StorageOption.h

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// # StorageOption.h: Options defining how table files are organized
// # Copyright (C) 2014
// # 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 receied 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_STORAGEOPTION_H
#define TABLES_STORAGEOPTION_H
 
// # Includes
#include <casacore/casa/aips.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// <summary>
// Options defining how table files are organized
// </summary>
 
// <use visibility=export>
 
// <reviewed reviewer="TPPR" date="08.11.94" tests="tTable.cc">
// </reviewed>
 
// <synopsis>
// This class can be used to define how the files of a table are organized.
// There are two ways:
// <ol>
//  <li> The old way where each storage manager has its own file(s).
//  <li> Using MultiFile that storage managers can use to combine about all
//       table files in a single file. This mode is particularly useful
//       for new file systems (like Lustre) requiring large block sizes.
//       <br>The block size to be used in a MultiFile can be defined in
//           this class. Default is 4 MByte.
//  <li> Using MultiHDF5 which behaves similar to MultiFile but uses an
//       HDF5 file instead of a regular file. Note that it requires that
//       support for HDF5 has been used in the build system.
// </ol>
// It is possible to specify the storage type and block size using aipsrc.
// The aipsrc variables are:
// <ul>
//  <li> <src>table.storage.option</src>. The (case-insensitive) value can be
//       'multifile' or 'multihdf5'.
//       Another value means the old way (separate files).
//  <li> <src>table.storage.blocksize</src> gives the default blocksize to be
//       used for the multifile and multihdf5 option.
// <li> <src>table.storage.odirect</src> can be true or false. It tells if the
//       O_DIRECT option has to be used to let the kernel bypass its filecache
//       for more predictable I/O behaviour. It's only used for MultiFile and
//       only if the OS supports O_DIRECT.
// </ul>
// </synopsis>
 
class StorageOption {
 public:
  // Define the possible options how table files are organized.
  enum Option {
    // Let storage managers use a combined MultiFile.
    MultiFile,
    // Let storage managers use a combined MultiHDF5.
    MultiHDF5,
    // Let storage managers use separate files.
    SepFile,
    // Use default (currently SepFile).
    Default,
    // Use as defined in the aipsrc file.
    Aipsrc
  };
 
  // Create an option object.
  // The parameter values are described in the synopsis.
  // The blocksize has to be given in bytes.
  // A size value -2 means reading that size from the aipsrc file.
  // A size value -1 means use the default of 4*1024*1024.
  // <br>useODirect<0 means reading the option from the aipsrc file.
  // It is only set if the OS supports O_DIRECT.
  StorageOption(Option option = Aipsrc, Int blockSize = -2, Int useODirect = -3);
 
  // Fill the option in case Aipsrc or Default was given.
  // It is done as explained in the synopsis.
  void fillOption();
 
  // Get the option.
  Option option() const { return itsOption; }
 
  // Set the option.
  void setOption(Option option) { itsOption = option; }
 
  // Get the block size (in bytes).
  uInt blockSize() const { return itsBlockSize; }
 
  // Set the block size (in bytes).
  void setBlockSize(Int blockSize) { itsBlockSize = blockSize; }
 
  // Get the O_DIRECT option.
  Bool useODirect() const { return itsUseODirect; }
 
  // Set the O_DIRECT option.
  // It is only set if the OS supports O_DIRECT.
  void setUseODirect(Bool useODirect);
 
 private:
  Option itsOption;
  Int itsBlockSize;
  Bool itsUseODirect;
  Bool itsUseAipsrcODirect;
};
 
}  // namespace casacore
 
#endif