extend singletoncache (#25)

Author: bitfaster

BitFaster.Caching/SingletonCache.cs

@@ -7,89 +7,88 @@
 
 namespace BitFaster.Caching
 {
-	/// <summary>
-	/// Cache a single value for each key, and maintain in memory only the values that have been acquired 
-	/// but not yet released.
-	/// </summary>
-	/// <typeparam name="TKey">The type of the key.</typeparam>
-	/// <typeparam name="TValue">The type of the value.</typeparam>
-	public class SingletonCache<TKey, TValue>
-			where TValue : new()
-	{
-		private readonly ConcurrentDictionary<TKey, ReferenceCount<TValue>> cache;
+    /// <summary>
+    /// Cache a single value for each key, and maintain in memory only the values that have been acquired 
+    /// but not yet released.
+    /// </summary>
+    /// <typeparam name="TKey">The type of the key.</typeparam>
+    /// <typeparam name="TValue">The type of the value.</typeparam>
+    public class SingletonCache<TKey, TValue>
+    {
+        private readonly ConcurrentDictionary<TKey, ReferenceCount<TValue>> cache;
 
-		public SingletonCache()
-		{
-			this.cache = new ConcurrentDictionary<TKey, ReferenceCount<TValue>>();
-		}
+        public SingletonCache()
+        {
+            this.cache = new ConcurrentDictionary<TKey, ReferenceCount<TValue>>();
+        }
 
-		public SingletonCache(int concurrencyLevel, int capacity, IEqualityComparer<TKey> comparer)
-		{
-			this.cache = new ConcurrentDictionary<TKey, ReferenceCount<TValue>>(concurrencyLevel, capacity, comparer);
-		}
+        public SingletonCache(int concurrencyLevel, int capacity, IEqualityComparer<TKey> comparer)
+        {
+            this.cache = new ConcurrentDictionary<TKey, ReferenceCount<TValue>>(concurrencyLevel, capacity, comparer);
+        }
 
-		public Handle Acquire(TKey key)
-		{
-			var refCount = this.cache.AddOrUpdate(key,
-					(_) => new ReferenceCount<TValue>(new TValue()),
-					(_, existingRefCount) => existingRefCount.IncrementCopy());
+        public Handle Acquire(TKey key, Func<TKey, TValue> valueFactory)
+        {
+            var refCount = this.cache.AddOrUpdate(key,
+                    (_) => new ReferenceCount<TValue>(valueFactory(_)),
+                    (_, existingRefCount) => existingRefCount.IncrementCopy());
 
-			return new Handle(key, refCount.Value, this);
-		}
+            return new Handle(key, refCount.Value, this);
+        }
 
-		private void Release(TKey key)
-		{
-			while (true)
-			{
-				var oldRefCount = this.cache[key];
-				var newRefCount = oldRefCount.DecrementCopy();
-				if (this.cache.TryUpdate(key, newRefCount, oldRefCount))
-				{
-					if (newRefCount.Count == 0)
-					{
-						// This will remove from dictionary only if key and the value with ReferenceCount (== 0) matches (under a lock)
-						if (((IDictionary<TKey, ReferenceCount<TValue>>)this.cache).Remove(new KeyValuePair<TKey, ReferenceCount<TValue>>(key, newRefCount)))
-						{
-							if (newRefCount.Value is IDisposable d)
-							{
-								d.Dispose();
-							}
-						}
-					}
-					break;
-				}
-			}
-		}
+        private void Release(TKey key)
+        {
+            while (true)
+            {
+                var oldRefCount = this.cache[key];
+                var newRefCount = oldRefCount.DecrementCopy();
+                if (this.cache.TryUpdate(key, newRefCount, oldRefCount))
+                {
+                    if (newRefCount.Count == 0)
+                    {
+                        // This will remove from dictionary only if key and the value with ReferenceCount (== 0) matches (under a lock)
+                        if (((IDictionary<TKey, ReferenceCount<TValue>>)this.cache).Remove(new KeyValuePair<TKey, ReferenceCount<TValue>>(key, newRefCount)))
+                        {
+                            if (newRefCount.Value is IDisposable d)
+                            {
+                                d.Dispose();
+                            }
+                        }
+                    }
+                    break;
+                }
+            }
+        }
 
-		public sealed class Handle : IDisposable
-		{
-			private TKey key;
-			private TValue value;
-			private SingletonCache<TKey, TValue> cache;
+        public sealed class Handle : IDisposable
+        {
+            private TKey key;
+            private TValue value;
+            private SingletonCache<TKey, TValue> cache;
 
-			public Handle(TKey key, TValue value, SingletonCache<TKey, TValue> cache)
-			{
-				this.key = key;
-				this.value = value;
-				this.cache = cache;
-			}
+            public Handle(TKey key, TValue value, SingletonCache<TKey, TValue> cache)
+            {
+                this.key = key;
+                this.value = value;
+                this.cache = cache;
+            }
 
-			public TValue Value
-			{
-				get
-				{
-					return this.value;
-				}
-			}
+            public TValue Value
+            {
+                get
+                {
+                    return this.value;
+                }
+            }
 
-			public void Dispose()
-			{
-				if (this.cache != null)
-				{
-					this.cache.Release(this.key);
-					this.cache = null;
-				}
-			}
-		}
-	}
+            public void Dispose()
+            {
+                if (this.cache != null)
+                {
+                    this.cache.Release(this.key);
+                    this.cache = null;
+                }
+            }
+        }
+    }
 }

BitFaster.Caching/SingletonCacheExtensions.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace BitFaster.Caching
+{
+    public static class SingletonCacheExtensions
+    {
+        public static SingletonCache<TKey, TValue>.Handle Acquire<TKey, TValue>(this SingletonCache<TKey, TValue> cache, TKey key) 
+            where TValue : new()
+        {
+            return cache.Acquire(key, _ => new TValue());
+        }
+    }
+}