code: function parse_SupBook(blob, length, opts) {
  	var end = blob.l + length;
  	var ctab = blob.read_shift(2);
  	var cch = blob.read_shift(2);
  	opts.sbcch = cch;
  	if(cch == 0x0401 || cch == 0x3A01) return [cch, ctab];
  	if(cch < 0x01 || cch >0xff) throw new Error("Unexpected SupBook type: "+cch);
  	var virtPath = parse_XLUnicodeStringNoCch(blob, cch);
  	/* TODO: 2.5.277 Virtual Path */
  	var rgst = [];
  	while(end > blob.l) rgst.push(parse_XLUnicodeString(blob));
  	return [cch, ctab, virtPath, rgst];
  }
docs: TODO: parse 2.4.136 /* [MS-XLS] 2.4.271