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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: aips2-request@nrao.edu.
//# Postal address: AIPS++ Project Office
//# National Radio Astronomy Observatory
//# 520 Edgemont Road
//# Charlottesville, VA 22903-2475 USA
//#
//# $Id: StorageOption.h 20859 2010-02-03 13:14:15Z gervandiepen $
#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 - END
#endif
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