# File lib/gettext/tools/parser/ruby.rb, line 275
    def detect_encoding(source)
      binary_source = source.dup.force_encoding("ASCII-8BIT")
      if /\A.*coding\s*[=:]\s*([[:alnum:]\-_]+)/ =~ binary_source
        $1.gsub(/-(?:unix|mac|dos)\z/, "")
      else
        nil
      end
    end