BucketBase.h

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// # BucketBase.h: Abstract base class for Bucket classes
// # 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 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 CASA_BUCKETBASE_H
#define CASA_BUCKETBASE_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/casa/IO/BucketFile.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// <summary>
// Abstract base class for Bucket classes.
// </summary>
 
// <use visibility=local>
 
// <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="" demos="">
// </reviewed>
 
// <prerequisite>
// # Classes you should understand before using this one.
//   <li> <linkto class=BucketFile>BucketFile</linkto>
// </prerequisite>
 
// <synopsis>
// BucketBase is the abstract baseclass for the various Bucket classes
// like BucketMapped and BucketBuffered.
// It is used by TSMCube to do the IO in the required way.
// </synopsis>
 
class BucketBase {
 public:
  // Create the bucket access for (part of) a file.
  // The file part starts at startOffset. Its length is
  // bucketSize*nrOfBuckets bytes.
  // If the file is smaller, the remainder is indicated as an extension
  // similarly to the behaviour of function extend.
  BucketBase(BucketFile* file, Int64 startOffset, uInt bucketSize, uInt nrOfBuckets);
 
  // Detach the file. The BucketFile is not closed.
  virtual ~BucketBase();
 
  // Flush the cached buckets.
  // Possibly remaining uninitialized buckets will be initialized first.
  // A True status is returned if buckets had to be written.
  // The actual flushing is done using <src>doFlush</src> in the derived
  // class.
  Bool flush();
 
  // Resynchronize the object (after another process updated the file).
  // It remaps the file if the nr of buckets has changed.
  // the new sizes.
  virtual void resync(uInt nrBucket);
 
  // Get the current nr of buckets in the file.
  uInt nBucket() const { return itsCurNrOfBuckets; }
 
  // Extend the file with the given number of buckets.
  // The buckets get initialized when they are acquired
  // (using getBucket) for the first time.
  void extend(uInt nrBucket);
 
  // Set that data has been written.
  void setWritten() { itsHasWritten = True; }
 
 protected:
  // Copy constructor is not possible.
  BucketBase(const BucketBase&);
 
  // Assignment is not possible.
  BucketBase& operator=(const BucketBase&);
 
  // Do the actual flushing.
  virtual void doFlush() = 0;
 
  // Do the actual resync-ing.
  virtual void doResync() = 0;
 
  // Do the actual extension of the file.
  // Note that itsNewNrOfBuckets has been increased before doExtend is called.
  virtual void doExtend(uInt nrBucket) = 0;
 
  // Initialize the bucket buffer.
  // The uninitialized buckets before this bucket are also initialized.
  virtual void initializeBuckets(uInt bucketNr) = 0;
 
  // The file used.
  BucketFile* itsFile;
  // The starting offsets of the buckets in the file.
  Int64 itsStartOffset;
  // The bucket size.
  uInt itsBucketSize;
  // The current nr of buckets in the file.
  uInt itsCurNrOfBuckets;
  // The new nr of buckets in the file (after extension).
  uInt itsNewNrOfBuckets;
  // Have data been written?
  Bool itsHasWritten;
};
 
}  // namespace casacore
 
#endif