Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/Util/SimpleRecyclingCache.cs

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+//------------------------------------------------------------------------------
+// <copyright file="SimpleRecyclingCache.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+//------------------------------------------------------------------------------
+
+/*
+ * SimpleRecyclingCache class
+ * 
+ * Copyright (c) 1999 Microsoft Corporation
+ */
+
+namespace System.Web.Util {
+
+using System.Collections;
+
+/*
+ * The purpose of this class is to provide a simple and efficient cache.
+ * Instead of using fancy logic to expire items, it uses a simple heuristic:
+ * when the number of entry reaches a fixed limit, the cache is reset.
+ */
+internal class SimpleRecyclingCache {
+
+    private const int MAX_SIZE = 100;
+    private static Hashtable _hashtable;
+
+    internal SimpleRecyclingCache() {
+        CreateHashtable();
+    }
+
+    // Create or recreate the hastable
+    private void CreateHashtable() {
+        _hashtable = new Hashtable(MAX_SIZE, StringComparer.OrdinalIgnoreCase);
+    }
+
+    internal object this[object key] {
+        get {
+            return _hashtable[key];
+        }
+        set {
+            lock (this) {
+                // The limit was reached, so reset everything
+                if (_hashtable.Count >= MAX_SIZE)
+                    _hashtable.Clear();
+
+                _hashtable[key] = value;
+            }
+        }
+    }
+
+}
+
+}