Function getcrc4

libapp2sys/src/main/cpp/util.h:168–179

static const uint8_t crc4_table[16] = {0, 3, 6, 5, 12, 15, 10, 9, 11, 8, 13, 14, 7, 4, 1, 2};

static uint32_t getcrc4(void *data, uint32_t len) {  // RETURN  4 bit crc
    uint8_t *p = (uint8_t *) data;

    uint8_t crc = 0;
    for (uint32_t k = 0; k < len; k++) {
        crc ^= p[k] >> 4;
        crc = crc4_table[crc];
        crc ^= p[k] & 0xF;
        crc = crc4_table[crc];
    }
    return crc;
}

static unsigned int Crc32Table[256] = {0};