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#ifndef DataFormats_Common_ValidHandle_h
#define DataFormats_Common_ValidHandle_h
/*----------------------------------------------------------------------
Handle: Non-owning "smart pointer" for reference to products and
their provenances.
The data product is always guaranteed to be valid for this handle type.
----------------------------------------------------------------------*/
#include <utility>
#include "DataFormats/Provenance/interface/ProductID.h"
namespace edm {
namespace vhhelper {
void throwIfNotValid(const void*) noexcept(false);
}
template <typename T>
class ValidHandle {
public:
using element_type = T;
ValidHandle() = delete;
ValidHandle(T const* prod, ProductID id) noexcept(false) : product_(prod), id_(id) {
vhhelper::throwIfNotValid(prod);
}
//NOTE: C++ disallows references to null
ValidHandle(T const& prod, ProductID id) noexcept(true) : product_(&prod), id_(id) {}
ValidHandle(const ValidHandle<T>&) = default;
ValidHandle<T>& operator=(ValidHandle<T> const& rhs) = default;
~ValidHandle() = default;
ProductID const& id() const noexcept(true) { return id_; }
T const* product() const noexcept(true) { return product_; }
T const* operator->() const noexcept(true) { return product(); }
T const& operator*() const noexcept(true) { return *product(); }
private:
T const* product_;
ProductID id_;
};
/** Take a handle (e.g. edm::Handle<T> or edm::OrphanHandle<T> and
create a edm::ValidHandle<T>. If the argument is an invalid handle,
an exception will be thrown.
*/
template <typename U>
auto makeValid(const U& iOtherHandleType) noexcept(false) {
vhhelper::throwIfNotValid(iOtherHandleType.product());
//because of the check, we know this is valid and do not have to check again
return ValidHandle<typename U::element_type>(*iOtherHandleType.product(), iOtherHandleType.id());
}
} // namespace edm
#endif
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