Function ifc_name2unit

freebsd/net/if_clone.c:578–606

* A utility function to extract unit numbers from interface names of * the form name###. * * Returns 0 on success and an error on failure. */

 * Returns 0 on success and an error on failure.
 */
int
ifc_name2unit(const char *name, int *unit)
{
	const char	*cp;
	int		cutoff = INT_MAX / 10;
	int		cutlim = INT_MAX % 10;

	for (cp = name; *cp != '\0' && (*cp < '0' || *cp > '9'); cp++)
		;
	if (*cp == '\0') {
		*unit = -1;
	} else if (cp[0] == '0' && cp[1] != '\0') {
		/* Disallow leading zeroes. */
		return (EINVAL);
	} else {
		for (*unit = 0; *cp != '\0'; cp++) {
			if (*cp < '0' || *cp > '9') {
				/* Bogus unit number. */
				return (EINVAL);
			}
			if (*unit > cutoff ||
			    (*unit == cutoff && *cp - '0' > cutlim))
				return (EINVAL);
			*unit = (*unit * 10) + (*cp - '0');
		}
	}

	return (0);
}

static int
ifc_alloc_unit_specific(struct if_clone *ifc, int *unit)