{

// We do extraction on the low level to efficiently determine if the message

// contains an object inheriting MergeInterface or TObject. If we did it the

// the following way and catch an exception:

// framework::DataRefUtils::as<MergeInterface>(ref)

// it could cause a memory leak if `ref` contained a non-owning TCollection.

// This way we also avoid doing most of the checks twice.

const static std::string errorPrefix = "Could not extract object to be merged: ";

using DataHeader = o2::header::DataHeader;

auto header = framework::DataRefUtils::getHeader<const DataHeader*>(ref);

if (header->payloadSerializationMethod != o2::header::gSerializationMethodROOT) {

throw std::runtime_error(errorPrefix + "It is not ROOT-serialized");

}

o2::framework::FairTMessage ftm(const_cast<char*>(ref.payload), o2::framework::DataRefUtils::getPayloadSize(ref));

auto* storedClass = ftm.GetClass();

if (storedClass == nullptr) {

throw std::runtime_error(errorPrefix + "Unknown stored class");

}

auto* mergeInterfaceClass = TClass::GetClass(typeid(MergeInterface));

auto* tObjectClass = TClass::GetClass(typeid(TObject));

bool inheritsFromMergeInterface = storedClass->InheritsFrom(mergeInterfaceClass);

bool inheritsFromTObject = storedClass->InheritsFrom(tObjectClass);

if (!inheritsFromMergeInterface && !inheritsFromTObject) {

throw std::runtime_error(

errorPrefix + "Class '" + storedClass->GetName() + "'does not inherit from MergeInterface nor TObject");

}

auto* object = ftm.ReadObjectAny(storedClass);

if (object == nullptr) {

throw std::runtime_error(

errorPrefix + "Failed to read object with name '" + storedClass->GetName() + "' from message using ROOT serialization.");

}

if (inheritsFromMergeInterface) {

MergeInterface* objectAsMergeInterface = inheritsFromTObject ? dynamic_cast<MergeInterface*>(static_cast<TObject*>(object)) : static_cast<MergeInterface*>(object);

if (objectAsMergeInterface == nullptr) {

throw std::runtime_error(errorPrefix + "Could not cast '" + storedClass->GetName() + "' to MergeInterface");

}

objectAsMergeInterface->postDeserialization();

return MergeInterfacePtr(objectAsMergeInterface);

} else {

return TObjectPtr(static_cast<TObject*>(object), algorithm::deleteTCollections);

}