LUHN checksum

Algorithm for generating the checksum digit :
 1) Format the smart card number as a decimal number, mormally unsing 11 digits.
 2) Starting with the least significant digit, multiply every 2nd digit by 2.
 3) Res = Add all individual digits in the result.
 4) Check digit = (10 - (Res MOD 10)) MOD 10.

example :
 1. smart card number = 001 4277 3428
 2. (2*0)+0+(2*1) + 4+(2*2)+7+(2*7) + 3+(2*4)+2+(2*8)
 3. Res = 0+0+2 + 4+4+7+1+4 + 3+8+2+1+6 = 42
 4. Check digit = (10 - (42 MOD 10)) MOD 10 = 8

The checksum digit is 8, so smart card number to present on screen is :
Card number : 001 4278 3428 - 8

/* LUHN checksum */
U32 sum = 0;
U8    NumberDigits, OddEven, Digit, value;
char CardNumberChar[255];

sprintf(CardNumberChar, "%011d", CardNumber);
NumberDigits = strlen(CardNumberChar);
OddEven = NumberDigits & 0x01;  // NumberDigits :: 11 ->  Odd : 1

for(i = 0; i < NumberDigits; i++)
{
    value = (int)((CardNumberChar[i] & 0x0F));

    if((i & 0x01) ^ OddEven)
    {
        value = value * 2;
        if (value > 9)
            value -= 9;
    }
    sum += value;
}
//printf ("%d\n", sum);
printf("[Smartcard] Card Number :: %s-%d\n", CardNumberChar, (10 - (sum % 10)) % 10);