# File lib/rack/urlmap.rb, line 42
    def call(env)
      path = env["PATH_INFO"]
      script_name = env['SCRIPT_NAME']
      hHost, sName, sPort = env.values_at('HTTP_HOST','SERVER_NAME','SERVER_PORT')
      @mapping.each { |host, location, match, app|
        next unless (hHost == host || sName == host \
          || (host.nil? && (hHost == sName || hHost == sName+':'+sPort)))
        next unless path.to_s =~ match && rest = $1
        next unless rest.empty? || rest[0] == ?/
        env.merge!('SCRIPT_NAME' => (script_name + location), 'PATH_INFO' => rest)
        return app.call(env)
      }
      [404, {"Content-Type" => "text/plain", "X-Cascade" => "pass"}, ["Not Found: #{path}"]]
    ensure
      env.merge! 'PATH_INFO' => path, 'SCRIPT_NAME' => script_name
    end