Filename: //usr/include/c++/10/bits/gslice.h

// The template and inlines for the -*- C++ -*- gslice class. // Copyright (C) 1997-2020 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file bits/gslice.h * This is an internal header file, included by other library headers. * Do not attempt to use it directly. @headername{valarray} */ // Written by Gabriel Dos Reis <Gabriel.Dos-Reis@DPTMaths.ENS-Cachan.Fr> #ifndef _GSLICE_H #define _GSLICE_H 1 #pragma GCC system_header namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION /** * @addtogroup numeric_arrays * @{ */ /** * @brief Class defining multi-dimensional subset of an array. * * The slice class represents a multi-dimensional subset of an array, * specified by three parameter sets: start offset, size array, and stride * array. The start offset is the index of the first element of the array * that is part of the subset. The size and stride array describe each * dimension of the slice. Size is the number of elements in that * dimension, and stride is the distance in the array between successive * elements in that dimension. Each dimension's size and stride is taken * to begin at an array element described by the previous dimension. The * size array and stride array must be the same size. * * For example, if you have offset==3, stride[0]==11, size[1]==3, * stride[1]==3, then slice[0,0]==array[3], slice[0,1]==array[6], * slice[0,2]==array[9], slice[1,0]==array[14], slice[1,1]==array[17], * slice[1,2]==array[20]. */ class gslice { public: /// Construct an empty slice. gslice(); /** * @brief Construct a slice. * * Constructs a slice with as many dimensions as the length of the @a l * and @a s arrays. * * @param __o Offset in array of first element. * @param __l Array of dimension lengths. * @param __s Array of dimension strides between array elements. */ gslice(size_t __o, const valarray<size_t>& __l, const valarray<size_t>& __s); // XXX: the IS says the copy-ctor and copy-assignment operators are // synthesized by the compiler but they are just unsuitable // for a ref-counted semantic /// Copy constructor. gslice(const gslice&); /// Destructor. ~gslice(); // XXX: See the note above. /// Assignment operator. gslice& operator=(const gslice&); /// Return array offset of first slice element. size_t start() const; /// Return array of sizes of slice dimensions. valarray<size_t> size() const; /// Return array of array strides for each dimension. valarray<size_t> stride() const; private: struct _Indexer { size_t _M_count; size_t _M_start; valarray<size_t> _M_size; valarray<size_t> _M_stride; valarray<size_t> _M_index; // Linear array of referenced indices _Indexer() : _M_count(1), _M_start(0), _M_size(), _M_stride(), _M_index() {} _Indexer(size_t, const valarray<size_t>&, const valarray<size_t>&); void _M_increment_use() { ++_M_count; } size_t _M_decrement_use() { return --_M_count; } }; _Indexer* _M_index; template<typename _Tp> friend class valarray; }; inline size_t gslice::start() const { return _M_index ? _M_index->_M_start : 0; } inline valarray<size_t> gslice::size() const { return _M_index ? _M_index->_M_size : valarray<size_t>(); } inline valarray<size_t> gslice::stride() const { return _M_index ? _M_index->_M_stride : valarray<size_t>(); } // _GLIBCXX_RESOLVE_LIB_DEFECTS // 543. valarray slice default constructor inline gslice::gslice() : _M_index(new gslice::_Indexer()) {} inline gslice::gslice(size_t __o, const valarray<size_t>& __l, const valarray<size_t>& __s) : _M_index(new gslice::_Indexer(__o, __l, __s)) {} inline gslice::gslice(const gslice& __g) : _M_index(__g._M_index) { if (_M_index) _M_index->_M_increment_use(); } inline gslice::~gslice() { if (_M_index && _M_index->_M_decrement_use() == 0) delete _M_index; } inline gslice& gslice::operator=(const gslice& __g) { if (__g._M_index) __g._M_index->_M_increment_use(); if (_M_index && _M_index->_M_decrement_use() == 0) delete _M_index; _M_index = __g._M_index; return *this; } // @} group numeric_arrays _GLIBCXX_END_NAMESPACE_VERSION } // namespace #endif /* _GSLICE_H */

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