Addition of an integer with an hex string

What should I do to add an integer to an hex string.

Say my hex string is:

11'h000

And I want to add integer 7 to it. Output it should give should be

11'h007

If given 11'h00e, Adding integer 1 to it should give me 11'h00f.

Are there any predefined functions in c++? I could have write my switch-case statements to get it but looking for a compact way.