class Rcov::TextCoverageDiff

def compare_state
  return unless verify_diff_available
  begin
    format, prev_state = File.open(@state_file){|f| self.SERIALIZER.load(f) }
  rescue
    $stderr.puts <<-EOF
    Couldn't load coverage data from #{@state_file}.
    EOF
    return # '
  end
  if !(Array === format) or
    FORMAT_VERSION[0] != format[0] || FORMAT_VERSION[1] < format[1]
    $stderr.puts <<-EOF
    Couldn't load coverage data from #{@state_file}.
    The file is saved in the format  #{format.inspect[0..20]}.
    This rcov executable understands #{FORMAT_VERSION.inspect}.
    EOF
    return # '
  end
  each_file_pair_sorted do |filename, fileinfo|
    old_data = Tempfile.new("#{mangle_filename(filename)}-old")
    new_data = Tempfile.new("#{mangle_filename(filename)}-new")
    if prev_state.has_key? filename
      old_code, old_cov = prev_state[filename].values_at(:lines, :coverage)
      old_code.each_with_index do |line, i|
        prefix = old_cov[i] ? "   " : "!! "
        old_data.write "#{prefix}#{line}"
      end
    else
      old_data.write ""
    end
    old_data.close
    SCRIPT_LINES__[filename].each_with_index do |line, i|
      prefix = fileinfo.coverage[i] ? "   " : "!! "
      new_data.write "#{prefix}#{line}"
    end
    new_data.close
    diff = `#{@diff_cmd} -u "#{old_data.path}" "#{new_data.path}"`
    new_uncovered_hunks = process_unified_diff(filename, diff)
    old_data.close!
    new_data.close!
    display_hunks(filename, new_uncovered_hunks)
  end
end