classic arg (#348)

Author: bitfaster

BitFaster.Caching.UnitTests/Lru/ClassicLruTests.cs

@@ -181,6 +181,17 @@ public void WhenKeyIsRequestedItIsCreatedAndCached()
             result1.Should().Be(result2);
         }
 
+
+        [Fact]
+        public void WhenKeyIsRequestedWithArgItIsCreatedAndCached()
+        {
+            var result1 = lru.GetOrAdd(1, valueFactory.Create, "x");
+            var result2 = lru.GetOrAdd(1, valueFactory.Create, "y");
+
+            valueFactory.timesCalled.Should().Be(1);
+            result1.Should().Be(result2);
+        }
+
         [Fact]
         public async Task WhenKeyIsRequesteItIsCreatedAndCachedAsync()
         {
@@ -191,6 +202,16 @@ public async Task WhenKeyIsRequesteItIsCreatedAndCachedAsync()
             result1.Should().Be(result2);
         }
 
+        [Fact]
+        public async Task WhenKeyIsRequestedWithArgItIsCreatedAndCachedAsync()
+        {
+            var result1 = await lru.GetOrAddAsync(1, valueFactory.CreateAsync, "x").ConfigureAwait(false);
+            var result2 = await lru.GetOrAddAsync(1, valueFactory.CreateAsync, "y").ConfigureAwait(false);
+
+            valueFactory.timesCalled.Should().Be(1);
+            result1.Should().Be(result2);
+        }
+
         [Fact]
         public void WhenDifferentKeysAreRequestedValueIsCreatedForEach()
         {

BitFaster.Caching/Lru/ClassicLru.cs

@@ -113,15 +113,9 @@ public bool TryGet(K key, out V value)
             return false;
         }
 
-        ///<inheritdoc/>
-        public V GetOrAdd(K key, Func<K, V> valueFactory)
+        private bool TryAdd(K key, V value)
         {
-            if (this.TryGet(key, out var value))
-            {
-                return value;
-            }
-
-            var node = new LinkedListNode<LruItem>(new LruItem(key, valueFactory(key)));
+            var node = new LinkedListNode<LruItem>(new LruItem(key, value));
 
             if (this.dictionary.TryAdd(key, node))
             {
@@ -152,57 +146,101 @@ public V GetOrAdd(K key, Func<K, V> valueFactory)
                     Disposer<V>.Dispose(removed.Value.Value);
                 }
 
-                return node.Value.Value;
+                return true;
             }
 
-            return this.GetOrAdd(key, valueFactory);
+            return false;
         }
 
         ///<inheritdoc/>
-        public async ValueTask<V> GetOrAddAsync(K key, Func<K, Task<V>> valueFactory)
+        public V GetOrAdd(K key, Func<K, V> valueFactory)
         {
             if (this.TryGet(key, out var value))
             {
                 return value;
             }
 
-            var node = new LinkedListNode<LruItem>(new LruItem(key, await valueFactory(key)));
+            value = valueFactory(key);
 
-            if (this.dictionary.TryAdd(key, node))
+            if (TryAdd(key, value))
             {
-                LinkedListNode<LruItem> first = null;
+                return value;
+            }
 
-                lock (this.linkedList)
-                {
-                    if (linkedList.Count >= capacity)
-                    {
-                        first = linkedList.First;
-                        linkedList.RemoveFirst();
-                    }
+            return this.GetOrAdd(key, valueFactory);
+        }
 
-                    linkedList.AddLast(node);
-                }
+        /// <summary>
+        /// Adds a key/value pair to the cache if the key does not already exist. Returns the new value, or the 
+        /// existing value if the key already exists.
+        /// </summary>
+        /// <typeparam name="TArg">The type of an argument to pass into valueFactory.</typeparam>
+        /// <param name="key">The key of the element to add.</param>
+        /// <param name="valueFactory">The factory function used to generate a value for the key.</param>
+        /// <param name="factoryArgument">An argument value to pass into valueFactory.</param>
+        /// <returns>The value for the key. This will be either the existing value for the key if the key is already 
+        /// in the cache, or the new value if the key was not in the cache.</returns>
+        public V GetOrAdd<TArg>(K key, Func<K, TArg, V> valueFactory, TArg factoryArgument)
+        {
+            if (this.TryGet(key, out var value))
+            {
+                return value;
+            }
 
-                // Remove from the dictionary outside the lock. This means that the dictionary at this moment
-                // contains an item that is not in the linked list. If another thread fetches this item, 
-                // LockAndMoveToEnd will ignore it, since it is detached. This means we potentially 'lose' an 
-                // item just as it was about to move to the back of the LRU list and be preserved. The next request
-                // for the same key will be a miss. Dictionary and list are eventually consistent.
-                // However, all operations inside the lock are extremely fast, so contention is minimized.
-                if (first != null)
-                {
-                    dictionary.TryRemove(first.Value.Key, out var removed);
+            value = valueFactory(key, factoryArgument);
 
-                    Interlocked.Increment(ref this.metrics.evictedCount);
-                    Disposer<V>.Dispose(removed.Value.Value);
-                }
+            if (TryAdd(key, value))
+            {
+                return value;
+            }
+
+            return this.GetOrAdd(key, valueFactory, factoryArgument);
+        }
+
+        ///<inheritdoc/>
+        public async ValueTask<V> GetOrAddAsync(K key, Func<K, Task<V>> valueFactory)
+        {
+            if (this.TryGet(key, out var value))
+            {
+                return value;
+            }
+
+            value = await valueFactory(key);
 
-                return node.Value.Value;
+            if (TryAdd(key, value))
+            {
+                return value;
             }
 
             return await this.GetOrAddAsync(key, valueFactory);
         }
 
+        /// <summary>
+        /// Adds a key/value pair to the cache if the key does not already exist. Returns the new value, or the 
+        /// existing value if the key already exists.
+        /// </summary>
+        /// <typeparam name="TArg">The type of an argument to pass into valueFactory.</typeparam>
+        /// <param name="key">The key of the element to add.</param>
+        /// <param name="valueFactory">The factory function used to asynchronously generate a value for the key.</param>
+        /// <param name="factoryArgument">An argument value to pass into valueFactory.</param>
+        /// <returns>A task that represents the asynchronous GetOrAdd operation.</returns>
+        public async ValueTask<V> GetOrAddAsync<TArg>(K key, Func<K, TArg, Task<V>> valueFactory, TArg factoryArgument)
+        {
+            if (this.TryGet(key, out var value))
+            {
+                return value;
+            }
+
+            value = await valueFactory(key, factoryArgument);
+
+            if (TryAdd(key, value))
+            {
+                return value;
+            }
+
+            return await this.GetOrAddAsync(key, valueFactory, factoryArgument);
+        }
+
         ///<inheritdoc/>
         public bool TryRemove(K key)
         {