Apply micro-optimisation for Nearest API (#6944)

Author: SiarheiFedartsou

CHANGELOG.md

@@ -24,6 +24,7 @@
     - NodeJS:
       - CHANGED: Use node-api instead of NAN. [#6452](https://github.com/Project-OSRM/osrm-backend/pull/6452)
     - Misc:
+      - CHANGED: Apply micro-optimisation for Nearest API. [#6944](https://github.com/Project-OSRM/osrm-backend/pull/6944)
       - CHANGED: Avoid copy of intersection in totalTurnAngle. [#6938](https://github.com/Project-OSRM/osrm-backend/pull/6938)
       - CHANGED: Use std::unordered_map::emplace instead of operator[] when producing JSONs. [#6936](https://github.com/Project-OSRM/osrm-backend/pull/6936)
       - CHANGED: Avoid copy of vectors in MakeRoute function. [#6939](https://github.com/Project-OSRM/osrm-backend/pull/6939)

include/engine/api/nearest_api.hpp

@@ -100,23 +100,23 @@ class NearestAPI final : public BaseAPI
                                auto waypoint = MakeWaypoint({phantom_node});
 
                                util::json::Array nodes;
+                               nodes.values.reserve(2);
 
                                auto node_values = MakeNodes(phantom_node);
 
-                               nodes.values.push_back(node_values.first);
-                               nodes.values.push_back(node_values.second);
-                               waypoint.values["nodes"] = std::move(nodes);
-
+                               nodes.values.emplace_back(node_values.first);
+                               nodes.values.emplace_back(node_values.second);
+                               waypoint.values.emplace("nodes", std::move(nodes));
                                return waypoint;
                            });
-            response.values["waypoints"] = std::move(waypoints);
+            response.values.emplace("waypoints", std::move(waypoints));
         }
 
-        response.values["code"] = "Ok";
+        response.values.emplace("code", "Ok");
         auto data_timestamp = facade.GetTimestamp();
         if (!data_timestamp.empty())
         {
-            response.values["data_version"] = data_timestamp;
+            response.values.emplace("data_version", data_timestamp);
         }
     }