Function pbuf_cat

components/net/lwip/lwip-2.1.2/src/core/pbuf.c:852–875

* @ingroup pbuf * Concatenate two pbufs (each may be a pbuf chain) and take over * the caller's reference of the tail pbuf. * * @note The caller MAY NOT reference the tail pbuf afterwards. * Use pbuf_chain() for that purpose. * * This function explicitly does not check for tot_len overflow to prevent * failing to queue too long pbufs. This can produce invalid pbufs, so * handle with care!

 * @see pbuf_chain()
 */
void
pbuf_cat(struct pbuf *h, struct pbuf *t)
{
  struct pbuf *p;

  LWIP_ERROR("(h != NULL) && (t != NULL) (programmer violates API)",
             ((h != NULL) && (t != NULL)), return;);

  /* proceed to last pbuf of chain */
  for (p = h; p->next != NULL; p = p->next) {
    /* add total length of second chain to all totals of first chain */
    p->tot_len = (u16_t)(p->tot_len + t->tot_len);
  }
  /* { p is last pbuf of first h chain, p->next == NULL } */
  LWIP_ASSERT("p->tot_len == p->len (of last pbuf in chain)", p->tot_len == p->len);
  LWIP_ASSERT("p->next == NULL", p->next == NULL);
  /* add total length of second chain to last pbuf total of first chain */
  p->tot_len = (u16_t)(p->tot_len + t->tot_len);
  /* chain last pbuf of head (p) with first of tail (t) */
  p->next = t;
  /* p->next now references t, but the caller will drop its reference to t,
   * so netto there is no change to the reference count of t.
   */
}

/**
 * @ingroup pbuf