pool.h

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    // pre: 'chunk' must have been previously
    //        returned by *this.malloc().
    void free(void * const chunk)
    { store().free(chunk); }

    // pre: 'chunk' must have been previously
    //        returned by *this.malloc().
    void ordered_free(void * const chunk)
    { store().ordered_free(chunk); }

    // pre: 'chunk' must have been previously
    //        returned by *this.malloc(n).
    void ordered_free(void * const chunks, const size_type n)
    {
      const size_type partition_size = alloc_size();
      const size_type total_req_size = n * requested_size;
      const size_type num_chunks = total_req_size / partition_size +
          ((total_req_size % partition_size)!=0);

      store().ordered_free_n(chunks, num_chunks, partition_size);
    }

    // pre: 'chunk' must have been previously
    //        returned by *this.malloc(n).
    void free(void * const chunks, const size_type n)
    {
      const size_type partition_size = alloc_size();
      const size_type total_req_size = n * requested_size;
      const size_type num_chunks = total_req_size / partition_size +
          static_cast<bool>( (total_req_size % partition_size) != 0 );

      store().free_n(chunks, num_chunks, partition_size);
    }

};




template <typename UserAllocator>
bool pool<UserAllocator>::purge_memory()
{
  PODptr<size_type> iter = list;

  if (!iter.valid())
    return false;

  do
  {
    // hold "next" pointer
    const PODptr<size_type> next = iter.next();

    // delete the storage
    UserAllocator::free(iter.begin());

    // increment iter
    iter = next;
  } while (iter.valid());

  list.invalidate();
  this->first = 0;

  return true;
}
template <typename UserAllocator>
bool pool<UserAllocator>::release_memory()
{
  // This is the return value: it will be set to true when we actually call
  //  UserAllocator::free(..)
  bool ret = false;

  // This is a current & previous iterator pair over the memory block list
  PODptr<size_type> ptr = list;
  PODptr<size_type> prev;

  // This is a current & previous iterator pair over the free memory chunk list
  //  Note that "prev_free" in this case does NOT point to the previous memory
  //  chunk in the free list, but rather the last free memory chunk before the
  //  current block.
  void * free = this->first;
  void * prev_free = 0;

  const size_type partition_size = alloc_size();

  // Search through all the all the allocated memory blocks
  while (ptr.valid())
  {
    // At this point:
    //  ptr points to a valid memory block
    //  free points to either:
    //    0 if there are no more free chunks
    //    the first free chunk in this or some next memory block
    //  prev_free points to either:
    //    the last free chunk in some previous memory block
    //    0 if there is no such free chunk

    // If there are no more free memory chunks, then every remaining
    //  block is allocated out to its fullest capacity, and we can't
    //  release any more memory
    if (free == 0)
      return ret;

    // We have to check all the chunks.  If they are *all* free (i.e., present
    //  in the free list), then we can free the block.
    bool all_chunks_free = true;

    // Iterate 'i' through all chunks in the memory block
    for (char * i = ptr.begin(); i != ptr.end(); i += partition_size)
    {
      // If this chunk is not free
      if (i != free)
      {
        // We won't be able to free this block
        all_chunks_free = false;

        // Abort searching the chunks; we won't be able to free this
        //  block because a chunk is not free.
        break;
      }

      // We do not increment prev_free because we are in the same block
      free = nextof(free);
    }

    const PODptr<size_type> next = ptr.next();

    if (!all_chunks_free)
    {
      // Rush through all free chunks from this block
      std::less<void *> lt;
      void * const last = ptr.end() - partition_size;
      do
      {
        free = nextof(free);
      } while (lt(free, last));

      // Increment free one more time and set prev_free to maintain the
      //  invariants:
      //     free points to the first free chunk in some next memory block, or
      //       0 if there is no such chunk.
      //     prev_free points to the last free chunk in this memory block.
      prev_free = free;
      free = nextof(free);
    }
    else
    {
      // All chunks from this block are free

      // Remove block from list
      if (prev.valid())
        prev.next(next);
      else
        list = next;

      // Remove all entries in the free list from this block
      if (prev_free != 0)
        nextof(prev_free) = free;
      else
        this->first = free;

      // And release memory
      UserAllocator::free(ptr.begin());
      ret = true;
    }

    // Increment ptr
    ptr = next;
  }

  return ret;
}
template <typename UserAllocator>
void * pool<UserAllocator>::ordered_malloc(const size_type n)
{
  const size_type partition_size = alloc_size();
  const size_type total_req_size = n * requested_size;
  const size_type num_chunks = total_req_size / partition_size +
      ((total_req_size % partition_size)!=0 );

  void * ret = store().malloc_n(num_chunks, partition_size);

  if (ret != 0)
    return ret;

  // Not enougn memory in our storages; make a new storage,
  next_size = max(next_size, num_chunks);
  const size_type POD_size = next_size * partition_size +
      min_alloc_size2 + sizeof(size_type);
  char* const ptr = UserAllocator::malloc(POD_size);
  if (ptr == 0)
    return 0;
  const PODptr<size_type> node(ptr, POD_size);

  // Split up block so we can use what wasn't requested
  //  (we can use "add_block" here because we know that
  //  the free list is empty, so we don't have to use
  //  the slower ordered version)
  if (next_size > num_chunks)
    store().add_block(node.begin() + num_chunks * partition_size,
        node.element_size() - num_chunks * partition_size, partition_size);

  next_size <<= 1;

  //  insert it into the list,
  //   handle border case
  if (!list.valid() || std::greater<void *>()(list.begin(), node.begin()))
  {
    node.next(list);
    list = node;
  }
  else
  {
    PODptr<size_type> prev = list;

    while (true)
    {
      // if we're about to hit the end or
      //  if we've found where "node" goes
      if (prev.next_ptr() == 0
          || std::greater<void *>()(prev.next_ptr(), node.begin()))
        break;

      prev = prev.next();
    }

    node.next(prev.next());
    prev.next(node);
  }

  //  and return it.
  return node.begin();
}

template <typename SizeType>
void * simple_segregated_storage<SizeType>::malloc_n(const size_type n,
    const size_type partition_size)
{
  void * start = &first;
  void * iter;
  do
  {
    if (nextof(start) == 0)
      return 0;
    iter = try_malloc_n(start, n, partition_size);
  } while (iter == 0);
  void * const ret = nextof(start);
  nextof(start) = nextof(iter);
  return ret;
}

template <typename SizeType>
void * simple_segregated_storage<SizeType>::find_prev(void * const ptr)
{
  // Handle border case
  if (first == 0 || std::greater<void *>()(first, ptr))
    return 0;

  void * iter = first;
  while (true)
  {
    // if we're about to hit the end or
    //  if we've found where "ptr" goes
    if (nextof(iter) == 0 || std::greater<void *>()(nextof(iter), ptr))
      return iter;

    iter = nextof(iter);
  }
}


template <typename SizeType>
void * simple_segregated_storage<SizeType>::segregate(
    void * const block,
    const size_type sz,
    const size_type partition_sz,
    void * const end)
{
  // Get pointer to last valid chunk, preventing overflow on size calculations
  //  The division followed by the multiplication just makes sure that
  //    old == block + partition_sz * i, for some integer i, even if the
  //    block size (sz) is not a multiple of the partition size.
  char * old = static_cast<char *>(block)
      + ((sz - partition_sz) / partition_sz) * partition_sz;

  // Set it to point to the end
  nextof(old) = end;

  // Handle border case where sz == partition_sz (i.e., we're handling an array
  //  of 1 element)
  if (old == block)
    return block;

  // Iterate backwards, building a singly-linked list of pointers
  for (char * iter = old - partition_sz; iter != block;
      old = iter, iter -= partition_sz)
    nextof(iter) = old;

  // Point the first pointer, too
  nextof(block) = old;

  return block;
}

// The following function attempts to find n contiguous chunks
//  of size partition_size in the free list, starting at start.
// If it succeds, it returns the last chunk in that contiguous
//  sequence, so that the sequence is known by [start, {retval}]
// If it fails, it does do either because it's at the end of the
//  free list or hits a non-contiguous chunk.  In either case,
//  it will return 0, and set start to the last considered
//  chunk.  You are at the end of the free list if
//  nextof(start) == 0.  Otherwise, start points to the last
//  chunk in the contiguous sequence, and nextof(start) points
//  to the first chunk in the next contiguous sequence (assuming
//  an ordered free list)
template <typename SizeType>
void * simple_segregated_storage<SizeType>::try_malloc_n(
    void * & start, size_type n, const size_type partition_size)
{
  void * iter = nextof(start);
  while (--n != 0)
  {
    void * next = nextof(iter);
    if (next != static_cast<char *>(iter) + partition_size)
    {
      // next == 0 (end-of-list) or non-contiguous chunk found
      start = iter;
      return 0;
    }
    iter = next;
  }
  return iter;
}
template <typename UserAllocator>
void * pool<UserAllocator>::ordered_malloc_need_resize()
{
  // No memory in any of our storages; make a new storage,
  const size_type partition_size = alloc_size();
  const size_type POD_size = next_size * partition_size +
      min_alloc_size2 + sizeof(size_type);
  char * const ptr = UserAllocator::malloc(POD_size);
  if (ptr == 0)
    return 0;
  const PODptr<size_type> node(ptr, POD_size);
  next_size <<= 1;

  //  initialize it,
  //  (we can use "add_block" here because we know that
  //  the free list is empty, so we don't have to use
  //  the slower ordered version)
  store().add_block(node.begin(), node.element_size(), partition_size);

  //  insert it into the list,
  //   handle border case
  if (!list.valid() || std::greater<void *>()(list.begin(), node.begin()))
  {
    node.next(list);
    list = node;
  }
  else
  {
    PODptr<size_type> prev = list;

    while (true)
    {
      // if we're about to hit the end or
      //  if we've found where "node" goes
      if (prev.next_ptr() == 0
          || std::greater<void *>()(prev.next_ptr(), node.begin()))
        break;

      prev = prev.next();
    }

    node.next(prev.next());
    prev.next(node);
  }

  //  and return a chunk from it.
  return store().malloc();
}
CL_NS_END

#endif //LUCENE_ENABLE_MEMORY_POOL
#endif  //lucene_debug_pool