Setup routing.

include/internal/vase/iterators/line.h

@@ -19,4 +19,56 @@ struct LineIterator {
   bool next(std::string *line);
   uint64_t byte_offset();
 };
+
+struct Iterator {
+  Shard *root;
+  std::string line;
+
+  Iterator(Shard *root, uint64_t line_num)
+      : root(root), it(root, line_num, Direction::Forward) {
+    Shard::retain(root);
+  }
+
+  ~Iterator() {
+    Shard::release(root);
+  }
+
+  Iterator(const Iterator &other)
+      : root(other.root), it(other.it) {
+    Shard::retain(root);
+  }
+
+  Iterator &operator=(const Iterator &other) {
+    if (this != &other) {
+      Shard::retain(other.root);
+      Shard::release(root);
+      root = other.root;
+      it = other.it;
+    }
+    return *this;
+  }
+
+  Iterator(Iterator &&other) noexcept
+      : root(other.root), it(std::move(other.it)) {
+    other.root = nullptr;
+  }
+
+  Iterator &operator=(Iterator &&other) noexcept {
+    if (this != &other) {
+      Shard::release(root);
+      root = other.root;
+      it = std::move(other.it);
+      other.root = nullptr;
+    }
+    return *this;
+  }
+
+  std::string &next() {
+    it.next(&line);
+    return line;
+  }
+
+private:
+  LineIterator it;
+};
 } // namespace crib::internal::vase