add_line_numbers

# File lib/rdoc/generator/markup.rb, line 68
  def add_line_numbers(src)
    if src =~ /\A.*, line (\d+)/ then
      first = $1.to_i - 1
      last  = first + src.count("\n")
      size = last.to_s.length

      line = first
      src.gsub!(/^/) do
        res = if line == first then
                " " * (size + 2)
              else
                "%2$*1$d: " % [size, line]
              end

        line += 1
        res
      end
    end
  end