code: func ChecksumCombine(a, b uint16) uint16 {
  	v := uint32(a) + uint32(b)
  	return uint16(v + v>>16)
  }
docs: // ChecksumCombine combines the two uint16 to form their checksum. This is done
  // by adding them and the carry.
  //
  // Note that checksum a must have been computed on an even number of bytes.