template project, first version

DirectXTK/Src/DemandCreate.h

@@ -0,0 +1,51 @@
+//--------------------------------------------------------------------------------------
+// File: DemandCreate.h
+//
+// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
+// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
+// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
+// PARTICULAR PURPOSE.
+//
+// Copyright (c) Microsoft Corporation. All rights reserved.
+//
+// http://go.microsoft.com/fwlink/?LinkId=248929
+//--------------------------------------------------------------------------------------
+
+#pragma once
+
+#include "PlatformHelpers.h"
+
+
+namespace DirectX
+{
+    // Helper for lazily creating a D3D resource.
+    template<typename T, typename TCreateFunc>
+    static T* DemandCreate(Microsoft::WRL::ComPtr<T>& comPtr, std::mutex& mutex, TCreateFunc createFunc)
+    {
+        T* result = comPtr.Get();
+
+        // Double-checked lock pattern.
+        MemoryBarrier();
+
+        if (!result)
+        {
+            std::lock_guard<std::mutex> lock(mutex);
+
+            result = comPtr.Get();
+        
+            if (!result)
+            {
+                // Create the new object.
+                ThrowIfFailed(
+                    createFunc(&result)
+                );
+
+                MemoryBarrier();
+
+                comPtr.Attach(result);
+            }
+        }
+
+        return result;
+    }
+}