+--------------------------+
|      disk_io_thread      |
|   (manages piece cache)  |
+--------------------------+
              ^
              |
              v
+--------------------------+
|      piece_manager       |
|  (maps pieces to slots)  |
+--------------------------+
              ^
              |
              v customization point
/--------------------------\      +------------------+
|          storage         |<---->| file_pool        |
| cGRE                     |      | open file cache  |
| (maps slots to file and  |      +------------------+
| offset. reads and writes |
| to disk)                 |      +------------------+
|                          |<-----+ file_storage     |
\--------------------------/      | standard slot to |
              ^                   | file mapping     |
              |                   +------------------+
              v
+--------------------------+
|           file           |
| (file class reads and    |
| writes files)            |
+--------------------------+