/* To query the number of bytes available, call swb_inc_{u,i} with an increment of zero.  */
static __inline__ unsigned int __swb_inc_u(vwsnd_port_t *port, int inc)
/* To query the number of bytes available, call swb_inc_{u,i} with an increment of zero.  */
static __inline__ unsigned int __swb_inc_u(vwsnd_port_t *port, int inc)
{
	if (inc) {
		port->swb_u_idx += inc;
		port->swb_u_idx %= port->swbuf_size;
		port->swb_u_avail -= inc;
		port->swb_i_avail += inc;
	}
	return port->swb_u_avail;
}