Function pbuf_get_contiguous

components/net/lwip/lwip-2.1.2/src/core/pbuf.c:1073–1098

* @ingroup pbuf * Get part of a pbuf's payload as contiguous memory. The returned memory is * either a pointer into the pbuf's payload or, if split over multiple pbufs, * a copy into the user-supplied buffer. * * @param p the pbuf from which to copy data * @param buffer the application supplied buffer * @param bufsize size of the application supplied buffer * @param len length of data to c

 * @return the number of bytes copied, or 0 on failure
 */
void *
pbuf_get_contiguous(const struct pbuf *p, void *buffer, size_t bufsize, u16_t len, u16_t offset)
{
  const struct pbuf *q;
  u16_t out_offset;

  LWIP_ERROR("pbuf_get_contiguous: invalid buf", (p != NULL), return NULL;);
  LWIP_ERROR("pbuf_get_contiguous: invalid dataptr", (buffer != NULL), return NULL;);
  LWIP_ERROR("pbuf_get_contiguous: invalid dataptr", (bufsize >= len), return NULL;);

  q = pbuf_skip_const(p, offset, &out_offset);
  if (q != NULL) {
    if (q->len >= (out_offset + len)) {
      /* all data in this pbuf, return zero-copy */
      return (u8_t *)q->payload + out_offset;
    }
    /* need to copy */
    if (pbuf_copy_partial(q, buffer, len, out_offset) != len) {
      /* copying failed: pbuf is too short */
      return NULL;
    }
    return buffer;
  }
  /* pbuf is too short (offset does not fit in) */
  return NULL;
}

#if LWIP_TCP && TCP_QUEUE_OOSEQ && LWIP_WND_SCALE
/**