CRC校验基础介绍与C代码示例

来源：码农爱学习 嵌入式技术 1 次阅读
摘要：1 CRC简介 CRC （Cyclic Redundancy Check）循环冗余校验，是一种基于二进制模 2 除法的数据校验算法。它通过对原始数据进行数学运算，生成一段固定长度的校验码（CRC 值），接收方或读取方使用相同算法重新计算 CRC 值，与校验值对比，判断数据是否完整或传输是否出错。 2 CRC算法的5个参数 一套 CRC 算法由以下 5 个参数唯一确定： 位宽（Width）：CRC

1 CRC简介

CRC （Cyclic Redundancy Check）循环冗余校验，是一种基于二进制模 2 除法的数据校验算法。它通过对原始数据进行数学运算，生成一段固定长度的校验码（CRC 值），接收方或读取方使用相同算法重新计算 CRC 值，与校验值对比，判断数据是否完整或传输是否出错。

2 CRC算法的5个参数

一套 CRC 算法由以下 5 个参数唯一确定：

  • 位宽（Width）：CRC 结果长度，常见 8/16/32 位
  • 多项式（Poly）：算法核心除数，决定校验特性
  • 初始值（Init）：计算开始时寄存器的初始状态
  • 输入反转（RefIn）：是否对每个字节按位反转
  • 输出反转与异或（RefOut/XorOut）：结果最终处理方式

常用 CRC 的参数对照表：

CRC 名称 位宽 Width 多项式 Poly 初始值 Init 输入反转 RefIn 输出反转 RefOut 结果异或 XorOut
CRC-8 8 0x07 0x00 false false 0x00
CRC-8/MAXIM 8 0x31 0x00 true true 0x00
CRC-16/MODBUS 16 0x8005 0xFFFF true true 0x0000
CRC-16/CCITT-FALSE 16 0x1021 0xFFFF false false 0x0000
CRC-16/X25 16 0x1021 0xFFFF true true 0xFFFF
CRC-16/XMODEM 16 0x1021 0x0000 false false 0x0000
CRC-16/IBM 16 0x8005 0x0000 true true 0x0000
CRC-32 (IEEE 标准) 32 0x04C11DB7 0xFFFFFFFF true true 0xFFFFFFFF
CRC-32C 32 0x1EDC6F41 0xFFFFFFFF true true 0xFFFFFFFF
CRC-32/MPEG-2 32 0x04C11DB7 0xFFFFFFFF false false 0x00000000

3 C语言代码示例

CRC-16举例

// gcc test1.c -o test1
#include <stdio.h>
#include <stdint.h>
#include <string.h>

// CRC16(modbus)
constuint16_t crc16_table[256] = 
{
    0x0000,0xC0C1,0xC181,0x0140,0xC301,0x03C0,0x0280,0xC241,
    0xC601,0x06C0,0x0780,0xC741,0x0500,0xC5C1,0xC481,0x0440,
    0xCC01,0x0CC0,0x0D80,0xCD41,0x0F00,0xCFC1,0xCE81,0x0E40,
    0x0A00,0xCAC1,0xCB81,0x0B40,0xC901,0x09C0,0x0880,0xC841,
    0xD801,0x18C0,0x1980,0xD941,0x1B00,0xDBC1,0xDA81,0x1A40,
    0x1E00,0xDEC1,0xDF81,0x1F40,0xDD01,0x1DC0,0x1C80,0xDC41,
    0x1400,0xD4C1,0xD581,0x1540,0xD701,0x17C0,0x1680,0xD641,
    0xD201,0x12C0,0x1380,0xD341,0x1100,0xD1C1,0xD081,0x1040,
    0xF001,0x30C0,0x3180,0xF141,0x3300,0xF3C1,0xF281,0x3240,
    0x3600,0xF6C1,0xF781,0x3740,0xF501,0x35C0,0x3480,0xF441,
    0x3C00,0xFCC1,0xFD81,0x3D40,0xFF01,0x3FC0,0x3E80,0xFE41,
    0xFA01,0x3AC0,0x3B80,0xFB41,0x3900,0xF9C1,0xF881,0x3840,
    0x2800,0xE8C1,0xE981,0x2940,0xEB01,0x2BC0,0x2A80,0xEA41,
    0xEE01,0x2EC0,0x2F80,0xEF41,0x2D00,0xEDC1,0xEC81,0x2C40,
    0xE401,0x24C0,0x2580,0xE541,0x2700,0xE7C1,0xE681,0x2640,
    0x2200,0xE2C1,0xE381,0x2340,0xE101,0x21C0,0x2080,0xE041,
    0xA001,0x60C0,0x6180,0xA141,0x6300,0xA3C1,0xA281,0x6240,
    0x6600,0xA6C1,0xA781,0x6740,0xA501,0x65C0,0x6480,0xA441,
    0x6C00,0xACC1,0xAD81,0x6D40,0xAF01,0x6FC0,0x6E80,0xAE41,
    0xAA01,0x6AC0,0x6B80,0xAB41,0x6900,0xA9C1,0xA881,0x6840,
    0x7800,0xB8C1,0xB981,0x7940,0xBB01,0x7BC0,0x7A80,0xBA41,
    0xBE01,0x7EC0,0x7F80,0xBF41,0x7D00,0xBDC1,0xBC81,0x7C40,
    0xB401,0x74C0,0x7580,0xB541,0x7700,0xB7C1,0xB681,0x7640,
    0x7200,0xB2C1,0xB381,0x7340,0xB101,0x71C0,0x7080,0xB041,
    0x5000,0x90C1,0x9181,0x5140,0x9301,0x53C0,0x5280,0x9241,
    0x9601,0x56C0,0x5780,0x9741,0x5500,0x95C1,0x9481,0x5440,
    0x9C01,0x5CC0,0x5D80,0x9D41,0x5F00,0x9FC1,0x9E81,0x5E40,
    0x5A00,0x9AC1,0x9B81,0x5B40,0x9901,0x59C0,0x5880,0x9841,
    0x8801,0x48C0,0x4980,0x8941,0x4B00,0x8BC1,0x8A81,0x4A40,
    0x4E00,0x8EC1,0x8F81,0x4F40,0x8D01,0x4DC0,0x4C80,0x8C41,
    0x4400,0x84C1,0x8581,0x4540,0x8701,0x47C0,0x4680,0x8641,
    0x8201,0x42C0,0x4380,0x8341,0x4100,0x81C1,0x8081,0x4040
};

typedefstruct {
    int   ID;    
    float width;   
    float height;  
    char  res[4]; 
} DeviceConfig;

DeviceConfig g_cfg = {0};
uint16_t g_cfgCrcValue = 0;

uint16_t crc16_calc(const uint8_t *data, uint16_t len)
{
    uint16_t crc = 0xFFFF;
    for (uint16_t i = 0; i < len; i++) 
    {
        uint8_t idx = crc ^ data[i];
        crc >>= 8;
        crc ^= crc16_table[idx];
    }
    return crc;
}

int check_config_valid()
{
    // 对整个结构体内存计算 CRC
    uint16_t calc_crc = crc16_calc((constuint8_t*)&g_cfg, sizeof(DeviceConfig));
    
    if (calc_crc == g_cfgCrcValue)
    {
        printf("cfg data ok, calc_crc:0X%X\n", calc_crc);
    } 
    else
    {
        printf("cfg data err！ calc_crc:0X%X != g_cfgCrcValue:0X%X\n", calc_crc, g_cfgCrcValue);
    }
}

void write_config(const DeviceConfig *cfg)
{
    memcpy(&g_cfg, cfg, sizeof(DeviceConfig));
    g_cfgCrcValue = crc16_calc((constuint8_t*)cfg, sizeof(DeviceConfig));
}

void read_config(DeviceConfig *cfg)
{
    memcpy(cfg, &g_cfg, sizeof(DeviceConfig));
}

int main(void)
{
    DeviceConfig cfg = {0};
    
    read_config(&cfg);
    cfg.ID = 1;
    cfg.width = 16.2;
    cfg.height = 83.2;
    write_config(&cfg);

    // 第一次：正常结构体，校验应该通过
    check_config_valid();

    // 人为修改一个字节，模拟数据损坏
    g_cfg.width = 55.9f;

    // 再次校验
    check_config_valid();

    return0;
}

运行结果：

xxpcb@ubuntuTest:~/myTest/linux/crc$ ./test1
cfg data ok, calc_crc:0XD4FD
cfg data err！ calc_crc:0X788C != g_cfgCrcValue:0XD4FD
xxpcb@ubuntuTest:~/myTest/linux/crc$ 

CRC-32举例

// gcc test2.c -o test2
#include <stdio.h>
#include <stdint.h>
#include <string.h>

// CRC32 (IEEE 802.3)
staticconstuint32_t crc32_table[256] = {
    0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA,
    0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
    0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
    0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
    0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
    0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
    0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC,
    0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
    0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
    0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
    0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940,
    0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
    0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116,
    0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
    0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
    0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
    0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A,
    0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
    0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818,
    0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
    0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
    0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
    0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C,
    0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
    0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
    0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
    0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
    0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
    0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086,
    0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
    0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4,
    0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
    0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A,
    0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
    0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
    0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
    0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE,
    0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
    0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
    0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
    0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252,
    0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
    0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60,
    0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
    0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
    0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
    0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04,
    0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
    0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A,
    0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
    0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38,
    0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
    0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E,
    0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
    0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
    0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
    0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
    0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
    0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0,
    0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
    0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6,
    0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
    0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
    0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
};

typedefstruct {
    int   ID;    
    float width;   
    float height;  
    char  res[4]; 
} DeviceConfig;

DeviceConfig g_cfg = {0};
uint32_t g_cfgCrcValue = 0;

uint32_t crc32_calc(const void *data, size_t len)
{
    uint32_t crc = 0xFFFFFFFF;
    constuint8_t *p = (constuint8_t *)data;

    while (len--)
    {
        crc = crc32_table[(crc ^ *p++) & 0xFF] ^ (crc >> 8);
    }

    return crc ^ 0xFFFFFFFF;
}

int check_config_valid()
{
    // 对整个结构体内存计算 CRC
    uint32_t calc_crc = crc32_calc((constuint8_t*)&g_cfg, sizeof(DeviceConfig));
    
    if (calc_crc == g_cfgCrcValue)
    {
        printf("cfg data ok, calc_crc:0X%X\n", calc_crc);
    } 
    else
    {
        printf("cfg data err！ calc_crc:0X%X != g_cfgCrcValue:0X%X\n", calc_crc, g_cfgCrcValue);
    }
}

void write_config(const DeviceConfig *cfg)
{
    memcpy(&g_cfg, cfg, sizeof(DeviceConfig));
    g_cfgCrcValue = crc32_calc((constuint8_t*)cfg, sizeof(DeviceConfig));
}

void read_config(DeviceConfig *cfg)
{
    memcpy(cfg, &g_cfg, sizeof(DeviceConfig));
}

int main(void)
{
    DeviceConfig cfg = {0};
    
    read_config(&cfg);
    cfg.ID = 1;
    cfg.width = 16.2;
    cfg.height = 83.2;
    write_config(&cfg);

    // 第一次：正常结构体，校验应该通过
    check_config_valid();

    // 人为修改一个字节，模拟数据损坏
    g_cfg.width = 55.9f;

    // 再次校验
    check_config_valid();

    return0;
}

运行结果：

xxpcb@ubuntuTest:~/myTest/linux/crc$ ./test2
cfg data ok, calc_crc:0XB5DB232A
cfg data err！ calc_crc:0XCD8EA015 != g_cfgCrcValue:0XB5DB232A
xxpcb@ubuntuTest:~/myTest/linux/crc$ 

4 总结

本篇介绍了CRC的一些基础概念，其本质是模2除法，以及5个参数，最后使用C代码给出示例。

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