Implement LinkedListAllocator::size_align

src/allocator/linked_list.rs

@@ -103,6 +103,19 @@ impl LinkedListAllocator {
         // region suitable for allocation
         Ok(alloc_start)
     }
+
+    /// Adjust the given layout so that the resulting allocated memory
+    /// region is also capable of storing a `ListNode`.
+    ///
+    /// Returns the adjusted size and alignment as a (size, align) tuple.
+    fn size_align(layout: Layout) -> (usize, usize) {
+        let layout = layout
+            .align_to(mem::align_of::<ListNode>())
+            .expect("adjusting alignment failed")
+            .pad_to_align();
+        let size = layout.size().max(mem::size_of::<ListNode>());
+        (size, layout.align())
+    }
 }
 
 unsafe impl GlobalAlloc for Locked<LinkedListAllocator> {