align.go

// Taken from https://github.com/mdempsky/maligned/blob/master/maligned.go#L227.
// Corrected for the negative x.

// align returns the smallest y >= x such that y % a == 0.
func align(x, a int64) int64 {
	sign := int64(1)
	if x < 0 {
		x = -x
		sign = -1
	}

	if a < 0 {
		a = -a // align size is always positive
	}
	y := x + a - 1
	return sign * (y - y%a)
}

Working code - http://play.golang.org/p/WtFXA4CI-b