Add concurrent implementation of an ObjectPool to reuse small objects like Node instances

diff --git a/mcs/class/corlib/System.Collections.Concurrent/ObjectPool.cs b/mcs/class/corlib/System.Collections.Concurrent/ObjectPool.cs
new file mode 100644 (file)
index 0000000..cee3702
--- /dev/null
+++ b/mcs/class/corlib/System.Collections.Concurrent/ObjectPool.cs
@@ -0,0 +1,96 @@
+// ObjectPool.cs
+//
+// Copyright (c) 2011 Novell
+//
+// Authors: 
+//      Jérémie "garuma" Laval
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+//
+
+#if NET_4_0 || MOBILE
+
+using System;
+using System.Threading;
+using System.Collections;
+using System.Collections.Generic;
+using System.Runtime.Serialization;
+
+namespace System.Collections.Concurrent
+{
+       internal abstract class ObjectPool<T> where T : class
+       {
+               const int capacity = 20;
+               const int bit = 0x8000000;
+
+               readonly T[] buffer;
+               int addIndex;
+               int removeIndex;
+
+               public ObjectPool ()
+               {
+                       buffer = new T[capacity];
+                       for (int i = 0; i < capacity; i++)
+                               buffer[i] = Creator ();
+                       addIndex = capacity - 1;
+               }
+
+               protected abstract T Creator ();
+
+               public T Take ()
+               {
+                       if ((addIndex & ~bit) - 1 == removeIndex)
+                               return Creator ();
+
+                       int i;
+                       T result;
+
+                       do {
+                               i = removeIndex;
+                               if ((addIndex & ~bit) - 1 == i)
+                                       return Creator ();
+                               result = buffer[i % capacity];
+                       } while (Interlocked.CompareExchange (ref removeIndex, i + 1, i) != i);
+
+                       return result;
+               }
+
+               public void Release (T obj)
+               {
+                       if (obj == null || addIndex - removeIndex >= capacity - 1)
+                               return;
+
+                       int i;
+                       int tries = 3;
+                       do {
+                               do {
+                                       i = addIndex;
+                               } while ((i & bit) > 0);
+                               if (i - removeIndex >= capacity - 1)
+                                       return;
+                       } while (Interlocked.CompareExchange (ref addIndex, i + 1 + bit, i) != i && --tries > 0);
+
+                       buffer[i % capacity] = obj;
+                       addIndex = addIndex - bit;
+               }
+       }
+}
+
+#endif

diff --git a/mcs/class/corlib/corlib.dll.sources b/mcs/class/corlib/corlib.dll.sources
index 3c4146135e528a6ec987edb83923cee53d2a90ee..8002099a2300eb46ecf28aa8198fc976fae14a9d 100644 (file)
--- a/mcs/class/corlib/corlib.dll.sources
+++ b/mcs/class/corlib/corlib.dll.sources
@@ -1575,3 +1575,4 @@ System.Threading.Tasks/ParallelLoopState.cs
 System/AggregateException.cs
 System.Threading.Tasks/SimpleConcurrentBag.cs
 System.Threading.Tasks/UnobservedTaskExceptionEventArgs.cs
+System.Collections.Concurrent/ObjectPool.cs