HCMethods.h

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#ifndef Framework_HCMethods_h
#define Framework_HCMethods_h
// -*- C++ -*-
//
// Package:     HeteroContainer
// Module:      HCMethods
//
// Description: Templated methods to be used to 'construct' a
//              heterogenous container
//
// Usage:
//    <usage>
//
// Author:      Chris D. Jones
// Created:     Sun Mar 27 15:58:05 EDT 2005
//
 
// system include files
 
#include "FWCore/Framework/interface/HCTypeTag.h"
#include <type_traits>
// user include files
 
namespace edm {
  namespace eventsetup {
    namespace heterocontainer {
      template <class Type, class Key, class IdTag>
      inline Key makeKey(const IdTag& iIdTag) {
        HCTypeTag typeTag = HCTypeTag::make<Type>();
        return Key(typeTag, iIdTag);
      }
 
      template <class Type, class Key>
      inline Key makeKey() {
        HCTypeTag typeTag = HCTypeTag::make<Type>();
        return Key(typeTag);
      }
 
      //NOTE: the following functions use this struct to determine
      //  how to find the 'Type' (what is returned from the Storage)
      //  when given only an ItemType (what is stored in Storage).
      //  This allows the Storage to be composed of proxies instead of
      //  the 'Type' themselves
      template <class Key, class ItemType>
      struct type_from_itemtype {
        typedef typename std::remove_const<ItemType>::type Type;
      };
 
      template <class Key, class ItemType, class Storage, class IdTag>
      inline bool insert(Storage& iStorage, ItemType* iItem, const IdTag& iIdTag) {
        return iStorage.insert(makeKey<typename type_from_itemtype<Key, ItemType>::Type, Key>(iIdTag), iItem);
      }
 
      template <class Key, class ItemType, class Storage>
      inline bool insert(Storage& iStorage, ItemType* iItem) {
        return iStorage.insert(makeKey<ItemType, Key>(), iItem);
      }
 
      template <class Key, class ItemType, class Storage, class IdTag>
      inline ItemType* find(const Storage& iStorage, const IdTag& iIdTag) {
        //The cast should be safe since the Key tells us the type
        return static_cast<ItemType*>(
            iStorage.find(makeKey<typename type_from_itemtype<Key, ItemType>::Type, Key>(iIdTag)));
      }
 
      template <class Key, class ItemType, class Storage>
      inline ItemType* find(const Storage& iStorage) {
        //The cast should be safe since the Key tells us the type
        return static_cast<ItemType*>(iStorage.find(makeKey<typename type_from_itemtype<Key, ItemType>::Type, Key>()));
      }
    }  // namespace heterocontainer
  }    // namespace eventsetup
}  // namespace edm
#endif