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annotate miscutil/imei-luhn.c @ 310:083f262b7bbe

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author Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
date Mon, 17 Mar 2014 05:56:06 +0000
parents cd043e690621
children
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271
cd043e690621 imei-luhn utility written
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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1 /*
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2 * This program computes the Luhn check digit for an IMEI number given
cd043e690621 imei-luhn utility written
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3 * the first 14 digits, or verifies the correctness of this check digit
cd043e690621 imei-luhn utility written
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4 * given a 15-digit number as input.
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5 *
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6 * The number given on the command line may optionally include punctuation,
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7 * which is skipped and ignored.
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8 */
cd043e690621 imei-luhn utility written
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9
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10 #include <stdio.h>
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11 #include <ctype.h>
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12 #include <stdlib.h>
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13
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14 char digits[15];
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15
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16 compute_cd()
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17 {
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18 int i, dig, sum;
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19
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20 sum = 0;
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21 for (i = 0; i < 14; i++) {
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22 dig = digits[i];
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23 if (i & 1) {
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24 dig *= 2;
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25 if (dig > 9)
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26 dig -= 9;
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27 }
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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28 sum += dig;
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29 }
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30 dig = sum % 10;
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31 if (dig)
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32 dig = 10 - dig;
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33 return dig;
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34 }
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35
cd043e690621 imei-luhn utility written
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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36 main(argc, argv)
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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37 char **argv;
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38 {
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39 char *cp;
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40 int i;
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41
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42 if (argc != 2) {
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43 usage: fprintf(stderr, "usage: %s number\n", argv[0]);
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44 exit(2);
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45 }
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46 cp = argv[1];
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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47 if (!isdigit(*cp))
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48 goto usage;
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49 for (i = 0; *cp; ) {
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50 if (ispunct(*cp))
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51 cp++;
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52 if (!isdigit(*cp))
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53 goto usage;
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54 if (i >= 15) {
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55 wrong_len: fprintf(stderr,
cd043e690621 imei-luhn utility written
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56 "error: argument must have 14 or 15 digits\n");
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57 exit(2);
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58 }
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59 digits[i++] = *cp++ - '0';
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60 }
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61 switch (i) {
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62 case 14:
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63 printf("%d\n", compute_cd());
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64 exit(0);
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65 case 15:
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66 if (digits[14] == compute_cd()) {
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67 printf("IMEI OK\n");
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68 exit(0);
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69 } else {
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70 printf("Check digit mismatch!\n");
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71 exit(1);
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72 }
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73 default:
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74 goto wrong_len;
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75 }
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76 }