blender/intern/memutil/MEM_RefCountPtr.h

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/**
* $Id$
* ***** 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_RefCountPtr.h
* Declaration of MEM_RefCounted and MEM_RefCountable classes.
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* @author Laurence
*/
#ifndef NAN_INCLUDED_MEM_RefCountPtr_h
#define NAN_INCLUDED_MEM_RefCountPtr_h
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#include <stdlib.h> // for NULL !
/**
* @section MEM_RefCountable
* This is a base class for reference countable objects.
* If you want an object to be shared using a reference
* counted system derrivce from this class. All subclasses
* should insist that they are created on the heap, this
* can be done by makeing all constructors private and
* defining a static New() method that returns a ref counted
* ptr to a new()ly allocated instance.
*
* @section Example subclass
*
*
* class MySharedObject : public MEM_RefCountable {
*
* private :
* MySharedObject() : MEM_RefCountable() { //class specific initialization};
* MySharedObject(const MySharedObject &other) // not implemented
* public :
* static
* MEM_RefCountPtr<MySharedObject>
* New(
* ) {
* return MEM_RefCountPtr<MySharedObject>( new MySharedObject());
* }
*
* // other member functions
* };
*
* Alternitively you may first wish to define a fully functional
* class and then define a reference counting wrapper for this class.
* This is useful when the base type can be used without reference
* counting.
*
* E.g.
* class UsefullClass {
* private :
* ...
* public :
*
* UsefullClass()
* UsefullMethod(...)
* AnotherUsefullMethod(...)
* };
*
* class RcUsefullClass : public UsefullClass, public MEM_RefCountable
* {
* private :
* // Override base class public constructor --- forces
* // use of New(...)
* RcUsefullClass(...)
* public :
*
* // Override each public constructor of UsefullClass with
* // an equivalent static New method returning a MEM_RefCountPtr
*
* static
* MEM_RefCountPtr<RcUsefullClass>
* New(...){
* return MEM_RefCountPtr<RcUsefullClass> output(
* new UsefullClass(...)
* );
* }
*
* // warning never call destructor directly allow ref counting
* // mechanism to handle object lifetime.
* ~RcUsefullClass();
* };
*
*
*/
class MEM_RefCountable {
private :
/**
* The reference count!
* We use mutable here because we would like to
* share references of const objects!
* Maybe should think about having decRef()
* another value because we should not be deleting
* non-const objects
*/
mutable int m_count;
protected :
/**
* Protected constructors
* This class is not for direct instanciation. Sub classes
* should only be allocated on the heap.
*/
MEM_RefCountable (
) :
m_count (0)
{
};
MEM_RefCountable (
const MEM_RefCountable & other
) :
m_count (0)
{
}
public :
void
IncRef(
) const {
m_count++;
}
int
DecRef(
) {
return (--m_count);
}
~MEM_RefCountable(
) {
//nothing to do
}
};
/**
* @section MEM_RefCountPtr
*/
template
< class T >
class MEM_RefCountPtr {
public :
/**
* Construction from reference - share ownership with
* the right hand side.
*/
MEM_RefCountPtr(
const MEM_RefCountPtr &rhs
) : m_val (NULL) {
ShareOwnership(rhs.m_val);
}
/**
* Construction from ptr - this class shares
* ownership of object val.
*/
MEM_RefCountPtr(
const T* val
) :
m_val (NULL)
{
ShareOwnership(val);
}
/**
* Default constructor
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*/
MEM_RefCountPtr(
) :
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.
*/
operator T * () const {
return m_val;
}
MEM_RefCountPtr & operator=(
const MEM_RefCountPtr &rhs
) {
if (this->m_val != rhs.m_val) {
ReleaseOwnership();
ShareOwnership(rhs.m_val);
}
return *this;
}
/**
* Overload the operator -> so that it's possible to access
* all the normal methods of the internal ptr.
*/
T * operator->() const {
return m_val;
}
/**
* Returrn a reference to the shared object.
*/
T&
Ref(
) {
return *m_val;
}
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/**
* Destructor - deletes object if it's ref count is zero.
*/
~MEM_RefCountPtr(
) {
ReleaseOwnership();
}
private :
/// The ptr owned by this class.
T * m_val;
void
ShareOwnership(
const T * val
) {
if (val != NULL) {
val->IncRef();
}
m_val = const_cast<T *>(val);
}
void
ReleaseOwnership(
) {
if (m_val) {
if (m_val->DecRef() == 0) {
delete(m_val);
m_val = NULL;
}
}
}
};
#endif