sclass LimitedOutputStream extends CountingOutputStream {
  long limit;
  
  *(OutputStream out) { super(out); }
  *(OutputStream out, long *limit) { super(out); }
  
  @Override
  public void write(int b) throws IOException {
    checkLimit();
    super.write(b);
  }

  @Override
  public void write(byte[] b) throws IOException {
    checkLimit();
    super.write(b);
  }

  @Override
  public void write(byte[] b, int off, int len) throws IOException {
    checkLimit();
    super.write(b, off, len);
  }
  
  void checkLimit {
    if (counter >= limit)
      fail("Write limit reached (" + n2(limit) + " bytes)");
  }
}