Refactor project structure

kernel/libs/aster-util/src/union_read_ptr.rs

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use core::marker::PhantomData;
+
+use pod::Pod;
+
+/// This ptr is designed to read union field safely.
+/// Write to union field is safe operation. While reading union field is UB.
+/// However, if this field is Pod, we can safely read that field.
+pub struct UnionReadPtr<'a, T: Pod> {
+    bytes: &'a [u8],
+    marker: PhantomData<&'a mut T>,
+}
+
+impl<'a, T: Pod> UnionReadPtr<'a, T> {
+    pub fn new(object: &'a T) -> Self {
+        let bytes = object.as_bytes();
+        Self {
+            bytes,
+            marker: PhantomData,
+        }
+    }
+
+    pub fn read_at<F: Pod>(&self, offset: *const F) -> F {
+        let offset = offset as usize;
+        F::from_bytes(&self.bytes[offset..])
+    }
+}
+
+/// FIXME: This macro requires the first argument to be a `reference` of a Pod type.
+/// This is because the value_offset macro requires
+#[macro_export]
+macro_rules! read_union_fields {
+    ($container:ident) => ({
+        let offset = value_offset!($container);
+        let union_read_ptr = UnionReadPtr::new(&*$container);
+        union_read_ptr.read_at(offset)
+    });
+    ($container:ident.$($field:ident).*) => ({
+        let field_offset = aster_frame::value_offset!($container.$($field).*);
+        let union_read_ptr = UnionReadPtr::new(&*$container);
+        union_read_ptr.read_at(field_offset)
+    });
+}