add last method to queue

src/datastructures/queue.rs

@@ -137,6 +137,28 @@ impl<T: FromBytes + FromZeroes + AsBytes + Unaligned + Clone + Copy> FilePointer
         Some(queue)
     }
 
+    pub fn is_empty(self, reader: &impl ReaderTrait) -> bool {
+        self.length(reader) == 0
+    }
+
+    pub fn last(self, reader: &impl ReaderTrait) -> Option<T> {
+        let this = reader.read(self);
+
+        if this.length.get() == 0 {
+            return None;
+        }
+
+        let mut next = this.head;
+
+        for _ in 1..this.length.get() {
+            // println!("free [{i}] {ptr:?}");
+
+            next = *reader.read(field_ptr!(next, QueueElement<T>, next));
+        }
+
+        Some(*reader.read(field_ptr!(next, QueueElement<T>, data)))
+    }
+
     pub fn length(self, reader: &impl ReaderTrait) -> u64 {
         reader.read(field_ptr!(self, Queue<T>, length)).get()
     }