请教CRC校验算法

[haogaoxiao]

有这样一个字符条码 VIPY 1D 000007 其中1D是VIPY000007的校验码，请大侠们帮看看CRC算法改怎么写，下面有厂商提供的算法，能否帮改写成C#的

unsigned char RedGetFc(char *pack,unsigned int len)
{
  #define CRCNUM 0xa001
  unsigned char test,crclow,crchigh,recode;
  unsigned int i,j,crcnum=0xffff,t;
  if(len==0)
    return(-1);
  for(i=1;i<=len;i++)
  {
    test=*pack;
    crclow=(char)crcnum;
    crchigh=(char)(crcnum>>8);
    crcnum=(unsighed int)(test^crclow)+((unsighed int)crchigh)*256;
    for(j=1;j<=8;j++)
    {
      t=crcnum&0x0001;
      crcnum=crcnum>>1;
      if(t)
      {
        crcnum=crcnum^CRCNUM;
      }
    }
    pack++;
  }
  recode=(unsighed char)crcnum;
  return(recode);
}

[haogaoxiao]

多谢wuyazhe，1楼的算法和我另外找的算法得到一样的结果
用VIPY000007来计算，得到的 crcnum 都是 56859

然后这样转换

byte[] rebuf = BitConverter.GetBytes(crcnum);
string Re = Convert.ToBase64String(rebuf);

rebuf[0]=27,rebuf[1]=222
1楼的算法得到的是27
转换的Re="G94="
算法估计没有错，但是不知道怎么转换得到校验码1D
Encoding.Default.GetBytes("1D")得到buf[0]=49,buf[1]=68

[兔子-顾问]

byte RedGetFc(string pack, uint len)
{
    const ushort CRCNUM = 0xa001;
    byte test, crclow, crchigh, recode;
    uint j, crcnum = 0xffff, t;
    if (len == 0) return 0xFF;
    for (int i = 1; i <= len; i++)
    {
        test = (byte)pack[i - 1];
        crclow = (byte)crcnum;
        crchigh = (byte)(crcnum >> 8);
        crcnum = (uint)(test ^ crclow) + ((uint)crchigh) * 256;
        for (j = 1; j <= 8; j++)
        {
            t = crcnum & 0x0001;
            crcnum = crcnum >> 1;
            if (t != 0)
            {
                crcnum = crcnum ^ CRCNUM;
            }
        }
    }
    recode = (byte)crcnum;
    return (recode);
}

[兔子-顾问]

string checksum = RedGetFc("VIPY000007",(uint)"VIPY000007".Length).ToString("X2");
结果是1B