IBAN Checker with Modulo 97 Algorithm

Lets take iban number for a Central Bank of the Republic of Turkey and disect the steps.

1. Move last four to the end

   TR470000100100000350930001 -> 0000100100000350930001TR47

2. Replace characters with digits

   0000100100000350930001TR47 -> 0000100100000350930001292747

3. Start iteration over nine digit numbers

   1. N = 000010010, d = N % 97 = 19
   2. N = 19000035093, d = N % 97 = 43
   3. N = 430001292747, d = N % 97 = 1

4. If d == 1 then valid; otherwise invalid.

The implemention make us of a specialized "iterator" that perform step 1 and 2 without any allocations.