ISMIndex.h

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// # ISMIndex.h: The Index of the Incremental Storage Manager
// # Copyright (C) 1996,1997,1999,2005
// # 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_ISMINDEX_H
#define TABLES_ISMINDEX_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/casa/Containers/Block.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// # Forward declarations
class ISMBase;
class AipsIO;
 
// <summary>
// The Index of the Incremental Storage Manager
// </summary>
 
// <use visibility=local>
 
// <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="">
// </reviewed>
 
// <prerequisite>
// # Classes you should understand before using this one.
//   <li> <linkto class=ISMBase>ISMBase</linkto>
// </prerequisite>
 
// <etymology>
// ISMIndex represents the index in the Incremental Storage Manager.
// </etymology>
 
// <synopsis>
// ISMIndex maintains an index of all buckets in an ISM (Incremental Storage
// Manager). The index consists of the starting row number and the
// bucket number of each bucket in the BucketCache object of the ISM.
// When the ISM is opened, the entire index is read in and kept in memory.
// When the ISM is closed or flushed, the index is written back after
// all buckets in the file. A little header at the beginning of the file
// indicates the starting offset of the index.
// </synopsis>
 
// <motivation>
// ISMIndex encapsulates all operations on the ISM index.
// </motivation>
 
// # <todo asof="$DATE:$">
// # A List of bugs, limitations, extensions or planned refinements.
// # </todo>
 
class ISMIndex {
 public:
  ISMIndex();
 
  // The destructor closes the file (if opened).
  ~ISMIndex();
 
  // Forbid copy constructor.
  ISMIndex(const ISMIndex&) = delete;
 
  // Forbid assignment.
  ISMIndex& operator=(const ISMIndex&) = delete;
 
  // Add a row.
  void addRow(rownr_t nrrow);
 
  // Remove a row from the index.
  // If the result of this is that the entire bucket gets empty,
  // that bucketnr is returned. Otherwise -1 is returned.
  Int removeRow(rownr_t rownr);
 
  // Get the bucket number for the given row.
  // Also return the start row of the bucket and the number of rows in it.
  uInt getBucketNr(rownr_t rownr, rownr_t& bucketStartRow, rownr_t& bucketNrrow) const;
 
  // Read the bucket index from the AipsIO object.
  void get(AipsIO& os);
 
  // Write the bucket index into the AipsIO object.
  void put(AipsIO& os);
 
  // Add a bucket number to the index.
  // Argument <src>rownr</src> gives the starting row of the bucket.
  // It is used to add the bucket number at the correct place
  // (such that the row numbers are kept in ascending order).
  void addBucketNr(rownr_t rownr, uInt bucketNr);
 
  // Get the number of the next bucket from the index and return
  // it in <src>bucketNr</src>. The starting row of that bucket and
  // the number of rows in the bucket are also returned.
  // Return status False indicates that no more buckets are available.
  // <br>The start of the iteration is indicated by cursor=0.
  // The first bucket returned is the bucket containing the rownr
  // given in <src>bucketStartRow</src> (thus set bucketStartRow
  // to 0 if you want to start at the first bucket).
  // <br>The next iterations return the next bucket number and fill
  // the starting row and number of rows.
  Bool nextBucketNr(uInt& cursor, rownr_t& bucketStartRow, rownr_t& bucketNrrow,
                    uInt& bucketNr) const;
 
  // Show the index.
  void show(std::ostream&) const;
 
 private:
  // Get the index of the bucket containing the given row.
  uInt getIndex(rownr_t rownr) const;
 
  // # Declare member variables.
  //  Number of entries used.
  uInt nused_p;
  // Rownr index (i.e. row rows_p[i] starts in bucketNr_p[i]).
  Block<rownr_t> rows_p;
  // Corresponding bucket number.
  Block<uInt> bucketNr_p;
};
 
}  // namespace casacore
 
#endif