safe_mode.hpp

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    unchecked_(it.unchecked_)
  {
    attach(it.cont);
  }

  safe_iterator_base& operator=(const safe_iterator_base& it)
  {
    unchecked_=it.unchecked_;
    safe_container_base* new_cont=it.cont;
    if(cont!=new_cont){
      detach();
      attach(new_cont);
    }
    return *this;
  }

  ~safe_iterator_base()
  {
    detach();
  }

  const safe_container_base* owner()const{return cont;}

BOOST_MULTI_INDEX_PRIVATE_IF_MEMBER_TEMPLATE_FRIENDS:
  friend class safe_container_base;

#if !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
  template<typename>          friend class safe_mode::safe_container;
  template<typename Iterator> friend
    void safe_mode::detach_equivalent_iterators(Iterator&);
#endif

  inline void attach(safe_container_base* cont_);

  safe_container_base* cont;
  safe_iterator_base*  next;
  bool                 unchecked_;
};

class safe_container_base:private noncopyable
{
public:
  safe_container_base(){}

BOOST_MULTI_INDEX_PROTECTED_IF_MEMBER_TEMPLATE_FRIENDS:
  friend class safe_iterator_base;

#if !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
  template<typename Iterator> friend
    void safe_mode::detach_equivalent_iterators(Iterator&);
#endif

  ~safe_container_base()
  {
    /* Detaches all remaining iterators, which by now will
     * be those pointing to the end of the container.
     */

    for(safe_iterator_base* it=header.next;it;it=it->next)it->cont=0;
    header.next=0;
  }

  void swap(safe_container_base& x)
  {
    for(safe_iterator_base* it0=header.next;it0;it0=it0->next)it0->cont=&x;
    for(safe_iterator_base* it1=x.header.next;it1;it1=it1->next)it1->cont=this;
    std::swap(header.cont,x.header.cont);
    std::swap(header.next,x.header.next);
  }

  safe_iterator_base header;

#if defined(BOOST_HAS_THREADS)
  boost::detail::lightweight_mutex mutex;
#endif
};

void safe_iterator_base::attach(safe_container_base* cont_)
{
  cont=cont_;
  if(cont){
#if defined(BOOST_HAS_THREADS)
    boost::detail::lightweight_mutex::scoped_lock lock(cont->mutex);
#endif

    next=cont->header.next;
    cont->header.next=this;
  }
}

void safe_iterator_base::detach()
{
  if(cont){
#if defined(BOOST_HAS_THREADS)
    boost::detail::lightweight_mutex::scoped_lock lock(cont->mutex);
#endif

    safe_iterator_base *prev_,*next_;
    for(prev_=&cont->header;(next_=prev_->next)!=this;prev_=next_){}
    prev_->next=next;
    cont=0;
  }
}

} /* namespace multi_index::detail */

namespace safe_mode{

/* In order to enable safe mode on a container:
 *   - The container must derive from safe_container<container_type>,
 *   - iterators must be generated via safe_iterator, which adapts a
 *     preexistent unsafe iterator class.
 */
 
template<typename Container>
class safe_container;

template<typename Iterator,typename Container>
class safe_iterator:
  public detail::iter_adaptor<safe_iterator<Iterator,Container>,Iterator>,
  public detail::safe_iterator_base
{
  typedef detail::iter_adaptor<safe_iterator,Iterator> super;
  typedef detail::safe_iterator_base                   safe_super;

public:
  typedef Container                                    container_type;
  typedef typename Iterator::reference                 reference;
  typedef typename Iterator::difference_type           difference_type;

  safe_iterator(){}
  explicit safe_iterator(safe_container<container_type>* cont_):
    safe_super(cont_){}
  template<typename T0>
  safe_iterator(const T0& t0,safe_container<container_type>* cont_):
    super(Iterator(t0)),safe_super(cont_){}
  template<typename T0,typename T1>
  safe_iterator(
    const T0& t0,const T1& t1,safe_container<container_type>* cont_):
    super(Iterator(t0,t1)),safe_super(cont_){}

  safe_iterator& operator=(const safe_iterator& x)
  {
    BOOST_MULTI_INDEX_CHECK_VALID_ITERATOR(x);
    this->base_reference()=x.base_reference();
    safe_super::operator=(x);
    return *this;
  }

  const container_type* owner()const
  {
    return
      static_cast<const container_type*>(
        static_cast<const safe_container<container_type>*>(
          this->safe_super::owner()));
  }

  /* get_node is not to be used by the user */

  typedef typename Iterator::node_type node_type;

  node_type* get_node()const{return this->base_reference().get_node();}

private:
  friend class boost::multi_index::detail::iter_adaptor_access;

  reference dereference()const
  {
    BOOST_MULTI_INDEX_CHECK_VALID_ITERATOR(*this);
    BOOST_MULTI_INDEX_CHECK_DEREFERENCEABLE_ITERATOR(*this);
    return *(this->base_reference());
  }

  bool equal(const safe_iterator& x)const
  {
    BOOST_MULTI_INDEX_CHECK_VALID_ITERATOR(*this);
    BOOST_MULTI_INDEX_CHECK_VALID_ITERATOR(x);
    BOOST_MULTI_INDEX_CHECK_SAME_OWNER(*this,x);
    return this->base_reference()==x.base_reference();
  }

  void increment()
  {
    BOOST_MULTI_INDEX_CHECK_VALID_ITERATOR(*this);
    BOOST_MULTI_INDEX_CHECK_INCREMENTABLE_ITERATOR(*this);
    ++(this->base_reference());
  }

  void decrement()
  {
    BOOST_MULTI_INDEX_CHECK_VALID_ITERATOR(*this);
    BOOST_MULTI_INDEX_CHECK_DECREMENTABLE_ITERATOR(*this);
    --(this->base_reference());
  }

  void advance(difference_type n)
  {
    BOOST_MULTI_INDEX_CHECK_VALID_ITERATOR(*this);
    BOOST_MULTI_INDEX_CHECK_IN_BOUNDS(*this,n);
    this->base_reference()+=n;
  }

  difference_type distance_to(const safe_iterator& x)const
  {
    BOOST_MULTI_INDEX_CHECK_VALID_ITERATOR(*this);
    BOOST_MULTI_INDEX_CHECK_VALID_ITERATOR(x);
    BOOST_MULTI_INDEX_CHECK_SAME_OWNER(*this,x);
    return x.base_reference()-this->base_reference();
  }

#if !defined(BOOST_MULTI_INDEX_DISABLE_SERIALIZATION)
  /* Serialization. Note that Iterator::save and Iterator:load
   * are assumed to be defined and public: at first sight it seems
   * like we could have resorted to the public serialization interface
   * for doing the forwarding to the adapted iterator class:
   *   ar<<base_reference();
   *   ar>>base_reference();
   * but this would cause incompatibilities if a saving
   * program is in safe mode and the loading program is not, or
   * viceversa --in safe mode, the archived iterator data is one layer
   * deeper, this is especially relevant with XML archives.
   * It'd be nice if Boost.Serialization provided some forwarding
   * facility for use by adaptor classes.
   */ 

  friend class boost::serialization::access;

  BOOST_SERIALIZATION_SPLIT_MEMBER()

  template<class Archive>
  void save(Archive& ar,const unsigned int version)const
  {
    BOOST_MULTI_INDEX_CHECK_VALID_ITERATOR(*this);
    this->base_reference().save(ar,version);
  }

  template<class Archive>
  void load(Archive& ar,const unsigned int version)
  {
    this->base_reference().load(ar,version);
    safe_super::uncheck();
  }
#endif
};

template<typename Container>
class safe_container:public detail::safe_container_base
{
  typedef detail::safe_container_base super;

public:
  void detach_dereferenceable_iterators()
  {
    typedef typename Container::iterator iterator;

    iterator end_=static_cast<Container*>(this)->end();
    iterator *prev_,*next_;
    for(
      prev_=static_cast<iterator*>(&this->header);
      (next_=static_cast<iterator*>(prev_->next))!=0;){
      if(*next_!=end_){
        prev_->next=next_->next;
        next_->cont=0;
      }
      else prev_=next_;
    }
  }

  void swap(safe_container<Container>& x)
  {
    super::swap(x);
  }
};

} /* namespace multi_index::safe_mode */

} /* namespace multi_index */

} /* namespace boost */

#endif /* BOOST_MULTI_INDEX_ENABLE_SAFE_MODE */

#endif