TableExprId.h

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// # TableExprId.h: The identification of a TaQL selection subject
// # Copyright (C) 2000
// # 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_TABLEEXPRID_H
#define TABLES_TABLEEXPRID_H
 
// # Includes
#include <casacore/casa/aips.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// # Forward Declarations
class RecordInterface;
class TableExprData;
 
// <summary>
// The identification of a TaQL selection subject.
// </summary>
 
// <use visibility=export>
 
// <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="">
// </reviewed>
 
// <prerequisite>
//   <li> <linkto class="TableExprNode">TableExprNode</linkto>.
// </prerequisite>
 
// <synopsis>
// This class provides the user the ability to identify the data objects
// to test in a TaQL expression. In this way a TaQL expression is not
// limited to tables, but can be used for any set of data.
// Three types are available:
// <ol>
//  <li> A row number giving the row to test in a table.
//       It also contains a sequence number (0..n) which is used to get the
//       result calculated by aggregate functions.
//  <li> A <linkto class=RecordInterface>RecordInterface</linkto>
//       object giving the record to test.
//  <li> A <linkto class=TableExprData>TableExprData</linkto>
//       object giving the abstract base class of an object holding
//       the data to test. In this way any data can be used.
// </ol>
// The TaQL expression must be setup with this in mind by constructing
// the appropriate <linkto class=TableExprNode>TableExprNode</linkto>
// leaf objects.
// <br>
// When used for tables, the function <linkto class=Table>Table::col</linkto>
// should be used to create the <src>TableExprNode</src> objects for the
// table columns to be used in the expression.
// <br>
// For the other cases class
// <linkto class=TableExprNodeRecordField>TableExprNodeRecordField</linkto>
// has to be used to know the index of the fields in the expression.
// It uses a record (description) for this purpose.
// </synopsis>
 
// <example>
// <srcblock>
// </srcBlock>
// </example>
 
// <motivation>
// This class makes it possible that TaQL can be used in a very versatile way.
// </motivation>
 
// # <todo asof="1996/03/12">
// # </todo>
 
class TableExprId {
 public:
  // Default constructor sets rownr to -1.
  TableExprId();
 
  // Construct it from a row number.
  TableExprId(rownr_t rowNumber);
 
  // Construct it from a Record object.
  TableExprId(const RecordInterface&);
 
  // Construct it from pointers to data.
  TableExprId(const TableExprData& data);
 
  ~TableExprId() {}
 
  // Is the id given by row number?
  Bool byRow() const;
 
  // Is the id given as a RecordInterface?
  Bool byRecord() const;
 
  // Is the id given as a TableExprData?
  Bool byData() const;
 
  // Get the row number.
  Int64 rownr() const;
 
  // Get the Record reference.
  const RecordInterface& record() const;
 
  // Get the data reference.
  const TableExprData& data() const;
  // Set the row number.
 
  void setRownr(rownr_t rownr);
 
  // Set the record.
  void setRecord(const RecordInterface&);
 
 private:
  Int type_p;
  union {
    Int64 row_p;
    const RecordInterface* record_p;
    const TableExprData* data_p;
  };
};
 
inline TableExprId::TableExprId() : type_p(0), row_p(-1) {}
 
inline TableExprId::TableExprId(rownr_t rowNumber) : type_p(0), row_p(rowNumber) {}
 
inline TableExprId::TableExprId(const RecordInterface& record) : type_p(-1), record_p(&record) {}
 
inline TableExprId::TableExprId(const TableExprData& data) : type_p(-2), data_p(&data) {}
 
inline Int64 TableExprId::rownr() const { return row_p; }
 
inline const RecordInterface& TableExprId::record() const { return *record_p; }
 
inline const TableExprData& TableExprId::data() const { return *data_p; }
 
inline void TableExprId::setRownr(rownr_t rownr) { row_p = rownr; }
 
inline void TableExprId::setRecord(const RecordInterface& record) { record_p = &record; }
 
inline Bool TableExprId::byRow() const { return type_p >= 0; }
 
inline Bool TableExprId::byRecord() const { return type_p == -1; }
 
inline Bool TableExprId::byData() const { return type_p == -2; }
 
}  // namespace casacore
 
#endif