Add std::hash<podio::ObjectID> specialization

AIDASoft · Feb 11, 2025 · 789f3c2 · 789f3c2
1 parent c9f1d04
commit 789f3c2
Showing 1 changed file with 13 additions and 0 deletions.
diff --git a/include/podio/ObjectID.h b/include/podio/ObjectID.h
@@ -2,6 +2,7 @@
 #define PODIO_OBJECTID_H
 
 #include <cstdint>
+#include <functional>
 #include <iomanip>
 #include <ostream>
 
@@ -49,4 +50,16 @@ inline void to_json(nlohmann::json& j, const podio::ObjectID& id) {
 
 } // namespace podio
 
+template<>
+struct std::hash<podio::ObjectID>
+{
+    std::size_t operator()(const podio::ObjectID& id) const noexcept
+    {
+        auto hash_collectionID = std::hash<uint32_t>{}(id.collectionID);
+        auto hash_index = std::hash<int>{}(id.index);
+
+        return hash_collectionID ^ hash_index;
+    }
+};
+
 #endif