sandbox: btree: add in-order tree traversal

sandbox/btree/btree.c

@@ -231,51 +231,6 @@ void btree_insert_fixup(btree_t *tree, btree_node_t *node)
 	insert_fixup(tree, node);
 }
 
-#if 0
-void btree_insert(btree_t *tree, btree_node_t *node)
-{
-	if (!tree->b_root) {
-		tree->b_root = node;
-		node->b_parent = NULL;
-		node->b_height = 1;
-		return;
-	}
-
-	btree_node_t *cur = tree->b_root;
-	while (1) {
-		btree_node_t **nextp = NULL;
-
-		if (node->b_key == cur->b_key) {
-			return;
-		}
-
-		if (node->b_key >= cur->b_key) {
-			nextp = &cur->b_right;
-		} else {
-			nextp = &cur->b_left;
-		}
-
-		if (*nextp) {
-			cur = *nextp;
-		} else {
-			node->b_parent = cur;
-			*nextp = node;
-			break;
-		}
-	}
-
-	node->b_height = 0;
-
-	cur = node;
-	while (cur) {
-		update_height(cur);
-		cur = cur->b_parent;
-	}
-
-	insert_fixup(tree, node);
-}
-#endif
-
 static btree_node_t *remove_node_with_no_children(btree_t *tree, btree_node_t *node)
 {
 	btree_node_t *w = node->b_parent;
@@ -412,3 +367,75 @@ void btree_delete(btree_t *tree, btree_node_t *node)
 
 	node->b_left = node->b_right = node->b_parent = NULL;
 }
+
+btree_node_t *btree_first(btree_t *tree)
+{
+	btree_node_t *cur = tree->b_root;
+	if (!cur) {
+		return NULL;
+	}
+	
+	while (cur->b_left) {
+		cur = cur->b_left;
+	}
+
+	return cur;
+}
+
+btree_node_t *btree_last(btree_t *tree)
+{
+	btree_node_t *cur = tree->b_root;
+	if (!cur) {
+		return NULL;
+	}
+	
+	while (cur->b_right) {
+		cur = cur->b_right;
+	}
+
+	return cur;
+}
+
+btree_node_t *btree_next(btree_node_t *node)
+{
+	if (!node) {
+		return NULL;
+	}
+
+	if (node->b_right) {
+		btree_node_t *cur = node->b_right;
+		while (cur->b_left) {
+			cur = cur->b_left;
+		}
+
+		return cur;
+	}
+
+	while (node->b_parent && node->b_parent->b_left != node) {
+		node = node->b_parent;
+	}
+		
+	return node->b_parent;
+}	
+
+btree_node_t *btree_prev(btree_node_t *node)
+{
+	if (!node) {
+		return NULL;
+	}
+
+	if (node->b_left) {
+		btree_node_t *cur = node->b_left;
+		while (cur->b_right) {
+			cur = cur->b_right;
+		}
+
+		return cur;
+	}
+
+	while (node->b_parent && node->b_parent->b_right != node) {
+		node = node->b_parent;
+	}
+		
+	return node->b_parent;
+}