G4ReferenceCountedHandle.hh

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// 
// Class G4ReferenceCountedHandle
//
// Class description:
//
// A class to provide reference counting mechanism.
// It is a templated class, acting as a smart pointer,
// wrapping the type to be counted. It performs the reference counting
// during the life-time of the counted object. When its count reaches zero
// the counted object is destroyed by explicit call to its destructor.
// This class provides overloaded operators *() and ->() to allow similar
// syntax as for the normal "dumb" pointers.
// The basic rule for the use of this class is that a handle must always
// be exchanged by reference never dinamically allocated (i.e. never
// instantiated using 'new').
// The validity of a smart pointer object can be verified by using the
// operator !() or operator bool(). I.e.:
//    if( !smartPtrObj ) { ... } // Problem! We must initialize it first!
//    else               { ... } // OK!
// Trying to 'delete' a smart pointer object will generate a compilation
// error (since we're dealing with objects, not pointers!).

// Author:      Radovan Chytracek, CERN  (Radovan.Chytracek@cern.ch)
// Date:        November 2001
// ----------------------------------------------------------------------
#ifndef _G4REFERENCECOUNTEDHANDLE_H_
#define _G4REFERENCECOUNTEDHANDLE_H_ 1

#include "G4Types.hh"
#include "G4Allocator.hh"

template <class X> class G4CountedObject;

template <class X>
class G4ReferenceCountedHandle
{

public:  // with description

  inline G4ReferenceCountedHandle( X* rep = 0 );
    // Constructor.
  
  inline G4ReferenceCountedHandle( const G4ReferenceCountedHandle<X>& right );
    // Copy constructor.

  inline ~G4ReferenceCountedHandle();
    // Destructor.
  
  inline G4ReferenceCountedHandle<X>& operator =( const G4ReferenceCountedHandle<X>& right );
    // Assignment operator by reference.
  
  inline G4ReferenceCountedHandle<X>& operator =( X* objPtr );
    // Assignment operator by pointer.
  
  inline unsigned int Count() const;
    // Forward to Counter class.
  
  inline X* operator ->() const;
    // Operator -> allowing the access to counted object.
    // The check for 0-ness is left out for performance reasons,
    // see operator () below.
    // May be called on initialised smart-pointer only!
  
  inline G4bool operator !() const;
    // Validity test operator.
  
  inline operator bool() const;
    // Boolean operator.
  
  inline X* operator ()() const;
    // Functor operator (for convenience).
  
  // There is no provision that this class is subclassed.
  // If it is subclassed & new data members are added then the
  // following "new" & "delete" will fail and give errors. 
  //
  inline void* operator new( size_t );
    // Operator new defined for G4Allocator.
  
  inline void operator delete( void *pObj );
    // Operator delete defined for G4Allocator.

private:

  G4CountedObject<X>*     fObj;
    // The object subject to reference counting.
};

extern G4GLOB_DLL
G4Allocator<G4ReferenceCountedHandle<void>>*& aRCHAllocator();

template <class X>
class G4CountedObject
{

  friend class G4ReferenceCountedHandle<X>;

public:  // with description

  G4CountedObject( X* pObj = 0 );
    // Constructor.

  ~G4CountedObject();
    // Destructor.

  inline void AddRef();
    // Increase the count.

  inline void Release();
    // Decrease the count and if zero destroy itself.
  
  // There is no provision that this class is subclassed.
  // If it is subclassed & new data members are added then the
  // following "new" & "delete" will fail and give errors.
  //
  inline void* operator new( size_t );
    // Operator new defined for G4Allocator.

  inline void operator delete( void *pObj );
    // operator delete defined for G4Allocator.

private:

  unsigned int fCount;
    // Reference counter.
  X* fRep;
    // The counted object.
};

extern G4GLOB_DLL
G4Allocator<G4CountedObject<void>>*& aCountedObjectAllocator();

// --------- G4CountedObject<X> Inline function definitions ---------

template <class X>
G4CountedObject<X>::G4CountedObject( X* pObj )
 : fCount(0), fRep( pObj )
{
    if( pObj != 0 ) fCount = 1;
}

template <class X>
G4CountedObject<X>::~G4CountedObject()
{
    delete fRep;
}
    
template <class X>
void G4CountedObject<X>::AddRef()
{
    ++fCount;
}
    
template <class X>
void G4CountedObject<X>::Release()
{
    if( --fCount == 0 ) delete this;
}

template <class X>
void* G4CountedObject<X>::operator new( size_t )
{
    if (!aCountedObjectAllocator())
      aCountedObjectAllocator() = new G4Allocator<G4CountedObject<void>>;
    return( (void *)aCountedObjectAllocator()->MallocSingle() );
}
    
template <class X>
void G4CountedObject<X>::operator delete( void *pObj )
{
    aCountedObjectAllocator()->FreeSingle( (G4CountedObject<void>*)pObj );
}

// --------- G4ReferenceCountedHandle<X> Inline function definitions ---------

template <class X>
G4ReferenceCountedHandle<X>::
 G4ReferenceCountedHandle( X* rep )
 : fObj( 0 )
{
    if( rep != 0 )
      fObj = new G4CountedObject<X>( rep );
}

template <class X>
G4ReferenceCountedHandle<X>::
 G4ReferenceCountedHandle( const G4ReferenceCountedHandle<X>& right )
 : fObj( right.fObj )
{
    fObj->AddRef();
}
  
template <class X>
G4ReferenceCountedHandle<X>::~G4ReferenceCountedHandle()
{
    if( fObj ) fObj->Release();
}
  
template <class X>
G4ReferenceCountedHandle<X>& G4ReferenceCountedHandle<X>::
 operator =( const G4ReferenceCountedHandle<X>& right )
{
    if( fObj != right.fObj )
    {
      if( fObj )
        fObj->Release();
      this->fObj = right.fObj;
      fObj->AddRef();
    }
    return *this;
}
  
template <class X>
G4ReferenceCountedHandle<X>& G4ReferenceCountedHandle<X>::
 operator =( X* objPtr )
{
    if( fObj )
      fObj->Release();
    this->fObj = new  G4CountedObject<X>( objPtr );
    return *this;
}
  
template <class X>
unsigned int G4ReferenceCountedHandle<X>::Count() const
{
    return( fObj ? fObj->fCount : 0 );
}
  
template <class X>
X* G4ReferenceCountedHandle<X>::operator ->() const
{
    return( fObj ? fObj->fRep : 0 );
}
  
template <class X>
G4bool G4ReferenceCountedHandle<X>::operator !() const
{
    return( ( !fObj ) ? true : false );
}
  
template <class X>
G4ReferenceCountedHandle<X>::operator bool() const
{
    return( ( fObj ) ? true : false );
}
  
template <class X>
X* G4ReferenceCountedHandle<X>::operator ()() const
{
    return( fObj ? fObj->fRep : 0 );
}
  
template <class X>
void* G4ReferenceCountedHandle<X>::operator new( size_t )
{
    if (!aRCHAllocator())
      aRCHAllocator() = new G4Allocator<G4ReferenceCountedHandle<void> >;
    return( (void *)aRCHAllocator()->MallocSingle() );
}
  
template <class X>
void G4ReferenceCountedHandle<X>::operator delete( void *pObj )
{
    aRCHAllocator()->FreeSingle( (G4ReferenceCountedHandle<void>*)pObj );
}

#endif // _G4REFERENCECOUNTEDHANDLE_H_