Preview: gslice.h
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/opt/rh/gcc-toolset-14/root/usr/include/c++/14/bits/gslice.h
// The template and inlines for the -*- C++ -*- gslice class.
// Copyright (C) 1997-2024 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)
{
// Safe for self-assignment. Checking for it would add overhead just to
// optimize a case that should never happen anyway.
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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