Function tskit::bindings::tsk_tree_get_total_branch_length

pub unsafe extern "C" fn tsk_tree_get_total_branch_length(
    self_: *const tsk_tree_t,
    u: tsk_id_t,
    ret_tbl: *mut f64
) -> c_int

@brief Computes the sum of the lengths of all branches reachable from the specified node, or from all roots if u=TSK_NULL.

@rst Return the total branch length in a particular subtree or of the entire tree. If the specified node is :c:macro:TSK_NULL (or the :ref:virtual root<sec_data_model_tree_roots>) the sum of the lengths of all branches reachable from roots is returned. Branch length is defined as difference between the time of a node and its parent. The branch length of a root is zero.

Note that if the specified node is internal its branch length is not* included, so that, e.g., the total branch length of a leaf node is zero. @endrst

@param self A pointer to a tsk_tree_t object. @param u The root of the subtree of interest, or TSK_NULL to return the total branch length of the tree. @param ret_tbl A double pointer to store the returned total branch length. @return 0 on success or a negative value on failure.