feat(ext2): Celled<Ext2> implements FileSystem

src/fs/error.rs

@@ -4,6 +4,8 @@ use alloc::string::String;
 use core::fmt;
 use core::fmt::Display;
 
+use crate::file::Type;
+
 /// Enumeration of possible errors encountered with [`FileSystem`](super::FileSystem)s' manipulation.
 #[allow(clippy::module_name_repetitions)]
 #[derive(Debug)]
@@ -25,6 +27,11 @@ pub enum FsError<E: core::error::Error> {
 
     /// Indicates that this error is coming from the filesystem's implementation.
     Implementation(E),
+
+    /// Tried to assign a wrong type to a file.
+    ///
+    /// `WrongFileType(expected, given)`
+    WrongFileType(Type, Type),
 }
 
 impl<E: core::error::Error> Display for FsError<E> {
@@ -37,6 +44,9 @@ impl<E: core::error::Error> Display for FsError<E> {
             Self::NoEnt(filename) => write!(formatter, "No entry: \"{filename}\" is an symbolic link pointing at an empty string"),
             Self::NotFound(filename) => write!(formatter, "Not found: \"{filename}\" has not been found"),
             Self::Implementation(err) => write!(formatter, "{err}"),
+            Self::WrongFileType(expected, given) => {
+                write!(formatter, "Wrong File Type: {expected:?} file type expected, {given:?} given")
+            },
         }
     }
 }

src/fs/ext2/error.rs

@@ -4,7 +4,6 @@ use core::error;
 use core::fmt::{self, Display};
 
 use super::superblock::EXT2_SIGNATURE;
-use crate::file::Type;
 
 /// Enumeration of possible errors encountered with Ext2's manipulation.
 #[allow(clippy::module_name_repetitions)]
@@ -59,9 +58,6 @@ pub enum Ext2Error {
 
     /// Tried to access a byte which is out of bounds.
     OutOfBounds(i128),
-
-    /// Tried to assign a wrong type to a file.
-    WrongFileType(Type, Type),
 }
 
 impl Display for Ext2Error {
@@ -105,9 +101,6 @@ impl Display for Ext2Error {
             Self::OutOfBounds(byte) => {
                 write!(formatter, "Out of Bounds: tried to access the {byte}th byte which is out of bounds")
             },
-            Self::WrongFileType(expected, given) => {
-                write!(formatter, "Wrong File Type: {expected:?} file type expected, {given:?} given")
-            },
         }
     }
 }

src/fs/ext2/mod.rs

@@ -10,8 +10,9 @@ use self::block::Block;
 use self::block_group::BlockGroupDescriptor;
 use self::error::Ext2Error;
 use self::file::{Directory, Regular, SymbolicLink};
-use self::inode::Inode;
+use self::inode::{Inode, ROOT_DIRECTORY_INODE};
 use self::superblock::{Superblock, SUPERBLOCK_START_BYTE};
+use super::FileSystem;
 use crate::dev::celled::Celled;
 use crate::dev::sector::Address;
 use crate::dev::Device;
@@ -214,6 +215,23 @@ impl<Dev: Device<u8, Ext2Error>> Celled<Ext2<Dev>> {
     }
 }
 
+impl<Dev: Device<u8, Ext2Error>> FileSystem<Directory<Dev>> for Celled<Ext2<Dev>> {
+    #[inline]
+    fn root(&self) -> Result<Directory<Dev>, Error<<Directory<Dev> as crate::file::Directory>::Error>> {
+        self.file(ROOT_DIRECTORY_INODE).and_then(|root| match root {
+            TypeWithFile::Directory(root_dir) => Ok(root_dir),
+            TypeWithFile::Regular(_) | TypeWithFile::SymbolicLink(_) | TypeWithFile::Other(_) => {
+                Err(Error::Fs(FsError::WrongFileType(Type::Directory, root.into())))
+            },
+        })
+    }
+
+    #[inline]
+    fn double_slash_root(&self) -> Result<Directory<Dev>, Error<<Directory<Dev> as crate::file::Directory>::Error>> {
+        self.root()
+    }
+}
+
 #[cfg(test)]
 mod test {
     use core::cell::RefCell;

src/fs/mod.rs

@@ -28,14 +28,22 @@ pub const PATH_MAX: usize = 4_096;
 /// A filesystem.
 pub trait FileSystem<Dir: Directory> {
     /// Returns the root directory of the filesystem.
-    fn root(&self) -> Dir;
+    ///
+    /// # Errors
+    ///
+    /// Returns a [`DevError`](crate::dev::error::DevError) if the device could not be read.
+    fn root(&self) -> Result<Dir, Error<Dir::Error>>;
 
     /// Returns the double slash root directory of the filesystem.
     ///
     /// If you do not have any idea of what this is, you are probably looking for [`root`](trait.FileSystem.html#tymethod.root).
     ///
     /// See [`Component::DoubleSlashRootDir`] and [`Path`] for more information.
-    fn double_slash_root(&self) -> Dir;
+    ///
+    /// # Errors
+    ///
+    /// Returns a [`DevError`](crate::dev::error::DevError) if the device could not be read.
+    fn double_slash_root(&self) -> Result<Dir, Error<Dir::Error>>;
 
     /// Performs a pathname resolution as described in [this POSIX definition](https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13).
     ///
@@ -96,14 +104,14 @@ pub trait FileSystem<Dir: Directory> {
                 match comp {
                     Component::RootDir => {
                         if pos == Position::First || pos == Position::Only {
-                            current_dir = fs.root();
+                            current_dir = fs.root()?;
                         } else {
                             unreachable!("The root directory cannot be encountered during the pathname resolution");
                         }
                     },
                     Component::DoubleSlashRootDir => {
                         if pos == Position::First || pos == Position::Only {
-                            current_dir = fs.double_slash_root();
+                            current_dir = fs.double_slash_root()?;
                         } else {
                             unreachable!("The double slash root directory cannot be encountered during the pathname resolution");
                         }