Guess I should put this under version control LOL

styles/src/stretch/id.rs

@@ -0,0 +1,36 @@
+//! Identifier for a Node
+//!
+//!
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub(crate) struct Id {
+    id: u32,
+    generation: u32,
+}
+
+pub(crate) struct Allocator {
+    new_id: u32,
+    free_ids: Vec<Id>,
+}
+
+impl Allocator {
+    pub fn new() -> Self {
+        Allocator { new_id: 0, free_ids: Vec::new() }
+    }
+
+    pub fn allocate(&mut self) -> Id {
+        // TODO: better balancing
+        match self.free_ids.pop() {
+            Some(id) => Id { id: id.id, generation: id.generation + 1 },
+            None => {
+                let id = self.new_id;
+                self.new_id += 1;
+                Id { id, generation: 0 }
+            }
+        }
+    }
+
+    pub fn free(&mut self, ids: &[Id]) {
+        self.free_ids.extend(ids);
+    }
+}