CRC 16 implementation in c#

[Sannesh10]

Hi

Can someone tell me if the c# implementation of a 16 bit crc code is correct.

A 128 bit message pointer is passed into the crc function to add 16 crc bits to the message.

The messsage generation function is:

void gen01dat( int data_len, int* out_array )
{
   randomize();
   // generate the random data and write it to the output array
 
   for(int t=0; t<data_len-16; t++)
      *(out_array+t)=(int) (rand()/(RAND_MAX/2)>0.5);
}
 
The crc calculation is:
 
//crc calculation function is 
void crc(int lenght,int* msg_array)
{
 
   for(int i=lenght-16; i<lenght; i++)
      msg_array[i]=0;
 
   int remainder[17];
   int crc_gen[17]={1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1 ,0 ,1};
 
   for(int i=0; i<17; i++)
   remainder[i]=0;
 
   for(int i=0; i<lenght; i++)
   {
      for(int j=0; j<16; j++)
      remainder[16-j]=remainder[15-j];
 
      remainder[0]= msg_array[i];
 
      if(remainder[16]==1)
      {
         for(int j=0; j<17; j++)
         remainder[j] ^= crc_gen[j];
      }
 
   }
 
   for(int i=lenght-16; i<lenght; i++)
   {
     msg_array[i]=remainder[-i+lenght-1];
   }
}
 
 
// the main function would read
int main(int argc, char* argv[])   //command line project
{
 
int msg_lenght=128;
 
int* data_n1=new int [msg_lenght];
 
gen01dat(msg_lenght,data_n1);
crc(msg_lenght,data_n1);
 
delete [] data_n1;
 
getchar(); 
return 0;
 
}

[sicarie]

Moving over to .NET Forum (just after I check to make sure there isn't a double-post in there) where our C# Experts will probably be able to help you better than I am...

[r035198x]

I assume by crc you mean Cyclic Redundancy Check? Well did you actually try out the code with known values to see if it works?
What happens to the function if a value less than 16 is passed to it as the length (which you were writting lenght)?

[thegeneralguy]

Since you are using pointers and pointer referencing (it looks like C++) you will need to explicitly tell the compiler to allow unsafe code. You will also need to declare the functions unsafe.