Changing Stateid openfst

I'm trying to read files in GFA format and then parse into an openfst format. In GFA format, each new line starts with a character that identifies what type of line it is. What I've done so far is if it starts with H, it ignore the rest of the line and go the next one. If it starts with S, it means it's a state, so it proceeds to identify each part of the line which consist of five strings including the S. After this, I add a state, but I want my state to hold the value of one of the strings identified in the line, which is a numerical value. As I understand, when you use an AddState, it return a Stateid which begins at zero, then increments by one. If it helps, I'm currently using a StdVectorFst object for the AddState function. I am reading about the SetState function from the vector_fst_base_impl class, would I be able to use this funcion to first get the StateId I want to change and then assign the new value? If so, would this cause any errors?

Thanks.