4.5 Creation

We need to write bst_create() to create an empty BST. All it takes is a little bit of memory allocation and initialization:

30. <BST creation function 30> =
struct bst_table *
bst_create (bst_comparison_func *compare, void *param,
            struct libavl_allocator *allocator) 
{
  struct bst_table *tree;

  assert (compare != NULL);

  if (allocator == NULL)
    allocator = &bst_allocator_default;

  tree = allocator->libavl_malloc (allocator, sizeof *tree);
  if (tree == NULL)
    return NULL;

  tree->bst_root = NULL;
  tree->bst_compare = compare;
  tree->bst_param = param;
  tree->bst_alloc = allocator;
  tree->bst_count = 0;
  tree->bst_generation = 0;

  return tree;
}

This code is included in 29, 145, and 196.