hash ^= sum64a(c)
		hash *= prime64
	}
	*s = hash
	return len(data), nil
}

func (s *sum128) Write(data []byte) (int, error) {
	for _, c := range data {
		// Compute the multiplication
		s0, s1 := bits.Mul64(prime128Lower, s[1])
		s0 += s[1]<<prime128Shift + prime128Lower*s[0]
		// Update the values
		s[1] = s1
		s[0] = s0
		s[1] ^= uint64(c)
	}
	return len(data), nil
}

	// invalid scalars and the zero value. BytesX returns an error for the point
	// at infinity, but in a prime order group such as the NIST curves that can
	// only be the result of a scalar multiplication if one of the inputs is the
	// zero scalar or the point at infinity.

	if boring.Enabled {
		return boring.ECDH(local.boring, remote.boring)
	}

	boring.Unreachable()

		computeDivMagic(&classes[i])
	}

	return classes
}

// computeDivMagic checks that the division required to compute object
// index from span offset can be computed using 32-bit multiplication.
// n / c.size is implemented as (n * (^uint32(0)/uint32(c.size) + 1)) >> 32
// for all 0 <= n <= c.npages * pageSize
func computeDivMagic(c *class) {
	// divisor
	d := c.size
	if d == 0 {
		return
	}