The flexible file queue can be set to either open any existing files it
finds, or always delete existing files when it is created using the
open_existing parameter in the contructor.
Note that the queue file is deleted in the following cases:
1. Upon calling the clear() method.
2. Upon calling pop() on an empty queue.
Boost Software License Version 1.0. See LICENSE_BOOST.txt for details.
Alternatively, this file may be distributed under the terms of the Tango
3-Clause BSD License (see LICENSE_BSD.txt for details).
File-based queue implementation.
The flexible file queue can be set to either open any existing files it finds, or always delete existing files when it is created using the open_existing parameter in the contructor.
Note that the queue file is deleted in the following cases: 1. Upon calling the clear() method. 2. Upon calling pop() on an empty queue.