gslice.h

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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>

#ifndef _GSLICE_H
#define _GSLICE_H 1

#pragma GCC system_header

namespace std
{
  class gslice
  {
  public:
    gslice ();

    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
    gslice(const gslice&);

    ~gslice();

    // XXX: See the note above.
    gslice& operator=(const gslice&);

    size_t           start() const;

    valarray<size_t> size() const;
    
    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++
// End:

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