Is it possible to write Quake's fast InvSqrt() function in Rust?

Question

This is just to satisfy my own curiosity.

Is there an implementation of this:

float InvSqrt (float x)
{
   float xh         


        

Answer 1

You may use std::mem::transmute to make needed conversion:

fn inv_sqrt(x: f32) -> f32 {
    let xhalf = 0.5f32 * x;
    let mut i: i32 = unsafe { std::mem::transmute(x) };
    i = 0x5f3759df - (i >> 1);
    let mut res: f32 = unsafe { std::mem::transmute(i) };
    res = res * (1.5f32 - xhalf * res * res);
    res
}

You can look for a live example here: here