uefi: handle: add constructor

This is a prerequisite for the next step.

Author: phip1611

uefi/CHANGELOG.md

@@ -20,6 +20,7 @@ details of the new `system`/`boot`/`runtime` modules, and upcoming deprecations.
   the implementations `MemoryMapRef`, `MemoryMapRefMut`, and `MemoryMapOwned`.
   This comes with some changes. Read below. We recommend to directly use the
   implementations instead of the traits.
+- Added `Handle::new`
 
 ## Changed
 - **Breaking:** `uefi::helpers::init` no longer takes an argument.

uefi/src/data_types/mod.rs

@@ -13,6 +13,16 @@ use core::ptr::{self, NonNull};
 pub struct Handle(NonNull<c_void>);
 
 impl Handle {
+    /// Creates a new [`Handle`].
+    ///
+    /// # Safety
+    /// This function is unsafe because the caller must be sure that the pointer
+    /// is valid. Otherwise, further operations on the object might result in
+    /// undefined behaviour, even if the methods aren't marked as unsafe.
+    pub const unsafe fn new(ptr: NonNull<c_void>) -> Self {
+        Self(ptr)
+    }
+
     /// Creates a new [`Handle`] from a raw address. The address might
     /// come from the Multiboot2 information structure or something similar.
     ///