Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Web/Util/WorkItem.cs

@@ -0,0 +1,98 @@
+//------------------------------------------------------------------------------
+// <copyright file="WorkItem.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+//------------------------------------------------------------------------------
+
+namespace System.Web.Util {
+
+    using System.Runtime.InteropServices;
+    using System.Security.Permissions;
+    using System.Threading;
+
+//
+// Support for positing of work items to a different thread
+//
+
+
+/// <devdoc>
+///    <para>[To be supplied.]</para>
+/// </devdoc>
+public delegate void WorkItemCallback();
+
+
+/// <devdoc>
+///    <para>[To be supplied.]</para>
+/// </devdoc>
+public class WorkItem {
+
+    private static bool _useQueueUserWorkItem = true;
+    private static WaitCallback _onQueueUserWorkItemCompletion = new WaitCallback(OnQueueUserWorkItemCompletion);
+
+
+    /// <devdoc>
+    ///    <para>[To be supplied.]</para>
+    /// </devdoc>
+
+    [SecurityPermission(SecurityAction.Demand, Unrestricted=true)]
+    public static void Post(WorkItemCallback callback) {
+#if !FEATURE_PAL // ROTORTODO
+        if (Environment.OSVersion.Platform != PlatformID.Win32NT)
+            throw new PlatformNotSupportedException(SR.GetString(SR.RequiresNT));
+#else // !FEATURE_PAL
+        throw new NotImplementedException("ROTORTODO");
+#endif // !FEATURE_PAL
+        PostInternal(callback);
+    }
+
+    // assert to disregard the user code up the compressed stack
+    [PermissionSet(SecurityAction.Assert, Unrestricted=true)]
+    private static void CallCallbackWithAssert(WorkItemCallback callback) {
+        callback();
+    }
+
+    private static void OnQueueUserWorkItemCompletion(Object state) {
+        WorkItemCallback callback = state as WorkItemCallback;
+
+        if (callback != null) {
+            CallCallbackWithAssert(callback);
+        }
+    }
+
+    internal static void PostInternal(WorkItemCallback callback) {
+        if (_useQueueUserWorkItem) {
+            ThreadPool.QueueUserWorkItem(_onQueueUserWorkItemCompletion, callback);
+        }
+        else {
+            WrappedWorkItemCallback w = new WrappedWorkItemCallback(callback);
+            w.Post();
+        }
+    }
+}
+
+internal class WrappedWorkItemCallback {
+    private GCHandle         _rootedThis;
+    private WorkItemCallback _originalCallback;
+    private WorkItemCallback _wrapperCallback;
+
+    internal WrappedWorkItemCallback(WorkItemCallback callback) {
+        _originalCallback = callback;
+        _wrapperCallback = new WorkItemCallback(this.OnCallback);
+    }
+
+    internal void Post() {
+        _rootedThis = GCHandle.Alloc(this);
+
+        if (UnsafeNativeMethods.PostThreadPoolWorkItem(_wrapperCallback) != 1) {
+            _rootedThis.Free();
+            throw new HttpException(SR.GetString(SR.Cannot_post_workitem));
+        }
+    }
+
+    private void OnCallback() {
+        _rootedThis.Free();
+        _originalCallback();
+    }
+}
+
+}