/*
* Search for the node which contains "value". The algorithm is a
* simple binary tree search.
*
* return value:
* NULL: the value is not in the AVL tree
* *where (if not NULL) is set to indicate the insertion point
* "void *" of the found tree node
*/
void *
avl_find(avl_tree_t *tree, const void *value, avl_index_t *where)
{
avl_node_t *node;
avl_node_t *prev = NULL;
int child = 0;
int diff;
size_t off = tree->avl_offset;
for (node = tree->avl_root; node != NULL;
node = node->avl_child[child]) {
prev = node;
diff = tree->avl_compar(value, AVL_NODE2DATA(node, off));
ASSERT(-1 <= diff && diff <= 1);
if (diff == 0) {
#ifdef DEBUG
if (where != NULL)
*where = 0;
#endif
return (AVL_NODE2DATA(node, off));
}
child = avl_balance2child[1 + diff];
}
if (where != NULL)
*where = AVL_MKINDEX(prev, child);
return (NULL);
}
/*
* Insert "new_data" in "tree" in the given "direction" either after or
* before (AVL_AFTER, AVL_BEFORE) the data "here".
*
* Insertions can only be done at empty leaf points in the tree, therefore
* if the given child of the node is already present we move to either
* the AVL_PREV or AVL_NEXT and reverse the insertion direction. Since
* every other node in the tree is a leaf, this always works.
*
* To help developers using this interface, we assert that the new node
* is correctly ordered at every step of the way in DEBUG kernels.
*/
void
avl_insert_here(
avl_tree_t *tree,
void *new_data,
void *here,
int direction)
{
avl_node_t *node;
int child = direction; /* rely on AVL_BEFORE == 0, AVL_AFTER == 1 */
#ifdef DEBUG
int diff;
#endif
//ASSERT(tree != NULL);
//ASSERT(new_data != NULL);
//ASSERT(here != NULL);
//ASSERT(direction == AVL_BEFORE || direction == AVL_AFTER);
/*
* If corresponding child of node is not NULL, go to the neighboring
* node and reverse the insertion direction.
*/
node = AVL_DATA2NODE(here, tree->avl_offset);
#ifdef DEBUG
diff = tree->avl_compar(new_data, here);
//ASSERT(-1 <= diff && diff <= 1);
//ASSERT(diff != 0);
//ASSERT(diff > 0 ? child == 1 : child == 0);
#endif
if (node->avl_child[child] != NULL) {
node = node->avl_child[child];
child = 1 - child;
while (node->avl_child[child] != NULL) {
#ifdef DEBUG
diff = tree->avl_compar(new_data,
AVL_NODE2DATA(node, tree->avl_offset));
//ASSERT(-1 <= diff && diff <= 1);
//ASSERT(diff != 0);
//ASSERT(diff > 0 ? child == 1 : child == 0);
#endif
node = node->avl_child[child];
}
#ifdef DEBUG
diff = tree->avl_compar(new_data,
AVL_NODE2DATA(node, tree->avl_offset));
//ASSERT(-1 <= diff && diff <= 1);
//ASSERT(diff != 0);
//ASSERT(diff > 0 ? child == 1 : child == 0);
#endif
}
//ASSERT(node->avl_child[child] == NULL);
avl_insert(tree, new_data, AVL_MKINDEX(node, child));
}
