Re: C++ Crc Method to C# Crc Method - C# Discussion Boards

C++ Crc Method to C# Crc Method

16-Sep-08 21:02

Here you are: SetLocalTime Function[^]

You will need P/Invoke to call it.

Giorgi Dalakishvili

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Programm3r16-Sep-08 20:56

16-Sep-08 20:56

Hi all,

i have athe following Crc16 method. I want to use it in my C# application but am not sure how to go about it. Can anyone please put some light on this issue.

short int crc16(char *pBuf, short int Len, short int InitialCrc){
short unsigned int crc=0, i=0;

    crc = 0;
    for (i = 0; i < Len; i++ ) {
        crc = (crc >> 8) | (crc << 8);
        crc = crc ^ *pBuf;
        crc = crc ^ ((crc & 0xff) >> 4);
        crc = crc ^ (crc << 12);
        crc = crc ^ ((crc & 0xff) << 5);
        pBuf++;
    }
    return(crc);
}

Many thanks in advance
Regards,

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Guffa16-Sep-08 21:24

16-Sep-08 21:24

First you have to decide how you want to handle the characters. A character in C++ is 8 bits, while a character in C# is 16 bits.

After that, the translation is pretty straight forward.

Despite everything, the person most likely to be fooling you next is yourself.

Programm3r16-Sep-08 21:40

16-Sep-08 21:40

Thank you for the response. Well I did the following to the method:

unsafe uint crc16(char* pBuf, ushort Len, ushort InitialCrc)
{
    uint crc = 0, i = 0;

    crc = 0;
    for (i = 0; i < Len; i++)
    {
        crc = (crc >> 8) | (crc << 8);
        crc = crc ^ *pBuf;
        crc = crc ^ ((crc & 0xff) >> 4);
        crc = crc ^ (crc << 12);
        crc = crc ^ ((crc & 0xff) << 5);
        pBuf++;
    }
    return (crc);
}

The other problem is how can I convert string to char*. I was looking at Marshal.StringToHGlobalAnsi, but cannot find the Marshal class in the namespace System.Runtime.InteropServices Confused | :confused:

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leppie16-Sep-08 21:48

leppie

16-Sep-08 21:48

Programm3r wrote:
The other problem is how can I convert string to char*

string foo = "Hello World";

fixed (char* fp = foo)
{
  var i = crc16(fp, (ushort) foo.Length, 0);
}

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Programm3r16-Sep-08 21:52

16-Sep-08 21:52

Thank you very much Smile | :)

Would you say that the Crc method look good after my C# interpretation?

Thanks again
Regards,

The only programmers that are better that C programmers are those who code in 1's and 0's Green Alien | [Alien]

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leppie16-Sep-08 22:09

leppie

16-Sep-08 22:09

Programm3r wrote:
Would you say that the Crc method look good after my C# interpretation?

I am not sure that it is correct, as the result (which should fit in a 16 bit number) overflowed. I have modified it slighty, best would be to test the output with the output of the native function.

static unsafe ushort crc16(char* pBuf, int Len, ushort InitialCrc)
{
  ushort crc = InitialCrc; //?

  for (int i = 0; i < Len; i++)
  {
    crc = (ushort)((crc >> 8) | (crc << 8));
    crc = (ushort)(crc ^ *pBuf);
    crc = (ushort)(crc ^ ((crc & 0xff) >> 4));
    crc = (ushort)(crc ^ (crc << 12));
    crc = (ushort)(crc ^ ((crc & 0xff) << 5));
    pBuf++;
  }

  return crc;
}

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Programm3r16-Sep-08 22:16

16-Sep-08 22:16

leppie, thank you very much. It looks perfect according to my previous results done in C++ ... five from me :

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Guffa16-Sep-08 22:49

Connection String Problem using textBox1.text

16-Sep-08 22:49

You have changed the type from ushort to uint, I'm not sure that works properly.

Do you really want to use unsafe code and pointers? Why not just use a string?

The InitialCrc value isn't used in the method at all, so you should remove it.

ushort crc16(string buffer) {
   ushort crc = 0;
   foreach (char c in buffer) {
      crc = (crc >> 8) | (crc << 8);
      crc ^= (ushort)c;
      crc ^= (crc & 0xff) >> 4;
      crc ^= crc << 12;
      crc ^= (crc & 0xff) << 5;
   }
   return crc;
}

Despite everything, the person most likely to be fooling you next is yourself.

M Riaz Bashir16-Sep-08 20:51

16-Sep-08 20:51

Hi,

kindly let me know that, how may I correct the following problem?

* this connection string works good :

string ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\BT.XLS;Extended Properties=""Excel 8.0;HDR=YES;""";

* but this does not work by using textBox1.text :

string ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+ textBox1.Text +";Extended Properties=""Excel 8.0;HDR=YES;""";

error is : "; expected"

Thank you in advance
(Riaz)

Giorgi Dalakishvili16-Sep-08 21:11

16-Sep-08 21:11

Did you try debugging to see what is the actual value of ConnectionString after assignment?

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Guffa16-Sep-08 21:14

16-Sep-08 21:14

He can't debug it as it doesn't compile.

Despite everything, the person most likely to be fooling you next is yourself.

Giorgi Dalakishvili16-Sep-08 21:17

16-Sep-08 21:17

Oh, I see. I thought he was getting error when he was trying to open excel workbook.

Giorgi Dalakishvili

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Programm3r16-Sep-08 21:12

16-Sep-08 21:12

What about: Sniff | :^)

<br />
string ConnectionString = String.Concat("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=", textBox1.Text ,";Extended Properties=""Excel 8.0;HDR=YES;"""; ) ;<br />

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Guffa16-Sep-08 21:12

16-Sep-08 21:12

You have forgotten the @ before the second literal string.

Despite everything, the person most likely to be fooling you next is yourself.

M Riaz Bashir16-Sep-08 21:16

16-Sep-08 21:16

kindly fix the problem of my mentioned connection string that where should be place @

Guffa16-Sep-08 21:27

16-Sep-08 21:27

You don't understand your own code?

You have a @ delimited string which you have split into two strings, but you have forgitten to put the @ delimiter before the second string.

Example:

string s = @"A ""string"" with some ""quotes"".";

Split into two strings:

string s = @"A ""string"" with " + @"some ""quotes"".";

Despite everything, the person most likely to be fooling you next is yourself.

M Riaz Bashir16-Sep-08 21:29

16-Sep-08 21:29

Thank you

Programm3r16-Sep-08 21:26

16-Sep-08 21:26

This should work:

To many qoutes according to me....

string ConnectionString = String.Concat(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=", textBox1.Text ,";Extended Properties=Excel 8.0;HDR=YES;");

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M Riaz Bashir16-Sep-08 21:28

16-Sep-08 21:28

thank you

Giorgi Dalakishvili16-Sep-08 21:37

16-Sep-08 21:37

You can build your string like this:

string ConnectionString = String.Format(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0};Extended Properties=""Excel 8.0;HDR=YES;""", textBox1.Text)

By the way, give your controls more meaningful names.

Giorgi Dalakishvili

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Vasanth.S.R17-Sep-08 0:58

Vasanth.S.R

17-Sep-08 0:58

Use it this way. @ comes before any string segment

string ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+ textBox1.Text + @";Extended Properties=""Excel 8.0;HDR=YES;""";