Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Configuration/System/Configuration/SafeBitVector32.cs

@@ -0,0 +1,57 @@
+//------------------------------------------------------------------------------
+// <copyright file="SimpleBitVector32.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+//------------------------------------------------------------------------------
+
+using System;
+using System.Threading;
+
+namespace System.Configuration {
+    //
+    // This is a multithreadsafe version of System.Collections.Specialized.BitVector32.
+    //
+    [Serializable]
+    internal struct SafeBitVector32 {
+        private volatile int _data;
+    
+        internal SafeBitVector32(int data) {
+            this._data = data;
+        }
+
+#if UNUSED_CODE
+        internal bool IsAnySet(int bitMask) {
+            int data = _data;
+            return (data & bitMask) != 0;
+        }
+#endif
+
+        internal bool this[int bit] {
+            get {
+                int data = _data;
+                return (data & bit) == bit;
+            }
+            set {
+                for (;;) {
+                    int oldData = _data;
+                    int newData;
+                    if (value) {
+                        newData = oldData | bit;
+                    }
+                    else {
+                        newData = oldData & ~bit;
+                    }
+
+#pragma warning disable 0420
+                    int result = Interlocked.CompareExchange(ref _data, newData, oldData);
+#pragma warning restore 0420
+
+                    if (result == oldData) {
+                        break;
+                    }
+                }
+            }
+        }
+    }
+}
+