start on recycling policy

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

src/lib.rs

@@ -7,6 +7,7 @@ use core::{cmp, fmt, mem::MaybeUninit, ops, ptr};
 mod macros;
 
 mod loom;
+mod recycle;
 mod util;
 mod wait;
 

src/recycle.rs

@@ -0,0 +1,25 @@
+pub trait Recycle<T> {
+    /// Returns a new instance of type `T`.
+    fn new_element(&self) -> T;
+
+    /// Resets `element` in place.
+    ///
+    /// Typically, this retains any previous allocations.
+    fn recycle(&self, element: &mut T);
+}
+
+#[derive(Debug, Default)]
+pub struct DefaultRecycle(());
+
+impl<T> Recycle<T> for DefaultRecycle
+where
+    T: Default + Clone,
+{
+    fn new_element(&self) -> T {
+        T::default()
+    }
+
+    fn recycle(&self, element: &mut T) {
+        element.clone_from(&T::default())
+    }
+}