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CdbBdb2RooNTupleConverter.hh

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#ifndef CDBROOCONVERSIONFWK_BDB_2_ROO_NTUPLE_CONVERTER_HH
#define CDBROOCONVERSIONFWK_BDB_2_ROO_NTUPLE_CONVERTER_HH

// File and Version Information:
//      $Id: CdbBdb2RooNTupleConverter.hh,v 1.2 2005/07/14 16:10:48 jtinslay Exp $

#include "CdbBase/CdbCPtr.hh"

#include "CdbRooConversionFwk/CdbBdb2RooPayloadConverter.hh"

#include "CdbBdbTable/CdbBdbNTupleConversionRules.hh"
#include "CdbRooTable/CdbRooNTupleConversionRules.hh"

/// The converter for Cdb N-Tuples
/**
  * This class represents a family of converters based on types of persistent
  * classes passed as template parameters.
  *
  * The parameters of the template are:
  *
  *   'P' - the input  "Bdb" object type. This type should be a model of
  *         CDB persistent N-Tuples  based on an abstract interface
  *         of the CdbBdbNTupleP class. 
  *
  *   'R' - the output "Roo" object type. The actual type has to be a model
  *         of the 'CdbRooNTupleR< R::element_type >' class.
  *
  *   'P_ELEMENT_CONVERSION_RULES' - rules for converting a persistent element type
  *                                  into its transient counterpart for the "Bdb" technology.
  *
  *   'R_ELEMENT_CONVERSION_RULES' - rules for converting a persistent element type
  *                                  into its transient counterpart for the "Roo" technology.
  *
  * Tests for a compatibility of actual types used as template parameters will be
  * be performed both at a compilation and run time.
  *
  * By default the converter will be using default conversion rules for element types,
  * which is good for elementary types. For complex user defined types the corresponding
  * element type converters must be provided.
  *
  * CLASS DESIGN NOTES:
  *
  *   1. The persistent type verification is performed by the direct base
  *      class of the converter and in the c-tor of the current class (for a compliance
  *      with the model of Generic N-tuples).
  *
  *   2. All (but the default) class's constructors, its assignment operator, and its destructor are
  *      generated automatically by a C++ compiler. They're all public.
  *
  *   3. Two element conversion rules (one for each technology) are needed to avoid
  *      knowing direct element type conversion rules like:
  *
  *        P::ElementType -> R::ElementType
  *
  *      We're replacing this with an indirect (through a common transient) type
  *      conversion chain:
  *
  *        P::ElementType -> T -> R::ElementType
  *
  *      See more details in the implementation file of the class.
  *
  * @see class CdbBdb2RooPayloadConverter
  * @see class CdbBdbNTupleConversionReverseRules_Default
  * @see class CdbRooNTupleConversionReverseRules_Default
  */
template< class P,
          class R,
          class P_ELEMENT_CONVERSION_RULES = CdbBdbNTupleConversionReverseRules_Default< typename P::ElementType >,
          class R_ELEMENT_CONVERSION_RULES = CdbRooNTupleConversionReverseRules_Default< typename R::ElementType > >

class CdbBdb2RooNTupleConverter : public CdbBdb2RooPayloadConverter<P,R> {

public:

  /// Default constructor
  /**
    * It will perform additional type checking for the specified persistent types.
    */
    CdbBdb2RooNTupleConverter( );

protected:

  /// Implement a user-defined conversion
  /**
    * Implements the corresponding method from the base class or interface.
    *
    * @see CdbRooConverterBase::userDefinedConversion()
    */
    virtual CdbStatus userDefinedConversion( const BdbRef(BdbObject)& theInputObjectRef,
                                             R*&                      theOutputObjectPtr
                                           ) const;
};

#ifdef     BABAR_COMP_INST
#include "CdbRooConversionFwk/CdbBdb2RooNTupleConverter.cc"
#endif  // BABAR_COMP_INST

#endif  // CDBROOCONVERSIONFWK_BDB_2_ROO_NTUPLE_CONVERTER_HH

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