Archives and protection
A level is exported as a folder, tar.gz or zip, optionally under a password: zip with AES-256 or OpenPGP. The SDK detects the format of a received file by its first bytes, not by its name
Export modes
A level leaves the device in one of the LevelExportMode forms:
| Value | Mode | What is written | Protection |
|---|---|---|---|
| 0 | Folder | a plain folder, the same shape as on disk | none |
| 1 | FolderProtectedLevel | a folder where only level.json.gpg is encrypted | OpenPGP |
| 2 | TarGz | <name>.tar.gz | none |
| 3 | TarGzProtected | <name>.tar.gz.gpg | OpenPGP |
| 4 | Zip | <name>.zip | none |
| 5 | ZipProtected | <name>.zip.gpg | OpenPGP |
| 6 | ZipEncrypted | <name>.zip with AES-256 entries | zip's own |
The number is the identity of the mode, it never changes. The order in the editor's dropdown is set separately (DisplayOrder)
Every format is an open standard. tar -xzf, gpg -d and any archiver open them without the game:
gpg -d level.tar.gz.gpg > level.tar.gz
tar -xzf level.tar.gzTwo protection schemes
ZipEncrypted is the default way to lock a level with a password. The recipient has an archiver, but most likely not gpg
OpenPGP locks a document, a folder and an archive with one scheme. Only it can protect a folder
In FolderProtectedLevel the metadata, the cover and the media stay readable. So the level browser still shows the card
The inner extension stays in the name: level.json.gpg. That is exactly what gpg -c level.json names the file, so the format is known without guessing
What goes inside
LevelArchiveBuilder works out the contents from the model, not from the list of files in the folder. A file the level does not reference stays outside. The report says how many such files were left
The level's references are handled like this:
- a resource with
AbsolutePathis copied into the archive. Its reference is rewritten toLevelPath, but only in the exported copy DirectUrlstays as is and goes into the report: a URL cannot travel inside a file- a missing file goes into the report with the code
archive.resource_missing
Detection by bytes
Anyone can write a file name. So ArchiveFormatSniffer decides by the first 8 bytes:
| First bytes | Format |
|---|---|
1F 8B | TarGz |
50 4B 03 04, 50 4B 05 06, 50 4B 07 08, 50 4B 30 30 | Zip |
37 7A BC AF 27 1C | SevenZip |
| an OpenPGP packet tag, checked last | OpenPgp: decrypted and detected again |
.7z is neither read nor written. It is detected only so that the refusal names it (Unsupported). Then a person repacks the level as zip instead of deciding the file is broken
Reading
LevelArchiveReader.ReadAsync takes a folder or a seekable Stream. It returns LevelArchiveContent, where LevelArchiveOpenResult is one of these values:
| Result | Meaning |
|---|---|
Ok | read |
PassphraseRequired | there is no password, it has to be asked for |
WrongPassphrase | the person has already entered a password, and it is wrong |
Damaged | the file is damaged |
NotAnArchive | this is not an archive |
Unsupported | the format is recognized but not supported |
PeekMetaAsync reads only the metadata, for a card or a catalog
A server reads whatever someone chose to upload. So the reader works within ArchiveLimits. By default these are:
- 4096 entries
- 512 MiB per entry
- 1 GiB in total
Nothing is unpacked outside the storage it was given
Export from the editor's side - Export and protection