In my code i need to calculate CRC-16 16 bit values for the HEX values stored as NSdata, below is the code snippet to calculate CRC-16 in c.
void UpdateCRC(unsigned short int *CRC, unsigned char x)
{
// This function uses the initial CRC value passed in the first
// argument, then modifies it using the single character passed
// as the second argument, according to a CRC-16 polynomial
// Arguments:
// CRC -- pointer to starting CRC value
// x -- new character to be processed
// Returns:
// The function does not return any values, but updates the variable
// pointed to by CRC
static int const Poly = 0xA001;
int i;
bool flag;
*CRC ^= x;
for (i=0; i<8; i++)
// CRC-16 polynomial
{
flag = ((*CRC & 1) == 1);
*CRC = (unsigned short int)(*CRC >> 1);
if (flag)
*CRC ^= Poly;
}
return;
}
NSdata which holds the hex values like below
const char connectByteArray[] = {
0x21,0x01,0x90,0x80,0x5F
};
NSData* data = [NSData dataWithBytes: connectByteArray length:sizeof(connectByteArray)];
I solved using the following C program, I hope it may help someone ..cheers!!!