div by const 10^16

div.go

func U128_div_10_16(hi, lo uint64) (q uint64) {
	const d uint64 = 10_000_000_000_000_000

	if hi == 0 {
		return lo / d
	}

	const M = 557518629963265578538392957
	const Mhi = M / (1 << 64)
	const Mlo = M % (1 << 64)

	lo = hi<<50 | lo>>14
	hi >>= 14

	b1, _ := bits.Mul64(lo, Mlo)
	c2, b2 := bits.Mul64(hi, Mlo)
	c3, b3 := bits.Mul64(lo, Mhi)
	c4 := hi * Mhi

	b, carry1 := bits.Add64(b1, b2, 0)
	_, carry2 := bits.Add64(b, b3, 0)

	return carry1 + carry2 + c2 + c3 + c4
}