code: func (w *Writer) Write(p []byte) (n int, err error) {
  	if w.closed {
  		return 0, ErrClosed
  	}
  
  	overwrite := false
  	if int64(len(p)) > w.pending {
  		p = p[0:w.pending]
  		overwrite = true
  	}
  
  	n, err = w.multi.Write(p)
  	w.pending -= int64(n)
  	if err == nil && overwrite {
  		err = ErrOverflow
  		return
  	}
  
  	return
  }
docs: // Write writes the object's contents. Write returns the error ErrOverflow if
  // more than size bytes are written after WriteHeader.