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// The template and inlines for the -*- C++ -*- gslice class.
// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2004, 2005
// 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 2, 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.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING. If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.
// As a special exception, you may use this file as part of a free software
// library without restriction. Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License. This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.
/** @file gslice.h
* This is an internal header file, included by other library headers.
* You should not attempt to use it directly.
*/
// Written by Gabriel Dos Reis <Gabriel.Dos-Reis@DPTMaths.ENS-Cachan.Fr>
#ifndef _GSLICE_H
#define _GSLICE_H 1
#pragma GCC system_header
_GLIBCXX_BEGIN_NAMESPACE(std)
/**
* @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, const valarray<size_t>&, const valarray<size_t>&);
// XXX: the IS says the copy-ctor and copy-assignment operators are
// synthetized 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(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>(); }
inline gslice::gslice () : _M_index(0) {}
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;
}
_GLIBCXX_END_NAMESPACE
#endif /* _GSLICE_H */
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