code: func calcMemSize64WithUint(off *big.Int, length64 uint64) (uint64, bool) {
  	// if length is zero, memsize is always zero, regardless of offset
  	if length64 == 0 {
  		return 0, false
  	}
  	// Check that offset doesn't overflow
  	if !off.IsUint64() {
  		return 0, true
  	}
  	offset64 := off.Uint64()
  	val := offset64 + length64
  	// if value < either of it's parts, then it overflowed
  	return val, val < offset64
  }
docs: // calcMemSize64WithUint calculates the required memory size, and returns
  // the size and whether the result overflowed uint64
  // Identical to calcMemSize64, but length is a uint64