bits mirror

0 000 000 000 0
1 001 010 100 4
2 010 100 010 2
3 011 110 110 6
4 100 001 001 1
5 101 011 101 5
6 110 101 011 3
7 111 111 111 7
// data: array
// N:size of array

void mirror(char *data, const int N)
{
 int target = 0;
 for (int position = 0; position< N; position++) {
   if (target > position) 
     swap(data[position], data[target];
   int Mask = N;
   while (target & Mask >>= 1){
     // unset
     target &= ~Mask;
   }
   target |= Mask;
 }
}