XTEA_DELTA
u32 limit = XTEA_DELTA * XTEA_ROUNDS;
sum += XTEA_DELTA;
sum = XTEA_DELTA * XTEA_ROUNDS;
sum -= XTEA_DELTA;
u32 limit = XTEA_DELTA * XTEA_ROUNDS;
sum += XTEA_DELTA;
sum = XTEA_DELTA * XTEA_ROUNDS;
sum -= XTEA_DELTA;