FreeCalypso > hg > freecalypso-tools
view miscutil/imei-luhn.c @ 921:74d284add54d
fc-fsio: guard against bogus readdir results from the target
If the FFS being operated on contains SE K2x0 extended filenames,
readdir will return strings that are bad for printing. We need to
guard against this possibility, and also against possible other
bogosity that could be sent by other alien firmwares.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Sat, 31 Dec 2022 22:55:23 +0000 |
parents | e7502631a0f9 |
children |
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/* * This program computes the Luhn check digit for an IMEI number given * the first 14 digits, or verifies the correctness of this check digit * given a 15-digit number as input. * * The number given on the command line may optionally include punctuation, * which is skipped and ignored. */ #include <stdio.h> #include <ctype.h> #include <stdlib.h> char digits[15]; compute_cd() { int i, dig, sum; sum = 0; for (i = 0; i < 14; 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; } main(argc, argv) char **argv; { char *cp; int i; if (argc != 2) { usage: fprintf(stderr, "usage: %s number\n", argv[0]); exit(2); } cp = argv[1]; if (!isdigit(*cp)) goto usage; for (i = 0; *cp; ) { if (ispunct(*cp)) cp++; if (!isdigit(*cp)) goto usage; if (i >= 15) { wrong_len: fprintf(stderr, "error: argument must have 14 or 15 digits\n"); exit(2); } digits[i++] = *cp++ - '0'; } switch (i) { case 14: printf("%d\n", compute_cd()); exit(0); case 15: if (digits[14] == compute_cd()) { printf("IMEI OK\n"); exit(0); } else { printf("Check digit mismatch!\n"); exit(1); } default: goto wrong_len; } }