P89LPC9xx CRC Calculation

用于对Sector中数据的校验， read sector crc， 经过很多努力才找到正确的算法：

 

unsigned long distribute(unsigned char data)
{
 unsigned long tap,a;
 unsigned char data2;
 tap=0;

 data2=data<<7;
 a=data2>>7;
 a=a<<0;
 tap=tap|a;

 data2=(data<<(8-1-1));
 a=data2>>7;
 a=a<<3;
 tap=tap|a;

 data2=(data<<(8-2-1));
 a=data2>>7;
 a=a<<5;
 tap=tap|a;

 data2=(data<<(8-3-1));
 a=data2>>7;
 a=a<<8;
 tap=tap|a;

 data2=(data<<(8-4-1));
 a=data2>>7;
 a=a<<10;
 tap=tap|a;

 data2=(data<<(8-5-1));
 a=data2>>7;
 a=a<<13;
 tap=tap|a;

 data2=(data<<(8-6-1));
 a=data2>>7;
 a=a<<16;
 tap=tap|a;

 data2=(data<<(8-7-1));
 a=data2>>7;
 a=a<<18;
 tap=tap|a;

 return tap;
}

unsigned long crc32(unsigned char* buffer,int len)
{
 unsigned long crc,tap,crc_flag;
 int i;
 unsigned char b;

 crc=0;
 tap=0;
 crc_flag=0;

 for(i=0;i<len;i++){
  b=buffer[i];

  crc_flag=crc>>31;
  crc=crc<<1;

  tap=distribute(b);

  crc=crc^tap;

  if(crc_flag==0){
  }
  else{
   crc=crc^0x00400007;
  }
 }

 return crc;
}

转载于:https://www.cnblogs.com/swnuwangyun/archive/2008/09/05/1285046.html