From d12c4f46624369d86d9a4c3c90d7042400f75a6f Mon Sep 17 00:00:00 2001
From: the_fiddler <the_fiddler@ebc5dd9b-fb1d-0410-b6f8-d24c324e9604>
Date: Fri, 17 Jul 2009 22:51:44 +0000
Subject: [PATCH] Added BlittableValueType struct that can be used to check
 whether any given value type is blittable.

---
 Source/OpenTK/BlittableValueType.cs | 98 +++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 Source/OpenTK/BlittableValueType.cs

diff --git a/Source/OpenTK/BlittableValueType.cs b/Source/OpenTK/BlittableValueType.cs
new file mode 100644
index 00000000..03744a75
--- /dev/null
+++ b/Source/OpenTK/BlittableValueType.cs
@@ -0,0 +1,98 @@
+#region License
+//
+// The Open Toolkit Library License
+//
+// Copyright (c) 2006 - 2009 the Open Toolkit library.
+//
+// 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.
+//
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Runtime.InteropServices;
+using System.Diagnostics;
+using System.Reflection;
+
+namespace OpenTK
+{
+    /// <summary>
+    /// Checks whether the specified type parameter is a blittable value type.
+    /// </summary>
+    /// <remarks>
+    /// A blittable value type is a struct that only references other value types recursively,
+    /// which allows it to be passed to unmanaged code directly.
+    /// </remarks>
+    /// <typeparam name="T">The struct to check.</typeparam>
+    /// <exception cref="System.NotSupportedException">Raised when T is not a blittable value type.</exception>
+    public struct BlittableValueType<T> where T : struct
+    {
+        /// <summary>
+        /// Gets the size of the type in bytes.
+        /// </summary>
+        public static readonly int Stride = Marshal.SizeOf(typeof(T));
+
+        static BlittableValueType()
+        {
+            Type type = typeof(T);
+            
+            if (!CheckStructLayoutAttribute(type))
+                Debug.Print("Warning: type {0} does not specify a StructLayoutAttribute with Pack=1. The memory layout of the struct may change between platforms.", type.Name);
+
+            if (!CheckType(type))
+                throw new NotSupportedException(String.Format("Type {0} contains non-primitive fields.", type.Name));
+        }
+
+        // Checks whether the parameter is a primitive type or consists of primitive types recursively.
+        // Throws a NotSupportedException if it is not.
+        static bool CheckType(Type type)
+        {
+            //Debug.Print("Checking type {0} (size: {1} bytes).", type.Name, Marshal.SizeOf(type));
+            if (type.IsPrimitive)
+                return true;
+
+            FieldInfo[] fields = type.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
+            Debug.Indent();
+            foreach (FieldInfo field in fields)
+            {
+                if (!CheckType(field.FieldType))
+                    return false;
+            }
+            Debug.Unindent();
+
+            return true;
+        }
+
+        // Checks whether the specified struct defines [StructLayout(LayoutKind.Sequential, Pack=1)]
+        // or [StructLayout(LayoutKind.Explicit)]
+        static bool CheckStructLayoutAttribute(Type type)
+        {
+            StructLayoutAttribute[] attr = (StructLayoutAttribute[])
+                type.GetCustomAttributes(typeof(StructLayoutAttribute), true);
+
+            if ((attr == null) ||
+                (attr != null && attr.Length > 0 && attr[0].Value != LayoutKind.Explicit && attr[0].Pack != 1))
+                return false;
+
+            return true;
+        }
+    }
+}