peek specific field from a protobuf message by field numbers

gistfile1.scala

  private[this] def peakNested(fid:Int, pbs:CodedInputStream):Option[CodedInputStream] = {
    val (_, res) = Iterator.continually(pbs.readTag()).span{tag =>
      (tag != 0) && (WireFormat.getTagFieldNumber(tag) != fid) && pbs.skipField(tag)
    }
    val lastid = WireFormat.getTagFieldNumber(res.next)
    if (lastid == fid) Some(pbs)
    else None
  }
  def recursivePeek[T](ids:Seq[Int], extract: (CodedInputStream=>T), pbs:CodedInputStream):Option[T] = {
    ids match {
      case h::Nil =>
        peakNested(h, pbs).map(s => extract(s))
      case h::ds =>
        peakNested(h, pbs).flatMap(s => {
          s.readRawVarint32()
          recursivePeek(ds, extract, pbs)
        })
    }
  }