refactor(tvix/castore/fs): add InodeData::as_fuse_{entry,file_attr} r/7921

Remove the now unused gen_file_attr (which had a wrong docstring).

Change-Id: Ie86b14d1ad798e6233bc44c43ace3f8b95c67ea9
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11430
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/tvix/castore/src/fs/inodes.rs b/tvix/castore/src/fs/inodes.rs
index 9131b703ba..69a75acb6b 100644
--- a/tvix/castore/src/fs/inodes.rs
+++ b/tvix/castore/src/fs/inodes.rs
@@ -1,5 +1,7 @@
 //! 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 crate::proto as castorepb;
 use crate::B3Digest;
 
@@ -10,6 +12,41 @@ pub enum InodeData {
     Directory(DirectoryInodeData), // either [DirectoryInodeData:Sparse] or [DirectoryInodeData:Populated]
 }
 
+impl InodeData {
+    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: match self {
+                InodeData::Regular(_, _, false) => libc::S_IFREG | 0o444, // no-executable files
+                InodeData::Regular(_, _, true) => libc::S_IFREG | 0o555,  // executable files
+                InodeData::Symlink(_) => libc::S_IFLNK | 0o444,
+                InodeData::Directory(_) => libc::S_IFDIR | 0o555,
+            },
+            ..Default::default()
+        }
+    }
+
+    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()
+        }
+    }
+}
+
 /// 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