[pbs-devel] [RFC proxmox-backup 33/39] tools: async lru cache: implement insert, remove and contains methods

[Christian Ebner]

Add methods to insert new cache entries without using the cacher,
remove cache entries given their key and check if the cache contains
a key, marking it the most recently used one if it does.

These methods will be used to implement the local datastore cache
which stores the values (chunks) on the filesystem rather than
keeping track of them by storing them in-memory in the cache. The lru
cache will only be used to allow for fast lookup and keep track of
the lookup order.

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
 pbs-tools/src/async_lru_cache.rs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/pbs-tools/src/async_lru_cache.rs b/pbs-tools/src/async_lru_cache.rs
index 141114933..3a975de32 100644
--- a/pbs-tools/src/async_lru_cache.rs
+++ b/pbs-tools/src/async_lru_cache.rs
@@ -87,6 +87,29 @@ impl<K: std::cmp::Eq + std::hash::Hash + Copy, V: Clone + Send + 'static> AsyncL
 
         result
     }
+
+    /// Insert an item as the most recently used one into the cache, calling the removed callback
+    /// on the evicted cache item, if any.
+    pub fn insert<F>(&self, key: K, value: V, removed: F) -> Result<(), Error>
+    where
+        F: Fn(K) -> Result<(), Error>,
+    {
+        let mut maps = self.maps.lock().unwrap();
+        maps.0.insert(key, value.clone(), removed)?;
+        Ok(())
+    }
+
+    /// Check if the item exists and if so, mark it as the most recently uses one.
+    pub fn contains(&self, key: K) -> bool {
+        let mut maps = self.maps.lock().unwrap();
+        maps.0.get_mut(key).is_some()
+    }
+
+    /// Remove the item from the cache.
+    pub fn remove(&self, key: K) {
+        let mut maps = self.maps.lock().unwrap();
+        maps.0.remove(key);
+    }
 }
 
 #[cfg(test)]
-- 
2.39.5