sprint/container/shared_ptr.h

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/******************************************************************************
*   sprint::shared_ptr
*
*   Copyright (C) 2005-2011  Paolo Medici <www.pmx.it>
*
*  This library is free software; you can redistribute it and/or
*  modify it under the terms of the GNU Lesser General Public
*  License as published by the Free Software Foundation; either
*  version 2.1 of the License, 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
*  Lesser General Public License for more details.
*
*  You should have received a copy of the GNU Lesser General Public
*  License along with this library; if not, write to the Free Software
*  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*
*******************************************************************************/
#ifndef _SPRINT_SHARED_PTR_H
#define _SPRINT_SHARED_PTR_H

namespace sprint {

struct sharable {
      mutable long m_refCount;
      sharable() : m_refCount(0) { }
      long use_count() const { return m_refCount; }
      };
      
template<class T>
void add_ref(T * obj) { obj->m_refCount ++; }      

template<class T>
void release(T * obj) 
     { 
       if(obj)
           {
           obj->m_refCount --; 
           if(obj->m_refCount == 0)
             delete obj;
           }
     }      
          
template<class T>
class shared_ptr {
 T *m_ptr;
 public:
  
  shared_ptr(T * obj) : m_ptr(obj) 
  { 
    sprint::add_ref(m_ptr);
  }
  shared_ptr(const shared_ptr<T> & obj) : m_ptr(obj.get())  // non explicit (avoid bogus copy costructor)
  { 
    sprint::add_ref(m_ptr);
  }
  template<class R>
  explicit shared_ptr(const shared_ptr<R> & obj) : m_ptr(obj.get()) 
  { 
    sprint::add_ref(m_ptr);
  }
  
  ~shared_ptr() 
  { 
    sprint::release(m_ptr);
  }
   
  inline shared_ptr & operator = ( const shared_ptr<T> & a)
  {
    sprint::release(m_ptr);
    m_ptr = a.m_ptr;
    sprint::add_ref(m_ptr);
    return *this;
  }
  
  inline T & operator *() const
  {
    return *m_ptr;
  }
  
  inline T * operator->() const
  {
    return m_ptr;
  }
  inline T * get() const
  {
      return m_ptr;
  }

  int use_count() const {
        return m_ptr->m_refCount;
  }
      
  void swap(shared_ptr & b) 
    {
      T * tmp;
      tmp = b.m_ptr;
      b.m_ptr = m_ptr;
      m_ptr = tmp;
    }
};

}

#endif