Function pbuf_copy_partial

components/net/lwip/lwip-2.1.2/src/core/pbuf.c:1026–1057

* @ingroup pbuf * Copy (part of) the contents of a packet buffer * to an application supplied buffer. * * @param buf the pbuf from which to copy data * @param dataptr the application supplied buffer * @param len length of data to copy (dataptr must be big enough). No more * than buf->tot_len will be copied, irrespective of len * @param offset offset into the packet buffer from where to beg

 * @return the number of bytes copied, or 0 on failure
 */
u16_t
pbuf_copy_partial(const struct pbuf *buf, void *dataptr, u16_t len, u16_t offset)
{
  const struct pbuf *p;
  u16_t left = 0;
  u16_t buf_copy_len;
  u16_t copied_total = 0;

  LWIP_ERROR("pbuf_copy_partial: invalid buf", (buf != NULL), return 0;);
  LWIP_ERROR("pbuf_copy_partial: invalid dataptr", (dataptr != NULL), return 0;);

  /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
  for (p = buf; len != 0 && p != NULL; p = p->next) {
    if ((offset != 0) && (offset >= p->len)) {
      /* don't copy from this buffer -> on to the next */
      offset = (u16_t)(offset - p->len);
    } else {
      /* copy from this buffer. maybe only partially. */
      buf_copy_len = (u16_t)(p->len - offset);
      if (buf_copy_len > len) {
        buf_copy_len = len;
      }
      /* copy the necessary parts of the buffer */
      MEMCPY(&((char *)dataptr)[left], &((char *)p->payload)[offset], buf_copy_len);
      copied_total = (u16_t)(copied_total + buf_copy_len);
      left = (u16_t)(left + buf_copy_len);
      len = (u16_t)(len - buf_copy_len);
      offset = 0;
    }
  }
  return copied_total;
}

/**
 * @ingroup pbuf