libstdc++
gslice.h
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1 // The template and inlines for the -*- C++ -*- gslice class.
2 
3 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2004, 2005, 2006, 2009
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 3, or (at your option)
10 // any later version.
11 
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14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
16 
17 // Under Section 7 of GPL version 3, you are granted additional
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19 // 3.1, as published by the Free Software Foundation.
20 
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25 
26 /** @file gslice.h
27  * This is an internal header file, included by other library headers.
28  * You should not attempt to use it directly.
29  */
30 
31 // Written by Gabriel Dos Reis <Gabriel.Dos-Reis@DPTMaths.ENS-Cachan.Fr>
32 
33 #ifndef _GSLICE_H
34 #define _GSLICE_H 1
35 
36 #pragma GCC system_header
37 
38 _GLIBCXX_BEGIN_NAMESPACE(std)
39 
40  /**
41  * @addtogroup numeric_arrays
42  * @{
43  */
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  // synthesized 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  {
106  size_t _M_count;
107  size_t _M_start;
108  valarray<size_t> _M_size;
109  valarray<size_t> _M_stride;
110  valarray<size_t> _M_index; // Linear array of referenced indices
111 
112  _Indexer()
113  : _M_count(1), _M_start(0), _M_size(), _M_stride(), _M_index() {}
114 
115  _Indexer(size_t, const valarray<size_t>&,
116  const valarray<size_t>&);
117 
118  void
119  _M_increment_use()
120  { ++_M_count; }
121 
122  size_t
123  _M_decrement_use()
124  { return --_M_count; }
125  };
126 
127  _Indexer* _M_index;
128 
129  template<typename _Tp> friend class valarray;
130  };
131 
132  inline size_t
133  gslice::start() const
134  { return _M_index ? _M_index->_M_start : 0; }
135 
136  inline valarray<size_t>
137  gslice::size() const
138  { return _M_index ? _M_index->_M_size : valarray<size_t>(); }
139 
140  inline valarray<size_t>
141  gslice::stride() const
142  { return _M_index ? _M_index->_M_stride : valarray<size_t>(); }
143 
144  // _GLIBCXX_RESOLVE_LIB_DEFECTS
145  // 543. valarray slice default constructor
146  inline
147  gslice::gslice()
148  : _M_index(new gslice::_Indexer()) {}
149 
150  inline
151  gslice::gslice(size_t __o, const valarray<size_t>& __l,
152  const valarray<size_t>& __s)
153  : _M_index(new gslice::_Indexer(__o, __l, __s)) {}
154 
155  inline
156  gslice::gslice(const gslice& __g)
157  : _M_index(__g._M_index)
158  { if (_M_index) _M_index->_M_increment_use(); }
159 
160  inline
162  {
163  if (_M_index && _M_index->_M_decrement_use() == 0)
164  delete _M_index;
165  }
166 
167  inline gslice&
169  {
170  if (__g._M_index)
171  __g._M_index->_M_increment_use();
172  if (_M_index && _M_index->_M_decrement_use() == 0)
173  delete _M_index;
174  _M_index = __g._M_index;
175  return *this;
176  }
177 
178  // @} group numeric_arrays
179 
180 _GLIBCXX_END_NAMESPACE
181 
182 #endif /* _GSLICE_H */
gslice & operator=(const gslice &)
Assignment operator.
Definition: gslice.h:168
~gslice()
Destructor.
Definition: gslice.h:161
gslice()
Construct an empty slice.
Definition: gslice.h:147
Class defining multi-dimensional subset of an array.
Definition: gslice.h:63