pbuf.c

基于DM642的网络传输

 * pbufs at the head of this chain or queue.
 *
 * Decrements the pbuf reference count. If it reaches zero, the pbuf is
 * deallocated.
 *
 * For a pbuf chain, this is repeated for each pbuf in the chain,
 * up to the first pbuf which has a non-zero reference count after
 * decrementing. So, when all reference counts are one, the whole
 * chain is free'd.
 *
 * @param pbuf The pbuf (chain) to be dereferenced.
 *
 * @return the number of pbufs that were de-allocated
 * from the head of the chain.
 *
 * @note MUST NOT be called on a packet queue (Not verified to work yet).
 * @note the reference counter of a pbuf equals the number of pointers
 * that refer to the pbuf (or into the pbuf).
 *
 * @internal examples:
 *
 * Assuming existing chains a->b->c with the following reference
 * counts, calling pbuf_free(a) results in:
 * 
 * 1->2->3 becomes ...1->3
 * 3->3->3 becomes 2->3->3
 * 1->1->2 becomes ......1
 * 2->1->1 becomes 1->1->1
 * 1->1->1 becomes .......
 *
 */
u8_t pbuf_free(struct pbuf *p)
{
	  struct pbuf *q;
	  u8_t count;
//	  SYS_ARCH_DECL_PROTECT(old_level);
	
//	  LWIP_ASSERT("p != NULL", p != NULL);
	  /* if assertions are disabled, proceed with debug output */
	  if (p == NULL) 
	  {
//		    LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_free(p == NULL) was called.\n"));
		    return 0;
	  }
//	  LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_free(%p)\n", (void *)p));
	
//	  PERF_START;
	
//	  LWIP_ASSERT("pbuf_free: sane flags",
//	    p->flags == PBUF_FLAG_RAM || p->flags == PBUF_FLAG_ROM ||
//	    p->flags == PBUF_FLAG_REF || p->flags == PBUF_FLAG_POOL);
	
	  count = 0;
	  /* Since decrementing ref cannot be guaranteed to be a single machine operation
	   * we must protect it. Also, the later test of ref must be protected.
	   */
//	  SYS_ARCH_PROTECT(old_level);
	  /* de-allocate all consecutive pbufs from the head of the chain that
	   * obtain a zero reference count after decrementing*/
	  while (p != NULL) 
	  {
		    /* all pbufs in a chain are referenced at least once */
//		    LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
		    /* decrease reference count (number of pointers to pbuf) */
		    p->ref--;
		    /* this pbuf is no longer referenced to? */
		    if (p->ref == 0) 
		    {
			      /* remember next pbuf in chain for next iteration */
			      q = p->next;
//			      LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: deallocating %p\n", (void *)p));
			      /* is this a pbuf from the pool? */
			      if (p->flags == PBUF_FLAG_POOL) 
			      {
				        p->len=PBUF_POOL_BUFSIZE;
				        p->tot_len =PBUF_POOL_BUFSIZE; 
				        p->payload = (void *)((u8_t *)p + sizeof(struct pbuf));
				        PBUF_POOL_FREE(p);
				      /* is this a ROM or RAM referencing pbuf? */
			      } 
			      else 
			      {
			         if (p->flags == PBUF_FLAG_ROM || p->flags == PBUF_FLAG_REF)
			         {
				          memp_free(MEMP_PBUF, p);
				          /* p->flags == PBUF_FLAG_RAM */
				     }
				     else
				     {
				           mem_free(p);
				     }
			      } 
			      count++;
			      /* proceed to next pbuf */
			      p = q;
			    /* p->ref > 0, this pbuf is still referenced to */
			    /* (and so the remaining pbufs in chain as well) */
		    } 
		    else 
		    {
//			      LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: %p has ref %u, ending here.\n", (void *)p, (unsigned int)p->ref));
			      /* stop walking through the chain */
			      p = NULL;
		    }
	  }
//	  SYS_ARCH_UNPROTECT(old_level);
//	  PERF_STOP("pbuf_free");
	  /* return number of de-allocated pbufs */
	  return count;
}

/**
 * Count number of pbufs in a chain
 *
 * @param p first pbuf of chain
 * @return the number of pbufs in a chain
 */

u8_t pbuf_clen(struct pbuf *p)
{
	  u8_t len;
	
	  len = 0;
	  while (p != NULL)
	  {
	    ++len;
	    p = p->next;
	  }
	  return len;
}

/**
 * Increment the reference count of the pbuf.
 *
 * @param p pbuf to increase reference counter of
 *
 */
void
pbuf_ref(struct pbuf *p)
{
//  SYS_ARCH_DECL_PROTECT(old_level);
  /* pbuf given? */
  if (p != NULL) {
//    SYS_ARCH_PROTECT(old_level);
    ++(p->ref);
//   SYS_ARCH_UNPROTECT(old_level);
  }
}

/**
 * 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.
 * 
 * @see pbuf_chain()
 */

void
pbuf_cat(struct pbuf *h, struct pbuf *t)
{
  struct pbuf *p;

//  LWIP_ASSERT("h != NULL", h != NULL);
//  LWIP_ASSERT("t != NULL", t != NULL);
  if ((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 += 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);
  /* add total length of second chain to last pbuf total of first chain */
  p->tot_len += t->tot_len;
  /* chain last pbuf of head (p) with first of tail (t) */
  p->next = t;
}

/**
 * Chain two pbufs (or pbuf chains) together.
 * 
 * The caller MUST call pbuf_free(t) once it has stopped
 * using it. Use pbuf_cat() instead if you no longer use t.
 * 
 * @param h head pbuf (chain)
 * @param t tail pbuf (chain)
 * @note The pbufs MUST belong to the same packet.
 * @note MAY NOT be called on a packet queue.
 *
 * The ->tot_len fields of all pbufs of the head chain are adjusted.
 * The ->next field of the last pbuf of the head chain is adjusted.
 * The ->ref field of the first pbuf of the tail chain is adjusted.
 *
 */
void
pbuf_chain(struct pbuf *h, struct pbuf *t)
{
  pbuf_cat(h, t);
  /* t is now referenced by h */
  pbuf_ref(t);
//  LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t));
}

/* For packet queueing. Note that queued packets must be dequeued first
 * before calling any pbuf functions. */
#if ARP_QUEUEING
/**
 * Add a packet to the end of a queue.
 *
 * @param q pointer to first packet on the queue
 * @param n packet to be queued
 *
 */
void
pbuf_queue(struct pbuf *p, struct pbuf *n)
{
#if PBUF_DEBUG /* remember head of queue */
  struct pbuf *q = p;
#endif
  /* programmer stupidity checks */
//  LWIP_ASSERT("p != NULL", p != NULL);
//  LWIP_ASSERT("n != NULL", n != NULL);
  if ((p == NULL) || (n == NULL)) return;

  /* iterate through all packets on queue */
  while (p->next != NULL) {
/* be very picky about pbuf chain correctness */
#if PBUF_DEBUG
    /* iterate through all pbufs in packet */
    while (p->tot_len != p->len) {
      /* make sure invariant condition holds */
//      LWIP_ASSERT("p->len < p->tot_len", p->len < p->tot_len);
      /* make sure each packet is complete */
//      LWIP_ASSERT("p->next != NULL", p->next != NULL);
      p = p->next;
      /* { p->tot_len == p->len => p is last pbuf of a packet } */
    }
    /* { p is last pbuf of a packet } */
    /* proceed to next packet on queue */
#endif
    /* proceed to next pbuf */
    if (p->next != NULL) p = p->next;
  }
  /* { p->tot_len == p->len and p->next == NULL } ==>
   * { p is last pbuf of last packet on queue } */
  /* chain last pbuf of queue with n */
  p->next = n;
  /* n is now referenced to by the (packet p in the) queue */
  pbuf_ref(n);
#if PBUF_DEBUG
//  LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2,
//    ("pbuf_queue: newly queued packet %p sits after packet %p in queue %p\n",
    (void *)n, (void *)p, (void *)q));
#endif
}

/**
 * Remove a packet from the head of a queue.
 *
 * The caller MUST reference the remainder of the queue (as returned). The
 * caller MUST NOT call pbuf_ref() as it implicitly takes over the reference
 * from p.
 * 
 * @param p pointer to first packet on the queue which will be dequeued.
 * @return first packet on the remaining queue (NULL if no further packets).
 *
 */
struct pbuf *
pbuf_dequeue(struct pbuf *p)
{
  struct pbuf *q;
//  LWIP_ASSERT("p != NULL", p != NULL);

  /* iterate through all pbufs in packet p */
  while (p->tot_len != p->len) {
    /* make sure invariant condition holds */
//    LWIP_ASSERT("p->len < p->tot_len", p->len < p->tot_len);
    /* make sure each packet is complete */
//    LWIP_ASSERT("p->next != NULL", p->next != NULL);
    p = p->next;
  }
  /* { p->tot_len == p->len } => p is the last pbuf of the first packet */
  /* remember next packet on queue in q */
  q = p->next;
  /* dequeue p from queue */
  p->next = NULL;
  /* any next packet on queue? */
  if (q != NULL) {
    /* although q is no longer referenced by p, it MUST be referenced by
     * the caller, who is maintaining this packet queue. So, we do not call
     * pbuf_free(q) here, resulting in an implicit pbuf_ref(q) for the caller. */
//    LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: first remaining packet on queue is %p\n", (void *)q));
  } else {
//    LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: no further packets on queue\n"));
  }
  return q;
}
#endif

/**
 *
 * Create PBUF_POOL (or PBUF_RAM) copies of PBUF_REF pbufs.
 *
 * Used to queue packets on behalf of the lwIP stack, such as
 * ARP based queueing.
 *
 * Go through a pbuf chain and replace any PBUF_REF buffers
 * with PBUF_POOL (or PBUF_RAM) pbufs, each taking a copy of
 * the referenced data.
 *
 * @note You MUST explicitly use p = pbuf_take(p);
 * The pbuf you give as argument, may have been replaced
 * by a (differently located) copy through pbuf_take()!
 *
 * @note Any replaced pbufs will be freed through pbuf_free().
 * This may deallocate them if they become no longer referenced.
 *
 * @param p Head of pbuf chain to process
 *
 * @return Pointer to head of pbuf chain
 */
struct pbuf *
pbuf_take(struct pbuf *p)
{
  struct pbuf *q , *prev, *head;
//  LWIP_ASSERT("pbuf_take: p != NULL\n", p != NULL);
//  LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_take(%p)\n", (void*)p));

  prev = NULL;
  head = p;
  /* iterate through pbuf chain */
  do
  {
    /* pbuf is of type PBUF_REF? */
    if (p->flags == PBUF_FLAG_REF) {
//      LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE, ("pbuf_take: encountered PBUF_REF %p\n", (void *)p));
      /* allocate a pbuf (w/ payload) fully in RAM */
      /* PBUF_POOL buffers are faster if we can use them */
      if (p->len <= PBUF_POOL_BUFSIZE) {
        q = pbuf_alloc(PBUF_RAW, p->len, PBUF_POOL);
        if (q == NULL) {
//          LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: Could not allocate PBUF_POOL\n"));
        }
      } else {
        /* no replacement pbuf yet */
        q = NULL;
//        LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: PBUF_POOL too small to replace PBUF_REF\n"));
      }
      /* no (large enough) PBUF_POOL was available? retry with PBUF_RAM */
      if (q == NULL) {
        q = pbuf_alloc(PBUF_RAW, p->len, PBUF_RAM);
        if (q == NULL) {
//          LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: Could not allocate PBUF_RAM\n"));
        }
      }
      /* replacement pbuf could be allocated? */
      if (q != NULL)
      {
        /* copy p to q */
        /* copy successor */
        q->next = p->next;
        /* remove linkage from original pbuf */
        p->next = NULL;
        /* remove linkage to original pbuf */
        if (prev != NULL) {
          /* prev->next == p at this point */
//          LWIP_ASSERT("prev->next == p", prev->next == p);
          /* break chain and insert new pbuf instead */
          prev->next = q;
        /* prev == NULL, so we replaced the head pbuf of the chain */
        } else {
          head = q;
        }
        /* copy pbuf payload */
        memcpy(q->payload, p->payload, p->len);
        q->tot_len = p->tot_len;
        q->len = p->len;
        /* in case p was the first pbuf, it is no longer refered to by
         * our caller, as the caller MUST do p = pbuf_take(p);
         * in case p was not the first pbuf, it is no longer refered to
         * by prev. we can safely free the pbuf here.
         * (note that we have set p->next to NULL already so that
         * we will not free the rest of the chain by accident.)
         */
        pbuf_free(p);
        /* do not copy ref, since someone else might be using the old buffer */
//        LWIP_DEBUGF(PBUF_DEBUG, ("pbuf_take: replaced PBUF_REF %p with %p\n", (void *)p, (void *)q));
        p = q;
      } else {
        /* deallocate chain */
        pbuf_free(head);
//        LWIP_DEBUGF(PBUF_DEBUG | 2, ("pbuf_take: failed to allocate replacement pbuf for %p\n", (void *)p));
        return NULL;
      }
    /* p->flags != PBUF_FLAG_REF */
    } else {
//      LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: skipping pbuf not of type PBUF_REF\n"));
    }
    /* remember this pbuf */
    prev = p;
    /* proceed to next pbuf in original chain */
    p = p->next;
  } while (p);
//  LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: end of chain reached.\n"));

  return head;
}

/**
 * Dechains the first pbuf from its succeeding pbufs in the chain.
 *
 * 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 | DBG_STATE, ("pbuf_dechain: unreferencing %p\n", (void *)q));
    tail_gone = pbuf_free(q);
    if (tail_gone > 0) {
//      LWIP_DEBUGF(PBUF_DEBUG | DBG_STATE,
//                  ("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);
}