libstdc++
gslice.h
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1 // The template and inlines for the -*- C++ -*- gslice class.
2 
3 // Copyright (C) 1997-2021 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 
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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
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>
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
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
164  {
165  if (_M_index && _M_index->_M_decrement_use() == 0)
166  delete _M_index;
167  }
168 
169  inline gslice&
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 */
~gslice()
Destructor.
Definition: gslice.h:163
gslice()
Construct an empty slice.
Definition: gslice.h:149
gslice & operator=(const gslice &)
Assignment operator.
Definition: gslice.h:170
size_t start() const
Return array offset of first slice element.
Definition: gslice.h:135
valarray< size_t > stride() const
Return array of array strides for each dimension.
Definition: gslice.h:143
valarray< size_t > size() const
Return array of sizes of slice dimensions.
Definition: gslice.h:139
ISO C++ entities toplevel namespace is std.
Class defining multi-dimensional subset of an array.
Definition: gslice.h:65