slink.H

/*
  This file is part of Aleph system

  Copyright (c) 2002, 2003, 2004, 2005, 2006
  UNIVERSITY LOS ANDES (ULA) Merida - REPÚBLICA BOLIVARIANA DE VENEZUELA  

  - Center of Studies in Microelectronics & Distributed Systems (CEMISID) 
  - ULA Computer Science Department
  - FUNDACITE Mérida - Ministerio de Ciencia y Tecnología

  PERMISSION TO USE, COPY, MODIFY AND DISTRIBUTE THIS SOFTWARE AND ITS
  DOCUMENTATION IS HEREBY GRANTED, PROVIDED THAT BOTH THE COPYRIGHT
  NOTICE AND THIS PERMISSION NOTICE APPEAR IN ALL COPIES OF THE
  SOFTWARE, DERIVATIVE WORKS OR MODIFIED VERSIONS, AND ANY PORTIONS
  THEREOF, AND THAT BOTH NOTICES APPEAR IN SUPPORTING DOCUMENTATION.

  Aleph 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.

  UNIVERSIDAD DE LOS ANDES requests users of this software to return to 

  Leandro Leon
  CEMISID 
  Ed La Hechicera 
  3er piso, ala sur
  Facultad de Ingenieria 
  Universidad de Los Andes 
  Merida - REPÚBLICA BOLIVARIANA DE VENEZUELA    or

  lrleon@ula.ve

  any improvements or extensions that they make and grant Universidad 
  de Los Andes (ULA) the rights to redistribute these changes. 

  Aleph is (or was) granted by: 
  - Consejo de Desarrollo Cientifico, Humanistico, Tecnico de la ULA 
    (CDCHT)
  - Fundacite Mérida
*/


# ifndef SLINK_H
# define SLINK_H

# include <aleph.H>

using namespace Aleph;

namespace Aleph {

class Slink
{
  protected:
    Slink* next;

public:

  Slink() : next(this) { /* Empty */ }

  Slink(const Slink & link)
  {
    if (not link.is_empty())
      throw std::invalid_argument ("link is not empty");

    next = this; 
  }

  Slink & operator = (const Slink & link)
  {

    if (&link == this)
      return *this;

    if (not is_empty())
      throw std::invalid_argument("link is not empty");

    if (not link.is_empty())
      throw std::invalid_argument ("link is not empty");

    next = this; 
  }

  void reset() 
  {

    I(this not_eq NULL);

    next = this; 
  }

  bool is_empty() const 
  {

    I(this not_eq NULL);

    return next == this; 
  }

  Slink * get_next() const 
  {

    I(this not_eq NULL);

    return next; 
  }

  void insert_next(Slink * p)
  {

    I(this not_eq NULL);
    I(p not_eq NULL);
    I(p->is_empty());

    p->next = next;
    next = p;
  }
  Slink * remove_next()
  {

    I(this not_eq NULL);

    Slink * ret_val = next;
    next = ret_val->next;
    ret_val->reset();

    return ret_val;
  }  
};

# define SLINK_TO_TYPE(type_name, link_name) \
static type_name * slink_to_type(Slink * link) \
{ \
  type_name * ptr_zero = 0; \
  size_t offset_link   = reinterpret_cast<size_t>(&(ptr_zero->link_name)); \
  char * address_type  = reinterpret_cast<char*>(link) - offset_link; \
  return reinterpret_cast<type_name *>(address_type); \
} 

} // end namespace Aleph
# endif /* SLINK_H */

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