1 // The template and inlines for the -*- C++ -*- gslice class.
2
3 // Copyright (C) 1997-2023 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24
25 /** @file bits/gslice.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{valarray}
28 */
29
30 // Written by Gabriel Dos Reis <Gabriel.Dos-Reis@DPTMaths.ENS-Cachan.Fr>
31
32 #ifndef _GSLICE_H
33 #define _GSLICE_H 1
34
35 #pragma GCC system_header
36
37 namespace std _GLIBCXX_VISIBILITY(default)
38 {
39 _GLIBCXX_BEGIN_NAMESPACE_VERSION
40
41 /**
42 * @addtogroup numeric_arrays
43 * @{
44 */
45
46 /**
47 * @brief Class defining multi-dimensional subset of an array.
48 *
49 * The slice class represents a multi-dimensional subset of an array,
50 * specified by three parameter sets: start offset, size array, and stride
51 * array. The start offset is the index of the first element of the array
52 * that is part of the subset. The size and stride array describe each
53 * dimension of the slice. Size is the number of elements in that
54 * dimension, and stride is the distance in the array between successive
55 * elements in that dimension. Each dimension's size and stride is taken
56 * to begin at an array element described by the previous dimension. The
57 * size array and stride array must be the same size.
58 *
59 * For example, if you have offset==3, stride[0]==11, size[1]==3,
60 * stride[1]==3, then slice[0,0]==array[3], slice[0,1]==array[6],
61 * slice[0,2]==array[9], slice[1,0]==array[14], slice[1,1]==array[17],
62 * slice[1,2]==array[20].
63 */
64 class gslice
65 {
66 public:
67 /// Construct an empty slice.
68 gslice();
69
70 /**
71 * @brief Construct a slice.
72 *
73 * Constructs a slice with as many dimensions as the length of the @a l
74 * and @a s arrays.
75 *
76 * @param __o Offset in array of first element.
77 * @param __l Array of dimension lengths.
78 * @param __s Array of dimension strides between array elements.
79 */
80 gslice(size_t __o, const valarray<size_t>& __l,
81 const valarray<size_t>& __s);
82
83 // XXX: the IS says the copy-ctor and copy-assignment operators are
84 // synthesized by the compiler but they are just unsuitable
85 // for a ref-counted semantic
86 /// Copy constructor.
87 gslice(const gslice&);
88
89 /// Destructor.
90 ~gslice();
91
92 // XXX: See the note above.
93 /// Assignment operator.
94 gslice& operator=(const gslice&);
95
96 /// Return array offset of first slice element.
97 size_t start() const;
98
99 /// Return array of sizes of slice dimensions.
100 valarray<size_t> size() const;
101
102 /// Return array of array strides for each dimension.
103 valarray<size_t> stride() const;
104
105 private:
106 struct _Indexer
107 {
108 size_t _M_count;
109 size_t _M_start;
110 valarray<size_t> _M_size;
111 valarray<size_t> _M_stride;
112 valarray<size_t> _M_index; // Linear array of referenced indices
113
114 _Indexer()
115 : _M_count(1), _M_start(0), _M_size(), _M_stride(), _M_index() {}
116
117 _Indexer(size_t, const valarray<size_t>&,
118 const valarray<size_t>&);
119
120 void
121 _M_increment_use()
122 { ++_M_count; }
123
124 size_t
125 _M_decrement_use()
126 { return --_M_count; }
127 };
128
129 _Indexer* _M_index;
130
131 template<typename _Tp> friend class valarray;
132 };
133
134 inline size_t
135 gslice::start() const
136 { return _M_index ? _M_index->_M_start : 0; }
137
138 inline valarray<size_t>
139 gslice::size() const
140 { return _M_index ? _M_index->_M_size : valarray<size_t>(); }
141
142 inline valarray<size_t>
143 gslice::stride() const
144 { return _M_index ? _M_index->_M_stride : valarray<size_t>(); }
145
146 // _GLIBCXX_RESOLVE_LIB_DEFECTS
147 // 543. valarray slice default constructor
148 inline
149 gslice::gslice()
150 : _M_index(new gslice::_Indexer()) {}
151
152 inline
153 gslice::gslice(size_t __o, const valarray<size_t>& __l,
154 const valarray<size_t>& __s)
155 : _M_index(new gslice::_Indexer(__o, __l, __s)) {}
156
157 inline
158 gslice::gslice(const gslice& __g)
159 : _M_index(__g._M_index)
160 { if (_M_index) _M_index->_M_increment_use(); }
161
162 inline
163 gslice::~gslice()
164 {
165 if (_M_index && _M_index->_M_decrement_use() == 0)
166 delete _M_index;
167 }
168
169 inline gslice&
170 gslice::operator=(const gslice& __g)
171 {
172 if (__g._M_index)
173 __g._M_index->_M_increment_use();
174 if (_M_index && _M_index->_M_decrement_use() == 0)
175 delete _M_index;
176 _M_index = __g._M_index;
177 return *this;
178 }
179
180 /// @} group numeric_arrays
181
182 _GLIBCXX_END_NAMESPACE_VERSION
183 } // namespace
184
185 #endif /* _GSLICE_H */