tools: LRU cache to use for pxar FUSE implementation.

Implements a cache with least recently used cache replacement policy.
Internally the state is tracked by a HashMap (for fast access) and a doubly
linked list (for the access order).

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>

src/tools.rs

@@ -23,6 +23,7 @@ pub mod async_io;
 pub mod borrow;
 pub mod daemon;
 pub mod fs;
+pub mod lru_cache;
 pub mod runtime;
 pub mod ticket;
 pub mod timer;