void fft2InPlace(complex * _c, unsigned int _n)
{
	unsigned int m = _n;
	if(m > 0x0FFFFFFF) return;
	if(m & (m - 1)) return;
	complex * c0 = _c;
	m <<= 3;
	complex * cn = c0 + 2 * m;
	complex * cm = cn - 1;
	float s = PI / m;
	float t = 0.0f;
	complex y;
	y.r = 1.0f;
	y.i = 0.0f;
	complex * c = c0;
	complex * d = c0 + m;
	for(;;)
	{
		complex tc = *c;
		complex td = *d;
		c->i = tc.i + td.i;
		d->i = tc.i - td.i;
		c->r = tc.r + td.r;
		d->r = td.r - td.r;
		d->r = td.r * y.r - td.i * y.i;
		d->i = td.r * y.i + td.i * y.r;
		c += 2 * m;
		d += 2 * m;
		if(c >= cn)
		{
			if(c != cm)
			{
				c += c0 - cn + sizeof(complex);
				d += c0 - cn + sizeof(complex);
				t += s;
				y.r = cos(t);
				y.i = sin(t);
			}
			else
			{
				if(m == sizeof(complex)) return;
				m >>= 1;
				cm = cn + cm - sizeof(complex);
				c = c0;
				d = c0 + m;
				s *= 2;
				t = 0.0f;
				y.r = 1.0f;
				y.i = 0.0f;
			}
		}
	}
}