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ByteIO.h
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1 //# ByteIO.h: Abstract base class for IO on a byte stream
2 //# Copyright (C) 1996,1999,2001
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_BYTEIO_H
29 #define CASA_BYTEIO_H
30 
31 //# Includes
32 #include <casacore/casa/aips.h>
34 
35 
36 namespace casacore { //# NAMESPACE CASACORE - BEGIN
37 
38 // <summary>Abstract base class for IO on a byte stream.</summary>
39 
40 // <use visibility=export>
41 
42 // <reviewed reviewer="Friso Olnon" date="1996/11/06" tests="tByteIO" demos="">
43 // </reviewed>
44 
45 // <synopsis>
46 // ByteIO is the abstract base class for all classes doing IO on
47 // byte streams. Examples of derived classes are
48 // <linkto class=RegularFileIO>RegularFileIO</linkto> and
49 // <linkto class=MemoryIO>MemoryIO</linkto>.
50 // <p>
51 // ByteIO contains two enumerations, which define the possible
52 // open and seek options on byte streams. These enumerations
53 // are used throughout the IO framework.
54 // </synopsis>
55 
56 // <motivation>
57 // Make polymorphic operations on byte streams possible.
58 // </motivation>
59 
60 
61 class ByteIO
62 {
63 public:
64  // Define the possible ByteIO open options.
65  enum OpenOption {
66  Old=1,
67  // read/write; file must exist.
69  // read/write; create file if not exist.
71  // read/write; create file if not exist.
72  New,
73  // read/write; file may not exist yet.
75  // read/write; delete file at close.
77  // read/write; file must exist; delete at close.
79  };
80 
81  // Define the possible seek options.
82  enum SeekOption {
83  // Seek from beginning of file.
84  Begin=1,
85  // Seek from current position.
87  // Seek from the end of the file.
89  };
90 
91 
92  // The constructor does nothing.
93  ByteIO();
94 
95  virtual ~ByteIO();
96 
97  // Write <src>size</src> bytes to the byte stream.
98  virtual void write (Int64 size, const void* buf) = 0;
99 
100  // Write <src>size</src> bytes to the byte stream at <src>offset</src>.
101  // The file offset is not changed
102  virtual void pwrite (Int64 size, Int64 offset, const void* buf);
103 
104  // Read <src>size</src> bytes from the byte stream. Returns the number of
105  // bytes actually read, or a negative number if an error occurred. Will also
106  // throw an Exception (AipsError) if the requested number of bytes could
107  // not be read unless throwException is set to False.
108  virtual Int64 read (Int64 size, void* buf, Bool throwException=True) = 0;
109 
110  // Like read but reads from offset of start of the file
111  // The file offset is not changed
112  virtual Int64 pread (Int64 size, Int64 offset, void* buf, Bool throwException=True);
113 
114  // Reopen the underlying IO stream for read/write access.
115  // Nothing will be done if the stream is writable already.
116  // Otherwise it will be reopened and an exception will be thrown
117  // if it is not possible to reopen it for read/write access.
118  // The default implementation in this base class throws a "not possible"
119  // exception if a reopen has to be done.
120  virtual void reopenRW();
121 
122  // This function sets the position on the given offset.
123  // The seek option defines from which file position the seek is done.
124  // -1 is returned if not seekable.
125  // <group>
128  // </group>
129 
130  // Flush the data to the file.
131  // The default implementation does nothing.
132  virtual void flush();
133 
134  // Fsync the file (i.e. force the data to be physically written).
135  // The default implementation does nothing.
136  virtual void fsync();
137 
138  // Resync the file (i.e. empty the current buffer).
139  // The default implementation does nothing.
140  virtual void resync();
141 
142  // Get the file name of the file attached.
143  // The default implementation returns an empty string.
144  virtual String fileName() const;
145 
146  // Get the length of the byte stream.
147  virtual Int64 length() = 0;
148 
149  // Is the byte stream readable?
150  virtual Bool isReadable() const = 0;
151 
152  // Is the byte stream writable?
153  virtual Bool isWritable() const = 0;
154 
155  // Is the byte stream seekable?
156  virtual Bool isSeekable() const = 0;
157 
158 
159 protected:
160  // Make copy constructor and assignment protected, so a user cannot
161  // use them (but a derived class can).
162  // <group>
163  ByteIO (const ByteIO& byteIO);
164  ByteIO& operator= (const ByteIO& byteIO);
165  // </group>
166 
167  virtual Int64 doSeek (Int64 offset, ByteIO::SeekOption) = 0;
168 };
169 
170 
171 
173 {}
174 
175 inline ByteIO::ByteIO (const ByteIO&)
176 {}
177 
179 {
180  return *this;
181 }
182 
184 {
185  return doSeek (offset, option);
186 }
187 inline Int64 ByteIO::seek (Int offset, ByteIO::SeekOption option)
188 {
189  return doSeek (Int64(offset), option);
190 }
191 
192 
193 } //# NAMESPACE CASACORE - END
194 
195 #endif
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
read/write; file may not exist yet.
Definition: ByteIO.h:74
virtual Bool isSeekable() const =0
Is the byte stream seekable?
ByteIO()
The constructor does nothing.
Definition: ByteIO.h:172
virtual Int64 length()=0
Get the length of the byte stream.
SeekOption
Define the possible seek options.
Definition: ByteIO.h:82
virtual Bool isReadable() const =0
Is the byte stream readable?
read/write; delete file at close.
Definition: ByteIO.h:76
size_t size() const
virtual String fileName() const
Get the file name of the file attached.
virtual ~ByteIO()
read/write; file must exist; delete at close.
Definition: ByteIO.h:78
ByteIO & operator=(const ByteIO &byteIO)
Definition: ByteIO.h:178
virtual void write(Int64 size, const void *buf)=0
Write size bytes to the byte stream.
virtual Bool isWritable() const =0
Is the byte stream writable?
virtual void reopenRW()
Reopen the underlying IO stream for read/write access.
Abstract base class for IO on a byte stream.
Definition: ByteIO.h:61
Int64 seek(Int offset, ByteIO::SeekOption=ByteIO::Begin)
This function sets the position on the given offset.
Definition: ByteIO.h:187
Seek from current position.
Definition: ByteIO.h:86
bool Bool
Define the standard types used by Casacore.
Definition: aipstype.h:42
read/write; create file if not exist.
Definition: ByteIO.h:70
Seek from beginning of file.
Definition: ByteIO.h:84
Seek from the end of the file.
Definition: ByteIO.h:88
read/write; file must exist.
Definition: ByteIO.h:68
virtual Int64 doSeek(Int64 offset, ByteIO::SeekOption)=0
read/write; create file if not exist.
Definition: ByteIO.h:72
OpenOption
Define the possible ByteIO open options.
Definition: ByteIO.h:65
virtual void flush()
Flush the data to the file.
virtual Int64 read(Int64 size, void *buf, Bool throwException=True)=0
Read size bytes from the byte stream.
String: the storage and methods of handling collections of characters.
Definition: String.h:223
virtual void fsync()
Fsync the file (i.e.
const Bool True
Definition: aipstype.h:43
virtual Int64 pread(Int64 size, Int64 offset, void *buf, Bool throwException=True)
Like read but reads from offset of start of the file The file offset is not changed.
virtual void resync()
Resync the file (i.e.
virtual void pwrite(Int64 size, Int64 offset, const void *buf)
Write size bytes to the byte stream at offset.
#define casacore
&lt;X11/Intrinsic.h&gt; #defines true, false, casacore::Bool, and String.
Definition: X11Intrinsic.h:42