sclass StringBufferWithMaxSize implements Appendable {
  int maxSize; // in characters
  new StringBuilder buf;
  
  *(int *maxSize) {}
  
  public Appendable append(char c) { ret append(str(c)); }
  public Appendable append(CharSequence csq, int start, int end) { ret append(csq.subSequence(start, end)); }
  
  int size() { ret l(buf); }
  
  public synchronized Appendable append(CharSequence csq) {
    if (full()) this;
    int n = l(csq);
    if (size()+n > maxSize)
      buf.append(subCharSequence(csq, maxSize-size()));
    else
      buf.append(csq);
    this;
  }
  
  bool full() { ret size() >= maxSize; }
  
  synchronized toString { ret str(buf); }
}