pbuf.c

DM642上的TCP/IP代码 LWIP 是TCP/ IP 在嵌入式系统中应用很多的代码

#include "pbuf.h"

#include "mem.h"
#include "tcpmem.h"

static u8_t pbuf_pool_memory[(PBUF_POOL_SIZE * MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE + sizeof(struct pbuf)))];

#if !SYS_LIGHTWEIGHT_PROT
static volatile u8_t pbuf_pool_free_lock, pbuf_pool_alloc_lock;
static u8_t pbuf_pool_free_sem;
#endif

static struct pbuf *pbuf_pool = NULL;

/**
 * Initializes the pbuf module.
 *
 * A large part of memory is allocated for holding the pool of pbufs.
 * The size of the individual pbufs in the pool is given by the size
 * parameter, and the number of pbufs in the pool by the num parameter.
 *
 * After the memory has been allocated, the pbufs are set up. The
 * ->next pointer in each pbuf is set up to point to the next pbuf in
 * the pool.
 *
 */
void pbuf_init(void)
{
  struct pbuf *p, *q = NULL;
  u16_t i;

  pbuf_pool = (struct pbuf *)&pbuf_pool_memory[0];
//  LWIP_ASSERT("pbuf_init: pool aligned", (mem_ptr_t)pbuf_pool % MEM_ALIGNMENT == 0);

#if PBUF_STATS
  lwip_stats.pbuf.avail = PBUF_POOL_SIZE;
#endif /* PBUF_STATS */

  /* Set up ->next pointers to link the pbufs of the pool together */
  p = pbuf_pool;

  for(i = 0; i < PBUF_POOL_SIZE; ++i) {
    p->next = (struct pbuf *)((u8_t *)p + PBUF_POOL_BUFSIZE + sizeof(struct pbuf));
    p->len = p->tot_len = PBUF_POOL_BUFSIZE;
    p->payload = (void *)((u8_t *)p + sizeof(struct pbuf));
    p->flags = PBUF_FLAG_POOL;
    q = p;
    p = p->next;
  }

  /* The ->next pointer of last pbuf is NULL to indicate that there
     are no more pbufs in the pool */
  q->next = NULL;

#if !SYS_LIGHTWEIGHT_PROT
  pbuf_pool_alloc_lock = 0;
  pbuf_pool_free_lock = 0;
//  pbuf_pool_free_sem = sys_sem_new(1);
#endif
}

/**
 * @internal only called from pbuf_alloc()
 */
static struct pbuf *
pbuf_pool_alloc(void)
{
  struct pbuf *p = NULL;

//  SYS_ARCH_DECL_PROTECT(old_level);
//  SYS_ARCH_PROTECT(old_level);

#if !SYS_LIGHTWEIGHT_PROT
  /* Next, check the actual pbuf pool, but if the pool is locked, we
     pretend to be out of buffers and return NULL. */
  if (pbuf_pool_free_lock) 
  {
#if PBUF_STATS
      ++lwip_stats.pbuf.alloc_locked;
#endif /* PBUF_STATS */
      return NULL;
  }
  pbuf_pool_alloc_lock = 1;
  if (!pbuf_pool_free_lock) 
  {
#endif /* SYS_LIGHTWEIGHT_PROT */
    p = pbuf_pool;
    if (p) 
    {
      pbuf_pool = p->next;
    }
#if !SYS_LIGHTWEIGHT_PROT
#if PBUF_STATS
  } else {
    ++lwip_stats.pbuf.alloc_locked;
#endif /* PBUF_STATS */
  }
  pbuf_pool_alloc_lock = 0;
#endif /* SYS_LIGHTWEIGHT_PROT */

#if PBUF_STATS
  if (p != NULL) {
    ++lwip_stats.pbuf.used;
    if (lwip_stats.pbuf.used > lwip_stats.pbuf.max) {
      lwip_stats.pbuf.max = lwip_stats.pbuf.used;
    }
  }
#endif /* PBUF_STATS */

//  SYS_ARCH_UNPROTECT(old_level);
  return p;
}


/**
 * Allocates a pbuf.
 *
 * The actual memory allocated for the pbuf is determined by the
 * layer at which the pbuf is allocated and the requested size
 * (from the size parameter).
 *
 * @param flag this parameter decides how and where the pbuf
 * should be allocated as follows:
 *
 * - PBUF_RAM: buffer memory for pbuf is allocated as one large
 *             chunk. This includes protocol headers as well.
 * - PBUF_ROM: no buffer memory is allocated for the pbuf, even for
 *             protocol headers. Additional headers must be prepended
 *             by allocating another pbuf and chain in to the front of
 *             the ROM pbuf. It is assumed that the memory used is really
 *             similar to ROM in that it is immutable and will not be
 *             changed. Memory which is dynamic should generally not
 *             be attached to PBUF_ROM pbufs. Use PBUF_REF instead.
 * - PBUF_REF: no buffer memory is allocated for the pbuf, even for
 *             protocol headers. It is assumed that the pbuf is only
 *             being used in a single thread. If the pbuf gets queued,
 *             then pbuf_take should be called to copy the buffer.
 * - PBUF_POOL: the pbuf is allocated as a pbuf chain, with pbufs from
 *              the pbuf pool that is allocated during pbuf_init().
 *
 * @return the allocated pbuf. If multiple pbufs where allocated, this
 * is the first pbuf of a pbuf chain.
 */
struct pbuf *
pbuf_alloc(pbuf_layer l, u16_t length, pbuf_flag flag)
{
  struct pbuf *p, *q, *r;
  u16_t offset;
  s32_t rem_len; /* remaining length */
//  LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_alloc(length=%u)\n", length));

  /* determine header offset */
  offset = 0;
  switch (l) {
  case PBUF_TRANSPORT:
    /* add room for transport (often TCP) layer header */
    offset += PBUF_TRANSPORT_HLEN;
    /* FALLTHROUGH */
  case PBUF_IP:
    /* add room for IP layer header */
    offset += PBUF_IP_HLEN;
    /* FALLTHROUGH */
  case PBUF_LINK:
    /* add room for link layer header */
    offset += PBUF_LINK_HLEN;
    break;
  case PBUF_RAW:
    break;
  default:
//    LWIP_ASSERT("pbuf_alloc: bad pbuf layer", 0);
    return NULL;
  }

  switch (flag) 
  {
    case PBUF_POOL:
    /* allocate head of pbuf chain into p */
    p = pbuf_pool_alloc();
    if (p == NULL) 
    {
#if PBUF_STATS
        ++lwip_stats.pbuf.err;
#endif /* PBUF_STATS */
        return NULL;
    }
    p->next = NULL;

    /* make the payload pointer point 'offset' bytes into pbuf data memory */
    p->payload = (void *)((u8_t *)p + (sizeof(struct pbuf) + offset));
//    LWIP_ASSERT("pbuf_alloc: pbuf p->payload properly aligned",
//            ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
    /* the total length of the pbuf chain is the requested size */
    p->tot_len = length;
    /* set the length of the first pbuf in the chain */
    p->len = length > PBUF_POOL_BUFSIZE - offset? PBUF_POOL_BUFSIZE - offset: length;
    /* set reference count (needed here in case we fail) */
    p->ref = 1;

    /* now allocate the tail of the pbuf chain */

    /* remember first pbuf for linkage in next iteration */
    r = p;
    /* remaining length to be allocated */
    rem_len = length - p->len;
    /* any remaining pbufs to be allocated? */
    while (rem_len > 0) {
      q = pbuf_pool_alloc();
      if (q == NULL) {
//       LWIP_DEBUGF(PBUF_DEBUG | 2, ("pbuf_alloc: Out of pbufs in pool.\n"));
#if PBUF_STATS
        ++lwip_stats.pbuf.err;
#endif /* PBUF_STATS */
        /* free chain so far allocated */
        pbuf_free(p);
        /* bail out unsuccesfully */
        return NULL;
      }
      q->next = NULL;
      /* make previous pbuf point to this pbuf */
      r->next = q;
      /* set total length of this pbuf and next in chain */
      q->tot_len = rem_len;
      /* this pbuf length is pool size, unless smaller sized tail */
      q->len = rem_len > PBUF_POOL_BUFSIZE? PBUF_POOL_BUFSIZE: rem_len;
      q->payload = (void *)((u8_t *)q + sizeof(struct pbuf));
//      LWIP_ASSERT("pbuf_alloc: pbuf q->payload properly aligned",
//              ((mem_ptr_t)q->payload % MEM_ALIGNMENT) == 0);
      q->ref = 1;
      /* calculate remaining length to be allocated */
      rem_len -= q->len;
      /* remember this pbuf for linkage in next iteration */
      r = q;
    }
    /* end of chain */
    /*r->next = NULL;*/

    break;
  case PBUF_RAM:
    /* If pbuf is to be allocated in RAM, allocate memory for it. */
    p = mem_malloc(MEM_ALIGN_SIZE(sizeof(struct pbuf) + offset) + MEM_ALIGN_SIZE(length));
    if (p == NULL) {
      return NULL;
    }
    /* Set up internal structure of the pbuf. */
    p->payload = MEM_ALIGN((void *)((u8_t *)p + sizeof(struct pbuf) + offset));
    p->len = p->tot_len = length;
    p->next = NULL;
    p->flags = PBUF_FLAG_RAM;

//    LWIP_ASSERT("pbuf_alloc: pbuf->payload properly aligned",
//           ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
    break;
  /* pbuf references existing (static constant) ROM payload? */
  case PBUF_ROM:
  /* pbuf references existing (externally allocated) RAM payload? */
  case PBUF_REF:
    /* only allocate memory for the pbuf structure */
    p = memp_malloc(MEMP_PBUF);
    if (p == NULL) {
//      LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n", flag == PBUF_ROM?"ROM":"REF"));
      return NULL;
    }
    /* caller must set this field properly, afterwards */
    p->payload = NULL;
    p->len = p->tot_len = length;
    p->next = NULL;
    p->flags = (flag == PBUF_ROM? PBUF_FLAG_ROM: PBUF_FLAG_REF);
    break;
  default:
//    LWIP_ASSERT("pbuf_alloc: erroneous flag", 0);
    return NULL;
  }
  /* set reference count */
  p->ref = 1;
//  LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_alloc(length=%u) == %p\n", length, (void *)p));
  return p;
}


#if PBUF_STATS
#define DEC_PBUF_STATS do { --lwip_stats.pbuf.used; } while (0)
#else /* PBUF_STATS */
#define DEC_PBUF_STATS
#endif /* PBUF_STATS */

#define PBUF_POOL_FAST_FREE(p)  do {                                    \
                                  p->next = pbuf_pool;                  \
                                  pbuf_pool = p;                        \
                                  DEC_PBUF_STATS;                       \
                                } while (0)

#if SYS_LIGHTWEIGHT_PROT
#define PBUF_POOL_FREE(p)  do {                                         \
                                SYS_ARCH_DECL_PROTECT(old_level);       \
                                SYS_ARCH_PROTECT(old_level);            \
                                PBUF_POOL_FAST_FREE(p);                 \
                                SYS_ARCH_UNPROTECT(old_level);          \
                               } while (0)
#else /* SYS_LIGHTWEIGHT_PROT */
#define PBUF_POOL_FREE(p)  do {                                         \
                             PBUF_POOL_FAST_FREE(p);                    \
                           } while (0)
#endif /* SYS_LIGHTWEIGHT_PROT */

/**
 * Shrink a pbuf chain to a desired length.
 *
 * @param p pbuf to shrink.
 * @param new_len desired new length of pbuf chain
 *
 * Depending on the desired length, the first few pbufs in a chain might
 * be skipped and left unchanged. The new last pbuf in the chain will be
 * resized, and any remaining pbufs will be freed.
 *
 * @note If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.
 * @note May not be called on a packet queue.
 *
 * @bug Cannot grow the size of a pbuf (chain) (yet).
 */
void
pbuf_realloc(struct pbuf *p, u16_t new_len)
{
  struct pbuf *q;
  u16_t rem_len; /* remaining length */
  s16_t grow;

//  LWIP_ASSERT("pbuf_realloc: sane p->flags", p->flags == PBUF_FLAG_POOL ||
//              p->flags == PBUF_FLAG_ROM ||
//              p->flags == PBUF_FLAG_RAM ||
//              p->flags == PBUF_FLAG_REF);

  /* desired length larger than current length? */
  if (new_len >= p->tot_len) {
    /* enlarging not yet supported */
    return;
  }

  /* the pbuf chain grows by (new_len - p->tot_len) bytes
   * (which may be negative in case of shrinking) */
  grow = new_len - p->tot_len;

  /* first, step over any pbufs that should remain in the chain */
  rem_len = new_len;
  q = p;
  /* should this pbuf be kept? */
  while (rem_len > q->len) {
    /* decrease remaining length by pbuf length */
    rem_len -= q->len;
    /* decrease total length indicator */
    q->tot_len += grow;
    /* proceed to next pbuf in chain */
    q = q->next;
  }
  /* we have now reached the new last pbuf (in q) */
  /* rem_len == desired length for pbuf q */

  /* shrink allocated memory for PBUF_RAM */
  /* (other types merely adjust their length fields */
  if ((q->flags == PBUF_FLAG_RAM) && (rem_len != q->len)) {
    /* reallocate and adjust the length of the pbuf that will be split */
    mem_realloc(q, (u8_t *)q->payload - (u8_t *)q + rem_len);
  }
  /* adjust length fields for new last pbuf */
  q->len = rem_len;
  q->tot_len = q->len;

  /* any remaining pbufs in chain? */
  if (q->next != NULL) {
    /* free remaining pbufs in chain */
    pbuf_free(q->next);
  }
  /* q is last packet in chain */
  q->next = NULL;

}

/**
 * Adjusts the payload pointer to hide or reveal headers in the payload.
 *
 * Adjusts the ->payload pointer so that space for a header
 * (dis)appears in the pbuf payload.
 *
 * The ->payload, ->tot_len and ->len fields are adjusted.
 *
 * @param hdr_size_inc Number of bytes to increment header size which
 * increases the size of the pbuf. New space is on the front.
 * (Using a negative value decreases the header size.)
 * If hdr_size_inc is 0, this function does nothing and returns succesful.
 *
 * PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so
 * the call will fail. A check is made that the increase in header size does
 * not move the payload pointer in front of the start of the buffer.
 * @return non-zero on failure, zero on success.
 *
 */
u8_t pbuf_header(struct pbuf *p, s16_t header_size_increment)
{
	  void *payload;
	
	//  LWIP_ASSERT("p != NULL", p != NULL);
	  if ((header_size_increment == 0) || (p == NULL)) return 0;
	 
	  /* remember current payload pointer */
	  payload = p->payload;
	
	  /* pbuf types containing payloads? */
	  if (p->flags == PBUF_FLAG_RAM || p->flags == PBUF_FLAG_POOL) 
	  {
	    /* set new payload pointer */
		    p->payload = (u8_t *)p->payload - header_size_increment;
		    /* boundary check fails? */
		    if ((u8_t *)p->payload < (u8_t *)p + sizeof(struct pbuf))
		     {
			//      LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_header: failed as %p < %p (not enough space for new header size)\n",
			//        (void *)p->payload,
			//        (void *)(p + 1)));\
			      /* restore old payload pointer */
			      p->payload = payload;
			      /* bail out unsuccesfully */
		      return 1;
		    }
	  /* pbuf types refering to external payloads? */
	  } 
	  else if (p->flags == PBUF_FLAG_REF || p->flags == PBUF_FLAG_ROM) 
	  {
	    /* hide a header in the payload? */
		    if ((header_size_increment < 0) && (header_size_increment - p->len <= 0))
		    {
			      /* increase payload pointer */
			      p->payload = (u8_t *)p->payload - header_size_increment;
		    } 
		    else 
		    {
			      /* cannot expand payload to front (yet!)
			       * bail out unsuccesfully */
			      return 1;
		    }
	  }
	  /* modify pbuf length fields */
	  p->len += header_size_increment;
	  p->tot_len += header_size_increment;
	
	//  LWIP_DEBUGF( PBUF_DEBUG, ("pbuf_header: old %p new %p (%d)\n",
	//    (void *)payload, (void *)p->payload, header_size_increment));
	
	  return 0;
}

/**
 * Dereference a pbuf chain or queue and deallocate any no-longer-used