Data model

This provides some more notes on the fields used in castore.proto.

See //tvix/store/docs/api.md for the full context.

Directory message

Directory messages use the blake3 hash of their canonical protobuf serialization as its identifier.

A Directory message contains three lists, directories, files and symlinks, holding DirectoryNode, FileNode and SymlinkNode messages respectively. They describe all the direct child elements that are contained in a directory.

All three message types have a name field, specifying the (base)name of the element (which MUST not contain slashes or null bytes, and MUST not be '.' or '..'). For reproducibility reasons, the lists MUST be sorted by that name and the name MUST be unique across all three lists.

In addition to the name field, the various *Node messages have the following fields:

DirectoryNode

A DirectoryNode message represents a child directory.

It has a digest field, which points to the identifier of another Directory message, making a Directory a merkle tree (or strictly speaking, a graph, as two elements pointing to a child directory with the same contents would point to the same Directory message).

There's also a size field, containing the (total) number of all child elements in the referenced Directory, which helps for inode calculation.

FileNode

A FileNode message represents a child (regular) file.

Its digest field contains the blake3 hash of the file contents. It can be looked up in the BlobService.

The size field contains the size of the blob the digest field refers to.

The executable field specifies whether the file should be marked as executable or not.

SymlinkNode

A SymlinkNode message represents a child symlink.

In addition to the name field, the only additional field is the target, which is a string containing the target of the symlink.