writer (online)
• SmileBASIC API Team - TypeScript file parser / writer
• third item