sclass TailFileLinewise {
  settable File file;
  settable long startOffset;
  settable int interval = 1000;
  
  TailFile tf;
  LineBuffer lineBuffer = new(voidfunc(S s) { newLine(s) });
  
  event newLine(S line);
  
  void start {
    if (tf == null) ret;
    initialFileSize = l(file);
    tf = new TailFile(file, interval, s -> lineBuffer.append(s));
    tf.l = startOffset;
    tf.start();
  }
  
  bool readingHistory() {
    ret tf.currentFileSize() >= initialFileSize;
  }
}