spirv backend: simplify the adapt.rs indexing by using the constructors previously created

crates/spirv_backend/src/support.rs

@@ -1,3 +1,5 @@
+use core::ops::Index;
+
 use coremem_types::compound::Optional;
 use coremem_types::vec::Vec3u;
 
@@ -12,6 +14,8 @@ pub const MAX_UNSIZED_ARRAY: usize = 0x1ff_ffff;
 pub struct UnsizedArray<T>(pub [T; MAX_UNSIZED_ARRAY]);
 
 impl<T: Copy> UnsizedArray<T> {
+    /// user is responsible for bounds-checking the index before calling this.
+    /// unsafe because this can trigger OOB reads if used incorrectly.
     pub unsafe fn index(&self, index: usize) -> T {
         // *self.0.index(index)
         self.0[index]
@@ -25,13 +29,19 @@ impl<T: Copy> UnsizedArray<T> {
         //    index = in(reg) index,
         //}
     }
+}
 
+impl<T> UnsizedArray<T> {
+    /// user is responsible for bounds-checking the index before calling this.
+    /// unsafe because this can trigger OOB writes if used incorrectly.
     pub unsafe fn write(&mut self, index: usize, value: T) {
         self.0[index] = value;
     }
 }
 
 impl<T> UnsizedArray<T> {
+    /// user is responsible for bounds-checking the index before calling this.
+    /// unsafe because this can trigger OOB access if used incorrectly.
     pub unsafe fn index_ref(&self, index: usize) -> &T {
         &self.0[index]
     }
@@ -142,7 +152,7 @@ impl<'a, T> Array3<'a, T> {
 
 impl<'a, T: Copy + Default> Array3<'a, T> {
     pub fn get(&self, idx: Vec3u) -> Optional<T> {
-        let idx = self.index(idx);
+        let idx = checked_index(idx, self.dim);
         if idx.is_some() {
             Optional::some(unsafe {
                 self.data.index(idx.unwrap())
@@ -153,6 +163,16 @@ impl<'a, T: Copy + Default> Array3<'a, T> {
     }
 }
 
+impl<'a, T> Index<Vec3u> for Array3<'a, T> {
+    type Output = T;
+    fn index(&self, idx: Vec3u) -> &Self::Output {
+        let idx = checked_index(idx, self.dim).unwrap();
+        unsafe {
+            self.data.index_ref(idx)
+        }
+    }
+}
+
 /// 3d dynamically-sized array backed by a mutably borrowed buffer.
 pub struct Array3Mut<'a, T> {
     data: &'a mut UnsizedArray<T>,