instance method translate_offset

# File activesupport/lib/active_support/multibyte/chars.rb, line 218
        def translate_offset(byte_offset)
          return nil if byte_offset.nil?
          return 0   if @wrapped_string == ""

          begin
            @wrapped_string.byteslice(0...byte_offset).unpack("U*").length
          rescue ArgumentError
            byte_offset -= 1
            retry
          end
        end