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diff --git a/source/blender/io/common/IO_dupli_persistent_id.hh b/source/blender/io/common/IO_dupli_persistent_id.hh
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+++ b/source/blender/io/common/IO_dupli_persistent_id.hh
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+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2020 Blender Foundation.
+ * All rights reserved.
+ */
+#ifndef __IO_COMMON_DUPLI_PERSISTENT_ID_H__
+#define __IO_COMMON_DUPLI_PERSISTENT_ID_H__
+
+#include "BKE_duplilist.h"
+
+#include "DNA_object_types.h" /* For MAX_DUPLI_RECUR */
+
+#include <array>
+#include <optional>
+#include <ostream>
+
+namespace blender::io {
+
+/* Wrapper for DupliObject::persistent_id that can act as a map key. */
+class PersistentID {
+ protected:
+  constexpr static int array_length_ = MAX_DUPLI_RECUR;
+  typedef std::array<int, array_length_> PIDArray;
+  PIDArray persistent_id_;
+
+  explicit PersistentID(const PIDArray &persistent_id_values);
+
+ public:
+  PersistentID();
+  explicit PersistentID(const DupliObject *dupli_ob);
+
+  /* Return true iff the persistent IDs are the same, ignoring the first digit. */
+  bool is_from_same_instancer_as(const PersistentID &other) const;
+
+  /* Construct the persistent ID of this instance's instancer. */
+  PersistentID instancer_pid() const;
+
+  /* Construct a string representation by reversing the persistent ID.
+   * In case of a duplicator that is duplicated itself as well, this
+   * results in strings like:
+   * "3" for the duplicated duplicator, and
+   * "3-0", "3-1", etc. for its duplis. */
+  std::string as_object_name_suffix() const;
+
+  friend bool operator==(const PersistentID &persistent_id_a, const PersistentID &persistent_id_b);
+  friend bool operator<(const PersistentID &persistent_id_a, const PersistentID &persistent_id_b);
+  friend std::ostream &operator<<(std::ostream &os, const PersistentID &persistent_id);
+
+ private:
+  void copy_values_from(const PIDArray &persistent_id_values);
+};
+
+}  // namespace blender::io
+
+#endif  // __IO_COMMON_DUPLI_PARENT_FINDER_H__