casacore
Conversion.h
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1//# Conversion.h: A class with general conversion definitions
2//# Copyright (C) 1996,1999,2001,2002,2003
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_CONVERSION_H
29#define CASA_CONVERSION_H
30
31//# Includes
32#include <casacore/casa/aips.h>
33#include <casacore/casa/string.h> // needed for memcpy
34
35
36namespace casacore { //# NAMESPACE CASACORE - BEGIN
37
38// <summary>
39// A class with general conversion definitions
40// </summary>
41
42// <use visibility=export>
43
44// <reviewed reviewer="Friso Olnon" date="1996/11/06" tests="tConversion" demos="">
45// </reviewed>
46
47// <synopsis>
48// This class contains the general definitions for the Conversion classes.
49// <ul>
50// <li>
51// It defines the signature for the functions converting from input
52// to output format (e.g. from local to canonical format). There is
53// a version where the number of values is given and a version where
54// the number of bytes is given. The latter is there to be able to use
55// memcpy as a conversion function (which will often be the case).
56// Note that the signatures only differ in return value.
57// <li>
58// It defines functions to convert Bools to bits and vice-versa.
59// These are used elsewhere to store Bools as space efficient as possible.
60// Note that these functions are machine independent (they work on little
61// and big endian machines).
62// <li>
63// It defines a private version of memcpy for compilers having a
64// different signature for memcpy (e.g. ObjectCenter and DEC-Alpha).
65// </ul>
66// Static functions in the classes
67// <linkto class=CanonicalConversion>CanonicalConversion</linkto>,
68// <linkto class=VAXConversion>VAXConversion</linkto>, and
69// <linkto class=IBMConversion>IBMConversion</linkto> convert data
70// from/to canonical, VAX, and IBM/360 format, resp..
71// <br>Classes derived from
72// <linkto class=DataConversion>DataConversion</linkto>
73// provide the same functionality in a polymorphic way.
74// </synopsis>
75
76// <motivation>
77// This provides a common place for definitions used elsewhere.
78// It also provides a uniform interface to memcpy.
79// </motivation>
80
81//# <todo asof="$DATE$">
82//# </todo>
83
84
86{
87public:
88 // Define the signature of a function converting <src>nvalues</src>
89 // values from internal to external format or vice-versa.
90 // These functions are used in the <linkto class=TypeIO>IO framework
91 // </linkto>, but are also used in the table system.
92 // Examples of such conversions are:
93 // <br>- local <-> canonical (when storing in canonical format)
94 // <br>- local <-> local (when storing in local format)
95 // <br>- binary <-> ASCII
96 // <br>It returns the number of bytes in <em>external</em> format.
97 // (For example the ToLocal/FromLocal functions in class
98 // <linkto class=CanonicalConversion>CanonicalConversion</linkto>
99 // return the number of bytes in canonical format).
100 typedef size_t ValueFunction (void* to, const void* from,
101 size_t nvalues);
102
103 // Define the signature of a function converting from one
104 // format to another providing the number of bytes.
105 // It returns the <src>to</src> pointer (similar to memcpy).
106 // (For example the byteTo/FromLocalXXX functions in class
107 // <linkto class=CanonicalConversion>CanonicalConversion</linkto>.
108 typedef void* ByteFunction (void* to, const void* from,
109 size_t nbytes);
110
111 // Convert a stream of Bools to output format (as bits).
112 // The variable <src>startBit</src> (0-relative) indicates
113 // where to start in the <src>to</src> buffer.
114 // <group>
115 static size_t boolToBit (void* to, const void* from,
116 size_t nvalues);
117 static void boolToBit (void* to, const void* from,
118 size_t startBit,
119 size_t nvalues);
120 // </group>
121
122 // Convert a stream of Bools to output format (as bits).
123 // The variable <src>startBit</src> (0-relative) indicates
124 // where to start in the <src>from</src> buffer.
125 // <group>
126 static size_t bitToBool (void* to, const void* from,
127 size_t nvalues);
128 static void bitToBool (void* to, const void* from,
129 size_t startBit,
130 size_t nvalues);
131 // </group>
132
133 // Copy a value using memcpy.
134 // It differs from memcpy in the return value.
135 // <note> This version has the <src>ValueFunction</src> signature,
136 // but it expects as input the number of bytes.
137 // </note>
138 static size_t valueCopy (void* to, const void* from,
139 size_t nbytes);
140
141 // Get a pointer to the memcpy function.
142 static ByteFunction* getmemcpy();
143
144private:
145 // Copy bits to Bool in an unoptimized way needed when 'to' is not
146 // aligned properly.
147 static size_t bitToBool_ (void* to, const void* from,
148 size_t nvalues);
149};
150
151
153{
154 return memcpy;
155}
156
157
158
159} //# NAMESPACE CASACORE - END
160
161#endif
size_t ValueFunction(void *to, const void *from, size_t nvalues)
Define the signature of a function converting nvalues values from internal to external format or vice...
Definition: Conversion.h:100
static void boolToBit(void *to, const void *from, size_t startBit, size_t nvalues)
void * ByteFunction(void *to, const void *from, size_t nbytes)
Define the signature of a function converting from one format to another providing the number of byte...
Definition: Conversion.h:108
static size_t bitToBool(void *to, const void *from, size_t nvalues)
Convert a stream of Bools to output format (as bits).
static size_t valueCopy(void *to, const void *from, size_t nbytes)
Copy a value using memcpy.
static size_t bitToBool_(void *to, const void *from, size_t nvalues)
Copy bits to Bool in an unoptimized way needed when 'to' is not aligned properly.
static size_t boolToBit(void *to, const void *from, size_t nvalues)
Convert a stream of Bools to output format (as bits).
static ByteFunction * getmemcpy()
Get a pointer to the memcpy function.
Definition: Conversion.h:152
static void bitToBool(void *to, const void *from, size_t startBit, size_t nvalues)
this file contains all the compiler specific defines
Definition: mainpage.dox:28