crc.c

CRC校验程序

#include <string.h>
#include <reg51.h>
#include <crc.h>
void LShift(unsigned char buf[10],unsigned char len)
{
     unsigned char newhbit,oldhbit;
     char i;

     oldhbit=buf[0]/0x80;
     for(i=len-1;i>=0;i--)
     {
         newhbit=buf[i]/0x80;
         buf[i]<<=1;
         buf[i] ^= oldhbit;
         oldhbit=newhbit;
     }
}

void GenCRC(unsigned char *rdata, unsigned char *crc, unsigned char len)
{
     unsigned char bitlen,hbit;
     unsigned char buf[10];
     memcpy(buf,rdata,len);
     buf[len]=buf[len+1]=0;
     len+=2;
     for(bitlen=len*8;bitlen>16;bitlen--)
     {
         hbit=buf[0] & 0x80;
         LShift(buf,len);
         if(hbit)
         {
	     buf[0]^=0x80;	buf[1]^=0x05;
	 }
     }
     memcpy(crc,buf,2);
}

void AppendCRC(unsigned char *buf,unsigned char len)
{
     unsigned char crc[2];

     GenCRC(buf,crc,len);
     memcpy(buf+len,crc,2);
     buf[len+2]=0;
}

int CheckCRC(unsigned char *buf,unsigned char len)
{
     unsigned char crc[2];

     GenCRC(buf,crc,len);
     if(crc[0]==0 && crc[1]==0)
	return 1;
     else return 0;
}