Function av_tree_enumerate

pub unsafe extern "C" fn av_tree_enumerate(
    t: *mut AVTreeNode,
    opaque: *mut c_void,
    cmp: Option<unsafe extern "C" fn(*mut c_void, *mut c_void) -> i32>,
    enu: Option<unsafe extern "C" fn(*mut c_void, *mut c_void) -> i32>,
)

Apply enu(opaque, &elem) to all the elements in the tree in a given range.

@param cmp a comparison function that returns < 0 for an element below the range, > 0 for an element above the range and == 0 for an element inside the range

@note The cmp function should use the same ordering used to construct the tree.