Calls func for each element in the queue passing user_data to the function.
It is safe for func to remove the element from queue, but it must not modify any part of the queue after that element.
the function to call for each element's data
user data to pass to func
2.4
Calls func for each element in the queue passing user_data to the function.
It is safe for func to remove the element from queue, but it must not modify any part of the queue after that element.