docs: function write_biff2_buf(wb/*:Workbook*/, opts/*:WriteOpts*/) {
  	var o = opts || {};
  	if(DENSE != null && o.dense == null) o.dense = DENSE;
  	var ba = buf_array();
  	var idx = 0;
  	for(var i=0;i<wb.SheetNames.length;++i) if(wb.SheetNames[i] == o.sheet) idx=i;
  	if(idx == 0 && !!o.sheet && wb.SheetNames[0] != o.sheet) throw new Error("Sheet not found: " + o.sheet);
  	write_biff_rec(ba, 0x0009, write_BOF(wb, 0x10, o));
  	/* ... */
  	write_ws_biff2(ba, wb.Sheets[wb.SheetNames[idx]], idx, o, wb);
  	/* ... */
  	write_biff_rec(ba, 0x000A);
  	return ba.end();
  }