CRC计算

参考，(159条消息) CRC16常见几个标准的算法及C语言实现_leumber的博客-CSDN博客_crc16

#include<stdio.h>
/****************************Info********************************************** 
 * Name:    InvertUint8 
 * Note:     把字节颠倒过来，如0x12变成0x48
            0x12: 0001 0010
            0x48: 0100 1000
 *****************************************************************************/
void InvertUint8(unsigned char *dBuf,unsigned char *srcBuf)
{
    int i;
    unsigned char tmp[4]={0};
 
    for(i=0;i< 8;i++)
    {
        if(srcBuf[0]& (1 << i))
        tmp[0]|=1<<(7-i);
    }
    dBuf[0] = tmp[0];
    
}

void InvertUint16(unsigned short *dBuf,unsigned short *srcBuf)
{
    int i;
    unsigned short tmp[4]={0};
 
    for(i=0;i< 16;i++)
    {
        if(srcBuf[0]& (1 << i))
        tmp[0]|=1<<(15 - i);
    }
    dBuf[0] = tmp[0];
}

/****************************Info********************************************** 
 * Name:    CRC-16/CCITT        x16+x12+x5+1 
 * Width:    16
 * Poly:    0x1021 
 * Init:    0x0000 
 * Refin:   True 
 * Refout:  True 
 * Xorout:  0x0000 
 * Alias:   CRC-CCITT,CRC-16/CCITT-TRUE,CRC-16/KERMIT 
 *****************************************************************************/ 
unsigned short CRC16_CCITT(unsigned char *data, unsigned int datalen)
{
    unsigned short wCRCin = 0x0000;
    unsigned short wCPoly = 0x1021;
    unsigned char wChar = 0;
    
    while (datalen--)     
    {
        wChar = *(data++);
        InvertUint8(&wChar,&wChar);
        wCRCin ^= (wChar << 8);
        for(int i = 0;i < 8;i++)
        {
            if(wCRCin & 0x8000)
                wCRCin = (wCRCin << 1) ^ wCPoly;
            else
                wCRCin = wCRCin << 1;
        }
    }
    InvertUint16(&wCRCin,&wCRCin);
    return (wCRCin);
}

int main()
{
    unsigned char buf[2]={1,2};
    unsigned short crc16=CRC16_CCITT(buf, 2);
    printf("%x", crc16);
}