source: trunk/yat/utility/SmartPtr.h @ 1486

#ifndef _theplu_yat_utility_smart_ptr_
#define _theplu_yat_utility_smart_ptr_

// $Id: SmartPtr.h 1486 2008-09-09 21:17:19Z jari $

/*
  Copyright (C) 2008 Jari Häkkinen, Peter Johansson

  This file is part of the yat library, http://dev.thep.lu.se/yat

  The yat 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 3 of the
  License, or (at your option) any later version.

  The yat 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 program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  02111-1307, USA.
*/

#include "yat_assert.h"

namespace theplu {
namespace yat {
namespace utility {

  /**
     SmartPtr is a wrapper around a pointer. Default SmartPtr is set
     to be owner of pointer, which implies pointer will be deleted in
     destructor. Pointer can be shared between many SmartPtr, in which
     case a counter is kept updated in copying and assignment telling
     how many owners there are. When the counter reaches zero, the
     pointer is deleted.
  */
  template<typename T>
  class SmartPtr 
  {
  public:
    /**
       \brief Constructor

       \param p underlying pointer
       \param owner if true SmartPtr will be owner of pointer and if
       there is no more owner delete it in destructor.

       Never use this constructor to create two SmartPtr to the same
       pointer such as
       \code
       MyClass* my_pointer = new MyClass;
       SmartPtr<MyClass> sp(my_pointer);
       SmartPtr<MyClass> sp2(my_pointer); // this is evil
       \endcode
       since this will cause multiple deletion. Instead use copy constructor
       \code
       MyClass* my_pointer = new MyClass;
       SmartPtr<MyClass> sp(my_pointer);
       SmartPtr<MyClass> sp2(sp);
       \endcode
       so the internal reference counter is updated.
    */
    explicit SmartPtr(T* p=NULL, bool owner=true)
      : pointee_(p) 
    {
      if (owner)
        ref_count_ = new unsigned int(1);
      else
        ref_count_ = NULL;
    }

    /**
       \brief Copy constructor
     */
    SmartPtr(const SmartPtr& other)
      : pointee_(other.pointee_), ref_count_(other.ref_count_)
    {
      if (ref_count_)
        ++(*ref_count_);
    }
    
    /**
       \brief Destructor

       If SmartPtr is owner and the only owner, underlying pointer is deleted.
     */
    virtual ~SmartPtr()
    {
      detach();
    }

    /**
       If SmartPtr is owner and the only owner, underlying pointer is deleted.

       If rhs is owner, lhs become also owner.
     */
    SmartPtr& operator=(const SmartPtr& rhs)
    {
      if (pointee_!=rhs.pointee_){
        detach();
        pointee_ = rhs.pointee_;
        ref_count_= rhs.ref_count_;
        if (ref_count_)
          ++(*ref_count_);
      }
      return *this;
    }

    /**
       \return underlying pointer
     */
    T* operator->(void) const
    {
      return pointee_;
    }

    /**
       \return reference to underlying object
     */
    T& operator*(void) const
    {
      return *pointee_;
    }

  private:
    T* pointee_;
    unsigned int* ref_count_;

    void detach(void)
    {
      if (ref_count_)
        if (!--(*ref_count_))
          delete pointee_;
    }     
  };

  




}}} // of namespace utility, yat, and theplu

#endif