ClientFilestore: make dat optional

Cargo.toml

@@ -133,4 +133,4 @@ features = ["serde-extensions", "virt"]
 rustdoc-args = ["--cfg", "docsrs"]
 
 [patch.crates-io]
-littlefs2 = { git = "https://github.com/trussed-dev/littlefs2.git", rev = "ebd27e49ca321089d01d8c9b169c4aeb58ceeeca" }
+littlefs2 = { git = "https://github.com/sosthene-nitrokey/littlefs2.git", rev = "2b45a7559ff44260c6dd693e4cb61f54ae5efc53" }

src/api.rs

@@ -244,7 +244,7 @@ pub mod request {
         ReadDirFirst:
           - location: Location
           - dir: PathBuf
-          - not_before_filename: Option<PathBuf>
+          - not_before: Option<(PathBuf, bool)>
 
         ReadDirNext:
 

src/client.rs

@@ -598,6 +598,9 @@ pub trait FilesystemClient: PollClient {
         self.request(request::DebugDumpStore {})
     }
 
+    /// Open a directory for iteration with `read_dir_next`
+    ///
+    /// For optimization, not_before_filename can be passed to begin the iteration at that file.
     fn read_dir_first(
         &mut self,
         location: Location,
@@ -607,7 +610,27 @@ pub trait FilesystemClient: PollClient {
         self.request(request::ReadDirFirst {
             location,
             dir,
-            not_before_filename,
+            not_before: not_before_filename.map(|p| (p, true)),
+        })
+    }
+
+    /// Open a directory for iteration with `read_dir_next`
+    ///
+    /// For optimization, not_before_filename can be passed to begin the iteration after the first file that is "alphabetically" before the original file
+    ///
+    /// <div class="warning">
+    /// The notion used here for "alphabetical" does not correspond to the order of iteration yielded by littlefs. This function should be used with caution. If `not_before_filename` was yielded from a previous use of read_dir, it can lead to entries being repeated.
+    /// </div>
+    fn read_dir_first_alphabetical(
+        &mut self,
+        location: Location,
+        dir: PathBuf,
+        not_before_filename: Option<PathBuf>,
+    ) -> ClientResult<'_, reply::ReadDirFirst, Self> {
+        self.request(request::ReadDirFirst {
+            location,
+            dir,
+            not_before: not_before_filename.map(|p| (p, false)),
         })
     }
 

src/service.rs

@@ -113,6 +113,11 @@ impl<P: Platform> ServiceResources<P> {
         ClientFilestore::new(client_id, self.platform.store())
     }
 
+    /// Get access to the filestore for the client without the `dat` intermediary
+    pub fn raw_filestore(&mut self, client_id: PathBuf) -> ClientFilestore<P::S> {
+        ClientFilestore::new_raw(client_id, self.platform.store())
+    }
+
     pub fn trussed_filestore(&mut self) -> ClientFilestore<P::S> {
         ClientFilestore::new(PathBuf::from("trussed"), self.platform.store())
     }
@@ -404,7 +409,10 @@ impl<P: Platform> ServiceResources<P> {
                 let maybe_entry = match filestore.read_dir_first(
                     &request.dir,
                     request.location,
-                    request.not_before_filename.as_deref(),
+                    request
+                        .not_before
+                        .as_ref()
+                        .map(|(path, require_equal)| (&**path, *require_equal)),
                 )? {
                     Some((entry, read_dir_state)) => {
                         ctx.read_dir_state = Some(read_dir_state);

src/store/filestore.rs

@@ -1,3 +1,5 @@
+use core::cmp::Ordering;
+
 use crate::{
     error::{Error, Result},
     // service::ReadDirState,
@@ -27,19 +29,29 @@ use littlefs2::{
     path::{Path, PathBuf},
 };
 
-pub type ClientId = PathBuf;
-
 pub struct ClientFilestore<S>
 where
     S: Store,
 {
-    client_id: ClientId,
+    base: PathBuf,
     store: S,
 }
 
 impl<S: Store> ClientFilestore<S> {
-    pub fn new(client_id: ClientId, store: S) -> Self {
-        Self { client_id, store }
+    /// Create a filestore that stores files in `<client_id>/dat/<file_path>`
+    pub fn new(client_id: PathBuf, store: S) -> Self {
+        let mut base = client_id;
+        base.push(path!("dat"));
+        Self { base, store }
+    }
+
+    /// Create a filestore that stores files in `<client_id>/<file_path>`
+    ///
+    /// Unlike [`ClientFilestore::new`](), it does not have the `dat` intermediary.
+    /// It is meant to be used by custom backends to save space in case the `dat` folder is not used and only wastes a littlefs block.
+    pub fn new_raw(client_id: PathBuf, store: S) -> Self {
+        let base = client_id;
+        Self { base, store }
     }
 
     /// Client files are store below `/<client_id>/dat/`.
@@ -49,9 +61,7 @@ impl<S: Store> ClientFilestore<S> {
             return Err(Error::InvalidPath);
         }
 
-        let mut path = PathBuf::new();
-        path.push(&self.client_id);
-        path.push(path!("dat"));
+        let mut path = self.base.clone();
         path.push(client_path);
         Ok(path)
     }
@@ -109,7 +119,7 @@ pub trait Filestore {
         &mut self,
         dir: &Path,
         location: Location,
-        not_before: Option<&Path>,
+        not_before: Option<(&Path, bool)>,
     ) -> Result<Option<(DirEntry, ReadDirState)>>;
 
     /// Continue iterating over entries of a directory.
@@ -145,7 +155,7 @@ impl<S: Store> ClientFilestore<S> {
         &mut self,
         clients_dir: &Path,
         location: Location,
-        not_before: Option<&Path>,
+        not_before: Option<(&Path, bool)>,
     ) -> Result<Option<(DirEntry, ReadDirState)>> {
         let fs = self.store.fs(location);
         let dir = self.actual_path(clients_dir)?;
@@ -163,8 +173,15 @@ impl<S: Store> ClientFilestore<S> {
                     .map(|(i, entry)| (i, entry.unwrap()))
                     // if there is a "not_before" entry, skip all entries before it.
                     .find(|(_, entry)| {
-                        if let Some(not_before) = not_before {
-                            entry.file_name() == not_before.as_ref()
+                        if let Some((not_before, require_equal)) = not_before {
+                            if require_equal {
+                                entry.file_name() == not_before
+                            } else {
+                                match entry.file_name().cmp_str(not_before) {
+                                    Ordering::Less => false,
+                                    Ordering::Equal | Ordering::Greater => true,
+                                }
+                            }
                         } else {
                             true
                         }
@@ -429,7 +446,7 @@ impl<S: Store> Filestore for ClientFilestore<S> {
         &mut self,
         clients_dir: &Path,
         location: Location,
-        not_before: Option<&Path>,
+        not_before: Option<(&Path, bool)>,
     ) -> Result<Option<(DirEntry, ReadDirState)>> {
         self.read_dir_first_impl(clients_dir, location, not_before)
     }