diff --git a/examples/shell.rs b/examples/shell.rs
index 7822dde..54f713d 100644
--- a/examples/shell.rs
+++ b/examples/shell.rs
@@ -69,11 +69,12 @@
 //! | `B:/BACKUP.000/NAMES.CSV`   | `B:`    | Yes      | `[BACKUP.000]`     | `NAMES.CSV`    | `B:/BACKUP.000/NAMES.CSV`      |
 //! | `B:../BACKUP.000/NAMES.CSV` | `B:`    | No       | `[.., BACKUP.000]` | `NAMES.CSV`    | `B:/BACKUP.000/NAMES.CSV`      |
 
-use std::io::prelude::*;
+use std::{cell::RefCell, io::prelude::*};
 
-use embedded_sdmmc::{
-    Error as EsError, RawDirectory, RawVolume, ShortFileName, VolumeIdx, VolumeManager,
-};
+use embedded_sdmmc::{Error as EsError, RawDirectory, RawVolume, ShortFileName, VolumeIdx};
+
+type VolumeManager = embedded_sdmmc::VolumeManager<LinuxBlockDevice, Clock, 8, 8, 4>;
+type Directory<'a> = embedded_sdmmc::Directory<'a, LinuxBlockDevice, Clock, 8, 8, 4>;
 
 use crate::linux::{Clock, LinuxBlockDevice};
 
@@ -182,21 +183,21 @@ struct VolumeState {
 }
 
 struct Context {
-    volume_mgr: VolumeManager<LinuxBlockDevice, Clock, 8, 8, 4>,
-    volumes: [Option<VolumeState>; 4],
+    volume_mgr: VolumeManager,
+    volumes: RefCell<[Option<VolumeState>; 4]>,
     current_volume: usize,
 }
 
 impl Context {
     fn current_path(&self) -> Vec<String> {
-        let Some(s) = &self.volumes[self.current_volume] else {
+        let Some(s) = &self.volumes.borrow()[self.current_volume] else {
             return vec![];
         };
         s.path.clone()
     }
 
     /// Print some help text
-    fn help(&mut self) -> Result<(), Error> {
+    fn help(&self) -> Result<(), Error> {
         println!("Commands:");
         println!("\thelp                -> this help text");
         println!("\t<volume>:           -> change volume/partition");
@@ -219,16 +220,15 @@ impl Context {
     }
 
     /// Print volume manager status
-    fn stat(&mut self) -> Result<(), Error> {
+    fn stat(&self) -> Result<(), Error> {
         println!("Status:\n{:#?}", self.volume_mgr);
         Ok(())
     }
 
     /// Print a directory listing
-    fn dir(&mut self, path: &Path) -> Result<(), Error> {
+    fn dir(&self, path: &Path) -> Result<(), Error> {
         println!("Directory listing of {:?}", path);
         let dir = self.resolve_existing_directory(path)?;
-        let dir = dir.to_directory(&mut self.volume_mgr);
         dir.iterate_dir(|entry| {
             if !entry.attributes.is_volume() && !entry.attributes.is_lfn() {
                 println!(
@@ -246,7 +246,7 @@ impl Context {
     }
 
     /// Print a recursive directory listing for the given path
-    fn tree(&mut self, path: &Path) -> Result<(), Error> {
+    fn tree(&self, path: &Path) -> Result<(), Error> {
         println!("Directory listing of {:?}", path);
         let dir = self.resolve_existing_directory(path)?;
         // tree_dir will close this directory, always
@@ -256,8 +256,7 @@ impl Context {
     /// Print a recursive directory listing for the given open directory.
     ///
     /// Will close the given directory.
-    fn tree_dir(&mut self, dir: RawDirectory) -> Result<(), Error> {
-        let dir = dir.to_directory(&mut self.volume_mgr);
+    fn tree_dir<'a>(&'a self, dir: Directory<'a>) -> Result<(), Error> {
         let mut children = Vec::new();
         dir.iterate_dir(|entry| {
             println!(
@@ -271,25 +270,20 @@ impl Context {
                 children.push(entry.name.clone());
             }
         })?;
-        // Be sure to close this, no matter what happens
-        let dir = dir.to_raw_directory();
         for child in children {
             println!("Entering {}", child);
-            let child_dir = match self.volume_mgr.open_dir(dir, &child) {
+            let child_dir = match dir.open_dir(&child) {
                 Ok(child_dir) => child_dir,
                 Err(e) => {
-                    self.volume_mgr.close_dir(dir).expect("close open dir");
                     return Err(e);
                 }
             };
             let result = self.tree_dir(child_dir);
             println!("Returning from {}", child);
             if let Err(e) = result {
-                self.volume_mgr.close_dir(dir).expect("close open dir");
                 return Err(e);
             }
         }
-        self.volume_mgr.close_dir(dir).expect("close open dir");
         Ok(())
     }
 
@@ -300,17 +294,17 @@ impl Context {
     ///   sub-folder, starting from the current directory on the current volume
     /// * An absolute path like `B:/FOO` changes the CWD on Volume 1 to path
     ///   `/FOO`
-    fn cd(&mut self, full_path: &Path) -> Result<(), Error> {
+    fn cd(&self, full_path: &Path) -> Result<(), Error> {
         let volume_idx = self.resolve_volume(full_path)?;
-        let d = self.resolve_existing_directory(full_path)?;
-        let Some(s) = &mut self.volumes[volume_idx] else {
-            self.volume_mgr.close_dir(d).expect("close open dir");
+        let (mut d, fragment) = self.resolve_filename(full_path)?;
+        d.change_dir(fragment)?;
+        let Some(s) = &mut self.volumes.borrow_mut()[volume_idx] else {
             return Err(Error::NoSuchVolume);
         };
         self.volume_mgr
             .close_dir(s.directory)
             .expect("close open dir");
-        s.directory = d;
+        s.directory = d.to_raw_directory();
         if full_path.is_absolute() {
             s.path.clear();
         }
@@ -327,9 +321,8 @@ impl Context {
     }
 
     /// print a text file
-    fn cat(&mut self, filename: &Path) -> Result<(), Error> {
+    fn cat(&self, filename: &Path) -> Result<(), Error> {
         let (dir, filename) = self.resolve_filename(filename)?;
-        let dir = dir.to_directory(&mut self.volume_mgr);
         let f = dir.open_file_in_dir(filename, embedded_sdmmc::Mode::ReadOnly)?;
         let mut data = Vec::new();
         while !f.is_eof() {
@@ -348,9 +341,8 @@ impl Context {
     }
 
     /// print a binary file
-    fn hexdump(&mut self, filename: &Path) -> Result<(), Error> {
+    fn hexdump(&self, filename: &Path) -> Result<(), Error> {
         let (dir, filename) = self.resolve_filename(filename)?;
-        let dir = dir.to_directory(&mut self.volume_mgr);
         let f = dir.open_file_in_dir(filename, embedded_sdmmc::Mode::ReadOnly)?;
         let mut data = Vec::new();
         while !f.is_eof() {
@@ -385,9 +377,8 @@ impl Context {
     }
 
     /// create a directory
-    fn mkdir(&mut self, dir_name: &Path) -> Result<(), Error> {
+    fn mkdir(&self, dir_name: &Path) -> Result<(), Error> {
         let (dir, filename) = self.resolve_filename(dir_name)?;
-        let dir = dir.to_directory(&mut self.volume_mgr);
         dir.make_dir_in_dir(filename)
     }
 
@@ -435,11 +426,10 @@ impl Context {
     /// * Relative names, like `../SOMEDIR` or `./SOMEDIR`, traverse
     ///   starting at the current volume and directory.
     /// * Absolute, like `B:/SOMEDIR/OTHERDIR` start at the given volume.
-    fn resolve_existing_directory(&mut self, full_path: &Path) -> Result<RawDirectory, Error> {
-        let (dir, fragment) = self.resolve_filename(full_path)?;
-        let mut work_dir = dir.to_directory(&mut self.volume_mgr);
-        work_dir.change_dir(fragment)?;
-        Ok(work_dir.to_raw_directory())
+    fn resolve_existing_directory<'a>(&'a self, full_path: &Path) -> Result<Directory<'a>, Error> {
+        let (mut dir, fragment) = self.resolve_filename(full_path)?;
+        dir.change_dir(fragment)?;
+        Ok(dir)
     }
 
     /// Either get the volume from the path, or pick the current volume.
@@ -464,33 +454,30 @@ impl Context {
     /// * Relative names, like `../SOMEDIR/SOMEFILE` or `./SOMEDIR/SOMEFILE`, traverse
     ///   starting at the current volume and directory.
     /// * Absolute, like `B:/SOMEDIR/SOMEFILE` start at the given volume.
-    fn resolve_filename<'path>(
-        &mut self,
+    fn resolve_filename<'a, 'path>(
+        &'a self,
         full_path: &'path Path,
-    ) -> Result<(RawDirectory, &'path str), Error> {
+    ) -> Result<(Directory<'a>, &'path str), Error> {
         let volume_idx = self.resolve_volume(full_path)?;
-        let Some(s) = &mut self.volumes[volume_idx] else {
+        let Some(s) = &self.volumes.borrow()[volume_idx] else {
             return Err(Error::NoSuchVolume);
         };
         let mut work_dir = if full_path.is_absolute() {
             // relative to root
             self.volume_mgr
                 .open_root_dir(s.volume)?
-                .to_directory(&mut self.volume_mgr)
+                .to_directory(&self.volume_mgr)
         } else {
             // relative to CWD
             self.volume_mgr
                 .open_dir(s.directory, ".")?
-                .to_directory(&mut self.volume_mgr)
+                .to_directory(&self.volume_mgr)
         };
 
         for fragment in full_path.iterate_dirs() {
             work_dir.change_dir(fragment)?;
         }
-        Ok((
-            work_dir.to_raw_directory(),
-            full_path.basename().unwrap_or("."),
-        ))
+        Ok((work_dir, full_path.basename().unwrap_or(".")))
     }
 
     /// Convert a volume index to a letter
@@ -507,7 +494,7 @@ impl Context {
 
 impl Drop for Context {
     fn drop(&mut self) {
-        for v in self.volumes.iter_mut() {
+        for v in self.volumes.borrow_mut().iter_mut() {
             if let Some(v) = v {
                 println!("Closing directory {:?}", v.directory);
                 self.volume_mgr
@@ -534,7 +521,7 @@ fn main() -> Result<(), Error> {
 
     let mut ctx = Context {
         volume_mgr: VolumeManager::new_with_limits(lbd, Clock, 100),
-        volumes: [None, None, None, None],
+        volumes: RefCell::new([None, None, None, None]),
         current_volume: 0,
     };
 
@@ -549,7 +536,7 @@ fn main() -> Result<(), Error> {
                 );
                 match ctx.volume_mgr.open_root_dir(volume) {
                     Ok(root_dir) => {
-                        ctx.volumes[volume_no] = Some(VolumeState {
+                        ctx.volumes.borrow_mut()[volume_no] = Some(VolumeState {
                             directory: root_dir,
                             volume,
                             path: vec![],