FreeCalypso > hg > freecalypso-sw
view miscutil/imei-luhn.c @ 675:029f631b22ff
starting to compile ALR
author | Michael Spacefalcon <msokolov@ivan.Harhan.ORG> |
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date | Mon, 29 Sep 2014 01:41:48 +0000 |
parents | cd043e690621 |
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; } }