casacore
MFFileIO.h
Go to the documentation of this file.
1 //# MFFileIO.h: Class for IO on a virtual file in a MultiFileBase
2 //# Copyright (C) 2014
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: RegularFileIO.h 20551 2009-03-25 00:11:33Z Malte.Marquarding $
27 
28 #ifndef CASA_MFFILEIO_H
29 #define CASA_MFFILEIO_H
30 
31 //# Includes
32 #include <casacore/casa/aips.h>
33 #include <casacore/casa/IO/ByteIO.h>
34 #include <casacore/casa/IO/MultiFileBase.h>
35 
36 
37 namespace casacore { //# NAMESPACE CASACORE - BEGIN
38 
39  // <summary>
40  // Class for IO on a virtual file in a MultiFileBase
41  // </summary>
42 
43  // <use visibility=export>
44 
45  // <reviewed reviewer="Friso Olnon" date="1996/11/06" tests="tByteIO" demos="">
46  // </reviewed>
47 
48  // <synopsis>
49  // This class is a specialization of class
50  // <linkto class=ByteIO>ByteIO</linkto>. It uses a
51  // <linkto class=MultiFileBase>MultiFileBase</linkto> as the data store.
52  // <p>
53  // Similar to a regular file it is possible to read and write data and to
54  // seek in the file. The object keeps track of the current file offset.
55  // </synopsis>
56 
57  // <example>
58  // <srcblock>
59  // // Create a new MultiFile using a block size of 1 MB.
60  // MultiFile mfile("file.mf', ByteIO::New, 1048576);
61  // // Create a virtual file in it.
62  // MFFileIO mf1(mfile, "mf1", ByteIO::New);
63  // // Use it (for example) as the sink of AipsIO.
64  // AipsIO stream (&mf1);
65  // // Write values.
66  // stream << (Int)10;
67  // stream << True;
68  // // Seek to beginning of file and read data in.
69  // stream.setpos (0);
70  // Int vali;
71  // Bool valb;
72  // stream >> vali >> valb;
73  // </srcblock>
74  // </example>
75 
76 
77  class MFFileIO: public ByteIO
78  {
79  public:
80  // Open or create a virtual file with the given name. Note that only the
81  // basename of the file name is actually used.
82  // It is created in the given MultiFileBase.
83  MFFileIO (MultiFileBase&, const String& name,
85 
86  // The destructor flushes and closes the file.
87  virtual ~MFFileIO();
88 
89  // Read <src>size</src> bytes from the byte stream. Returns the number of
90  // bytes actually read, or a negative number if an error occurred. Will also
91  // throw an Exception (AipsError) if the requested number of bytes could
92  // not be read unless throwException is set to False.
93  virtual Int64 read (Int64 size, void* buf, Bool throwException=True);
94 
95  // Write a block at the given offset.
96  virtual void write (Int64 size, const void* buffer);
97 
98  // Reopen the file (and possibly underlying MultiFileBase) for read/write access.
99  // Nothing will be done if the stream is writable already.
100  // An exception will be thrown if it is not possible to reopen it for
101  // read/write access.
102  virtual void reopenRW();
103 
104  // Remove the file from the MultiFileBase object.
105  // It makes the object invalid by setting the fileId to -1.
106  void remove();
107 
108  // Flush the file by writing all dirty data and all header info.
109  virtual void flush();
110 
111  // Get the length of the file.
112  virtual Int64 length();
113 
114  // The file is always readable.
115  virtual Bool isReadable() const;
116 
117  // Is the file writable?
118  virtual Bool isWritable() const;
119 
120  // The file is always seekable.
121  virtual Bool isSeekable() const;
122 
123  // Get the file name of the file attached.
124  virtual String fileName() const;
125 
126  // Fsync the file (i.e. force the data to be physically written).
127  virtual void fsync();
128 
129  // Reset the position pointer to the given value. It returns the
130  // new position.
132 
133  private:
134  //# Data members
139  };
140 
141 
142 } //# NAMESPACE CASACORE - END
143 
144 #endif
SeekOption
Define the possible seek options.
Definition: ByteIO.h:82
OpenOption
Define the possible ByteIO open options.
Definition: ByteIO.h:65
virtual Int64 doSeek(Int64 offset, ByteIO::SeekOption)
Reset the position pointer to the given value.
MultiFileBase & itsFile
Definition: MFFileIO.h:135
virtual void fsync()
Fsync the file (i.e.
void remove()
Remove the file from the MultiFileBase object.
virtual Int64 length()
Get the length of the file.
virtual Bool isReadable() const
The file is always readable.
virtual ~MFFileIO()
The destructor flushes and closes the file.
virtual void reopenRW()
Reopen the file (and possibly underlying MultiFileBase) for read/write access.
virtual String fileName() const
Get the file name of the file attached.
virtual void flush()
Flush the file by writing all dirty data and all header info.
MFFileIO(MultiFileBase &, const String &name, ByteIO::OpenOption=ByteIO::Old)
Open or create a virtual file with the given name.
virtual Bool isWritable() const
Is the file writable?
virtual void write(Int64 size, const void *buffer)
Write a block at the given offset.
virtual Bool isSeekable() const
The file is always seekable.
virtual Int64 read(Int64 size, void *buf, Bool throwException=True)
Read size bytes from the byte stream.
Abstract base class to combine multiple files in a single one.
String: the storage and methods of handling collections of characters.
Definition: String.h:225
this file contains all the compiler specific defines
Definition: mainpage.dox:28
long long Int64
Define the extra non-standard types used by Casacore (like proposed uSize, Size)
Definition: aipsxtype.h:38
int Int
Definition: aipstype.h:50
bool Bool
Define the standard types used by Casacore.
Definition: aipstype.h:42
const Bool True
Definition: aipstype.h:43