Reference counting is a technique used in smart pointers to manage memory allocation and deallocation. std::shared_ptr in C++ provides a built-in reference counting mechanism, but sometimes you may need to implement custom reference counting logic. In this blog post, we will explore how to achieve custom reference counting with std::shared_ptr in C++.

By default, std::shared_ptr uses a reference counter that increments and decrements the reference count for each shared ownership of an object. When the reference count reaches zero, the object is deallocated. However, in some scenarios, you may want to customize this behavior, such as adding additional logic or tracking the reference count using a different data structure.

To implement custom reference counting, we can create a wrapper class that encapsulates a std::shared_ptr and provides our custom reference counting logic. Here’s an example:

class CustomRefCount {
public:
    CustomRefCount() : refCount(0) {
        // Additional initialization logic
    }

    void incrementRefCount() {
        // Custom reference counting logic
        refCount++;
    }

    void decrementRefCount() {
        // Custom reference counting logic
        refCount--;

        if (refCount == 0) {
            // Deallocation logic
            delete this;
        }
    }

private:
    int refCount;
    std::shared_ptr<Object> wrappedPtr;
};

In the CustomRefCount class, we define two methods incrementRefCount and decrementRefCount. These methods are responsible for incrementing and decrementing the reference count, respectively, by applying our custom logic.

To use this custom reference counting wrapper, you can create an instance of CustomRefCount and initialize the wrappedPtr member with a std::shared_ptr to the object you want to reference count. For example:

// Creating an object and wrapping it with our custom reference counting logic
CustomRefCount* wrapper = new CustomRefCount;
wrapper->incrementRefCount();

This way, we have a std::shared_ptr-like mechanism with custom reference counting logic. It allows us to implement additional behavior, such as custom deallocation logic or tracking the reference count using a different data structure.

Using custom reference counting with std::shared_ptr can be useful in scenarios where you need to extend or modify the default behavior of smart pointers. However, it’s essential to understand the implications and potential pitfalls that come with customizing reference counting logic.

#programming #cplusplus