[DCS] Ensure DataPointCompositeObject is trivially copyable and add a getValue free function

Author: aphecetche

Detectors/DCS/include/DetectorsDCS/DataPointCompositeObject.h

@@ -254,8 +254,29 @@ struct alignas(128) DataPointCompositeObject final {
                  (char*)&dpcom.data.payload_pt1, 56);
     }
   }
+
+  /**
+    * The destructor for DataPointCompositeObject so it is not deleted
+    * and thus DataPointCompositeObject is trivially copyable
+    */
+  ~DataPointCompositeObject() noexcept = default;
   ClassDefNV(DataPointCompositeObject, 1);
 };
+
+/**
+  * Return the value contained in the DataPointCompositeObject, if possible.
+  *
+  * @tparam T the expected type of the value
+  *
+  * @param dpcom the DataPointCompositeObject the value is extracted from
+  *
+  * @returns the value of the data point
+  *
+  * @throws if the DeliveryType of the data point is not compatible with T
+  */
+template <typename T>
+T getValue(const DataPointCompositeObject& dpcom);
+
 } // namespace dcs
 } // namespace o2
 

Detectors/DCS/src/DataPointCompositeObject.cxx

@@ -13,3 +13,61 @@
 using namespace o2::dcs;
 
 ClassImp(DataPointCompositeObject);
+
+namespace o2::dcs
+{
+template<typename T, o2::dcs::DeliveryType dt>
+T getValueImpl(const DataPointCompositeObject& dpcom) {
+union Converter {
+  uint64_t raw_data;
+  T t_value;
+};
+  if (dpcom.id.get_type() != dt) {
+    throw std::runtime_error("DPCOM is of unexpected type " + o2::dcs::show(dt));
+  }
+  Converter converter;
+  converter.raw_data = dpcom.data.payload_pt1;
+  return converter.t_value;
+}
+
+// only specialize the getValue function for the types we support :
+//
+// - double
+// - uint32_t
+// - int32_t
+// - char 
+// - bool
+
+// template<>
+// double getValueImpl<double,DeliveryType::RAW_DOUBLE>(const DataPointCompositeObject&);
+//
+template<>
+double getValue(const DataPointCompositeObject& dpcom)
+{
+  return getValueImpl<double,DeliveryType::RAW_DOUBLE>(dpcom);
+}
+
+template <>
+uint32_t getValue(const DataPointCompositeObject& dpcom)
+{
+  return getValueImpl<uint32_t,DeliveryType::RAW_UINT>(dpcom);
+}
+
+template <>
+int32_t getValue(const DataPointCompositeObject& dpcom)
+{
+  return getValueImpl<int32_t,DeliveryType::RAW_INT>(dpcom);
+}
+
+template <>
+char getValue(const DataPointCompositeObject& dpcom)
+{
+  return getValueImpl<char,DeliveryType::RAW_CHAR>(dpcom);
+}
+
+template <>
+bool getValue(const DataPointCompositeObject& dpcom)
+{
+  return getValueImpl<bool,DeliveryType::RAW_BOOL>(dpcom);
+}
+} // namespace o2::dcs