1 files changed, 96 insertions, 0 deletions
diff --git a/tvix/castore/src/fs/inodes.rs b/tvix/castore/src/fs/inodes.rs
new file mode 100644
index 0000000000..bdd4595434
--- /dev/null
+++ b/tvix/castore/src/fs/inodes.rs
@@ -0,0 +1,96 @@
+//! This module contains all the data structures used to track information
+//! about inodes, which present tvix-castore nodes in a filesystem.
+use std::time::Duration;
+
+use bytes::Bytes;
+
+use crate::proto as castorepb;
+use crate::B3Digest;
+
+#[derive(Clone, Debug)]
+pub enum InodeData {
+    Regular(B3Digest, u64, 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, u64),                                  // digest, size
+    Populated(B3Digest, Vec<(u64, castorepb::node::Node)>), // [(child_inode, node)]
+}
+
+impl InodeData {
+    /// Constructs a new InodeData by consuming a [Node].
+    /// It splits off the orginal name, so it can be used later.
+    pub fn from_node(node: castorepb::node::Node) -> (Self, Bytes) {
+        match node {
+            castorepb::node::Node::Directory(n) => (
+                Self::Directory(DirectoryInodeData::Sparse(
+                    n.digest.try_into().unwrap(),
+                    n.size,
+                )),
+                n.name,
+            ),
+            castorepb::node::Node::File(n) => (
+                Self::Regular(n.digest.try_into().unwrap(), n.size, n.executable),
+                n.name,
+            ),
+            castorepb::node::Node::Symlink(n) => (Self::Symlink(n.target), n.name),
+        }
+    }
+
+    pub fn as_fuse_file_attr(&self, inode: u64) -> fuse_backend_rs::abi::fuse_abi::Attr {
+        fuse_backend_rs::abi::fuse_abi::Attr {
+            ino: inode,
+            // FUTUREWORK: play with this numbers, as it affects read sizes for client applications.
+            blocks: 1024,
+            size: match self {
+                InodeData::Regular(_, size, _) => *size,
+                InodeData::Symlink(target) => target.len() as u64,
+                InodeData::Directory(DirectoryInodeData::Sparse(_, size)) => *size,
+                InodeData::Directory(DirectoryInodeData::Populated(_, ref children)) => {
+                    children.len() as u64
+                }
+            },
+            mode: self.as_fuse_type() | self.mode(),
+            ..Default::default()
+        }
+    }
+
+    fn mode(&self) -> u32 {
+        match self {
+            InodeData::Regular(_, _, false) | InodeData::Symlink(_) => 0o444,
+            InodeData::Regular(_, _, true) | InodeData::Directory(_) => 0o555,
+        }
+    }
+
+    pub fn as_fuse_entry(&self, inode: u64) -> fuse_backend_rs::api::filesystem::Entry {
+        fuse_backend_rs::api::filesystem::Entry {
+            inode,
+            attr: self.as_fuse_file_attr(inode).into(),
+            attr_timeout: Duration::MAX,
+            entry_timeout: Duration::MAX,
+            ..Default::default()
+        }
+    }
+
+    /// Returns the u32 fuse type
+    pub fn as_fuse_type(&self) -> u32 {
+        #[allow(clippy::let_and_return)]
+        let ty = match self {
+            InodeData::Regular(_, _, _) => libc::S_IFREG,
+            InodeData::Symlink(_) => libc::S_IFLNK,
+            InodeData::Directory(_) => libc::S_IFDIR,
+        };
+        // libc::S_IFDIR is u32 on Linux and u16 on MacOS
+        #[cfg(target_os = "macos")]
+        let ty = ty as u32;
+
+        ty
+    }
+}