Fast Inverse Root from Quake implemented in Golang

fastisqrt.go

package quake

import "unsafe"

type float = float32

// FastISqrt implements Quake fast inverse square root
func FastISqrt(number float) float {
	type long = uint64
	const threehalf = 3. / 2.
	const wtf long = 0x5f3759df
	var i long
	var x2, y float
	x2 = number * 0.5
	y = number
	i = *(*long)(unsafe.Pointer(&y))
	i = wtf - (i >> 1)
	y = *(*float)(unsafe.Pointer(&i))
	y = y * (threehalf - (x2 * y * y))
	return y
}