Function pbuf_remove_header

components/net/lwip/lwip-2.1.2/src/core/pbuf.c:581–613

* Adjusts the payload pointer to hide headers in the payload. * * Adjusts the ->payload pointer so that space for a header * disappears in the pbuf payload. * * The ->payload, ->tot_len and ->len fields are adjusted. * * @param p pbuf to change the header size. * @param header_size_decrement Number of bytes to decrement header size which * decreases the size of the pbuf. *

 *
 */
u8_t
pbuf_remove_header(struct pbuf *p, size_t header_size_decrement)
{
  void *payload;
  u16_t increment_magnitude;

  LWIP_ASSERT("p != NULL", p != NULL);
  if ((p == NULL) || (header_size_decrement > 0xFFFF)) {
    return 1;
  }
  if (header_size_decrement == 0) {
    return 0;
  }

  increment_magnitude = (u16_t)header_size_decrement;
  /* Check that we aren't going to move off the end of the pbuf */
  LWIP_ERROR("increment_magnitude <= p->len", (increment_magnitude <= p->len), return 1;);

  /* remember current payload pointer */
  payload = p->payload;
  LWIP_UNUSED_ARG(payload); /* only used in LWIP_DEBUGF below */

  /* increase payload pointer (guarded by length check above) */
  p->payload = (u8_t *)p->payload + header_size_decrement;
  /* modify pbuf length fields */
  p->len = (u16_t)(p->len - increment_magnitude);
  p->tot_len = (u16_t)(p->tot_len - increment_magnitude);

  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_remove_header: old %p new %p (%"U16_F")\n",
              (void *)payload, (void *)p->payload, increment_magnitude));

  return 0;
}

static u8_t
pbuf_header_impl(struct pbuf *p, s16_t header_size_increment, u8_t force)