MappedArrayEngine.h

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// # MappedArrayEngine.h: Templated virtual column engine to map a table array
// # Copyright (C) 2005
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library is distributed in the hope that it will be useful, but WITHOUT
// # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
// #                        520 Edgemont Road
// #                        Charlottesville, VA 22903-2475 USA
 
#ifndef TABLES_MAPPEDARRAYENGINE_H
#define TABLES_MAPPEDARRAYENGINE_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/tables/DataMan/BaseMappedArrayEngine.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// <summary>
// Templated virtual column engine to map the data type of a table array
// </summary>
 
// <use visibility=export>
 
// <reviewed reviewer="Gareth Hunt" date="94Nov17" tests="">
// </reviewed>
 
// <prerequisite>
// # Classes you should understand before using this one.
//   <li> VirtualColumnEngine
//   <li> VirtualArrayColumn
// </prerequisite>
 
// <synopsis>
// MappedArrayEngine is a virtual column engine which maps an array
// of one type to another type (without any scaling).
//
// An engine object should be used for one column only, because the stored
// column name is part of the engine. If it would be used for more than
// one column, they would all share the same stored column.
// When the engine is bound to a column, it is checked if the name
// of that column matches the given virtual column name.
//
// The engine can be used for a column containing any kind of array
// (thus direct or indirect, fixed or variable shaped)) as long as the
// virtual array can be stored in the stored array. Thus a fixed shaped
// virtual can use a variable shaped stored, but not vice versa.
// A fixed shape indirect virtual can use a stored with direct arrays.
// </synopsis>
 
// <motivation>
// For precision it is sometimes needed to store the visibility data in a
// MeasurementSet in double precision. To be able to use other applications
// on such data, it is needed to map them to single precision.
//
// Because the engine can serve only one column, it was possible to
// combine the engine and the column functionality in one class.
// This has been achieved using multiple inheritance.
// The advantage of this is that only one templated class is used,
// so less template instantiations are needed.
// </motivation>
 
// <example>
// <srcblock>
// // Create the table description and 2 columns with indirect arrays in it.
// // The Int column will be stored, while the double will be
// // used as virtual.
// TableDesc tableDesc ("", TableDesc::Scratch);
// tableDesc.addColumn (ArrayColumnDesc<Int> ("storedArray"));
// tableDesc.addColumn (ArrayColumnDesc<double> ("virtualArray"));
//
// // Create a new table using the table description.
// SetupNewTable newtab (tableDesc, "tab.data", Table::New);
//
// // Create the array mapping engine to map from double to Int
// // and bind it to the double column.
// // Create the table.
// MappedArrayEngine<double,Int> mappingEngine("virtualArray",
//                                             "storedArray", 10);
// newtab.bindColumn ("virtualArray", mappingEngine);
// Table table (newtab);
//
// // Store a 3-D array (with dim. 2,3,4) into each row of the column.
// // The shape of each array in the column is implicitly set by the put
// // function. This will also set the shape of the underlying Int array.
// ArrayColumn data (table, "virtualArray");
// Array<double> someArray(IPosition(4,2,3,4));
// someArray = 0;
// for (rownr_t i=0, i<10; i++) {          // table will have 10 rows
//     table.addRow();
//     data.put (i, someArray)
// }
// </srcblock>
// </example>
 
// <templating arg=VirtualType>
//  <li> only suited for built-in numerics data types
// </templating>
// <templating arg=StoredType>
//  <li> only suited for built-in numerics data types
// </templating>
 
template <class VirtualType, class StoredType>
class MappedArrayEngine : public BaseMappedArrayEngine<VirtualType, StoredType> {
  // # Make members of parent class known.
 public:
  using BaseMappedArrayEngine<VirtualType, StoredType>::virtualName;
 
 protected:
  using BaseMappedArrayEngine<VirtualType, StoredType>::storedName;
  using BaseMappedArrayEngine<VirtualType, StoredType>::table;
  using BaseMappedArrayEngine<VirtualType, StoredType>::column;
  using BaseMappedArrayEngine<VirtualType, StoredType>::setNames;
 
 public:
  // Construct an engine to map all arrays in a column.
  // StoredColumnName is the name of the column where the mapped
  // data will be put and must have data type StoredType.
  // The virtual column using this engine must have data type VirtualType.
  MappedArrayEngine(const String& virtualColumnName, const String& storedColumnName);
 
  // Construct from a record specification as created by dataManagerSpec().
  MappedArrayEngine(const Record& spec);
 
  // Destructor is mandatory.
  ~MappedArrayEngine();
 
  // Assignment is not needed and therefore forbidden.
  MappedArrayEngine<VirtualType, StoredType>& operator=(
      const MappedArrayEngine<VirtualType, StoredType>&) = delete;
 
  // Return the type name of the engine (i.e. its class name).
  virtual String dataManagerType() const;
 
  // Get the name given to the engine (is the virtual column name).
  virtual String dataManagerName() const;
 
  // Record a record containing data manager specifications.
  virtual Record dataManagerSpec() const;
 
  // Return the name of the class.
  // This includes the names of the template arguments.
  static String className();
 
  // Register the class name and the static makeObject "constructor".
  // This will make the engine known to the table system.
  // The automatically invoked registration function in DataManReg.cc
  // contains MappedArrayEngine<double,Int>.
  // Any other instantiation of this class must be registered "manually"
  // (or added to DataManReg.cc).
  static void registerClass();
 
 private:
  // Copy constructor is only used by clone().
  // (so it is made private).
  MappedArrayEngine(const MappedArrayEngine<VirtualType, StoredType>&);
 
  // Clone the engine object.
  DataManager* clone() const;
 
  // Copy the stored array to the virtual array.
  virtual void mapOnGet(Array<VirtualType>& array, const Array<StoredType>& stored);
 
  // Copy the virtual array to the stored array.
  virtual void mapOnPut(const Array<VirtualType>& array, Array<StoredType>& stored);
 
 public:
  // Define the "constructor" to construct this engine when a
  // table is read back.
  // This "constructor" has to be registered by the user of the engine.
  // If the engine is commonly used, its registration can be added
  // to the registerAllCtor function in DataManReg.cc.
  // That function gets automatically invoked by the table system.
  static DataManager* makeObject(const String& dataManagerType, const Record& spec);
};
 
}  // namespace casacore
 
#ifndef CASACORE_NO_AUTO_TEMPLATES
#include <casacore/tables/DataMan/MappedArrayEngine.tcc>
#endif  // # CASACORE_NO_AUTO_TEMPLATES
#endif