how do i do this

[code]float Q_rsqrt( float number )
{
long i;
float x2, y;
const float threehalfs = 1.5F;
x2 = number * 0.5F;
y = number; i = ( long ) &y; // evil floating point bit level hacking
i = 0x5f3759df - ( i >> 1 ); // what the fuck?
y = ( float ) &i; y = y ( threehalfs - ( x2 y * y ) ); // 1st iteration
// y = y ( threehalfs - ( x2 y * y ) ); // 2nd iteration, this can be removed
return y;
}[/code]