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// The template and inlines for the -*- C++ -*- gslice class.

// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2004

// 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.

// Written by Gabriel Dos Reis <Gabriel.Dos-Reis@DPTMaths.ENS-Cachan.Fr>

/** @file gslice.h

 *  This is an internal header file, included by other library headers.

 *  You should not attempt to use it directly.

 */

#ifndef _GSLICE_H

#define _GSLICE_H 1

#pragma GCC system_header

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;

  }

} // std::

#endif /* _GSLICE_H */

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// mode:c++

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