BaseTabIter.h

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// # BaseTabIter.h: Base class for table iterator
// # Copyright (C) 1994,1995,1996,1997,1999
// # 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_BASETABITER_H
#define TABLES_BASETABITER_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/tables/Tables/Table.h>
#include <casacore/casa/Utilities/Compare.h>
#include <casacore/casa/Containers/Block.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// # Forward Declarations
class TableColumn;
class RefTable;
class String;
 
// <summary>
// Base class for table iterator
// </summary>
 
// <use visibility=local>
 
// <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="">
// </reviewed>
 
// <prerequisite>
// # Classes you should understand before using this one.
//   <li> BaseTable
//   <li> TableIterator
// </prerequisite>
 
// <etymology>
// BaseTableIterator is the base class for the classes doing
// the actual iterating through a table.
// </etymology>
 
// <synopsis>
// BaseTableIterator is the base class for the table iterators.
// It is a letter class of the envelope TableIterator.
// Currently there are no classes derived from BaseTableIterator,
// since it can do all the work itself. However, in the future
// this need not to be true anymore.
//
// BaseTableIterator iterates by sorting the table in the required
// order and then creating a RefTable for each step containing the
// rows for that iteration step. Each iteration step assembles the
// rows with equal key values.
// </synopsis>
 
// # <todo asof="$DATE:$">
// # A List of bugs, limitations, extensions or planned refinements.
// # </todo>
 
class BaseTableIterator {
 public:
  // Create the table iterator to iterate through the given
  // columns in the given order. The given compare objects
  // will be used for the sort and to compare if values are equal.
  // If a compare object in cmpObjs is null, the default ObjCompare<T>
  // will be used.
  // If cacheIterationBoundaries is set to true then the iteration
  // boundaries computed at construction time while sorting the table
  // are used when advancing with next(). Otherwise, for each next()
  // call the comparison functions are reevaluated again to get the
  // iteration boundary. This improves performance in general but will
  // break existing applications that change the comparison objects
  // (cmpObjs) between iterations.
  BaseTableIterator(const std::shared_ptr<BaseTable>&, const Block<String>& columnNames,
                    const Block<std::shared_ptr<BaseCompare>>& cmpObjs, const Block<Int>& orders,
                    int option, bool cacheIterationBoundaries = false);
 
  // Clone this iterator.
  BaseTableIterator* clone() const;
 
  virtual ~BaseTableIterator();
 
  // Assignment is not needed, because the assignment operator in
  // the envelope class TableIterator has reference semantics.
  BaseTableIterator& operator=(const BaseTableIterator&) = delete;
 
  // Reset the iterator (i.e. restart iteration).
  virtual void reset();
 
  // Return the next group.
  virtual std::shared_ptr<BaseTable> next();
 
  virtual void copyState(const BaseTableIterator&);
 
  // Report Name of slowest sort column that changed (according to the
  // comparison function) to terminate the most recent call to next()
  // Enables clients to sense iteration boundary properties
  // and organize associated iterations
  inline const String& keyChangeAtLastNext() const { return keyChangeAtLastNext_p; }
 
 protected:
  std::shared_ptr<BaseTable> sortTab_p;  // # Table sorted in iteration order
  rownr_t lastRow_p;                     // # last row used from reftab
  uInt nrkeys_p;                         // # nr of columns in group
  String keyChangeAtLastNext_p;          // # name of column that terminated most recent next()
  Block<BaseColumn*> colPtr_p;           // # pointer to column objects
  Block<std::shared_ptr<BaseCompare>> cmpObj_p;  // # comparison object per column
 
  // Copy constructor (to be used by clone)
  BaseTableIterator(const BaseTableIterator&);
 
  std::shared_ptr<BaseTable> noCachedIterBoundariesNext();
 
 private:
  Block<void*> lastVal_p;  // # last value per column
  Block<void*> curVal_p;   // # current value per column
 
  std::shared_ptr<Vector<rownr_t>> sortIterBoundaries_p;
  std::shared_ptr<Vector<size_t>> sortIterKeyIdxChange_p;
  Vector<rownr_t>::iterator sortIterBoundariesIt_p;
  Vector<size_t>::iterator sortIterKeyIdxChangeIt_p;
  RefTable* aRefTable_p;                    // # RefTable returned in each iteration
  std::shared_ptr<BaseTable> aBaseTable_p;  // # Same as above for automatic deletion
};
 
}  // namespace casacore
 
#endif