Scoped begin/end.

class IPersistentStorage
{
public:

    virtual ~IPersistentStorage() = default;

    virtual void put_string(const char* key, const char* value) = 0;
    virtual const char* get_string(const char* key);

    template<typename T>
    void array(const char* const array_name, const T& code)
    {
        do_begin_array(array_name);
        code();
        do_end_array();
    }

private:

    virtual void do_begin_array(const char* array_name) = 0;
    virtual void do_end_array() = 0;

};