Remove the shim kernel crate

kernel/src/fs/utils/dirent_visitor.rs

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: MPL-2.0
+
+#![allow(unused_variables)]
+
+use super::InodeType;
+use crate::prelude::*;
+
+/// A visitor for dir entries.
+pub trait DirentVisitor {
+    /// Visit a dir entry.
+    ///
+    /// If the visitor succeeds in visiting the given inode, an `Ok(())` is returned;
+    /// Otherwise, an error is returned. Different implementations for `DirentVisitor`
+    /// may choose to report errors for different reasons. Regardless of the exact
+    /// errors and reasons, `readdir`-family methods shall stop feeding the visitor
+    /// with the next inode as long as an error is returned by the visitor.
+    ///
+    /// # Example
+    ///
+    /// `Vec<String>` is implemented as `DirentVisitor` so that the file names
+    /// under a dir can be easily collected, which is convenient for testing purposes.
+    ///
+    /// ```no_run
+    /// let mut all_dirents = Vec::new();
+    /// let dir_inode = todo!("create an inode");
+    /// dir_inode.readdir_at(0, &mut all_dirents).unwrap();
+    /// ```
+    fn visit(&mut self, name: &str, ino: u64, type_: InodeType, offset: usize) -> Result<()>;
+}
+
+impl DirentVisitor for Vec<String> {
+    fn visit(&mut self, name: &str, ino: u64, type_: InodeType, offset: usize) -> Result<()> {
+        self.push(name.into());
+        Ok(())
+    }
+}