docs: function parse_BOF(blob, length) {
  	var o = {BIFFVer:0, dt:0};
  	o.BIFFVer = blob.read_shift(2); length -= 2;
  	if(length >= 2) { o.dt = blob.read_shift(2); blob.l -= 2; }
  	switch(o.BIFFVer) {
  		case 0x0600: /* BIFF8 */
  		case 0x0500: /* BIFF5 */
  		case 0x0400: /* BIFF4 */
  		case 0x0300: /* BIFF3 */
  		case 0x0200: /* BIFF2 */
  		case 0x0002: case 0x0007: /* BIFF2 */
  			break;
  		default: if(length > 6) throw new Error("Unexpected BIFF Ver " + o.BIFFVer);
  	}
  
  	blob.read_shift(length);
  	return o;
  }