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Made some comments more explicit.

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likewise 2004-07-25 23:41:01 +00:00
parent c2abae538b
commit 7c427a4dce
1 changed files with 16 additions and 11 deletions
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27
src/core/pbuf.c
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@ -520,7 +520,8 @@ pbuf_header(struct pbuf *p, s16_t header_size_increment)
* *
* For a pbuf chain, this is repeated for each pbuf in the chain, * 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 * up to the first pbuf which has a non-zero reference count after
* decrementing. (This might de-allocate the whole chain.) * decrementing. So, when all reference counts are one, the whole
* chain is free'd.
* *
* @param pbuf The pbuf (chain) to be dereferenced. * @param pbuf The pbuf (chain) to be dereferenced.
* *
@ -586,7 +587,7 @@ pbuf_free(struct pbuf *p)
p->len = p->tot_len = PBUF_POOL_BUFSIZE; p->len = p->tot_len = PBUF_POOL_BUFSIZE;
p->payload = (void *)((u8_t *)p + sizeof(struct pbuf)); p->payload = (void *)((u8_t *)p + sizeof(struct pbuf));
PBUF_POOL_FREE(p); PBUF_POOL_FREE(p);
/* a ROM or RAM referencing pbuf */ /* is this a ROM or RAM referencing pbuf? */
} else if (p->flags == PBUF_FLAG_ROM || p->flags == PBUF_FLAG_REF) { } else if (p->flags == PBUF_FLAG_ROM || p->flags == PBUF_FLAG_REF) {
memp_free(MEMP_PBUF, p); memp_free(MEMP_PBUF, p);
/* p->flags == PBUF_FLAG_RAM */ /* p->flags == PBUF_FLAG_RAM */
@ -600,7 +601,7 @@ pbuf_free(struct pbuf *p)
/* (and so the remaining pbufs in chain as well) */ /* (and so the remaining pbufs in chain as well) */
} else { } else {
LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: %p has ref %u, ending here.\n", (void *)p, (unsigned int)p->ref)); LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: %p has ref %u, ending here.\n", (void *)p, (unsigned int)p->ref));
/* stop walking through chain */ /* stop walking through the chain */
p = NULL; p = NULL;
} }
} }
@ -739,9 +740,10 @@ pbuf_queue(struct pbuf *p, struct pbuf *n)
p = p->next; p = p->next;
/* { p->tot_len == p->len => p is last pbuf of a packet } */ /* { p->tot_len == p->len => p is last pbuf of a packet } */
} }
#endif /* { p is last pbuf of a packet }
/* { p->tot_len == p->len and p is last pbuf of a packet } */
/* proceed to next packet on queue */ /* proceed to next packet on queue */
#endif
/* proceed to next pbuf */
if (p->next != NULL) p = p->next; if (p->next != NULL) p = p->next;
} }
/* { p->tot_len == p->len and p->next == NULL } ==> /* { p->tot_len == p->len and p->next == NULL } ==>
@ -760,7 +762,9 @@ pbuf_queue(struct pbuf *p, struct pbuf *n)
/** /**
* Remove a packet from the head of a queue. * Remove a packet from the head of a queue.
* *
* The caller MUST reference the remainder of the queue (as returned). * 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. * @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). * @return first packet on the remaining queue (NULL if no further packets).
@ -772,7 +776,7 @@ pbuf_dequeue(struct pbuf *p)
struct pbuf *q; struct pbuf *q;
LWIP_ASSERT("p != NULL", p != NULL); LWIP_ASSERT("p != NULL", p != NULL);
/* iterate through all pbufs in packet */ /* iterate through all pbufs in packet p */
while (p->tot_len != p->len) { while (p->tot_len != p->len) {
/* make sure invariant condition holds */ /* make sure invariant condition holds */
LWIP_ASSERT("p->len < p->tot_len", p->len < p->tot_len); LWIP_ASSERT("p->len < p->tot_len", p->len < p->tot_len);
@ -781,15 +785,16 @@ pbuf_dequeue(struct pbuf *p)
p = p->next; p = p->next;
} }
/* { p->tot_len == p->len } => p is the last pbuf of the first packet */ /* { p->tot_len == p->len } => p is the last pbuf of the first packet */
/* remember next packet on queue */ /* remember next packet on queue in q */
q = p->next; q = p->next;
/* dequeue p from queue */ /* dequeue p from queue */
p->next = NULL; p->next = NULL;
/* any next packet on queue? */ /* any next packet on queue? */
if (q != NULL) { if (q != NULL) {
/* although q is no longer referenced by p, it MUST be referenced by /* although q is no longer referenced by p, it MUST be referenced by
* the caller, who is maintaining this packet queue */ * the caller, who is maintaining this packet queue. So, we do not call
LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: at least one packet on queue, first %p\n", (void *)q)); * 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 { } else {
LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: no further packets on queue\n")); LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: no further packets on queue\n"));
} }
@ -810,7 +815,7 @@ pbuf_dequeue(struct pbuf *p)
* *
* @note You MUST explicitly use p = pbuf_take(p); * @note You MUST explicitly use p = pbuf_take(p);
* The pbuf you give as argument, may have been replaced * The pbuf you give as argument, may have been replaced
* by pbuf_take()! * by a (differently located) copy through pbuf_take()!
* *
* @note Any replaced pbufs will be freed through pbuf_free(). * @note Any replaced pbufs will be freed through pbuf_free().
* This may deallocate them if they become no longer referenced. * This may deallocate them if they become no longer referenced.