feat(nbstore): new doc sync engine (#8918)

packages/common/nbstore/src/utils/is-empty-update.ts

@@ -0,0 +1,13 @@
+/**
+ * Tell a binary is empty yjs binary or not.
+ *
+ * NOTE:
+ *   `[0, 0]` is empty yjs update binary
+ *   `[0]` is empty yjs state vector binary
+ */
+export function isEmptyUpdate(binary: Uint8Array) {
+  return (
+    binary.byteLength === 0 ||
+    (binary.byteLength === 2 && binary[0] === 0 && binary[1] === 0)
+  );
+}