void reverse_arr(char *buff){
        char temp;
        int i, blen;

        blen = sizeof(buff);
        printf("blen = %d\n", blen);

        for(i = 0; i < blen/2; i++){
                temp = buff[i];
                buff[i] = buff[blen - i - 1];
                buff[blen -i -1] = temp;
        }

        for(i = 0; i < blen; i++){
                printf("%d", buff[i]);
        }

        printf("\n");
}