view miscutil/imei-luhn.c @ 1012:11391cb6bdc0

patch from fixeria: doc change from SE K2x0 to K2xx Since their discovery in late 2022, Sony Ericsson K200 and K220 phones were collectively referred to as SE K2x0 in FreeCalypso documentation. However, now that SE K205 has been discovered as yet another member of the same family (same PCBA in different case), it makes more sense to refer to the whole family as SE K2xx.
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 23 Sep 2024 12:23:20 +0000
parents e7502631a0f9
children
line wrap: on
line source

/*
 * 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;
	}
}