// ======================================================================
//
// Copyright (c) 1999 The CGAL Consortium
//
// This software and related documentation is part of an INTERNAL release
// of the Computational Geometry Algorithms Library (CGAL). It is not
// intended for general use.
//
// ----------------------------------------------------------------------
// 
// release       : 
// release_date  : 
// 
// file          : Handle_for.h
// package       : Kernel_basic
// revision      : $Revision$
// revision_date : $Date$
// author(s)     : Stefan Schirra
//
//
// coordinator   : MPI, Saarbruecken  (<Stefan.Schirra@mpi-sb.mpg.de>)
// ======================================================================
 

#ifndef CGAL_HANDLE_FOR_H
#define CGAL_HANDLE_FOR_H
#include <CGAL/memory.h>

namespace CGAL {


template <class RefCounted, class Allocator> class Handle_for;
class Object;


class Ref_counted
{
  public:
    Ref_counted() : count(1) {}
    Ref_counted(const Ref_counted&) : count(1) {}

    void  add_reference() { ++count; }
    void  remove_reference() { --count; }
    bool  is_referenced() { return (count != 0); }
    bool  is_shared() { return (count > 1); }

  friend class Object;

  protected:
    unsigned int count;
};


template <class RefCounted,
          class Allocator = CGAL_ALLOCATOR(RefCounted) >
// RefCounted must provide
// add_reference()
// remove_reference()
// bool is_referenced()
// bool is_shared()
// and initialize count to 1 in default and copy constructor
class Handle_for
{
  public:

    typedef RefCounted element_type;

    Handle_for(const RefCounted& rc)
    {
      ptr = allocator.allocate(1);
      allocator.construct(ptr, rc);
    }

    Handle_for()
    {
      ptr = allocator.allocate(1);
    }

    Handle_for( const Handle_for& h)
    {
      ptr = h.ptr;
      ptr->add_reference();
    }

    ~Handle_for()
    {
      ptr->remove_reference();
      if ( !ptr->is_referenced() )
      {
        allocator.destroy( ptr);
        allocator.deallocate( ptr, 1);
      }
    }

    Handle_for&
    operator=( const Handle_for& h)
    {
      h.ptr->add_reference();
      ptr->remove_reference();
      if ( !ptr->is_referenced() )
      {
        allocator.destroy( ptr);
        allocator.deallocate( ptr, 1);
      }
      ptr = h.ptr;
      return *this;
    }

    void
    initialize_with( const RefCounted& rc)
    {
      allocator.construct(ptr, rc);
    }

    void
    copy_on_write()
    {
      if ( ptr->is_shared() )
      {
        RefCounted* tmp_ptr = allocator.allocate(1);
        allocator.construct( tmp_ptr, *ptr);
        ptr->remove_reference();
        ptr = tmp_ptr;
      }
    }

    bool
    identical( const Handle_for& h) const
    { return ptr == h.ptr; }

    long int
    id() const
    { return reinterpret_cast<long int>( &(*ptr)); }

    const typename Allocator::pointer
    Ptr() const
    { return ptr; }

  protected:
    static Allocator allocator;
    typename Allocator::pointer      ptr;
};


template <class RefCounted, class Allocator>
Allocator  Handle_for<RefCounted,Allocator>::allocator;

} // namespace CGAL
#endif // CGAL_HANDLE_FOR_H