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MEM_SmartPtr.h

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/**
 * $Id: MEM_SmartPtr.h,v 1.6 2002/12/30 12:11:02 maarten Exp $
 * ***** BEGIN GPL/BL DUAL LICENSE BLOCK *****
 *
 * This program 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 2
 * of the License, or (at your option) any later version. The Blender
 * Foundation also sells licenses for use in proprietary software under
 * the Blender License.  See http://www.blender.org/BL/ for information
 * about this.
 *
 * This program 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.
 *
 * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): none yet.
 *
 * ***** END GPL/BL DUAL LICENSE BLOCK *****
 */
/**
 * @file    MEM_SmartPtr.h
 * Declaration of MEM_RefCounted and MEM_RefCountable classes.
 * @author Laurence
 */

#ifndef NAN_INCLUDED_MEM_SmartPtr_h
#define NAN_INCLUDED_MEM_SmartPtr_h


#include <stdlib.h> // for NULL !


/**
 * @section MEM_SmartPtr 
 * This class defines a smart pointer similar to that defined in 
 * the Standard Template Library but without the painful get()
 * semantics to access the internal c style pointer.
 *
 * It is often useful to explicitely decalre ownership of memory
 * allocated on the heap within class or function scope. This
 * class helps you to encapsulate this ownership within a value
 * type. When an instance of this class goes out of scope it
 * makes sure that any memory associated with it's internal pointer
 * is deleted. It can help to inform users of an aggregate class
 * that it owns instances of it's members and these instances 
 * should not be shared. This is not reliably enforcable in C++
 * but this class attempts to make the 1-1 relationship clear.
 * 
 * @section Example usage
 *
 * class foo {
 *          ...constructors accessors etc.
 *          int x[1000];
 * }
 * 
 * class bar {
 *  public :
 *          static
 *                bar *
 *          New(
 *          ) {
 *                MEM_SmartPtr<foo> afoo = new foo();
 *                MEM_SmartPtr<bar> that = new bar();
 *
 *                if (foo == NULL || that == NULL) return NULL;
 *
 *                that->m_foo = afoo.Release();
 *                return that.Release();
 *          }
 *
 *          ~bar() {
 *                // smart ptr takes care of deletion
 *          }
 *    private :
 *          MEM_SmartPtr<foo> m_foo;
 *    }
 *                
 * You may also safely construct vectors of MEM_SmartPtrs and 
 * have the vector own stuff you put into it. 
 *
 * e.g.
 * { 
 * std::vector<MEM_SmartPtr<foo> > foo_vector;
 * foo_vector.push_back( new foo());
 * foo_vector.push_back( new foo());
 *
 * foo_vector[0]->bla();
 * } // foo_vector out of scope => heap memory freed for both foos
 *
 * @warning this class should only be used for objects created
 * on the heap via the new function. It will not behave correctly
 * if you pass ptrs to objects created with new[] nor with 
 * objects declared on the stack. Doing this is likely to crash
 * the program or lead to memory leaks.
 */

template 
      < class T >
00110 class MEM_SmartPtr {

public :

      /**
       * Construction from reference - this class
       * always assumes ownership from the rhs.
       */

00119       MEM_SmartPtr(
            const MEM_SmartPtr &rhs
      ){
            m_val = rhs.Release();
      }

      /**
       * Construction from ptr - this class always
       * assumes that it now owns the memory associated with the
       * ptr.
       */

00131       MEM_SmartPtr(
            T* val
      ) :
            m_val (val)
      {
      }
      
      /**
       * Defalut constructor
       */

00142       MEM_SmartPtr(
      ) :
            m_val (NULL)
      {
      }

      /**
       * Type conversion from this class to the type
       * of a pointer to the template parameter. 
       * This means you can pass an instance of this class
       * to a function expecting a ptr of type T.
       */

00155       operator T * () const {
            return m_val;
      }

      /**
       * Return a reference to the internal ptr class.
       * Use with care when you now that the internal ptr
       * is not NULL!
       */

            T &
00166       Ref(
      ) const {
            return *m_val;
      }     

      /** 
       * Assignment operator - ownership is transfered from rhs to lhs. 
       * There is an intenional side-effect of function of transferring
       * ownership from the const parameter rhs. This is to insure 
       * the 1-1 relationship.
       * The object associated with this instance is deleted if it 
       * is not the same as that contained in the rhs.
       */

00180       MEM_SmartPtr & operator=(
            const MEM_SmartPtr &rhs
      ) {
            if (this->m_val != rhs.m_val) {
                  delete this->m_val;
            }

            this->m_val = rhs.Release();
            return *this;
      }
      
      /** 
       * Overload the operator -> so that it's possible to access
       * all the normal methods of the internal ptr. 
       */
      
00196       T * operator->() const {
            return m_val;
      }

      /**
       * Caller takes ownership of the object - the object will not 
       * be deleted when the ptr goes out of scope.
       */

            T *
00206       Release(
      ) const {
            T* temp = m_val;
            (const_cast<MEM_SmartPtr *>(this))->m_val = NULL;     
            return temp;
      }

      /**
       * Force destruction of the internal object.
       */
      
            void
00218       Delete(
      ) {
            delete (m_val);
            m_val = NULL;
      }

      /** 
       * Destructor - deletes object if it exists
       */

00228       ~MEM_SmartPtr(
      ) {
            delete (m_val);
      }

private :
      
      /// The ptr owned by this class.
00236       T * m_val;
};

#endif


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