-OSDirTree *OSDirTree_Create();
-void OSDirTree_AddToTree(OSDirTree *tree, char *str, void *data, char sep);
-void *OSDirTree_SearchTree(OSDirTree *tree, char *str, char sep);
-
+OSDirTree *OSDirTree_Create(void);
+void OSDirTree_AddToTree(OSDirTree *tree, const char *str, void *data, char sep) __attribute__((nonnull(1, 2)));
+void *OSDirTree_SearchTree(const OSDirTree *tree, const char *str, char sep) __attribute__((nonnull));