[FEATURE REQUEST] CIA/CCI bundle format support

[PabloMK7]

Got a great idea on how to improve GodMode9?

First some background. Azahar has recently released a libretro core and one of the most important user experience issues we are facing is the lack of ability to install game updates, DLCs and other dependencies from the frontends. Right now the only solution is to place those in the virtual SD card folder and launch FBI to install the individual cia files.

To prevent that issue, I'm suggesting the creation of a format specification for CIA and CCI bundles.

Describe the feature you'd like

CIA and CCI bundles would allow users to dump application + update + dlc data to a single file. This would allow emulators and CIA installers to use those files to either install everything at the same time or run the emulated application without the user having to pre-install the dependencies.

The most sensible specification in my opinion would be to just use tar files. They are easy to build and read and do not care about the underlying file properties, which would allow to include encrypted, decrypted or compressed files. My proposal for the specification is therefore the following:

Bundled CCI/3DS (.bcci)

Bundled cci/3ds files are uncompressed tar files. Emulators would run the main application file and simulate the other files being installed titles (through hooks in the AM + FS modules). The tar file would contain the following subfiles:

• app: The main application cci/3ds file.
• update: Optionally, the application update cia file.
• dlc: Optionally, the application dlc cia file.
• Optionally any other cia file dependency that the emulator could use. For example, the system font or mii archive could be added here so that libretro users don't need to set them up. They are small enough to not be a big deal.

All files in the tar can either be encrypted, decrypted or compressed. GM9 could just implement the decrypted variant for broader compatibility, and consider compressed support in the future. Apps that use .bcci can determine the properties of the files on their own, by checking magics or header properties.

Bundled CIA (.bcia)

Bundled cia files are uncompressed tar files. The applications that would use such files would just install all the cia files contained in the tar. There is really no need to have a name convention here, but I think for best readibility we could just use the titleid as the name, with hex digits in caps.

Same way as .bcci, the cia files can be encrypted, decrypted or compressed. GM9 could just implement the decrypted variant for broader compatibility, and consider compressed support in the future.

[PabloMK7]

It's up to GodMode9 to decide how to create the bundle files, but I think a good place would be an extra entry when selecting an application in the title manager.

[MisterSheeple]

What exactly is the point of having .bcci be its own file format if it can also contain .cia updates and DLC within it? I think it would be best to rethink this and make a unified format that accompanies both .cia and .cci in one package.

Also, I think there should be support for multiple updates in a single bundle, so that the user can select between them. The best way to do this would be by just including the raw CDN-format contents, but with all of the necessary original information intact to be able to rebuild it into a .cia perfectly, if the user needs to do so. In fact, I'd recommend storing everything only as raw CDN-format contents to maximize compression. To my knowledge, 3DS software updates include all previous update contents, but with a different TMD that only points to the contents for the latest update. So you'd include all of the relevant contents with multiple TMDs, and a manifest file within the bundle would contain information about which updates belong to which contents/TMDs, allowing the user to select an update. On top of updates, this manifest file would also include a list of titles of all types that are included in the bundle. But of course, this should be optional, because most people are probably only going to bother to dump the latest update they have, and therefore won't bother grabbing previous TMDs.

[PabloMK7]

That just unneccessarily overcomplicates things. There are probably other established ways to achieve that for power users. This feature aims to help the less knowledgeable users, who often forget to dump the update data or don't know what is the difference.

There are no difference between bcci and bcia, they are both tar files that hold other files, and that's it. If anything, it could be made more unified if all files are just the title ID except for the cci which would be all zeroes.

Bundling everything into a single tar is easy for GM9 to implement, and easy for emulators to implement. Keep in mind that to support Azahar and compression, stuff needs to be derypted. If preservation has to be considered, then just using the original cia/cci files is good enough without any need for this.

[MisterSheeple]

There are probably other established ways to achieve that for power users.

There are lots of reasons why the average person might want to use older updates for games like, for example, Smash Bros, where each update has substantial changes and it may be considered beneficial to revert to older ones for purposes like viewing older replays. The feature can be made to serve the needs of both regular users and so-called "power users" alike by implementing a simple manifest file that can be generated by parsing the TMDs. In fact, a manifest may not even need to be included unless the user specifically has multiple updates.

[PabloMK7]

If that ever is implemented at all, there is no need to include a tmd or anything, the individual files can be parsed and get the needed info.