vb.netc3.js

Converting C# to VB code


I have this c# code that creates a CRC code. It works correctly in c#. I converted it to VB but it is not generating the correct CRC code. Could somebody please help me figure out what is wrong with the VB code.

you call GetMessageBytes with a string and get back a bytes array with the CRC added

    static byte[] GetMessageBytes(string text)
        {
        //Get bytes for command
        byte[] command = Encoding.ASCII.GetBytes(text);

        //Get CRC for command bytes
        ushort crc = CalculateCrc(command);

        //Append CRC and CR to command
        byte[] result = new byte[command.Length + 3];
        command.CopyTo(result, 0);
        result[result.Length - 3] = (byte)((crc >> 8) & 0xFF);
        result[result.Length - 2] = (byte)((crc >> 0) & 0xFF);
        result[result.Length - 1] = 0x0d;

        return result;
    }


    static ushort CalculateCrc(byte[] pin)
    {
        ushort crc;
        byte da;
        byte ptr;
        byte bCRCHign;
        byte bCRCLow;

        int len = pin.Length;

        ushort[] crc_ta = new ushort[]
            { 
                0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7,
                0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef
            };

        crc = 0;
        for (int index = 0; index < len; index++)
        {
            ptr = pin[index];

            da = (byte)(((byte)(crc >> 8)) >> 4);
            crc <<= 4;
            crc ^= crc_ta[da ^ (ptr >> 4)];
            da = (byte)(((byte)(crc >> 8)) >> 4);
            crc <<= 4;
            crc ^= crc_ta[da ^ (ptr & 0x0f)];
        }

        //Escape CR,LF,'H' characters
        bCRCLow = (byte)(crc & 0x00FF);
        bCRCHign = (byte)(crc >> 8);
        if (bCRCLow == 0x28 || bCRCLow == 0x0d || bCRCLow == 0x0a)
        {
            bCRCLow++;
        }
        if (bCRCHign == 0x28 || bCRCHign == 0x0d || bCRCHign == 0x0a)
        {
            bCRCHign++;
        }
        crc = (ushort)(((ushort)bCRCHign) << 8);
        crc |= bCRCLow;
        return crc;
    }

Here is the VB code.

    Private Function GetMessageBytes(text As String) As Byte()
    'Get bytes for command
    Dim command As Byte() = System.Text.Encoding.Unicode.GetBytes(text)

    'Get CRC for command bytes
    Dim crc As UShort = CalcCrcHalf(command)

    'Append CRC and CR to command
    Dim result As Byte() = New Byte(command.Length + 3) {}
    command.CopyTo(result, 0)
    result(result.Length - 3) = CByte((crc >> 8) And &HFF)
    result(result.Length - 2) = CByte((crc >> 0) And &HFF)
    result(result.Length - 1) = &HD

    Return result
End Function


Private Function CalculateCRC(pin As Byte()) As UShort
    Dim crc As UShort
    Dim da As Byte
    Dim ptr As Byte
    Dim bCRCHign As Byte
    Dim bCRCLow As Byte

    Dim len As Integer = pin.Length

    Dim crc_ta As UShort() = New UShort() {&H0, &H1021, &H2042, &H3063, &H4084, &H50A5, &H60C6, &H70E7, &H8108, &H9129, &HA14A, &HB16B, &HC18C, &HD1AD, &HE1CE, &HF1EF}

    crc = 0
    For index As Integer = 0 To len - 1
        ptr = pin(index)
        da = CByte(CByte(crc >> 8) >> 4)
        crc <<= 4
        crc = crc Xor crc_ta(da Xor (ptr >> 4))
        da = CByte(CByte(crc >> 8) >> 4)
        crc <<= 4
        crc = crc Xor crc_ta(da Xor (ptr And &HF))
    Next

    'Escape CR,LF,'H' characters
    bCRCLow = CByte(crc And &HFF)
    bCRCHign = CByte(crc >> 8)
    If bCRCLow = &H28 OrElse bCRCLow = &HD OrElse bCRCLow = &HA Then
        bCRCLow += 1
    End If
    If bCRCHign = &H28 OrElse bCRCHign = &HD OrElse bCRCHign = &HA Then
        bCRCHign += 1
    End If
    crc = CUShort(CUShort(bCRCHign) << 8)
    crc = crc Or bCRCLow

    Return crc

End Function

Solution

  • Thanks I got it working. It was the encoding.

    This is the correct code.

        retrun_string = System.Text.Encoding.GetEncoding(1252).GetString(result)