Function ng_sppp_get_unit

freebsd/netgraph/ng_sppp.c:112–144

* Find the first free unit number for a new interface. * Increase the size of the unit bitmap as necessary. */

 * Increase the size of the unit bitmap as necessary.
 */
static __inline void
ng_sppp_get_unit (int *unit)
{
	int index, bit;
	unsigned char mask;

	for (index = 0; index < ng_sppp_units_len
	    && ng_sppp_units[index] == 0xFF; index++);
	if (index == ng_sppp_units_len) {		/* extend array */
		unsigned char *newarray;
		int newlen;
		
		newlen = (2 * ng_sppp_units_len) + sizeof (*ng_sppp_units);
		newarray = malloc (newlen * sizeof (*ng_sppp_units),
		    M_NETGRAPH_SPPP, M_WAITOK);
		bcopy (ng_sppp_units, newarray,
		    ng_sppp_units_len * sizeof (*ng_sppp_units));
		bzero (newarray + ng_sppp_units_len,
		    newlen - ng_sppp_units_len);
		if (ng_sppp_units != NULL)
			free (ng_sppp_units, M_NETGRAPH_SPPP);
		ng_sppp_units = newarray;
		ng_sppp_units_len = newlen;
	}
	mask = ng_sppp_units[index];
	for (bit = 0; (mask & 1) != 0; bit++)
		mask >>= 1;
	KASSERT ((bit >= 0 && bit < NBBY),
	    ("%s: word=%d bit=%d", __func__, ng_sppp_units[index], bit));
	ng_sppp_units[index] |= (1 << bit);
	*unit = (index * NBBY) + bit;
	ng_units_in_use++;
}

/*
 * Free a no longer needed unit number.