计算体长

Question

def logTime(result: PlainResult): Result = {
  result.header.headers.get(HeaderNames.CONTENT_TYPE) match {
    case Some(ct) if ct.trim.startsWith(MimeTypes.JSON) => result match {
      case simple @ SimpleResult(header, content) =>
        val time = System.currentTimeMillis - start
        SimpleResult(header, content &> Enumeratee.map(a => { 
          play.Logger.info(s"${rh.method} ${rh.uri} took ${time}ms and returned ${header.status} with body ${a}")
          simple.writeable.transform(a) 
        }))
    }
    case ct => result
  }
}

内容是响应主体，我怎么知道内容有多长？

谁知道这个答案？渴望知道！