core: Remove generic-array dependency

By refactoring the Attribute struct using const generics, we can get rid
of the (public) generic-array dependency.

CHANGELOG.md

@@ -40,6 +40,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Removed `Path::from_bytes_with_nul_unchecked`.  Use `CStr::from_bytes_with_nul_unchecked` and `Path::from_cstr_unchecked` instead.
 - Removed `From<littlefs2::path::Error> for littlefs2::io::Error`.
 - Removed `object_safe::OpenOptionsCallback`.
+- Removed `consts::ATTRBYTES_MAX_TYPE`.
 
 [#47]: https://github.com/trussed-dev/littlefs2/pull/47
 [#57]: https://github.com/trussed-dev/littlefs2/pull/57

core/Cargo.toml

@@ -10,7 +10,6 @@ repository.workspace = true
 
 [dependencies]
 bitflags = "2.6.0"
-generic-array = "0.14"
 heapless = "0.7"
 serde = { version = "1", default-features = false, features = ["derive"], optional = true }
 

core/src/consts.rs

@@ -1,5 +1,3 @@
 pub const PATH_MAX: usize = 255;
 pub const PATH_MAX_PLUS_ONE: usize = PATH_MAX + 1;
 pub const ATTRBYTES_MAX: u32 = 1_022;
-#[allow(non_camel_case_types)]
-pub type ATTRBYTES_MAX_TYPE = generic_array::typenum::consts::U1022;

core/src/fs.rs

@@ -4,8 +4,6 @@ use bitflags::bitflags;
 
 use crate::path::{Path, PathBuf};
 
-pub type Bytes<SIZE> = generic_array::GenericArray<u8, SIZE>;
-
 bitflags! {
     /// Definition of file open flags which can be mixed and matched as appropriate. These definitions
     /// are reminiscent of the ones defined by POSIX.
@@ -92,15 +90,16 @@ impl Metadata {
 /// [`Filesystem::clear_attribute`](struct.Filesystem.html#method.clear_attribute).
 pub struct Attribute {
     id: u8,
-    pub data: Bytes<crate::consts::ATTRBYTES_MAX_TYPE>,
-    pub size: usize,
+    data: [u8; crate::consts::ATTRBYTES_MAX as _],
+    // invariant: size <= data.len()
+    size: usize,
 }
 
 impl Attribute {
     pub fn new(id: u8) -> Self {
         Attribute {
             id,
-            data: Default::default(),
+            data: [0; crate::consts::ATTRBYTES_MAX as _],
             size: 0,
         }
     }
@@ -115,6 +114,10 @@ impl Attribute {
         &self.data[..len]
     }
 
+    pub fn size(&self) -> usize {
+        self.size
+    }
+
     pub fn set_data(&mut self, data: &[u8]) -> &mut Self {
         let attr_max = crate::consts::ATTRBYTES_MAX as _;
         let len = cmp::min(attr_max, data.len());
@@ -125,6 +128,14 @@ impl Attribute {
         }
         self
     }
+
+    pub fn buffer_mut(&mut self) -> &mut [u8] {
+        &mut self.data
+    }
+
+    pub fn set_size(&mut self, size: usize) {
+        self.size = cmp::min(size, self.data.len());
+    }
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]

core/src/lib.rs

@@ -12,7 +12,7 @@ mod io;
 mod object_safe;
 mod path;
 
-pub use consts::{ATTRBYTES_MAX, ATTRBYTES_MAX_TYPE, PATH_MAX, PATH_MAX_PLUS_ONE};
+pub use consts::{ATTRBYTES_MAX, PATH_MAX, PATH_MAX_PLUS_ONE};
 pub use fs::{Attribute, DirEntry, FileOpenFlags, FileType, Metadata};
 pub use io::{Error, OpenSeekFrom, Read, Result, Seek, SeekFrom, Write};
 pub use object_safe::{DirEntriesCallback, DynFile, DynFilesystem, FileCallback, Predicate};

src/consts.rs

@@ -3,7 +3,7 @@
 /// Re-export of `typenum::consts`.
 pub use generic_array::typenum::consts::*;
 
-pub use littlefs2_core::{ATTRBYTES_MAX, ATTRBYTES_MAX_TYPE, PATH_MAX, PATH_MAX_PLUS_ONE};
+pub use littlefs2_core::{ATTRBYTES_MAX, PATH_MAX, PATH_MAX_PLUS_ONE};
 
 pub const FILENAME_MAX_PLUS_ONE: u32 = 255 + 1;
 pub const FILEBYTES_MAX: u32 = crate::ll::LFS_FILE_MAX as _;

src/fs.rs

@@ -5,7 +5,7 @@ use core::ptr::addr_of;
 use core::ptr::addr_of_mut;
 use core::{
     cell::{RefCell, UnsafeCell},
-    cmp, mem, slice,
+    mem, slice,
 };
 use generic_array::typenum::marker_traits::Unsigned;
 use littlefs2_sys as ll;
@@ -425,13 +425,13 @@ impl<Storage: driver::Storage> Filesystem<'_, Storage> {
                 &mut self.alloc.borrow_mut().state,
                 path.as_ptr(),
                 id,
-                &mut attribute.data as *mut _ as *mut c_void,
+                attribute.buffer_mut() as *mut _ as *mut c_void,
                 attr_max,
             )
         };
 
         if return_code >= 0 {
-            attribute.size = cmp::min(attr_max, return_code as u32) as usize;
+            attribute.set_size(return_code as usize);
             return Ok(Some(attribute));
         }
         if return_code == ll::lfs_error_LFS_ERR_NOATTR {
@@ -457,8 +457,8 @@ impl<Storage: driver::Storage> Filesystem<'_, Storage> {
                 &mut self.alloc.borrow_mut().state,
                 path.as_ptr(),
                 attribute.id(),
-                &attribute.data as *const _ as *const c_void,
-                attribute.size as u32,
+                attribute.data() as *const _ as *const c_void,
+                attribute.size() as u32,
             )
         };