1 files changed, 30 insertions, 0 deletions
diff --git a/ecs/src/entity.rs b/ecs/src/entity.rs
new file mode 100644
index 0000000..abc5991
--- /dev/null
+++ b/ecs/src/entity.rs
@@ -0,0 +1,30 @@
+use std::sync::atomic::{AtomicU64, Ordering};
+
+static NEXT_UID: AtomicU64 = AtomicU64::new(0);
+
+/// Unique entity ID.
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Uid
+{
+    inner: u64,
+}
+
+impl Uid
+{
+    pub fn new(uid: u64) -> Self
+    {
+        debug_assert!(
+            uid < NEXT_UID.load(Ordering::Relaxed),
+            "Invalid entity UID {uid}"
+        );
+
+        Self { inner: uid }
+    }
+
+    pub fn new_unique() -> Self
+    {
+        Self {
+            inner: NEXT_UID.fetch_add(1, Ordering::Relaxed),
+        }
+    }
+}