Is using a file type as a suffix something very common in cpp?

It seems to be a bit raw. Does cpp implements a standard dictionary object?

I think it's impossible to return an std::unordered_map directly with rust bindings but I'll see if there's any workaround. The other approach is perhaps creating an accessor function so that we can do something like

auto metadata = extract_metadata();
std::optional<> val = metadata.get(key);

@haixuanTao This new approach now provides access to metadata dict through getter and setter method. Due to constraints of the FFI interface I have to implement all the metadata types manually. If we want better interface, we can add a wrapper from C++ side to wrap the raw interface into template functions.