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BucketBuffered.h
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1 //# BucketBuffered.h: Use buffered file IO for buckets in a part of a file
2 //# Copyright (C) 2010
3 //# Associated Universities, Inc. Washington DC, USA.
4 //#
5 //# This library is free software; you can redistribute it and/or modify it
6 //# under the terms of the GNU Library General Public License as published by
7 //# the Free Software Foundation; either version 2 of the License, or (at your
8 //# option) any later version.
9 //#
10 //# This library is distributed in the hope that it will be useful, but WITHOUT
11 //# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 //# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
13 //# License for more details.
14 //#
15 //# You should have received a copy of the GNU Library General Public License
16 //# along with this library; if not, write to the Free Software Foundation,
17 //# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
18 //#
19 //# Correspondence concerning AIPS++ should be addressed as follows:
20 //# Internet email: aips2-request@nrao.edu.
21 //# Postal address: AIPS++ Project Office
22 //# National Radio Astronomy Observatory
23 //# 520 Edgemont Road
24 //# Charlottesville, VA 22903-2475 USA
25 //#
26 //# $Id$
27 
28 #ifndef CASA_BUCKETBUFFERED_H
29 #define CASA_BUCKETBUFFERED_H
30 
31 //# Includes
32 #include <casacore/casa/aips.h>
34 
35 
36 namespace casacore { //# NAMESPACE CASACORE - BEGIN
37 
38  //# Forward Declarations.
39  class FilebufIO;
40 
41 
42  // <summary>
43  // Use buffered file IO for buckets in a part of a file
44  // </summary>
45 
46  // <use visibility=export>
47 
48  // <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="" demos="">
49  // </reviewed>
50 
51  // <prerequisite>
52  //# Classes you should understand before using this one.
53  // <li> <linkto class=BucketFile>BucketFile</linkto>
54  // </prerequisite>
55 
56  // <synopsis>
57  // BucketBuffered is similar to class
58  // <linkto class=BucketCache>BucketCache</linkto> and is meant to be used by
59  // the storage managers of the Table System.
60  //
61  // It gives access to buckets in a file by means of memory-buffered files.
62  // However, its functionality is a subset of BucketCache and is only meant
63  // to be used by the Tiled Storage Managers. If The Standard and Incremental
64  // Storage Manager also want to use it, functions like <src>extend</src>
65  // needs to be added to this class. Also support for a free bucket list needs
66  // to be added.
67  // </synopsis>
68 
69  // <motivation>
70  // Use of BucketCache is sub-optimal when having large buckets and more or
71  // less random IO. Memory-buffering behaves much better.
72  // </motivation>
73 
74 
75  class BucketBuffered: public BucketBase
76  {
77  public:
78  // Create the object for (part of) a file.
79  // The file part buffered into memory starts at startOffset. Its length is
80  // bucketSize*nrOfBuckets bytes.
81  // If the file is smaller, the remainder is indicated as an extension
82  // similarly to the behaviour of function extend.
83  BucketBuffered (BucketFile* file, Int64 startOffset, uInt bucketSize,
84  uInt nrOfBuckets);
85 
86  virtual ~BucketBuffered();
87 
88  // Get a pointer to the buffer.
89  char* getBuffer()
90  { return itsBuffer; }
91 
92  // Read the given part into the internal buffer at the given offset.
93  void read (uInt bucketNr, uInt bucketOffset, uInt nbytes,
94  uInt bufferOffset=0);
95 
96  // Write the given part from the internal buffer.
97  void write (uInt bucketNr, uInt bucketOffset, uInt nbytes);
98 
99 private:
100  // Copy constructor is not possible.
102 
103  // Assignment is not possible.
105 
106  // Flush the file.
107  virtual void doFlush();
108 
109  // Do the actual resync-ing.
110  virtual void doResync();
111 
112  // Extend the file with the given number of buckets.
113  virtual void doExtend (uInt nrBucket);
114 
115  // Initialize the bucket buffer.
116  // The uninitialized buckets before this bucket are also initialized.
117  virtual void initializeBuckets (uInt bucketNr);
118 
119 
120  // Data buffer.
121  char* itsBuffer;
122 };
123 
124 
125 } //# NAMESPACE CASACORE - END
126 
127 #endif
File object for BucketCache.
Definition: BucketFile.h:107
virtual void doResync()
Do the actual resync-ing.
long long Int64
Define the extra non-standard types used by Casacore (like proposed uSize, Size)
Definition: aipsxtype.h:38
virtual void doExtend(uInt nrBucket)
Extend the file with the given number of buckets.
virtual void doFlush()
Flush the file.
void read(uInt bucketNr, uInt bucketOffset, uInt nbytes, uInt bufferOffset=0)
Read the given part into the internal buffer at the given offset.
char * getBuffer()
Get a pointer to the buffer.
Use buffered file IO for buckets in a part of a file.
virtual void initializeBuckets(uInt bucketNr)
Initialize the bucket buffer.
BucketBuffered & operator=(const BucketBuffered &)
Assignment is not possible.
void write(uInt bucketNr, uInt bucketOffset, uInt nbytes)
Write the given part from the internal buffer.
BucketBuffered(BucketFile *file, Int64 startOffset, uInt bucketSize, uInt nrOfBuckets)
Create the object for (part of) a file.
Abstract base class for Bucket classes.
Definition: BucketBase.h:59
char * itsBuffer
Data buffer.
unsigned int uInt
Definition: aipstype.h:51
Defines nreal time structures used by the VLA table filler.
Definition: nreal.h:100
#define casacore
&lt;X11/Intrinsic.h&gt; #defines true, false, casacore::Bool, and String.
Definition: X11Intrinsic.h:42