gslice.h revision 132720 
1// The template and inlines for the -*- C++ -*- gslice class.
2
3// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2004
4// Free Software Foundation, Inc.
5//
6// This file is part of the GNU ISO C++ Library.  This library is free
7// software; you can redistribute it and/or modify it under the
8// terms of the GNU General Public License as published by the
9// Free Software Foundation; either version 2, or (at your option)
10// any later version.
11
12// This library is distributed in the hope that it will be useful,
13// but WITHOUT ANY WARRANTY; without even the implied warranty of
14// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15// GNU General Public License for more details.
16
17// You should have received a copy of the GNU General Public License along
18// with this library; see the file COPYING.  If not, write to the Free
19// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
20// USA.
21
22// As a special exception, you may use this file as part of a free software
23// library without restriction.  Specifically, if other files instantiate
24// templates or use macros or inline functions from this file, or you compile
25// this file and link it with other files to produce an executable, this
26// file does not by itself cause the resulting executable to be covered by
27// the GNU General Public License.  This exception does not however
28// invalidate any other reasons why the executable file might be covered by
29// the GNU General Public License.
30
31// Written by Gabriel Dos Reis <Gabriel.Dos-Reis@DPTMaths.ENS-Cachan.Fr>
32
33/** @file gslice.h
34 *  This is an internal header file, included by other library headers.
35 *  You should not attempt to use it directly.
36 */
37
38#ifndef _GSLICE_H
39#define _GSLICE_H 1
40
41#pragma GCC system_header
42
43namespace std {
44
45  /**
46   *  @brief  Class defining multi-dimensional subset of an array.
47   *
48   *  The slice class represents a multi-dimensional subset of an array,
49   *  specified by three parameter sets: start offset, size array, and stride
50   *  array.  The start offset is the index of the first element of the array
51   *  that is part of the subset.  The size and stride array describe each
52   *  dimension of the slice.  Size is the number of elements in that
53   *  dimension, and stride is the distance in the array between successive
54   *  elements in that dimension.  Each dimension's size and stride is taken
55   *  to begin at an array element described by the previous dimension.  The
56   *  size array and stride array must be the same size.
57   *
58   *  For example, if you have offset==3, stride[0]==11, size[1]==3,
59   *  stride[1]==3, then slice[0,0]==array[3], slice[0,1]==array[6],
60   *  slice[0,2]==array[9], slice[1,0]==array[14], slice[1,1]==array[17],
61   *  slice[1,2]==array[20].
62   */
63    class gslice
64    {
65    public:
66      ///  Construct an empty slice.
67      gslice ();
68
69      /**
70       *  @brief  Construct a slice.
71       *
72       *  Constructs a slice with as many dimensions as the length of the @a l
73       *  and @a s arrays.
74       *
75       *  @param  o  Offset in array of first element.
76       *  @param  l  Array of dimension lengths.
77       *  @param  s  Array of dimension strides between array elements.
78       */
79      gslice(size_t, const valarray<size_t>&, const valarray<size_t>&);
80
81      // XXX: the IS says the copy-ctor and copy-assignment operators are
82      //      synthetized by the compiler but they are just unsuitable
83      //      for a ref-counted semantic
84      ///  Copy constructor.
85      gslice(const gslice&);
86
87      ///  Destructor.
88      ~gslice();
89
90      // XXX: See the note above.
91      ///  Assignment operator.
92      gslice& operator=(const gslice&);
93
94      ///  Return array offset of first slice element.
95      size_t           start() const;
96
97      ///  Return array of sizes of slice dimensions.
98      valarray<size_t> size() const;
99
100      ///  Return array of array strides for each dimension.
101      valarray<size_t> stride() const;
102
103    private:
104      struct _Indexer {
105	size_t _M_count;
106	size_t _M_start;
107	valarray<size_t> _M_size;
108	valarray<size_t> _M_stride;
109	valarray<size_t> _M_index; // Linear array of referenced indices
110	_Indexer(size_t, const valarray<size_t>&,
111		 const valarray<size_t>&);
112	void _M_increment_use() { ++_M_count; }
113	size_t _M_decrement_use() { return --_M_count; }
114      };
115
116      _Indexer* _M_index;
117
118      template<typename _Tp> friend class valarray;
119    };
120
121    inline size_t
122    gslice::start () const
123    { return _M_index ? _M_index->_M_start : 0; }
124
125    inline valarray<size_t>
126    gslice::size () const
127    { return _M_index ? _M_index->_M_size : valarray<size_t>(); }
128
129    inline valarray<size_t>
130    gslice::stride () const
131    { return _M_index ? _M_index->_M_stride : valarray<size_t>(); }
132
133    inline gslice::gslice () : _M_index(0) {}
134
135    inline
136    gslice::gslice(size_t __o, const valarray<size_t>& __l,
137                   const valarray<size_t>& __s)
138            : _M_index(new gslice::_Indexer(__o, __l, __s)) {}
139
140    inline
141    gslice::gslice(const gslice& __g) : _M_index(__g._M_index)
142    { if (_M_index) _M_index->_M_increment_use(); }
143
144    inline
145    gslice::~gslice()
146    { if (_M_index && _M_index->_M_decrement_use() == 0) delete _M_index; }
147
148    inline gslice&
149    gslice::operator= (const gslice& __g)
150    {
151        if (__g._M_index) __g._M_index->_M_increment_use();
152        if (_M_index && _M_index->_M_decrement_use() == 0) delete _M_index;
153        _M_index = __g._M_index;
154        return *this;
155    }
156
157
158} // std::
159
160
161#endif /* _GSLICE_H */
162
163// Local Variables:
164// mode:c++
165// End:
166