code: func tableSum(t *Table) uint16 {
  	var a [1024]byte
  	b := a[:0]
  	if t != nil {
  		for _, x := range t.entries {
  			b = appendUint16(b, x)
  		}
  	}
  	return ChecksumIBM(b)
  }
docs: // tableSum returns the IBM checksum of table t.