// ContentId.h

#ifndef ContentId_H
#define ContentId_H

// Class to specify the content of an ATLAS data object.
// The content specification includes type (class ID)
// and key.

#include <string>
#include <iosfwd>

class ContentId {

public:  // typedefs

  typedef unsigned long ClassId;
  typedef std::string Key;

public:  // functions

  // Constructor
  ContentId(ClassId clid=0, Key key="");

  // Validity.
  // Return true except for default constructor.
  bool is_valid() const;

  // Return the class ID.
  ClassId class_id() const { return m_clid; }

  // Return the key.
  Key key() const { return m_key; }

private:  //data

  ClassId m_clid;
  Key m_key;

};

// Ordering.
bool operator<(const ContentId& lhs, const ContentId& rhs);

// Equality.
bool operator==(const ContentId& lhs, const ContentId& rhs);

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

#endif