class Geo::GeoRefCount

Base class for reference counted resources.

This class makes it possible to implement a 'poor man's garbage collection' in C++. Each class derived from this base class maintains a reference count, initially zero, incremented by the AddRef() method and decremented by the Release() method. If the reference count is zero after Release() has decremented it the object deletes itself by calling the destructor.

Reference counting is designed to be used in conjunction with factory methods. For example one might define the class Foo which can be reference counted:

class Foo : public GeoRefCount
{
public:
    static Foo* CreateFoo()
    {
        Foo* myFoo = GEO_NEW(Foo);      // Ref count will be 0
        if (!myFoo)     return 0;
        if (!myFoo->Setup(...))
        {
            // failed!
            GEO_DELETE(Foo, myFoo);
            return 0;
        }
        // success!
        myFoo->AddRef();    // ref count -> 1
        return myFoo;
    }
protected:
    Foo()
    {
        // The constructor is protected so that Foo has to 
        // be allocated via the factory method. 
    }
};

...
Foo*    my_foo = Foo::CreateFoo();
SomeExcitingFunction(my_foo);
my_foo->Release();
...

The rule of thumb for reference counting is if you AddRef() or Create...() it, you must at some point Release() it.

GeoRefCount also allows the same class to be used in a non-ref-counted scenario. In this case you allow NEW and DELETE as usual, but once AddRef is called you must use Release. For instance, DirectGeoMeshLoader uses this strategy to return GeoMeshes which are "owned" by the caller, rather than just "existing" somewhere.

Variables

Functions

virtual Geo::GeoRefCount::~GeoRefCount

...

public: virtual ~GeoRefCount()

...

Virtual destructor required to make sure that the concrete class destructor gets called.

s32 Geo::GeoRefCount::AddRef

...

public: s32 AddRef()

...

Increments the reference count and return new value.

Returns

New value of reference count.

Geo::GeoRefCount::GeoRefCount

...

public: GeoRefCount()

...

Default constructor. The reference count is initially zero.

s32 Geo::GeoRefCount::Release

...

public: s32 Release()

...

Decrements the reference count, deleting the object if it reaches zero.

Returns

Returns reference count after decrement. 0 if deleted.