# File lib/ffi/struct.rb, line 149
    def add_field(name, type, offset = nil)
      field_class, info = field_class_from(type)
      off = calc_alignment_of(field_class, offset)
      calc_current_size(off, field_class.size / 8)
      @field_names << name
      @fields[name] = field_class.new(off, info)
      @min_align = field_class.align if field_class.align > @min_align
    end