code: func (l *charLobChunkWriter) runeCount(b []byte) int {
  	numChars := 0
  	for len(b) > 0 {
  		_, size := utf8.DecodeRune(b)
  		b = b[size:]
  		numChars++
  		if size == utf8.UTFMax {
  			numChars++
  		}
  	}
  	return numChars
  }
docs: // Caution: hdb counts 4 byte utf-8 encodings (cesu-8 6 bytes) as 2 (3 byte) chars