Fast square root in c

rsqrt.c

// Source: https://en.wikipedia.org/wiki/Fast_inverse_square_root
#include <stdint.h> // uint32_t
	
float Q_rsqrt(float number)
{
    union {
        float    f;
        uint32_t i;
    }
    conv = { .f = number };
    conv.i  = 0x5f3759df - (conv.i >> 1);
    conv.f *= 1.5F - (number * 0.5F * conv.f * conv.f);
    return conv.f;
}