1 files changed, 106 insertions, 0 deletions
diff --git a/src/owning_ref.rs b/src/owning_ref.rs
new file mode 100644
index 0000000..f7d2c5f
--- /dev/null
+++ b/src/owning_ref.rs
@@ -0,0 +1,106 @@
+//! Utility similar to provided by `owning_ref` crate.
+
+use std::fmt;
+use std::fmt::Debug;
+use std::ops::Deref;
+use std::sync::Arc;
+
+enum Owner<A: 'static> {
+    Arc(Arc<A>),
+    Static(&'static A),
+}
+
+impl<A: 'static> Deref for Owner<A> {
+    type Target = A;
+
+    fn deref(&self) -> &A {
+        match self {
+            Owner::Arc(a) => &*a,
+            Owner::Static(a) => a,
+        }
+    }
+}
+
+pub(crate) struct OwningRef<A: 'static, B: 'static> {
+    owner: Owner<A>,
+    ptr: *const B,
+}
+
+unsafe impl<A: Send + Sync + 'static, B: Send + Sync + 'static> Sync for OwningRef<A, B> {}
+unsafe impl<A: Send + Sync + 'static, B: Send + Sync + 'static> Send for OwningRef<A, B> {}
+
+impl<A: 'static, B: 'static> Deref for OwningRef<A, B> {
+    type Target = B;
+
+    fn deref(&self) -> &B {
+        // SAFETY: `self.owner` owns the data and it is not movable.
+        unsafe { &*self.ptr }
+    }
+}
+
+impl<A: 'static> Clone for Owner<A> {
+    fn clone(&self) -> Owner<A> {
+        match self {
+            Owner::Arc(arc) => Owner::Arc(arc.clone()),
+            Owner::Static(ptr) => Owner::Static(ptr),
+        }
+    }
+}
+
+impl<A: 'static, B: 'static> Clone for OwningRef<A, B> {
+    fn clone(&self) -> OwningRef<A, B> {
+        OwningRef {
+            ptr: self.ptr,
+            owner: self.owner.clone(),
+        }
+    }
+}
+
+impl<A: 'static, B: fmt::Debug + 'static> Debug for OwningRef<A, B> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        Debug::fmt(&**self, f)
+    }
+}
+
+impl<A: 'static> OwningRef<A, A> {
+    pub(crate) fn new_arc(arc: Arc<A>) -> OwningRef<A, A> {
+        OwningRef {
+            ptr: Arc::as_ptr(&arc),
+            owner: Owner::Arc(arc),
+        }
+    }
+
+    pub(crate) fn new_static(ptr: &'static A) -> OwningRef<A, A> {
+        OwningRef {
+            ptr,
+            owner: Owner::Static(ptr),
+        }
+    }
+
+    pub(crate) fn owner(&self) -> &A {
+        &self.owner
+    }
+}
+
+impl<A: 'static, B: 'static> OwningRef<A, B> {
+    pub(crate) fn _map<C>(self, f: impl FnOnce(&B) -> &C) -> OwningRef<A, C> {
+        let ptr = f(&*self);
+        OwningRef {
+            ptr,
+            owner: self.owner,
+        }
+    }
+
+    pub(crate) fn flat_map_slice<'x, C, T: FnOnce(&B) -> &[C]>(
+        &self,
+        f: T,
+    ) -> impl Iterator<Item = OwningRef<A, C>> + '_
+    where
+        C: 'static,
+    {
+        f(&self).into_iter().map(|ptr| OwningRef {
+            ptr,
+            owner: self.owner.clone(),
+        })
+    }
+}