c++校验和的2种实现方式

static unsigned char crc8_table[] = {
        0x00, 0x5e, 0xbc, 0xe2, 0x61, 0x3f, 0xdd, 0x83, 0xc2, 0x9c, 0x7e, 0x20, 0xa3, 0xfd, 0x1f, 0x41,
        0x9d, 0xc3, 0x21, 0x7f, 0xfc, 0xa2, 0x40, 0x1e, 0x5f, 0x01, 0xe3, 0xbd, 0x3e, 0x60, 0x82, 0xdc,
        0x23, 0x7d, 0x9f, 0xc1, 0x42, 0x1c, 0xfe, 0xa0, 0xe1, 0xbf, 0x5d, 0x03, 0x80, 0xde, 0x3c, 0x62,
        0xbe, 0xe0, 0x02, 0x5c, 0xdf, 0x81, 0x63, 0x3d, 0x7c, 0x22, 0xc0, 0x9e, 0x1d, 0x43, 0xa1, 0xff,
        0x46, 0x18, 0xfa, 0xa4, 0x27, 0x79, 0x9b, 0xc5, 0x84, 0xda, 0x38, 0x66, 0xe5, 0xbb, 0x59, 0x07,
        0xdb, 0x85, 0x67, 0x39, 0xba, 0xe4, 0x06, 0x58, 0x19, 0x47, 0xa5, 0xfb, 0x78, 0x26, 0xc4, 0x9a,
        0x65, 0x3b, 0xd9, 0x87, 0x04, 0x5a, 0xb8, 0xe6, 0xa7, 0xf9, 0x1b, 0x45, 0xc6, 0x98, 0x7a, 0x24,
        0xf8, 0xa6, 0x44, 0x1a, 0x99, 0xc7, 0x25, 0x7b, 0x3a, 0x64, 0x86, 0xd8, 0x5b, 0x05, 0xe7, 0xb9,
        0x8c, 0xd2, 0x30, 0x6e, 0xed, 0xb3, 0x51, 0x0f, 0x4e, 0x10, 0xf2, 0xac, 0x2f, 0x71, 0x93, 0xcd,
        0x32, 0x6c, 0x8e, 0xd0, 0x53, 0x0d, 0xef, 0xb1, 0xf0, 0xae, 0x4c, 0x12, 0x91, 0xcf, 0x2d, 0x73,
        0xca, 0x94, 0x76, 0x28, 0xab, 0xf5, 0x17, 0x49, 0x08, 0x56, 0xb4, 0xea, 0x69, 0x37, 0xd5, 0x8b,
        0x57, 0x09, 0xeb, 0xb5, 0x36, 0x68, 0x8a, 0xd4, 0x95, 0xcb, 0x29, 0x77, 0xf4, 0xaa, 0x48, 0x16,
        0xe9, 0xb7, 0x55, 0x0b, 0x88, 0xd6, 0x34, 0x6a, 0x2b, 0x75, 0x97, 0xc9, 0x4a, 0x14, 0xf6, 0xa8,
        0x74, 0x2a, 0xc8, 0x96, 0x15, 0x4b, 0xa9, 0xf7, 0xb6, 0xe8, 0x0a, 0x54, 0xd7, 0x89, 0x6b, 0x35
};

unsigned char spo2_crc(const unsigned char *buffer, short length) {

    unsigned char crc = 0;
    while (length--) {
        crc = crc8_table[crc ^ *(buffer++)];
    }
    //printf("gao: 校验和 %x\n",crc);
    return (crc);
}


int main()
{

    unsigned char packet[6] = {0xAA, 0x55, 0x50, 0x03, 0x02, 0x01};


    //cout << sizeof( packet ) << endl;

    unsigned char add = spo2_crc( packet ,sizeof( packet ) );

    unsigned char packet_add[7] = {0};

    memcpy( packet_add,packet,sizeof( packet ) );

    packet_add[6] = add;

    cout<< packet_add[0] << endl;
    cout<< packet_add[1] << endl;
    cout<< packet_add[2] << endl;
    cout<< packet_add[6] << endl;
    printf("spo2: 0 %x\n",packet_add[0] );
    printf("spo2: 校验和 %x\n",packet_add[6] );

    cout<< "=========================================" << endl;


    unsigned char packet1[7] = {0xAA, 0x55, 0x50, 0x03, 0x02, 0x01};

    //cout << sizeof( packet ) << endl;

    unsigned char add2 = spo2_crc( packet1 ,sizeof( packet1 )-1 );

    packet1[sizeof( packet1 )-1] = add2;

    cout<< packet1[0] << endl;
    cout<< packet1[1] << endl;
    cout<< packet1[2] << endl;
    cout<< packet1[6] << endl;
    printf("spo2: 0 %x\n",packet1[0] );
    printf("spo2: 校验和 %x\n",packet1[6] );



}