//10 times faster than (Math.log(x) / Math.LN
//but only for integers
//http://www.nbilyk.com/optimizing-actionscript-3
public function log2(x:int):int {
	var num:int = x >> 16;
	var sign:int = int(!num);
	var ans:int = (sign << 4) ^ 24;
 
	num = x >> (ans);
	sign = int(!num);
	ans = (sign << 3) ^ (ans + 4);		
 
	num = x >> (ans);
	sign = int(!num);
	ans = (sign << 2) ^ (ans + 2);
 
	num = x >> (ans);
	sign = int(!num);
	ans = (sign << 1) ^ (ans + 1);		
 
	num = x >> (ans);
	sign = int(!num);
	ans = sign ^ ans;
 
	return ans;
}