Is there a way to increase the efficiency of shared_ptr by storing the reference count inside the controlled object?

Question

This is becoming a common pattern in my code, for when I need to manage an object that needs to be noncopyable because either A. it is \"heavy\" or B. it is an operating sys

Answer 1

Use a boost::intrusive_ptr which is designed to work on a class with an embedded reference count.

Non-tested example based on example here:

class Resource; 

class Implementation : public boost::noncopyable 
{ 
    friend class Resource;
    HANDLE someData;
    int refCount; // The reference count.
    Implementation(HANDLE input) : someData(input) { refCount = 0; }; 
    void SomeMethodThatActsOnHandle() { 
        //Do stuff 
    }; 
public: 
    ~Implementation() { FreeHandle(someData) }; 
};

intrusive_ptr_add_ref(Implementation* imp) { imp->refCount++; }
intrusive_ptr_release(Implementation* imp) { if(--imp->refCount) == 0) delete imp; }

class Resource 
{ 
    boost::intrusive_ptr impl; 
public: 
    Resource(int argA) explicit { 
        HANDLE handle =  
            SomeLegacyCApiThatMakesSomething(argA); 
        if (handle == INVALID_HANDLE_VALUE) 
            throw SomeTypeOfException(); 
        impl.reset(new Implementation(handle)); 
    }; 
    void SomeMethodThatActsOnTheResource() { 
        impl->SomeMethodThatActsOnTheHandle(); 
    }; 
};