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TSMOption.h
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//# TSMOption.h: Options for the Tiled Storage Manager Access
//# Copyright (C) 2010
//# 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_TSMOPTION_H
#define TABLES_TSMOPTION_H
//# Includes
#include <casacore/casa/aips.h>
namespace casacore { //# NAMESPACE CASACORE - BEGIN
// <summary>
// Options for the Tiled Storage Manager Access
// </summary>
// <use visibility=export>
// <reviewed reviewer="TPPR" date="08.11.94" tests="tTiledShapeStMan.cc">
// </reviewed>
// <prerequisite>
//# Classes you should understand before using this one.
// <li> <linkto class=TiledStMan>TiledStMan</linkto>
// </prerequisite>
// <synopsis>
// This class can be used to define how the Tiled Storage Manager accesses
// its data. There are three ways:
// <ol>
// <li> Using a cache of its own. The cache size is derived using the hinted
// access pattern. The cache can be (too) large when using large tables
// with bad access patterns.
// A maximum cache size can be defined to overcome this problem, but
// that may result in poor caching behaviour.
// Until January 2010 this was the only way to access the data.
// <li> Use memory-mapped IO (mmap); the operating system take care of caching.
// On 32-bit systems mmap cannot be used for larger tables due to the
// 4 GB address space limit.
// When creating or extending files, mmap can be disadvantageous because
// extending the file requires remapping it.
// <li> Use buffered IO; the kernel's file cache should avoid unnecessary IO.
// Its performance is less than mmap, but it works well on 32-bit systems.
// The buffer size to be used can be defined.
// </ol>
//
// The constructor of the class can be used to define the options or
// to read options from the aipsrc file.
// <ul>
// <li> <src>TSMOption::Cache</src>
// Use unbuffered file IO with internal TSM caching. This is the old
// behaviour.
// The maximum cache size can be given as a constructor argument.
// <li> <src>TSMOption::MMap</src>
// Use memory-mapped IO.
// <li> <src>TSMOption::Buffer</src>
// Use buffered file IO without.
// The buffer size can be given as a constructor argument.
// <li> <src>TSMOption::Default</src>
// Use default. This is MMap for existing files on 64-bit systems,
// otherwise Buffer.
// <li> <src>TSMOption::Aipsrc</src>
// Use the option as defined in the aipsrc file.
// </ul>
// The aipsrc variables are:
// <ul>
// <li> <src>table.tsm.option</src> gives the option as the case-insensitive
// string value:
// <ul>
// <li> <src>cache</src> means TSMCache.
// <li> <src>mmap</src> (or <src>map</src>) means TSMMap.
// <li> <src>mmapold</src> (or <src>mapold</src>) means TSMMap for existing
// tables and TSMDefault for new tables.
// <li> <src>buffer</src> means TSMBuffer.
// <li> <src>default</src> means TSMDefault.
// </ul>
// It defaults to value <src>default</src>.
// Note that <src>mmapold</src> is almost the same as <src>default</src>.
// Only on 32-bit systems it is different.
// <li> <src>table.tsm.maxcachesizemb</src> gives the maximum cache size in
// MibiByte for option <src>TSMOption::Cache</src>. A value -1 means
// that the system determines the maximum. A value 0 means unlimited.
// It defaults to -1.
// Note it can always be overridden using class ROTiledStManAccessor.
// <li> <src>table.tsm.buffersize</src> gives the buffer size for option
// <src>TSMOption::Buffer</src>. A value <=0 means use the default 4096.
// It defaults to 0.
// </ul>
// </synopsis>
class TSMOption
{
public:
// Define the possible options how the TiledStMan accesses its data.
enum Option {
// Use unbuffered file IO with internal TSM caching.
Cache,
// Use buffered file IO without internal TSM caching.
Buffer,
// Use memory-mapped IO.
MMap,
// Use default.
Default,
// Use as defined in the aipsrc file.
Aipsrc
};
// Create an option object.
// The parameter values are described in the synopsis.
// A size value -2 means reading that size from the aipsrc file.
// The buffer size has to be given in bytes.
// The maximum cache size has to be given in MibiBytes (1024*1024 bytes).
TSMOption (Option option=Aipsrc, Int bufferSize=-2,
Int maxCacheSizeMB=-2);
// Fill the option in case Aipsrc or Default was given.
// It is done as explained in the synopsis.
void fillOption (Bool newFile);
// Get the option.
Option option() const
{ return itsOption; }
// Get the buffer size.
Int bufferSize() const
{ return itsBufferSize; }
// Get the maximum cache size (in MibiByte). -1 means undefined.
Int maxCacheSizeMB() const
{ return itsMaxCacheSize; }
private:
Option itsOption;
Int itsBufferSize;
Int itsMaxCacheSize;
};
} //# NAMESPACE CASACORE - END
#endif
casacore::TSMOption::bufferSize
Int bufferSize() const
Get the buffer size.
Definition TSMOption.h:148
casacore::TSMOption::itsOption
Option itsOption
Definition TSMOption.h:156
casacore::TSMOption::option
Option option() const
Get the option.
Definition TSMOption.h:144
casacore::TSMOption::itsMaxCacheSize
Int itsMaxCacheSize
Definition TSMOption.h:158
casacore::TSMOption::TSMOption
TSMOption(Option option=Aipsrc, Int bufferSize=-2, Int maxCacheSizeMB=-2)
Create an option object.
casacore::TSMOption::maxCacheSizeMB
Int maxCacheSizeMB() const
Get the maximum cache size (in MibiByte).
Definition TSMOption.h:152
casacore::TSMOption::fillOption
void fillOption(Bool newFile)
Fill the option in case Aipsrc or Default was given.
casacore::TSMOption::Option
Option
Define the possible options how the TiledStMan accesses its data.
Definition TSMOption.h:118
casacore::TSMOption::Default
@ Default
Use default.
Definition TSMOption.h:126
casacore::TSMOption::MMap
@ MMap
Use memory-mapped IO.
Definition TSMOption.h:124
casacore::TSMOption::Buffer
@ Buffer
Use buffered file IO without internal TSM caching.
Definition TSMOption.h:122
casacore::TSMOption::Aipsrc
@ Aipsrc
Use as defined in the aipsrc file.
Definition TSMOption.h:128
casacore::TSMOption::Cache
@ Cache
Use unbuffered file IO with internal TSM caching.
Definition TSMOption.h:120
casacore::TSMOption::itsBufferSize
Int itsBufferSize
Definition TSMOption.h:157
casacore
this file contains all the compiler specific defines
Definition mainpage.dox:28
casacore::Int
int Int
Definition aipstype.h:48
casacore::Bool
bool Bool
Define the standard types used by Casacore.
Definition aipstype.h:40