/usr/include/root/TGeoRCPtr.h is in libroot-geom-dev 5.34.19+dfsg-1.2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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* Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *
* All rights reserved. *
* *
* For the licensing terms see $ROOTSYS/LICENSE. *
* For the list of contributors see $ROOTSYS/README/CREDITS. *
*************************************************************************/
// Author: Andrei.Gheata@cern.ch 29/05/2013
//______________________________________________________________________________
// TGeoRCPtr - A reference counting-managed pointer for classes derived from
// TGeoExtension which can be used as C pointer. Based on
// CodeProject implementation example
//______________________________________________________________________________
/*______________________________________________________________________________
Example:
=======
class MyExtension : public TGeoExtension {
public:
MyExtension() : TGeoExtension(), fRC(0) {printf("Created MyExtension\n");}
virtual ~MyExtension() {printf("Deleted MyExtension\n");}
virtual TGeoExtension *Grab() const {fRC++; return (TGeoExtension*)this;}
virtual void Release() const {assert(fRC > 0); fRC--; if (fRC ==0) delete this;}
void print() const {printf("MyExtension object %p\n", this);}
private:
mutable Int_t fRC; // Reference counter
ClassDef(MyExtension,1)
};
Usage:
======
// Module 1 creates an object
TGeoRCPtr<MyExtension> a2 = new MyExtension(); //fRC=1
// Module 2 grabs object
TGeoRCPtr<MyExtension> ptr2 = a2; //fRC=2
// Module 2 invokes a method
ptr2->Print();
(*ptr2).Print();
// Module 1 no longer needs object
a2 = 0; //RC=1
// Module 2 no longer needs object
ptr2 = 0; //object will be destroyed here
Note:
=====
Event if one forgets to call ptr2 = 0, the object gets delete when the method
using ptr2 gets out of scope.
______________________________________________________________________________*/
template<class T>
class TGeoRCPtr
{
public:
//Construct using a C pointer, e.g. TGeoRCPtr<T> x = new T();
TGeoRCPtr(T* ptr = 0)
: fPtr(ptr)
{
if(ptr != 0) ptr->Grab();
}
//Copy constructor
TGeoRCPtr(const TGeoRCPtr &ptr)
: fPtr(ptr.fPtr)
{
if(fPtr != 0) fPtr->Grab();
}
~TGeoRCPtr()
{
if(fPtr != 0) fPtr->Release();
}
//Assign a pointer, e.g. x = new T();
TGeoRCPtr &operator=(T* ptr)
{
if(ptr != 0) ptr->Grab();
if(fPtr != 0) fPtr->Release();
fPtr = ptr;
return (*this);
}
//Assign another TGeoRCPtr
TGeoRCPtr &operator=(const TGeoRCPtr &ptr)
{
return (*this) = ptr.fPtr;
}
//Retrieve actual pointer
T* Get() const
{
return fPtr;
}
//Some overloaded operators to facilitate dealing with an TGeoRCPtr as a convetional C pointer.
//Without these operators, one can still use the less transparent Get() method to access the pointer.
T* operator->() const {return fPtr;} //x->member
T &operator*() const {return *fPtr;} //*x, (*x).member
operator T*() const {return fPtr;} //T* y = x;
operator bool() const {return fPtr != 0;} //if(x) {/*x is not NULL*/}
bool operator==(const TGeoRCPtr &ptr) {return fPtr == ptr.fPtr;}
bool operator==(const T *ptr) {return fPtr == ptr;}
private:
T *fPtr; //Actual pointer
};
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