mem.c

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#endif /* MEM_STATS */
    sys_sem_signal(mem_sem);
    return;
  }
  /* Get the corresponding struct mem ... */
  mem = (struct mem *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
  /* ... which has to be in a used state ... */
  LWIP_ASSERT("mem_free: mem->used", mem->used);
  /* ... and is now unused. */
  mem->used = 0;

  if (mem < lfree) {
    /* the newly freed struct is now the lowest */
    lfree = mem;
  }

#if MEM_STATS
  lwip_stats.mem.used -= mem->next - ((u8_t *)mem - ram);
#endif /* MEM_STATS */

  /* finally, see if prev or next are free also */
  plug_holes(mem);
  sys_sem_signal(mem_sem);
}

/**
 * In contrast to its name, mem_realloc can only shrink memory, not expand it.
 * Since the only use (for now) is in pbuf_realloc (which also can only shrink),
 * this shouldn't be a problem!
 *
 * @param rmem pointer to memory allocated by mem_malloc the is to be shrinked
 * @param newsize required size after shrinking (needs to be smaller than or
 *                equal to the previous size)
 * @return for compatibility reasons: is always == rmem, at the moment
 */
void *
mem_realloc(void *rmem, mem_size_t newsize)
{
  mem_size_t size;
  mem_size_t ptr, ptr2;
  struct mem *mem, *mem2;

  /* Expand the size of the allocated memory region so that we can
     adjust for alignment. */
  newsize = LWIP_MEM_ALIGN_SIZE(newsize);

  if(newsize < MIN_SIZE_ALIGNED) {
    /* every data block must be at least MIN_SIZE_ALIGNED long */
    newsize = MIN_SIZE_ALIGNED;
  }

  if (newsize > MEM_SIZE_ALIGNED) {
    return NULL;
  }

  LWIP_ASSERT("mem_realloc: legal memory", (u8_t *)rmem >= (u8_t *)ram &&
   (u8_t *)rmem < (u8_t *)ram_end);

  if ((u8_t *)rmem < (u8_t *)ram || (u8_t *)rmem >= (u8_t *)ram_end) {
    LWIP_DEBUGF(MEM_DEBUG | 3, ("mem_realloc: illegal memory\n"));
    return rmem;
  }
  /* Get the corresponding struct mem ... */
  mem = (struct mem *)((u8_t *)rmem - SIZEOF_STRUCT_MEM);
  /* ... and its offset pointer */
  ptr = (u8_t *)mem - ram;

  size = mem->next - ptr - SIZEOF_STRUCT_MEM;
  LWIP_ASSERT("mem_realloc can only shrink memory", newsize <= size);
  if (newsize > size) {
    /* not supported */
    return NULL;
  }
  if (newsize == size) {
    /* No change in size, simply return */
    return rmem;
  }

  /* protect the heap from concurrent access */
  sys_arch_sem_wait(mem_sem, 0);

#if MEM_STATS
  lwip_stats.mem.used -= (size - newsize);
#endif /* MEM_STATS */

  mem2 = (struct mem *)&ram[mem->next];
  if(mem2->used == 0) {
    /* The next struct is unused, we can simply move it at little */
    mem_size_t next;
    /* remember the old next pointer */
    next = mem2->next;
    /* create new struct mem which is moved directly after the shrinked mem */
    ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
    if (lfree == mem2) {
      lfree = (struct mem *)&ram[ptr2];
    }
    mem2 = (struct mem *)&ram[ptr2];
    mem2->used = 0;
    /* restore the next pointer */
    mem2->next = next;
    /* link it back to mem */
    mem2->prev = ptr;
    /* link mem to it */
    mem->next = ptr2;
    /* last thing to restore linked list: as we have moved mem2,
     * let 'mem2->next->prev' point to mem2 again. but only if mem2->next is not
     * the end of the heap */
    if (mem2->next != MEM_SIZE_ALIGNED) {
      ((struct mem *)&ram[mem2->next])->prev = ptr2;
    }
    /* no need to plug holes, we've already done that */
  } else if (newsize + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED <= size) {
    /* Next struct is used but there's room for another struct mem with
     * at least MIN_SIZE_ALIGNED of data.
     * Old size ('size') must be big enough to contain at least 'newsize' plus a struct mem
     * ('SIZEOF_STRUCT_MEM') with some data ('MIN_SIZE_ALIGNED').
     * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
     *       region that couldn't hold data, but when mem->next gets freed,
     *       the 2 regions would be combined, resulting in more free memory */
    ptr2 = ptr + SIZEOF_STRUCT_MEM + newsize;
    mem2 = (struct mem *)&ram[ptr2];
    if (mem2 < lfree) {
      lfree = mem2;
    }
    mem2->used = 0;
    mem2->next = mem->next;
    mem2->prev = ptr;
    mem->next = ptr2;
    if (mem2->next != MEM_SIZE_ALIGNED) {
      ((struct mem *)&ram[mem2->next])->prev = ptr2;
    }
    /* the original mem->next is used, so no need to plug holes! */
  }
  /* else {
    next struct mem is used but size between mem and mem2 is not big enough
    to create another struct mem
    -> don't do anyhting.
    -> the remaining space stays unused since it is too small
  } */
  sys_sem_signal(mem_sem);
  return rmem;
}

/**
 * Adam's mem_malloc() plus solution for bug #17922
 * Allocate a block of memory with a minimum of 'size' bytes.
 *
 * @param size is the minimum size of the requested block in bytes.
 * @return pointer to allocated memory or NULL if no free memory was found.
 *
 * Note that the returned value will always be aligned (as defined by MEM_ALIGNMENT).
 */
void *
mem_malloc(mem_size_t size)
{
  mem_size_t ptr, ptr2;
  struct mem *mem, *mem2;

  if (size == 0) {
    return NULL;
  }

  /* Expand the size of the allocated memory region so that we can
     adjust for alignment. */
  size = LWIP_MEM_ALIGN_SIZE(size);

  if(size < MIN_SIZE_ALIGNED) {
    /* every data block must be at least MIN_SIZE_ALIGNED long */
    size = MIN_SIZE_ALIGNED;
  }

  if (size > MEM_SIZE_ALIGNED) {
    return NULL;
  }

  /* protect the heap from concurrent access */
  sys_arch_sem_wait(mem_sem, 0);

  /* Scan through the heap searching for a free block that is big enough,
   * beginning with the lowest free block.
   */
  for (ptr = (u8_t *)lfree - ram; ptr < MEM_SIZE_ALIGNED - size;
       ptr = ((struct mem *)&ram[ptr])->next) {
    mem = (struct mem *)&ram[ptr];

    if ((!mem->used) &&
        (mem->next - (ptr + SIZEOF_STRUCT_MEM)) >= size) {
      /* mem is not used and at least perfect fit is possible:
       * mem->next - (ptr + SIZEOF_STRUCT_MEM) gives us the 'user data size' of mem */

      if (mem->next - (ptr + SIZEOF_STRUCT_MEM) >= (size + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED)) {
        /* (in addition to the above, we test if another struct mem (SIZEOF_STRUCT_MEM) containing
         * at least MIN_SIZE_ALIGNED of data also fits in the 'user data space' of 'mem')
         * -> split large block, create empty remainder,
         * remainder must be large enough to contain MIN_SIZE_ALIGNED data: if
         * mem->next - (ptr + (2*SIZEOF_STRUCT_MEM)) == size,
         * struct mem would fit in but no data between mem2 and mem2->next
         * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty
         *       region that couldn't hold data, but when mem->next gets freed,
         *       the 2 regions would be combined, resulting in more free memory
         */
        ptr2 = ptr + SIZEOF_STRUCT_MEM + size;
        /* create mem2 struct */
        mem2 = (struct mem *)&ram[ptr2];
        mem2->used = 0;
        mem2->next = mem->next;
        mem2->prev = ptr;
        /* and insert it between mem and mem->next */
        mem->next = ptr2;
        mem->used = 1;

        if (mem2->next != MEM_SIZE_ALIGNED) {
          ((struct mem *)&ram[mem2->next])->prev = ptr2;
        }
#if MEM_STATS
        lwip_stats.mem.used += (size + SIZEOF_STRUCT_MEM);
        if (lwip_stats.mem.max < lwip_stats.mem.used) {
          lwip_stats.mem.max = lwip_stats.mem.used;
        }
#endif /* MEM_STATS */
      } else {
        /* (a mem2 struct does no fit into the user data space of mem and mem->next will always
         * be used at this point: if not we have 2 unused structs in a row, plug_holes should have
         * take care of this).
         * -> near fit or excact fit: do not split, no mem2 creation
         * also can't move mem->next directly behind mem, since mem->next
         * will always be used at this point!
         */
        mem->used = 1;
#if MEM_STATS
        lwip_stats.mem.used += mem->next - ((u8_t *)mem - ram);
        if (lwip_stats.mem.max < lwip_stats.mem.used) {
          lwip_stats.mem.max = lwip_stats.mem.used;
        }
#endif /* MEM_STATS */
      }

      if (mem == lfree) {
        /* Find next free block after mem and update lowest free pointer */
        while (lfree->used && lfree != ram_end) {
          lfree = (struct mem *)&ram[lfree->next];
        }
        LWIP_ASSERT("mem_malloc: !lfree->used", ((lfree == ram_end) || (!lfree->used)));
      }
      sys_sem_signal(mem_sem);
      LWIP_ASSERT("mem_malloc: allocated memory not above ram_end.",
       (mem_ptr_t)mem + SIZEOF_STRUCT_MEM + size <= (mem_ptr_t)ram_end);
      LWIP_ASSERT("mem_malloc: allocated memory properly aligned.",
       (unsigned long)((u8_t *)mem + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT == 0);
      LWIP_ASSERT("mem_malloc: sanity check alignment",
        (((mem_ptr_t)mem) & (MEM_ALIGNMENT-1)) == 0);

      return (u8_t *)mem + SIZEOF_STRUCT_MEM;
    }
  }
  LWIP_DEBUGF(MEM_DEBUG | 2, ("mem_malloc: could not allocate %"S16_F" bytes\n", (s16_t)size));
#if MEM_STATS
  ++lwip_stats.mem.err;
#endif /* MEM_STATS */
  sys_sem_signal(mem_sem);
  return NULL;
}

#endif /* MEM_USE_POOLS */
/**
 * Contiguously allocates enough space for count objects that are size bytes
 * of memory each and returns a pointer to the allocated memory.
 *
 * The allocated memory is filled with bytes of value zero.
 *
 * @param count number of objects to allocate
 * @param size size of the objects to allocate
 * @return pointer to allocated memory / NULL pointer if there is an error
 */
void *mem_calloc(mem_size_t count, mem_size_t size)
{
  void *p;

  /* allocate 'count' objects of size 'size' */
  p = mem_malloc(count * size);
  if (p) {
    /* zero the memory */
    memset(p, 0, count * size);
  }
  return p;
}

#endif /* !MEM_LIBC_MALLOC */