replace lru with schnellru (#14539)

substrate/primitives/blockchain/src/header_metadata.rs

@@ -18,13 +18,12 @@
 //! Implements tree backend, cached header metadata and algorithms
 //! to compute routes efficiently over the tree of headers.
 
-use lru::LruCache;
 use parking_lot::RwLock;
+use schnellru::{ByLength, LruMap};
 use sp_runtime::traits::{Block as BlockT, Header, NumberFor, One};
-use std::num::NonZeroUsize;
 
 /// Set to the expected max difference between `best` and `finalized` blocks at sync.
-const LRU_CACHE_SIZE: usize = 5_000;
+const LRU_CACHE_SIZE: u32 = 5_000;
 
 /// Get lowest common ancestor between two blocks in the tree.
 ///
@@ -243,20 +242,19 @@ pub trait HeaderMetadata<Block: BlockT> {
 
 /// Caches header metadata in an in-memory LRU cache.
 pub struct HeaderMetadataCache<Block: BlockT> {
-	cache: RwLock<LruCache<Block::Hash, CachedHeaderMetadata<Block>>>,
+	cache: RwLock<LruMap<Block::Hash, CachedHeaderMetadata<Block>>>,
 }
 
 impl<Block: BlockT> HeaderMetadataCache<Block> {
 	/// Creates a new LRU header metadata cache with `capacity`.
-	pub fn new(capacity: NonZeroUsize) -> Self {
-		HeaderMetadataCache { cache: RwLock::new(LruCache::new(capacity)) }
+	pub fn new(capacity: u32) -> Self {
+		HeaderMetadataCache { cache: RwLock::new(LruMap::new(ByLength::new(capacity))) }
 	}
 }
 
 impl<Block: BlockT> Default for HeaderMetadataCache<Block> {
 	fn default() -> Self {
-		let cap = NonZeroUsize::new(LRU_CACHE_SIZE).expect("cache capacity is not zero");
-		HeaderMetadataCache { cache: RwLock::new(LruCache::new(cap)) }
+		HeaderMetadataCache { cache: RwLock::new(LruMap::new(ByLength::new(LRU_CACHE_SIZE))) }
 	}
 }
 
@@ -266,11 +264,11 @@ impl<Block: BlockT> HeaderMetadataCache<Block> {
 	}
 
 	pub fn insert_header_metadata(&self, hash: Block::Hash, metadata: CachedHeaderMetadata<Block>) {
-		self.cache.write().put(hash, metadata);
+		self.cache.write().insert(hash, metadata);
 	}
 
 	pub fn remove_header_metadata(&self, hash: Block::Hash) {
-		self.cache.write().pop(&hash);
+		self.cache.write().remove(&hash);
 	}
 }