Efficient ref-counting prototype for SGVector

gistfile1.cpp

template <typename T>
class SGVector
{
public:
	SGVector(int32_t len)
	{
		int32_t size = sizeof(T)*len + sizeof(int32_t);
		uchar *memory = malloc(size);
		m_buffer = memory + sizeof(int32_t);

		int32_t *ref_count = get_ref_count_pointer();
		*ref_count = 0;
	}

	SGVector(const SGVector& o)
	{
		m_len = o.m_len;
		m_buffer = o.m_buffer;

		// update ref-count
		int32_t *ref_count = get_ref_count_pointer();
		*ref_count += 1;
	}

	~SGVector()
	{
		// update ref-count
		int32_t *ref_count = get_ref_count_pointer();
		*ref_count -= 1;
		if (*ref_count <= 0)
			free(ref_count);
	}
private:
	int32_t *get_ref_count_pointer()
	{
		// ref-counting is stored before the buffer
		return ((uchar *)m_buffer) - sizeof(int32_t);
	}
	T *m_buffer;
	int32_t m_len;
};