// EdoHandle.h

#ifndef hes_EdoHandle_H
#define hes_EdoHandle_H

// David Adams
// February 2002
//
// Handle for an EDO. A handle used for writing an EDO includes
// the type and address of the transient representation of the EDO.
// A handle used for reading an EDO includes the data required to
// construct this transient representation.
//
// It is expected that there will be a subclass for each file type
// and possibly EDO type.

#include <iosfwd>

namespace hes {

class EdoType;
class FileType;

class EdoHandle {

public:  // functions

  // Make destructor virtual.
  virtual ~EdoHandle();

  // Return if this object is valid.
  // The object is valid if it holds the address of the persistent
  // representation or the data required to construct such an
  // object.
  virtual bool is_valid() const;

  // Return the ID for the type of the referenced object.
  // Should be valid if this object is valid.
  virtual EdoType edo_type() const =0;

  // Return the type of file to which this handle points.
  // Return is invalid if the file assignment is not known.
  virtual FileType file_type() const =0;

  // Return the address of the transient representation of
  // the EDO.
  // Returns 0 if the object has not been constructed.
  virtual const void* address() const =0;

};

}  // end namespace

// Output stream.
std::ostream& operator<<(std::ostream& lhs, const hes::EdoHandle& rhs);

#endif