read: use const generics in src/read/util.rs

.github/workflows/rust.yml

@@ -17,7 +17,7 @@ jobs:
             os: macOS-latest
     runs-on: ${{matrix.os}}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Install rust
       uses: dtolnay/rust-toolchain@master
       with:
@@ -42,7 +42,7 @@ jobs:
   msrv-read:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Install rust
       uses: dtolnay/[email protected]
     - name: Build
@@ -53,7 +53,7 @@ jobs:
   msrv:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Install rust
       uses: dtolnay/[email protected]
     - name: Build
@@ -65,20 +65,18 @@ jobs:
     name: Build fuzz targets
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install rust nightly
         uses: dtolnay/rust-toolchain@nightly
       - name: Install `cargo fuzz`
         run: cargo install cargo-fuzz --vers '^0.11.0'
       - run: cargo fuzz build -Oa
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         with:
           name: fuzz-targets
-          path: fuzz/target/x86_64-unknown-linux-gnu/release/debug_*
-      - uses: actions/upload-artifact@v3
-        with:
-          name: fuzz-targets
-          path: fuzz/target/x86_64-unknown-linux-gnu/release/eh_*
+          path: |
+            fuzz/target/x86_64-unknown-linux-gnu/release/debug_*
+            fuzz/target/x86_64-unknown-linux-gnu/release/eh_*
 
   run_fuzz_targets:
     strategy:
@@ -89,14 +87,15 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Clone the fuzz corpora
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: gimli-rs/gimli-libfuzzer-corpora
           path: corpora
       - name: Download fuzz targets
-        uses: actions/download-artifact@v1
+        uses: actions/download-artifact@v4
         with:
           name: fuzz-targets
+          path: fuzz-targets
         # Note: -max_total_time=300 == 300 seconds == 5 minutes.
       - name: Run `${{matrix.fuzz_target}}` fuzz target
         run: |
@@ -109,15 +108,15 @@ jobs:
       # can debug them.
       - name: Upload fuzz artifacts
         if: failure()
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: ${{matrix.fuzz_target}}_artifacts
           path: ./${{matrix.fuzz_target}}_artifacts
 
   features:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install rust stable
         uses: dtolnay/rust-toolchain@stable
       - uses: taiki-e/install-action@v2
@@ -130,7 +129,7 @@ jobs:
   bench:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install rust nightly
         uses: dtolnay/rust-toolchain@nightly
       - run: cargo bench
@@ -145,7 +144,7 @@ jobs:
           - powerpc64-unknown-linux-gnu
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install rust stable
         uses: dtolnay/rust-toolchain@stable
         with:
@@ -158,7 +157,7 @@ jobs:
   rustfmt:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install rust stable
         uses: dtolnay/rust-toolchain@stable
         with:
@@ -171,7 +170,7 @@ jobs:
       image: xd009642/tarpaulin
       options: --security-opt seccomp=unconfined
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install rust stable
         uses: dtolnay/rust-toolchain@stable
       - name: Run cargo-tarpaulin
@@ -185,7 +184,7 @@ jobs:
   doc:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install rust stable
         uses: dtolnay/rust-toolchain@stable
       - run: cargo doc

src/read/util.rs

@@ -41,70 +41,52 @@ pub trait ArrayLike: Sealed {
     fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<Self::Item>];
 }
 
-// Use macro since const generics can't be used due to MSRV.
-macro_rules! impl_array {
-    () => {};
-    ($n:literal $($rest:tt)*) => {
-        // SAFETY: does not modify the content in storage.
-        unsafe impl<T> Sealed for [T; $n] {
-            type Storage = [MaybeUninit<T>; $n];
-
-            fn new_storage() -> Self::Storage {
-                // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
-                unsafe { MaybeUninit::uninit().assume_init() }
-            }
-        }
+// SAFETY: does not modify the content in storage.
+unsafe impl<T, const N: usize> Sealed for [T; N] {
+    type Storage = [MaybeUninit<T>; N];
 
-        impl<T> ArrayLike for [T; $n] {
-            type Item = T;
+    fn new_storage() -> Self::Storage {
+        // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
+        unsafe { MaybeUninit::uninit().assume_init() }
+    }
+}
 
-            fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
-                storage
-            }
+impl<T, const N: usize> ArrayLike for [T; N] {
+    type Item = T;
 
-            fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
-                storage
-            }
-        }
+    fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
+        storage
+    }
 
-        impl_array!($($rest)*);
+    fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
+        storage
     }
 }
 
+// SAFETY: does not modify the content in storage.
 #[cfg(feature = "read")]
-macro_rules! impl_box {
-    () => {};
-    ($n:literal $($rest:tt)*) => {
-        // SAFETY: does not modify the content in storage.
-        unsafe impl<T> Sealed for Box<[T; $n]> {
-            type Storage = Box<[MaybeUninit<T>; $n]>;
-
-            fn new_storage() -> Self::Storage {
-                // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
-                Box::new(unsafe { MaybeUninit::uninit().assume_init() })
-            }
-        }
+unsafe impl<T, const N: usize> Sealed for Box<[T; N]> {
+    type Storage = Box<[MaybeUninit<T>; N]>;
 
-        impl<T> ArrayLike for Box<[T; $n]> {
-            type Item = T;
+    fn new_storage() -> Self::Storage {
+        // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
+        Box::new(unsafe { MaybeUninit::uninit().assume_init() })
+    }
+}
 
-            fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
-                &storage[..]
-            }
+#[cfg(feature = "read")]
+impl<T, const N: usize> ArrayLike for Box<[T; N]> {
+    type Item = T;
 
-            fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
-                &mut storage[..]
-            }
-        }
+    fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
+        &storage[..]
+    }
 
-        impl_box!($($rest)*);
+    fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
+        &mut storage[..]
     }
 }
 
-impl_array!(0 1 2 3 4 8 16 32 64 128 192);
-#[cfg(feature = "read")]
-impl_box!(0 1 2 3 4 8 16 32 64 128 192);
-
 #[cfg(feature = "read")]
 unsafe impl<T> Sealed for Vec<T> {
     type Storage = Box<[MaybeUninit<T>]>;