【C语言】使用查表法计算CRC8

笔者曾经在一个项目中，有一个数据协议对接需要用到简单的CRC8校验。当初我们实现的方法是使用查表法，现将实现代码分享下。

//CRC8查表法  
static uint8_t R_CRCTABLE[] =  //reversed, 8-bit, poly=0x07 
{ 
    0x00, 0x91, 0xE3, 0x72, 0x07, 0x96, 0xE4, 0x75, 
    0x0E, 0x9F, 0xED, 0x7C, 0x09, 0x98, 0xEA, 0x7B, 
    0x1C, 0x8D, 0xFF, 0x6E, 0x1B, 0x8A, 0xF8, 0x69, 
    0x12, 0x83, 0xF1, 0x60, 0x15, 0x84, 0xF6, 0x67, 
    0x38, 0xA9, 0xDB, 0x4A, 0x3F, 0xAE, 0xDC, 0x4D, 
    0x36, 0xA7, 0xD5, 0x44, 0x31, 0xA0, 0xD2, 0x43, 
    0x24, 0xB5, 0xC7, 0x56, 0x23, 0xB2, 0xC0, 0x51, 
    0x2A, 0xBB, 0xC9, 0x58, 0x2D, 0xBC, 0xCE, 0x5F, 
    0x70, 0xE1, 0x93, 0x02, 0x77, 0xE6, 0x94, 0x05, 
    0x7E, 0xEF, 0x9D, 0x0C, 0x79, 0xE8, 0x9A, 0x0B, 
    0x6C, 0xFD, 0x8F, 0x1E, 0x6B, 0xFA, 0x88, 0x19, 
    0x62, 0xF3, 0x81, 0x10, 0x65, 0xF4, 0x86, 0x17, 
    0x48, 0xD9, 0xAB, 0x3A, 0x4F, 0xDE, 0xAC, 0x3D, 
    0x46, 0xD7, 0xA5, 0x34, 0x41, 0xD0, 0xA2, 0x33, 
    0x54, 0xC5, 0xB7, 0x26, 0x53, 0xC2, 0xB0, 0x21, 
    0x5A, 0xCB, 0xB9, 0x28, 0x5D, 0xCC, 0xBE, 0x2F, 
    0xE0, 0x71, 0x03, 0x92, 0xE7, 0x76, 0x04, 0x95, 
    0xEE, 0x7F, 0x0D, 0x9C, 0xE9, 0x78, 0x0A, 0x9B, 
    0xFC, 0x6D, 0x1F, 0x8E, 0xFB, 0x6A, 0x18, 0x89, 
    0xF2, 0x63, 0x11, 0x80, 0xF5, 0x64, 0x16, 0x87, 
    0xD8, 0x49, 0x3B, 0xAA, 0xDF, 0x4E, 0x3C, 0xAD, 
    0xD6, 0x47, 0x35, 0xA4, 0xD1, 0x40, 0x32, 0xA3, 
    0xC4, 0x55, 0x27, 0xB6, 0xC3, 0x52, 0x20, 0xB1, 
    0xCA, 0x5B, 0x29, 0xB8, 0xCD, 0x5C, 0x2E, 0xBF, 
    0x90, 0x01, 0x73, 0xE2, 0x97, 0x06, 0x74, 0xE5, 
    0x9E, 0x0F, 0x7D, 0xEC, 0x99, 0x08, 0x7A, 0xEB, 
    0x8C, 0x1D, 0x6F, 0xFE, 0x8B, 0x1A, 0x68, 0xF9, 
    0x82, 0x13, 0x61, 0xF0, 0x85, 0x14, 0x66, 0xF7, 
    0xA8, 0x39, 0x4B, 0xDA, 0xAF, 0x3E, 0x4C, 0xDD, 
    0xA6, 0x37, 0x45, 0xD4, 0xA1, 0x30, 0x42, 0xD3, 
    0xB4, 0x25, 0x57, 0xC6, 0xB3, 0x22, 0x50, 0xC1, 
    0xBA, 0x2B, 0x59, 0xC8, 0xBD, 0x2C, 0x5E, 0xCF,
};

/**
 * copy from java code, warning "unsigned char" and "char"
 * 计算input的CRC
 * @param input
 * @return 返回CRC值
 */
uint8_t get_crc8(const void *Buf, uint32_t Len)
{
    uint8_t *input = (uint8_t*)Buf;
    uint8_t fcs = (uint8_t)0xFF;
    int32_t i;
    for (i = 0; i < (int32_t)Len; i++)
        fcs = R_CRCTABLE[fcs ^ (uint8_t)input[i]];

    return (uint8_t) (0xFF - fcs);
}

该段代码是成熟的代码，不过值得注意的是，像这种需要两边对等校验数据的通讯，在代码实现时，最好两边都使用相同实现的校验代码，保证不会因为校验算法的实现不同，而出现相同报文却计算出不同校验值的情况。

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