pbuf.c

lwip-1.4.0

 *
 * Makes p->tot_len field equal to p->len.
 * @param p pbuf to dechain
 * @return remainder of the pbuf chain, or NULL if it was de-allocated.
 * @note May not be called on a packet queue.
 */
struct pbuf *
pbuf_dechain(struct pbuf *p)
{
  struct pbuf *q;
  u8_t tail_gone = 1;
  /* tail */
  q = p->next;
  /* pbuf has successor in chain? */
  if (q != NULL) {
    /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
    LWIP_ASSERT("p->tot_len == p->len + q->tot_len", q->tot_len == p->tot_len - p->len);
    /* enforce invariant if assertion is disabled */
    q->tot_len = p->tot_len - p->len;
    /* decouple pbuf from remainder */
    p->next = NULL;
    /* total length of pbuf p is its own length only */
    p->tot_len = p->len;
    /* q is no longer referenced by p, free it */
    LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_dechain: unreferencing %p\n", (void *)q));
    tail_gone = pbuf_free(q);
    if (tail_gone > 0) {
      LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE,
                  ("pbuf_dechain: deallocated %p (as it is no longer referenced)\n", (void *)q));
    }
    /* return remaining tail or NULL if deallocated */
  }
  /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
  LWIP_ASSERT("p->tot_len == p->len", p->tot_len == p->len);
  return ((tail_gone > 0) ? NULL : q);
}

/**
 *
 * Create PBUF_RAM copies of pbufs.
 *
 * Used to queue packets on behalf of the lwIP stack, such as
 * ARP based queueing.
 *
 * @note You MUST explicitly use p = pbuf_take(p);
 *
 * @note Only one packet is copied, no packet queue!
 *
 * @param p_to pbuf destination of the copy
 * @param p_from pbuf source of the copy
 *
 * @return ERR_OK if pbuf was copied
 *         ERR_ARG if one of the pbufs is NULL or p_to is not big
 *                 enough to hold p_from
 */
err_t
pbuf_copy(struct pbuf *p_to, struct pbuf *p_from)
{
  u16_t offset_to=0, offset_from=0, len;

  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy(%p, %p)\n",
    (void*)p_to, (void*)p_from));

  /* is the target big enough to hold the source? */
  LWIP_ERROR("pbuf_copy: target not big enough to hold source", ((p_to != NULL) &&
             (p_from != NULL) && (p_to->tot_len >= p_from->tot_len)), return ERR_ARG;);

  /* iterate through pbuf chain */
  do
  {
    LWIP_ASSERT("p_to != NULL", p_to != NULL);
    /* copy one part of the original chain */
    if ((p_to->len - offset_to) >= (p_from->len - offset_from)) {
      /* complete current p_from fits into current p_to */
      len = p_from->len - offset_from;
    } else {
      /* current p_from does not fit into current p_to */
      len = p_to->len - offset_to;
    }
    MEMCPY((u8_t*)p_to->payload + offset_to, (u8_t*)p_from->payload + offset_from, len);
    offset_to += len;
    offset_from += len;
    LWIP_ASSERT("offset_to <= p_to->len", offset_to <= p_to->len);
    if (offset_to == p_to->len) {
      /* on to next p_to (if any) */
      offset_to = 0;
      p_to = p_to->next;
    }
    LWIP_ASSERT("offset_from <= p_from->len", offset_from <= p_from->len);
    if (offset_from >= p_from->len) {
      /* on to next p_from (if any) */
      offset_from = 0;
      p_from = p_from->next;
    }

    if((p_from != NULL) && (p_from->len == p_from->tot_len)) {
      /* don't copy more than one packet! */
      LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
                 (p_from->next == NULL), return ERR_VAL;);
    }
    if((p_to != NULL) && (p_to->len == p_to->tot_len)) {
      /* don't copy more than one packet! */
      LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
                  (p_to->next == NULL), return ERR_VAL;);
    }
  } while (p_from);
  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy: end of chain reached.\n"));
  return ERR_OK;
}

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

  left = 0;

  if((buf == NULL) || (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 -= p->len;
    } else {
      /* copy from this buffer. maybe only partially. */
      buf_copy_len = 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 += buf_copy_len;
      left += buf_copy_len;
      len -= buf_copy_len;
      offset = 0;
    }
  }
  return copied_total;
}

/**
 * Copy application supplied data into a pbuf.
 * This function can only be used to copy the equivalent of buf->tot_len data.
 *
 * @param buf pbuf to fill with data
 * @param dataptr application supplied data buffer
 * @param len length of the application supplied data buffer
 *
 * @return ERR_OK if successful, ERR_MEM if the pbuf is not big enough
 */
err_t
pbuf_take(struct pbuf *buf, const void *dataptr, u16_t len)
{
  struct pbuf *p;
  u16_t buf_copy_len;
  u16_t total_copy_len = len;
  u16_t copied_total = 0;

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

  if ((buf == NULL) || (dataptr == NULL) || (buf->tot_len < len)) {
    return ERR_ARG;
  }

  /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
  for(p = buf; total_copy_len != 0; p = p->next) {
    LWIP_ASSERT("pbuf_take: invalid pbuf", p != NULL);
    buf_copy_len = total_copy_len;
    if (buf_copy_len > p->len) {
      /* this pbuf cannot hold all remaining data */
      buf_copy_len = p->len;
    }
    /* copy the necessary parts of the buffer */
    MEMCPY(p->payload, &((char*)dataptr)[copied_total], buf_copy_len);
    total_copy_len -= buf_copy_len;
    copied_total += buf_copy_len;
  }
  LWIP_ASSERT("did not copy all data", total_copy_len == 0 && copied_total == len);
  return ERR_OK;
}

/**
 * Creates a single pbuf out of a queue of pbufs.
 *
 * @remark: Either the source pbuf 'p' is freed by this function or the original
 *          pbuf 'p' is returned, therefore the caller has to check the result!
 *
 * @param p the source pbuf
 * @param layer pbuf_layer of the new pbuf
 *
 * @return a new, single pbuf (p->next is NULL)
 *         or the old pbuf if allocation fails
 */
struct pbuf*
pbuf_coalesce(struct pbuf *p, pbuf_layer layer)
{
  struct pbuf *q;
  err_t err;
  if (p->next == NULL) {
    return p;
  }
  q = pbuf_alloc(layer, p->tot_len, PBUF_RAM);
  if (q == NULL) {
    /* @todo: what do we do now? */
    return p;
  }
  err = pbuf_copy(q, p);
  LWIP_ASSERT("pbuf_copy failed", err == ERR_OK);
  pbuf_free(p);
  return q;
}

#if LWIP_CHECKSUM_ON_COPY
/**
 * Copies data into a single pbuf (*not* into a pbuf queue!) and updates
 * the checksum while copying
 *
 * @param p the pbuf to copy data into
 * @param start_offset offset of p->payload where to copy the data to
 * @param dataptr data to copy into the pbuf
 * @param len length of data to copy into the pbuf
 * @param chksum pointer to the checksum which is updated
 * @return ERR_OK if successful, another error if the data does not fit
 *         within the (first) pbuf (no pbuf queues!)
 */
err_t
pbuf_fill_chksum(struct pbuf *p, u16_t start_offset, const void *dataptr,
                 u16_t len, u16_t *chksum)
{
  u32_t acc;
  u16_t copy_chksum;
  char *dst_ptr;
  LWIP_ASSERT("p != NULL", p != NULL);
  LWIP_ASSERT("dataptr != NULL", dataptr != NULL);
  LWIP_ASSERT("chksum != NULL", chksum != NULL);
  LWIP_ASSERT("len != 0", len != 0);

  if ((start_offset >= p->len) || (start_offset + len > p->len)) {
    return ERR_ARG;
  }

  dst_ptr = ((char*)p->payload) + start_offset;
  copy_chksum = LWIP_CHKSUM_COPY(dst_ptr, dataptr, len);
  if ((start_offset & 1) != 0) {
    copy_chksum = SWAP_BYTES_IN_WORD(copy_chksum);
  }
  acc = *chksum;
  acc += copy_chksum;
  *chksum = FOLD_U32T(acc);
  return ERR_OK;
}
#endif /* LWIP_CHECKSUM_ON_COPY */

 /** Get one byte from the specified position in a pbuf
 * WARNING: returns zero for offset >= p->tot_len
 *
 * @param p pbuf to parse
 * @param offset offset into p of the byte to return
 * @return byte at an offset into p OR ZERO IF 'offset' >= p->tot_len
 */
u8_t
pbuf_get_at(struct pbuf* p, u16_t offset)
{
  u16_t copy_from = offset;
  struct pbuf* q = p;

  /* get the correct pbuf */
  while ((q != NULL) && (q->len <= copy_from)) {
    copy_from -= q->len;
    q = q->next;
  }
  /* return requested data if pbuf is OK */
  if ((q != NULL) && (q->len > copy_from)) {
    return ((u8_t*)q->payload)[copy_from];
  }
  return 0;
}

/** Compare pbuf contents at specified offset with memory s2, both of length n
 *
 * @param p pbuf to compare
 * @param offset offset into p at wich to start comparing
 * @param s2 buffer to compare
 * @param n length of buffer to compare
 * @return zero if equal, nonzero otherwise
 *         (0xffff if p is too short, diffoffset+1 otherwise)
 */
u16_t
pbuf_memcmp(struct pbuf* p, u16_t offset, const void* s2, u16_t n)
{
  u16_t start = offset;
  struct pbuf* q = p;

  /* get the correct pbuf */
  while ((q != NULL) && (q->len <= start)) {
    start -= q->len;
    q = q->next;
  }
  /* return requested data if pbuf is OK */
  if ((q != NULL) && (q->len > start)) {
    u16_t i;
    for(i = 0; i < n; i++) {
      u8_t a = pbuf_get_at(q, start + i);
      u8_t b = ((u8_t*)s2)[i];
      if (a != b) {
        return i+1;
      }
    }
    return 0;
  }
  return 0xffff;
}

/** Find occurrence of mem (with length mem_len) in pbuf p, starting at offset
 * start_offset.
 *
 * @param p pbuf to search, maximum length is 0xFFFE since 0xFFFF is used as
 *        return value 'not found'
 * @param mem search for the contents of this buffer
 * @param mem_len length of 'mem'
 * @param start_offset offset into p at which to start searching
 * @return 0xFFFF if substr was not found in p or the index where it was found
 */
u16_t
pbuf_memfind(struct pbuf* p, const void* mem, u16_t mem_len, u16_t start_offset)
{
  u16_t i;
  u16_t max = p->tot_len - mem_len;
  if (p->tot_len >= mem_len + start_offset) {
    for(i = start_offset; i <= max; ) {
      u16_t plus = pbuf_memcmp(p, i, mem, mem_len);
      if (plus == 0) {
        return i;
      } else {
        i += plus;
      }
    }
  }
  return 0xFFFF;
}

/** Find occurrence of substr with length substr_len in pbuf p, start at offset
 * start_offset
 * WARNING: in contrast to strstr(), this one does not stop at the first \0 in
 * the pbuf/source string!
 *
 * @param p pbuf to search, maximum length is 0xFFFE since 0xFFFF is used as
 *        return value 'not found'
 * @param substr string to search for in p, maximum length is 0xFFFE
 * @return 0xFFFF if substr was not found in p or the index where it was found
 */
u16_t
pbuf_strstr(struct pbuf* p, const char* substr)
{
  size_t substr_len;
  if ((substr == NULL) || (substr[0] == 0) || (p->tot_len == 0xFFFF)) {
    return 0xFFFF;
  }
  substr_len = strlen(substr);
  if (substr_len >= 0xFFFF) {
    return 0xFFFF;
  }
  return pbuf_memfind(p, substr, (u16_t)substr_len, 0);
}