casacore
BucketMapped.h
Go to the documentation of this file.
1 //# BucketMapped.h: File buckets by means of file mapping
2 //# Copyright (C) 2009
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_BUCKETMAPPED_H
29 #define CASA_BUCKETMAPPED_H
30 
31 //# Includes
32 #include <casacore/casa/aips.h>
33 #include <casacore/casa/IO/BucketBase.h>
34 #include <casacore/casa/IO/MMapfdIO.h>
35 
36 
37 namespace casacore { //# NAMESPACE CASACORE - BEGIN
38 
39  // <summary>
40  // Use file mapping for buckets in a part of a file
41  // </summary>
42 
43  // <use visibility=export>
44 
45  // <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="" demos="">
46  // </reviewed>
47 
48  // <prerequisite>
49  //# Classes you should understand before using this one.
50  // <li> <linkto class=BucketFile>BucketFile</linkto>
51  // </prerequisite>
52 
53  // <etymology>
54  // BucketMapped uses memory-mapped files for bucket access.
55  // </etymology>
56 
57  // <synopsis>
58  // BucketMapped is similar to class
59  // <linkto class=BucketCache>BucketCache</linkto> and is meant to be used by
60  // the storage managers of the Table System.
61  //
62  // It gives access to buckets in a file by means of memory-mapped files.
63  // However, its functionality is a subset of BucketCache and is only meant
64  // to be used by the Tiled Storage Managers. If The Standard and Incremental
65  // Storage Manager also want to use it, functions like <src>extend</src>
66  // needs to be added to this class. Also support for a free bucket list needs
67  // to be added.
68  // </synopsis>
69 
70  // <motivation>
71  // Use of BucketCache is sub-optimal when having large buckets and more or
72  // less random IO. Memory-mapping behaves much better.
73  // </motivation>
74 
75 
76  class BucketMapped: public BucketBase
77  {
78  public:
79  // Create the cache for (part of) a file.
80  // The file part mapped into memory starts at startOffset. Its length is
81  // bucketSize*nrOfBuckets bytes.
82  // If the file is smaller, the remainder is indicated as an extension
83  // similarly to the behaviour of function extend.
84  BucketMapped (BucketFile* file, Int64 startOffset, uInt bucketSize,
85  uInt nrOfBuckets);
86 
87  // Unmap the file
89 
90  // Get a readonly pointer to the given bucket in memory.
91  const char* getBucket (uInt bucketNr);
92 
93  // Get a writable pointer to the given bucket in memory.
94  // It sets the hasWritten flag.
95  char* getrwBucket (uInt bucketNr)
96  {
98  return const_cast<char*>(getBucket(bucketNr));
99  }
100 
101 private:
102  // Copy constructor is not possible.
104 
105  // Assignment is not possible.
107 
108  // Flush the file.
109  virtual void doFlush();
110 
111  // Do the actual resync-ing.
112  virtual void doResync();
113 
114  // Extend the file with the given number of buckets.
115  virtual void doExtend (uInt nrBucket);
116 
117  // Initialize the bucket buffer.
118  // The uninitialized buckets before this bucket are also initialized.
119  virtual void initializeBuckets (uInt bucketNr);
120  };
121 
122 
123 } //# NAMESPACE CASACORE - END
124 
125 #endif
Bool itsHasWritten
Have data been written?
Definition: BucketBase.h:131
~BucketMapped()
Unmap the file.
virtual void initializeBuckets(uInt bucketNr)
Initialize the bucket buffer.
char * getrwBucket(uInt bucketNr)
Get a writable pointer to the given bucket in memory.
Definition: BucketMapped.h:95
const char * getBucket(uInt bucketNr)
Get a readonly pointer to the given bucket in memory.
virtual void doExtend(uInt nrBucket)
Extend the file with the given number of buckets.
BucketMapped(const BucketMapped &)
Copy constructor is not possible.
virtual void doResync()
Do the actual resync-ing.
virtual void doFlush()
Flush the file.
BucketMapped(BucketFile *file, Int64 startOffset, uInt bucketSize, uInt nrOfBuckets)
Create the cache for (part of) a file.
BucketMapped & operator=(const BucketMapped &)
Assignment is not possible.
this file contains all the compiler specific defines
Definition: mainpage.dox:28
unsigned int uInt
Definition: aipstype.h:51
long long Int64
Define the extra non-standard types used by Casacore (like proposed uSize, Size)
Definition: aipsxtype.h:38
const Bool True
Definition: aipstype.h:43