foyer-rs · MrCroxx · Jul 3, 2023 · Jul 3, 2023 · Jul 3, 2023
diff --git a/foyer-intrusive/src/core/adapter.rs b/foyer-intrusive/src/core/adapter.rs
@@ -69,6 +69,23 @@ pub unsafe trait KeyAdapter: Adapter {
     ) -> *const Self::Key;
 }
 
+/// # Safety
+///
+/// Pointer operations MUST be valid.
+///
+/// [`PriorityAdapter`] is recommanded to be generated by macro `priority_adapter!`.
+pub unsafe trait PriorityAdapter: Adapter {
+    type Priority: PartialEq + Eq + PartialOrd + Ord + Clone + Copy + Into<usize>;
+
+    /// # Safety
+    ///
+    /// Pointer operations MUST be valid.
+    unsafe fn item2priority(
+        &self,
+        item: *const <Self::PointerOps as PointerOps>::Item,
+    ) -> *const Self::Priority;
+}
+
 /// Macro to generate an implementation of [`Adapter`] for instrusive container and items.
 ///
 /// The basic syntax to create an adapter is:
@@ -234,14 +251,75 @@ macro_rules! key_adapter {
     };
 }
 
-macro_rules! t {
+/// Macro to generate an implementation of [`PriorityAdapter`] for instrusive container and items.
+/// ///
+/// The basic syntax to create an adapter is:
+///
+/// ```rust,ignore
+/// priority_adapter! { Adapter = Item { priority_field: PriorityType } }
+/// ```
+///
+/// # Generics
+///
+/// This macro supports generic arguments:
+///
+/// Note that due to macro parsing limitations, `T: Trait` bounds are not
+/// supported in the generic argument list. You must list any trait bounds in
+/// a separate `where` clause at the end of the macro.
+///
+/// # Examples
+///
+/// ```
+/// use foyer_intrusive::{intrusive_adapter, priority_adapter};
+/// use foyer_intrusive::core::adapter::{Adapter, PriorityAdapter, Link};
+/// use foyer_intrusive::core::pointer::PointerOps;
+/// use foyer_intrusive::eviction::EvictionPolicy;
+/// use std::sync::Arc;
+///
+/// #[derive(Debug)]
+/// pub struct Item<L>
+/// where
+///     L: Link
+/// {
+///     link: L,
+///     priority: usize,
+/// }
+///
+/// intrusive_adapter! { ItemAdapter<L> = Arc<Item<L>>: Item<L> { link: L} where L: Link }
+/// priority_adapter! { ItemAdapter<L> = Item<L> { priority: usize } where L: Link }
+/// ```
+#[macro_export]
+macro_rules! priority_adapter {
+    (@impl
+        $adapter:ident ($($args:tt),*) = $item:ty { $field:ident: $priority:ty } $($where_:tt)*
+    ) => {
+        unsafe impl<$($args),*> $crate::core::adapter::PriorityAdapter for $adapter<$($args),*> $($where_)*{
+            type Priority = $priority;
+
+            unsafe fn item2priority(
+                &self,
+                item: *const <Self::PointerOps as PointerOps>::Item,
+            ) -> *const Self::Priority {
+                (item as *const u8).add($crate::offset_of!($item, $field)) as *const _
+            }
+        }
+    };
+    (
+        $name:ident = $($rest:tt)*
+    ) => {
+        priority_adapter! {@impl
+            $name () = $($rest)*
+        }
+    };
     (
-        <$($args:tt),*>
-    ) => {};
+        $name:ident<$($args:tt),*> = $($rest:tt)*
+    ) => {
+        priority_adapter! {@impl
+            $name ($($args),*) = $($rest)*
+        }
+    };
 }
 
-t! { <A, B, C> }
-
 #[cfg(test)]
 mod tests {
     use itertools::Itertools;