@kirby @jeffcliff this is what they use to return a window id

float Q_rsqrt( float number )
{
long i;
float x2, y;
const float threehalfs = 1.5F;

x2 = number * 0.5F;
y = number;
i = * ( long * ) &y;
i = 0x5f3759df - ( i >> 1 );
y = * ( float * ) &i;
y = y * ( threehalfs - ( x2 * y * y ) );

#ifndef Q3_VM
#ifdef __linux__
assert( !isnan(y) );
#endif
#endif
return y;
}