add last method to segment list

Author: MarinPostma

libsql-wal/src/segment/list.rs

@@ -265,6 +265,23 @@ where
 
         (tokio_util::either::Either::Right(stream), new_current)
     }
+
+    pub(crate) fn last(&self) -> Option<Seg>
+        where Seg: Clone,
+    {
+        let mut current = self.list.head.load().clone();
+        loop {
+            match current.as_ref() {
+                Some(c) => {
+                    if c.next.load().is_none() {
+                        return Some(c.item.clone())
+                    }
+                    current = c.next.load().clone();
+                },
+                None => return None,
+            }
+        }
+    }
 }
 
 struct Node<T> {