uefi: allocator: implement Allocator trait from allocator_api

No need for this so far, but this provides downstream users more
flexibility.

Author: phip1611

uefi/CHANGELOG.md

@@ -41,8 +41,10 @@
 - The `Display` impl for `CStr8` now excludes the trailing null character.
 - `VariableKeys` initializes with a larger name buffer to work around firmware
   bugs on some devices.
-- The UEFI `allocator::Allocator` has been optimized for page-aligned 
+- The UEFI `allocator::Allocator` has been optimized for page-aligned
   allocations.
+- The UEFI `allocator::Allocator` now implements `core::alloc::Allocator`
+  (`allocator_api`), when the `unstable` feature is used.
 
 
 # uefi - 0.34.1 (2025-02-07)

uefi/src/allocator.rs

@@ -169,3 +169,17 @@ unsafe impl GlobalAlloc for Allocator {
         }
     }
 }
+
+#[cfg(feature = "unstable")]
+unsafe impl core::alloc::Allocator for Allocator {
+    fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, alloc_api::AllocError> {
+        let ptr = unsafe { <Allocator as GlobalAlloc>::alloc(self, layout) };
+        NonNull::new(ptr)
+            .ok_or(alloc_api::AllocError)
+            .map(|ptr| NonNull::slice_from_raw_parts(ptr, layout.size()))
+    }
+
+    unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+        unsafe { <Allocator as GlobalAlloc>::dealloc(self, ptr.as_ptr(), layout) }
+    }
+}

uefi/src/lib.rs

@@ -212,7 +212,7 @@
 //! [uefi-std-tr-issue]: https://github.com/rust-lang/rust/issues/100499
 //! [unstable features]: https://doc.rust-lang.org/unstable-book/
 
-#![cfg_attr(all(feature = "unstable", feature = "alloc"), feature(allocator_api))]
+#![cfg_attr(feature = "unstable", feature(allocator_api))]
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 #![no_std]
 #![deny(