COUNTER_BITS_TOTAL
#define COUNTER_WINDOW_SIZE (COUNTER_BITS_TOTAL - COUNTER_REDUNDANT_BITS)
unsigned long kp_backtrack[COUNTER_BITS_TOTAL / COUNTER_BITS];
top = MIN(index - index_current, COUNTER_BITS_TOTAL / COUNTER_BITS);
((COUNTER_BITS_TOTAL / COUNTER_BITS) - 1)] = 0;
index &= (COUNTER_BITS_TOTAL / COUNTER_BITS) - 1;