libstdc++-v3/include/bits/gslice.h

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