call

# File actionpack/lib/action_dispatch/middleware/static.rb, line 44
    def call(env)
      path      = env['PATH_INFO']
      gzip_path = gzip_file_path(path)

      if gzip_path && gzip_encoding_accepted?(env)
        env['PATH_INFO']            = gzip_path
        status, headers, body       = @file_server.call(env)
        if status == 304
          return [status, headers, body]
        end
        headers['Content-Encoding'] = 'gzip'
        headers['Content-Type']     = content_type(path)
      else
        status, headers, body = @file_server.call(env)
      end

      headers['Vary'] = 'Accept-Encoding' if gzip_path

      return [status, headers, body]
    ensure
      env['PATH_INFO'] = path
    end