1 files changed, 70 insertions, 0 deletions
diff --git a/tvix/store/src/fs/inodes.rs b/tvix/store/src/fs/inodes.rs
new file mode 100644
index 000000000000..928f51059002
--- /dev/null
+++ b/tvix/store/src/fs/inodes.rs
@@ -0,0 +1,70 @@
+//! This module contains all the data structures used to track information
+//! about inodes, which present tvix-store nodes in a filesystem.
+use tvix_castore::proto as castorepb;
+use tvix_castore::B3Digest;
+
+#[derive(Clone, Debug)]
+pub enum InodeData {
+    Regular(B3Digest, u32, bool),  // digest, size, executable
+    Symlink(bytes::Bytes),         // target
+    Directory(DirectoryInodeData), // either [DirectoryInodeData:Sparse] or [DirectoryInodeData:Populated]
+}
+
+/// This encodes the two different states of [InodeData::Directory].
+/// Either the data still is sparse (we only saw a [castorepb::DirectoryNode],
+/// but didn't fetch the [castorepb::Directory] struct yet, or we processed a
+/// lookup and did fetch the data.
+#[derive(Clone, Debug)]
+pub enum DirectoryInodeData {
+    Sparse(B3Digest, u32),                                  // digest, size
+    Populated(B3Digest, Vec<(u64, castorepb::node::Node)>), // [(child_inode, node)]
+}
+
+impl From<&castorepb::node::Node> for InodeData {
+    fn from(value: &castorepb::node::Node) -> Self {
+        match value {
+            castorepb::node::Node::Directory(directory_node) => directory_node.into(),
+            castorepb::node::Node::File(file_node) => file_node.into(),
+            castorepb::node::Node::Symlink(symlink_node) => symlink_node.into(),
+        }
+    }
+}
+
+impl From<&castorepb::SymlinkNode> for InodeData {
+    fn from(value: &castorepb::SymlinkNode) -> Self {
+        InodeData::Symlink(value.target.clone())
+    }
+}
+
+impl From<&castorepb::FileNode> for InodeData {
+    fn from(value: &castorepb::FileNode) -> Self {
+        InodeData::Regular(
+            value.digest.clone().try_into().unwrap(),
+            value.size,
+            value.executable,
+        )
+    }
+}
+
+/// Converts a DirectoryNode to a sparsely populated InodeData::Directory.
+impl From<&castorepb::DirectoryNode> for InodeData {
+    fn from(value: &castorepb::DirectoryNode) -> Self {
+        InodeData::Directory(DirectoryInodeData::Sparse(
+            value.digest.clone().try_into().unwrap(),
+            value.size,
+        ))
+    }
+}
+
+/// converts a proto::Directory to a InodeData::Directory(DirectoryInodeData::Populated(..)).
+/// The inodes for each child are 0, because it's up to the InodeTracker to allocate them.
+impl From<castorepb::Directory> for InodeData {
+    fn from(value: castorepb::Directory) -> Self {
+        let digest = value.digest();
+
+        let children: Vec<(u64, castorepb::node::Node)> =
+            value.nodes().map(|node| (0, node)).collect();
+
+        InodeData::Directory(DirectoryInodeData::Populated(digest, children))
+    }
+}