OrphanHandleBase.h

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#ifndef DataFormats_Common_OrphanHandleBase_h
#define DataFormats_Common_OrphanHandleBase_h
 
/*----------------------------------------------------------------------
  
OrphanHandle: Non-owning "smart pointer" for reference to EDProducts.
 
This is a very preliminary version, and lacks safety features and
elegance.
 
If the pointed-to WrapperBase is destroyed, use of the OrphanHandle
becomes undefined. There is no way to query the OrphanHandle to
discover if this has happened.
 
OrphanHandles can have:
  -- Product pointer null and id == 0;
  -- Product pointer valid and id != 0;
 
To check validity, one can use the isValid() function.
 
----------------------------------------------------------------------*/
 
#include "DataFormats/Provenance/interface/ProductID.h"
#include <cassert>
#include <algorithm>
 
namespace edm {
  class OrphanHandleBase {
  public:
    OrphanHandleBase() : product_(), id_(ProductID()) {}
 
    OrphanHandleBase(void const* iProd, ProductID const& iId) : product_(iProd), id_(iId) { assert(iProd); }
 
    ~OrphanHandleBase() {}
 
    void clear() {
      product_ = nullptr;
      id_ = ProductID();
    }
 
    void swap(OrphanHandleBase& other) {
      using std::swap;
      swap(product_, other.product_);
      std::swap(id_, other.id_);
    }
 
    OrphanHandleBase& operator=(OrphanHandleBase const& rhs) {
      OrphanHandleBase temp(rhs);
      this->swap(temp);
      return *this;
    }
 
    bool isValid() const { return product_ && id_ != ProductID(); }
 
    ProductID id() const;
 
  protected:
    void const* productStorage() const;
 
  private:
    void const* product_;
    ProductID id_;
  };
 
  // Free swap function
  inline void swap(OrphanHandleBase& a, OrphanHandleBase& b) { a.swap(b); }
}  // namespace edm
 
#endif