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Lots of comments added. Removed redundant assignment. Moved assertion.

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This commit is contained in:
likewise 2003-04-01 12:17:55 +00:00
parent 5f35f4bb3b
commit b04ac8f3be
1 changed files with 55 additions and 29 deletions
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84
src/core/pbuf.c
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@ -236,12 +236,15 @@ pbuf_alloc(pbuf_layer l, u16_t length, pbuf_flag flag)
offset = 0; offset = 0;
switch (l) { switch (l) {
case PBUF_TRANSPORT: case PBUF_TRANSPORT:
/* add room for transport (often TCP) layer header */
offset += PBUF_TRANSPORT_HLEN; offset += PBUF_TRANSPORT_HLEN;
/* FALLTHROUGH */ /* FALLTHROUGH */
case PBUF_IP: case PBUF_IP:
/* add room for IP layer header */
offset += PBUF_IP_HLEN; offset += PBUF_IP_HLEN;
/* FALLTHROUGH */ /* FALLTHROUGH */
case PBUF_LINK: case PBUF_LINK:
/* add room for link layer header */
offset += PBUF_LINK_HLEN; offset += PBUF_LINK_HLEN;
break; break;
case PBUF_RAW: case PBUF_RAW:
@ -263,15 +266,20 @@ pbuf_alloc(pbuf_layer l, u16_t length, pbuf_flag flag)
} }
p->next = NULL; p->next = NULL;
/* make the payload pointer point offset bytes into pbuf data memory */ /* make the payload pointer point 'offset' bytes into pbuf data memory */
p->payload = MEM_ALIGN((void *)((u8_t *)p + (sizeof(struct pbuf) + offset))); p->payload = MEM_ALIGN((void *)((u8_t *)p + (sizeof(struct pbuf) + offset)));
/* the total length of the pbuf is the requested size */ LWIP_ASSERT("pbuf_alloc: pbuf p->payload properly aligned",
((u32_t)p->payload % MEM_ALIGNMENT) == 0);
/* the total length of the pbuf chain is the requested size */
p->tot_len = length; p->tot_len = length;
/* set the length of the first pbuf in the chain */ /* set the length of the first pbuf in the chain */
p->len = length > PBUF_POOL_BUFSIZE - offset? PBUF_POOL_BUFSIZE - offset: length; p->len = length > PBUF_POOL_BUFSIZE - offset? PBUF_POOL_BUFSIZE - offset: length;
/* set pbuf type */
p->flags = PBUF_FLAG_POOL; p->flags = PBUF_FLAG_POOL;
/* allocate the tail of the pbuf chain. */ /* now allocate the tail of the pbuf chain */
/* remember first pbuf for linkage in next iteration */
r = p; r = p;
/* remaining length to be allocated */ /* remaining length to be allocated */
rem_len = length - p->len; rem_len = length - p->len;
@ -279,7 +287,7 @@ pbuf_alloc(pbuf_layer l, u16_t length, pbuf_flag flag)
while(rem_len > 0) { while(rem_len > 0) {
q = pbuf_pool_alloc(); q = pbuf_pool_alloc();
if (q == NULL) { if (q == NULL) {
DEBUGF(PBUF_DEBUG | 2, ("pbuf_alloc: Out of pbufs in pool.\n")); DEBUGF(PBUF_DEBUG | 2, ("pbuf_alloc: Out of pbufs in pool.\n"));
#ifdef PBUF_STATS #ifdef PBUF_STATS
++lwip_stats.pbuf.err; ++lwip_stats.pbuf.err;
#endif /* PBUF_STATS */ #endif /* PBUF_STATS */
@ -287,20 +295,24 @@ pbuf_alloc(pbuf_layer l, u16_t length, pbuf_flag flag)
pbuf_pool_free(p); pbuf_pool_free(p);
return NULL; return NULL;
} }
q->next = NULL; //q->next = NULL;
/* make previous pbuf point to this pbuf */
r->next = q; r->next = q;
/* set length of this pbuf */
q->len = rem_len > PBUF_POOL_BUFSIZE? PBUF_POOL_BUFSIZE: rem_len; q->len = rem_len > PBUF_POOL_BUFSIZE? PBUF_POOL_BUFSIZE: rem_len;
q->flags = PBUF_FLAG_POOL; q->flags = PBUF_FLAG_POOL;
q->payload = (void *)((u8_t *)q + sizeof(struct pbuf)); q->payload = (void *)((u8_t *)q + sizeof(struct pbuf));
r = q; LWIP_ASSERT("pbuf_alloc: pbuf q->payload properly aligned",
((u32_t)q->payload % MEM_ALIGNMENT) == 0);
q->ref = 1; q->ref = 1;
/* calculate remaining length to be allocated */
rem_len -= q->len; rem_len -= q->len;
/* remember this pbuf for linkage in next iteration */
r = q;
} }
/* end of chain */ /* end of chain */
r->next = NULL; r->next = NULL;
LWIP_ASSERT("pbuf_alloc: pbuf->payload properly aligned",
((u32_t)p->payload % MEM_ALIGNMENT) == 0);
break; break;
case PBUF_RAM: case PBUF_RAM:
/* If pbuf is to be allocated in RAM, allocate memory for it. */ /* If pbuf is to be allocated in RAM, allocate memory for it. */
@ -486,10 +498,12 @@ pbuf_realloc(struct pbuf *p, u16_t new_len)
} }
/** /**
* Adjusts the payload pointer +/- for header. * Adjusts the payload pointer to hide or reveal headers in the payload.
* *
* Adjusts the ->payload pointer so that space for a header appears in * Adjusts the ->payload pointer so that space for a header
* the pbuf. Also, the ->tot_len and ->len fields are adjusted. * (dis)appears in the pbuf payload.
*
* The ->payload, ->tot_len and ->len fields are adjusted.
* *
* @param hdr_size Number of bytes to increment header size which * @param hdr_size Number of bytes to increment header size which
* increases the size of the pbuf. New space is on the front. * increases the size of the pbuf. New space is on the front.
@ -543,15 +557,16 @@ pbuf_header(struct pbuf *p, s16_t header_size)
} }
/** /**
* Free a pbuf (chain) from its user, de-allocate if zero users. * Free a pbuf (chain) from usage, de-allocate non-used head of chain.
* *
* Decrements the pbuf reference count. If it reaches * Decrements the pbuf reference count. If it reaches
* zero, the pbuf is deallocated. * zero, the pbuf is deallocated.
* *
* This is repeated for each pbuf in the chain, until a non-zero * For a pbuf chain, this is repeated for each pbuf in the chain, until
* reference count is encountered, or the end of the chain is reached. * a non-zero reference count is encountered, or the end of the chain is
* reached.
* *
* @param pbuf pbuf (chain) to be freed from its user. * @param pbuf pbuf (chain) to be freed from one user.
* *
* @return the number of unreferenced pbufs that were de-allocated * @return the number of unreferenced pbufs that were de-allocated
* from the head of the chain. * from the head of the chain.
@ -714,6 +729,7 @@ pbuf_chain(struct pbuf *h, struct pbuf *t)
/* add total length of second chain to all totals of first chain */ /* add total length of second chain to all totals of first chain */
p->tot_len += t->tot_len; p->tot_len += t->tot_len;
} }
/* p is last pbuf of first h chain */
/* add total length of second chain to last pbuf total of first chain */ /* add total length of second chain to last pbuf total of first chain */
p->tot_len += t->tot_len; p->tot_len += t->tot_len;
/* chain last pbuf of h chain (p) with first of tail (t) */ /* chain last pbuf of h chain (p) with first of tail (t) */
@ -748,7 +764,7 @@ pbuf_dechain(struct pbuf *p)
/* total length of pbuf p is its own length only */ /* total length of pbuf p is its own length only */
p->tot_len = p->len; p->tot_len = p->len;
/* q is no longer referenced by p, free it */ /* q is no longer referenced by p, free it */
DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dechain: unreferencing %p\n", (void *) q)); DEBUGF(PBUF_DEBUG | DBG_STATE, ("pbuf_dechain: unreferencing %p\n", (void *) q));
tail_gone = pbuf_free(q); tail_gone = pbuf_free(q);
/* return remaining tail or NULL if deallocated */ /* return remaining tail or NULL if deallocated */
} }
@ -765,9 +781,10 @@ pbuf_dechain(struct pbuf *p)
* with PBUF_POOL (or PBUF_RAM) pbufs, each taking a copy of * with PBUF_POOL (or PBUF_RAM) pbufs, each taking a copy of
* the referenced data. * the referenced data.
* *
* @note The pbuf you give as argument, may have been replaced * @note You MUST explicitly use p = pbuf_take(p);
* by calling pbuf_take(p). You must therefore explicitly use * The pbuf you give as argument, may have been replaced
* p = pbuf_take(p); * by pbuf_take()!
*
* @note Any replaced pbufs will be freed through pbuf_free(). * @note Any replaced pbufs will be freed through pbuf_free().
* *
* Used to queue packets on behalf of the lwIP stack, such as * Used to queue packets on behalf of the lwIP stack, such as
@ -775,14 +792,13 @@ pbuf_dechain(struct pbuf *p)
* *
* @param f Head of pbuf chain to process * @param f Head of pbuf chain to process
* *
* @return Pointer to new head of pbuf chain (which may have been * @return Pointer to new head of pbuf chain
* replaced itself).
*/ */
struct pbuf * struct pbuf *
pbuf_take(struct pbuf *f) pbuf_take(struct pbuf *f)
{ {
struct pbuf *p, *prev, *top; struct pbuf *p, *prev, *top;
LWIP_ASSERT("pbuf_take: f != NULL", f != NULL); LWIP_ASSERT("pbuf_take: f != NULL\n", f != NULL);
DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_take(%p)\n", (void*)f)); DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_take(%p)\n", (void*)f));
prev = NULL; prev = NULL;
@ -814,7 +830,8 @@ pbuf_take(struct pbuf *f)
} }
/* replacement pbuf could be allocated? */ /* replacement pbuf could be allocated? */
if (q != NULL) if (q != NULL)
{ {
/* copy p to q */
/* copy successor */ /* copy successor */
q->next = p->next; q->next = p->next;
/* remove linkage from original pbuf */ /* remove linkage from original pbuf */
@ -825,14 +842,22 @@ pbuf_take(struct pbuf *f)
/* break chain and insert new pbuf instead */ /* break chain and insert new pbuf instead */
prev->next = q; prev->next = q;
/* prev == NULL, so we replaced the top pbuf of the chain */ /* prev == NULL, so we replaced the top pbuf of the chain */
} else } else {
top = q; top = q;
}
/* copy pbuf payload */ /* copy pbuf payload */
memcpy(q->payload, p->payload, p->len); memcpy(q->payload, p->payload, p->len);
q->tot_len = p->tot_len; q->tot_len = p->tot_len;
q->len = p->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 */ /* do not copy ref, since someone else might be using the old buffer */
/* pbuf is not freed, as this is the responsibility of the application */
DEBUGF(PBUF_DEBUG, ("pbuf_take: replaced PBUF_REF %p with %p\n", (void *)p, (void *)q)); DEBUGF(PBUF_DEBUG, ("pbuf_take: replaced PBUF_REF %p with %p\n", (void *)p, (void *)q));
/* p is no longer pointed to by prev or by our caller, /* p is no longer pointed to by prev or by our caller,
* as the caller must do p = pbuf_take(p); so free it * as the caller must do p = pbuf_take(p); so free it
@ -848,12 +873,13 @@ pbuf_take(struct pbuf *f)
DEBUGF(PBUF_DEBUG | 2, ("pbuf_take: failed to allocate replacement pbuf for %p\n", (void *)p)); DEBUGF(PBUF_DEBUG | 2, ("pbuf_take: failed to allocate replacement pbuf for %p\n", (void *)p));
return NULL; return NULL;
} }
/* p->flags != PBUF_FLAG_REF */
} else {
DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: skipping pbuf not of type PBUF_REF\n"));
} }
else { /* remember this pbuf */
DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: not PBUF_REF\n"));
}
prev = p; prev = p;
/* proceed to next pbuf in original chain */
p = p->next; p = p->next;
} while (p); } while (p);
DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: end of chain reached.\n")); DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: end of chain reached.\n"));