FreeCalypso > hg > fc-sim-tools
view libutil/iccid_luhn.c @ 53:fbedb67d234f
serial: fix parity for inverse coding convention
Important note: it is my (Mother Mychaela's) understanding that
SIM cards with inverse coding convention are extremely rare,
and I have never seen such a card. Therefore, our support for
the inverse coding convention will likely remain forever untested.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Sun, 21 Mar 2021 20:46:09 +0000 |
parents | 34bbb0585cab |
children |
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/* * This module implements a function for computing the Luhn check digit * for ICCIDs that follow the 18+1 convention. */ #include <sys/types.h> compute_iccid_luhn(digits) u_char *digits; { int i, dig, sum; sum = 0; for (i = 0; i < 18; i++) { dig = digits[i]; if (i & 1) { dig *= 2; if (dig > 9) dig -= 9; } sum += dig; } dig = sum % 10; if (dig) dig = 10 - dig; return dig; }