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comparison miscutil/imei-luhn.c @ 271:cd043e690621

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imei-luhn utility written
author Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
date Fri, 07 Feb 2014 05:00:24 +0000
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270:d1388095ab27 271:cd043e690621
1 /*
2 * This program computes the Luhn check digit for an IMEI number given
3 * the first 14 digits, or verifies the correctness of this check digit
4 * given a 15-digit number as input.
5 *
6 * The number given on the command line may optionally include punctuation,
7 * which is skipped and ignored.
8 */
9
10 #include <stdio.h>
11 #include <ctype.h>
12 #include <stdlib.h>
13
14 char digits[15];
15
16 compute_cd()
17 {
18 int i, dig, sum;
19
20 sum = 0;
21 for (i = 0; i < 14; i++) {
22 dig = digits[i];
23 if (i & 1) {
24 dig *= 2;
25 if (dig > 9)
26 dig -= 9;
27 }
28 sum += dig;
29 }
30 dig = sum % 10;
31 if (dig)
32 dig = 10 - dig;
33 return dig;
34 }
35
36 main(argc, argv)
37 char **argv;
38 {
39 char *cp;
40 int i;
41
42 if (argc != 2) {
43 usage: fprintf(stderr, "usage: %s number\n", argv[0]);
44 exit(2);
45 }
46 cp = argv[1];
47 if (!isdigit(*cp))
48 goto usage;
49 for (i = 0; *cp; ) {
50 if (ispunct(*cp))
51 cp++;
52 if (!isdigit(*cp))
53 goto usage;
54 if (i >= 15) {
55 wrong_len: fprintf(stderr,
56 "error: argument must have 14 or 15 digits\n");
57 exit(2);
58 }
59 digits[i++] = *cp++ - '0';
60 }
61 switch (i) {
62 case 14:
63 printf("%d\n", compute_cd());
64 exit(0);
65 case 15:
66 if (digits[14] == compute_cd()) {
67 printf("IMEI OK\n");
68 exit(0);
69 } else {
70 printf("Check digit mismatch!\n");
71 exit(1);
72 }
73 default:
74 goto wrong_len;
75 }
76 }