void main(void){
unsigned int buff32;
int i, buff = 0;
int datalength =4;
long oldval = 0;
long long counter = 0;

    for (i = 0; i <35; i++){
        buff++;
        buff &= 0x0F;
        buff32 = 1L << (datalength - 1);
        buff32 = (buff ^ buff32) - buff32;
        counter += (buff32 - oldval);
        oldval = counter;
        printf("counter = %i buff = %i\n", counter, buff);
    }
}

counter = 1 buff = 0
counter = 2 buff = 0
counter = 3 buff = 0
counter = 4 buff = 0
counter = 5 buff = 0
counter = 6 buff = 0
counter = 7 buff = 0
counter = -8 buff = 0
counter = -7 buff = 0
counter = -6 buff = 0
counter = -5 buff = 0
counter = -4 buff = 0
counter = -3 buff = 0
counter = -2 buff = 0
counter = -1 buff = 0
counter = 0 buff = 1
counter = 1 buff = 1
counter = 2 buff = 1
counter = 3 buff = 1
counter = 4 buff = 1
counter = 5 buff = 1
counter = 6 buff = 1
counter = 7 buff = 1
counter = -8 buff = 1
counter = -7 buff = 1
counter = -6 buff = 1
counter = -5 buff = 1
counter = -4 buff = 1
counter = -3 buff = 1
counter = -2 buff = 1
counter = -1 buff = 1
counter = 0 buff = 2
counter = 1 buff = 2
counter = 2 buff = 2
counter = 3 buff = 2