TableSyncData.h

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// # TableSyncData.h: Class to hold table synchronization data
// # Copyright (C) 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_TABLESYNCDATA_H
#define TABLES_TABLESYNCDATA_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/casa/Containers/Block.h>
#include <casacore/casa/IO/MemoryIO.h>
#include <casacore/casa/IO/AipsIO.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// <summary>
// Class to hold table synchronization data.
// </summary>
 
// <use visibility=local>
 
// <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="tTable" demos="">
// </reviewed>
 
// <prerequisite>
//    <li> class <linkto class=Table>TableLockData</linkto>
// </prerequisite>
 
// <synopsis>
// This class keeps counters to synchronize the table data when a table
// is locked or unlocked.
// <br>
// A few counters are kept by this class:
// <ul>
//  <li> The numbers of rows in the table.
//  <li> The number of columns in the table.
//  <li> The table change counter.
//  <li> A change counter per data manager.
// </ul>
// When a lock on the table is acquired, it reads the sync data from the
// lock file and determines if anything has changed. If so, the necessary
// steps are taken to reread the table data when needed.
// <br>
// When a lock on the table is released, it updates and writes the sync data
// which tells if table data have changed.
// <p>
// This class can also be used for the synchronization of tables and
// external fillers (see class
// <linkto class=ExternalLockSync>ExternalLockSync</linkto>). For this
// purpose it is sufficient to store the number of rows.
// </synopsis>
 
class TableSyncData {
 public:
  TableSyncData();
 
  ~TableSyncData();
 
  // Copy constructor is forbidden.
  TableSyncData(const TableSyncData& that) = delete;
 
  // Assignment is forbidden.
  TableSyncData& operator=(const TableSyncData& that) = delete;
 
  // Update the synchronization data and write it into the MemoryIO object.
  // This function is called when a table flush is done to reflect
  // if anything has changed compared to the previous flush.
  void write(rownr_t nrrow, uInt nrcolumn, Bool tableChanged, const Block<Bool>& dataManChanged);
 
  // Update the synchronization data and write it into the MemoryIO object.
  // This function should be used by an external filler when it flushes
  // its data.
  void write(rownr_t nrrow);
 
  // Read the synchronization data from the MemoryIO object.
  // This function is called when a lock is acquired to see if
  // table data has to be reread.
  // <br>It returns False when the MemoryIO object is empty.
  Bool read(rownr_t& nrrow, uInt& nrcolumn, Bool& tableChanged, Block<Bool>& dataManChanged);
 
  // Get the MemoryIO object.
  // This is used to let <src>LockFile</src> read or write the
  // synchronization data into it.
  MemoryIO& memoryIO();
 
  // Get the modify counter.
  uInt getModifyCounter() const;
 
 private:
  // # Member variables.
  rownr_t itsNrrow;
  Int itsNrcolumn;
  uInt itsModifyCounter;
  uInt itsTableChangeCounter;
  Block<uInt> itsDataManChangeCounter;
  std::shared_ptr<MemoryIO> itsMemIO;
  AipsIO itsAipsIO;
};
 
inline MemoryIO& TableSyncData::memoryIO() { return *itsMemIO; }
inline uInt TableSyncData::getModifyCounter() const { return itsModifyCounter; }
 
}  // namespace casacore
 
#endif