新手求助关于vc写的crc校验改用vb写的问题。

[sy123782568]

我以前有个vc写的crc校验，现在要改用vb写，不知哪里改错了，vb写出来的老是算不对。求大侠们帮忙看看程序。
vc代码
unsigned char CRC
CRC = CRC_Check(&comm_command[3],27);
comm_command[30] = CRC; 计算crc值，赋值到数据包最后一位


unsigned char CalHeaderCRC(unsigned char dataValue,unsigned char crcValue)
{
int crc;
unsigned char cc;

crc = crcValue ^ dataValue; /* XOR C7 ... C0 with D7 ... D0 */
crc = crc ^(crc<<1)^(crc<<2)^(crc<<3)\
^(crc<<4)^(crc<<5)^(crc<<6)^(crc<<7);
cc=unsigned char((crc&0xfe)^((crc>>8)&1));
return cc;
}
//计算CRC校验码
unsigned char CRC_Check(unsigned char * comm_command, int num)
{
unsigned char crc_code=0;
unsigned char crcValue=0xff;
int i;
for(i=0;i<num;i++)
crcValue=CalHeaderCRC(comm_command[i], crcValue);

crc_code=unsigned char(0xff-crcValue);

return(crc_code);
}
////////////////////////////////////////////////////////////////////////////
我用vb改写的代码


Dim crc As Byte
crcvalue = &HFF
For i = 3 To 29
crcvalue = CalHeaderCRC(SendData(i), crcvalue)
Next i
crc = CByte(&HFF - crcvalue)
SendData(30) = crc
计算crc值，赋值到数据包最后一位


Public Function CalHeaderCRC(ByVal dataValue As Byte, ByVal crcValue As Byte) As Byte

Dim crc As Byte
Dim cc As Byte

'On Error Resume Next
crc = crcValue Xor dataValue
crc = crc Xor (crc << 1) Xor (crc << 2) Xor (crc << 3) Xor (crc << 4) Xor (crc << 5) Xor (crc << 6) Xor (crc << 7)

cc = CByte(crc And &HFE) Xor ((crc >> 8) And 1)
Return cc
End Function

请大侠们帮忙看看，我断断续续调了几天了，也没出个结果。

[sy123782568]

谢谢楼上的兄弟，但是我不能改变现有的crc算法，还得等 明白的朋友指点了

[sy123782568]

自己顶下吧。帖子别沉底

[hjdf2000]

我一般都用查表法

[hjdf2000]

Function CRC(ByVal Data() As Byte) As String Dim i As Integer 'Dim CRC CRC = 0 For i = 0 To UBound(Data) CRC = GetCRC(CRC Xor Data(i)) Next i End Function Function GetCRC(ByVal Ind As Long) As Byte GetCRC = Choose(Ind + 1, 0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65, _ 157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220, _ 35, 125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98, _ 190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255, _ 70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7, _ 219, 133, 103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154, _ 101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36, _ 248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185, _ 140, 210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113, 147, 205, _ 17, 79, 173, 243, 112, 46, 204, 146, 211, 141, 111, 49, 178, 236, 14, 80, _ 175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82, 176, 238, _ 50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115, _ 202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139, _ 87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22, _ 233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168, _ 116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53) End Function

[hjdf2000]

以上是8位CRC