DataObjID.h

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#ifndef GAUDIKERNEL_DATAOBJID
#define GAUDIKERNEL_DATAOBJID 1

#include "GaudiKernel/ClassID.h"
#include "GaudiKernel/StatusCode.h"

#include <iostream>
#include <mutex>
#include <string>
#include <unordered_set>

//---------------------------------------------------------------------------

//---------------------------------------------------------------------------

struct DataObjID_Hasher;
class IClassIDSvc;

class DataObjID
{
public:
  friend DataObjID_Hasher;

  DataObjID()                   = default;
  DataObjID( const DataObjID& ) = default;
  DataObjID( const std::string& key );
  DataObjID( const CLID& clid, const std::string& key );
  DataObjID( const std::string& className, const std::string& key );

  // only return the last part of the key
  const std::string& key() const { return m_key; }

  bool empty() const { return m_key.empty(); }

  // combination of the key and the ClassName, mostly for debugging
  std::string fullKey() const;

  CLID clid() const { return m_clid; }

  void updateKey( const std::string& key );

  friend bool operator<( const DataObjID& lhs, const DataObjID& rhs ) { return lhs.m_hash < rhs.m_hash; }
  friend bool operator==( const DataObjID& lhs, const DataObjID& rhs ) { return lhs.m_hash == rhs.m_hash; }
  friend bool operator!=( const DataObjID& lhs, const DataObjID& rhs ) { return !( lhs == rhs ); }

  friend StatusCode parse( DataObjID& dest, const std::string& src );
  friend std::ostream& toStream( const DataObjID& v, std::ostream& o );
  friend std::ostream& operator<<( std::ostream& os, const DataObjID& d ) { return toStream( d, os ); }

private:
  void hashGen();
  void setClid();
  void setClassName();

  CLID        m_clid{0};
  std::size_t m_hash{0};

  std::string m_key{"INVALID"};
  std::string m_className;

  static IClassIDSvc*   p_clidSvc;
  static std::once_flag m_ip;
};

inline DataObjID::DataObjID( const std::string& key ) : m_key( key ) { hashGen(); }

inline DataObjID::DataObjID( const CLID& clid, const std::string& key ) : m_clid( clid ), m_key( key )
{
  setClassName();
  hashGen();
}

inline DataObjID::DataObjID( const std::string& className, const std::string& key )
    : m_key( key ), m_className( className )
{
  setClid();
  hashGen();
}

inline void DataObjID::updateKey( const std::string& key )
{
  m_key = key;
  hashGen();
}

struct DataObjID_Hasher {
  std::size_t operator()( const DataObjID& k ) const { return k.m_hash; }
};

using DataObjIDColl = std::unordered_set<DataObjID, DataObjID_Hasher>;

namespace Gaudi
{
  namespace Details
  {
    namespace Property
    {
      template <typename T>
      struct StringConverter;

      template <>
      struct StringConverter<DataObjIDColl> {
        std::string toString( const DataObjIDColl& v );
        DataObjIDColl fromString( const DataObjIDColl&, const std::string& );
      };
    }
  }
}

#endif