# ds-rom

Library for extracting and building matching Nintendo DS ROMs. DSi/DSiware not supported yet.

## Contents

- [Goals](#goals)
- [Extraction](#extraction)
- [Building](#building)
- [Command-line interface](#command-line-interface)

## Goals

- Extract all components of a ROM to files on disk.
- Build ROMs using those files.
- The files should be modifiable so that a modded ROM can be built.
- The built ROMs should exactly match the originals when the files are unmodified.

## Extraction

`ds-rom` has two representations of the ROM: raw and plain. To extract files from a ROM, it first reads the raw ROM, with the exact byte-for-byte content of the ROM file. Then, the plain ROM can extract all the components out of the raw ROM. Lastly, the plain ROM can be saved to files on disk.

```rs
use ds_rom::{rom::{raw, Rom}};

let raw_rom = raw::Rom::from_file("mygame.nds")?;
let rom = Rom::extract(&raw_rom)?;
rom.save("mygame_extracted/", None)?;
```

> [!IMPORTANT]
> If the raw ROM is encrypted, you must pass an encryption key to `Rom::save` in place of the `None` value. See an example of this [here](/cli/src/build.rs).

## Building

Building a ROM is exactly the opposite of extracting. `ds-rom` starts by loading a plain ROM from files on disk, the same files generated by `Rom::save`. Then, the raw ROM can be built and saved as a single ROM file.

```rs
use ds_rom::rom::Rom;

let rom = Rom::load("mygame_extracted/", None)?;
let raw_rom = rom.build(None)?;
raw_rom.save("mygame_rebuilt.nds")?;
```

> [!IMPORTANT]
> If the ROM is encrypted, you must pass an encryption key to `Rom::load` and optionally `Rom::build` in place of the `None` value. See an example of this [here](/cli/src/extract.rs).  
> (It is optional for `Rom::build` as it is only for computing a CRC checksum in the ROM header.)
>
> You can configure whether a ROM should be encrypted by editing the YAML files inside the extraction directory.

## Command-line interface

`ds-rom` is also available as a CLI, and you can download [the latest release here](https://github.com/AetiasHax/ds-rom/releases/latest). Use `dsrom --help` for a list of subcommands.