Function ddsrt_avl_root 

pub unsafe extern "C" fn ddsrt_avl_root(
    td: *const ddsrt_avl_treedef_t,
    tree: *const ddsrt_avl_tree_t,
) -> *mut c_void

@brief Get the root node

@param[in] td treedef of the tree @param[in] tree the avl tree @returns pointer to root node, NULL if tree is empty